Add description to file_store cargo metadata

chain to 0.4.0
electrum to 0.2.0
esplora to 0.2.0
file_store to 0.1.0

.github/ISSUE_TEMPLATE/enhancement_request.md

@@ -0,0 +1,17 @@
+---
+name: Enhancement request
+about: Request a new feature or change to an existing feature
+title: ''
+labels: 'enhancement'
+assignees: ''
+
+---
+
+**Describe the enhancement**  
+<!-- A clear and concise description of what you would like added or changed. -->
+
+**Use case**  
+<!-- Tell us how you or others will use this new feature or change to an existing feature. --> 
+
+**Additional context**
+<!-- Add any other context about the enhancement here. --> 

.github/ISSUE_TEMPLATE/minor_release.md

@@ -0,0 +1,99 @@
+---
+name: Minor Release
+about: Create a new minor release [for release managers only]
+title: 'Release MAJOR.MINOR+1.0'
+labels: 'release'
+assignees: ''
+
+---
+
+## Create a new minor release
+
+### Summary
+
+<--release summary to be used in announcements-->
+
+### Commit
+
+<--latest commit ID to include in this release-->
+
+### Changelog
+
+<--add notices from PRs merged since the prior release, see ["keep a changelog"]-->
+
+### Checklist
+
+Release numbering must follow [Semantic Versioning]. These steps assume the current `master`
+branch **development** version is *MAJOR.MINOR.0*.
+
+#### On the day of the feature freeze
+
+Change the `master` branch to the next MINOR+1 version:
+
+- [ ] Switch to the `master` branch.
+- [ ] Create a new PR branch called `bump_dev_MAJOR_MINOR+1`, eg. `bump_dev_0_22`.
+- [ ] Bump the `bump_dev_MAJOR_MINOR+1` branch to the next development MINOR+1 version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR+1.0`.
+  - Update the `CHANGELOG.md` file.
+  - The commit message should be "Bump version to MAJOR.MINOR+1.0".
+- [ ] Create PR and merge the `bump_dev_MAJOR_MINOR+1` branch to `master`.
+  - Title PR "Bump version to MAJOR.MINOR+1.0".
+
+Create a new release branch and release candidate tag:
+
+- [ ] Double check that your local `master` is up-to-date with the upstream repo.
+- [ ] Create a new branch called `release/MAJOR.MINOR+1` from `master`.
+- [ ] Bump the `release/MAJOR.MINOR+1` branch to `MAJOR.MINOR+1.0-rc.1` version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR+1.0-rc.1`.
+  - The commit message should be "Bump version to MAJOR.MINOR+1.0-rc.1".
+- [ ] Add a tag to the `HEAD` commit in the `release/MAJOR.MINOR+1` branch.
+  - The tag name should be `vMAJOR.MINOR+1.0-rc.1`
+  - Use message "Release MAJOR.MINOR+1.0 rc.1".
+  - Make sure the tag is signed, for extra safety use the explicit `--sign` flag.
+- [ ] Push the `release/MAJOR.MINOR` branch and new tag to the `bitcoindevkit/bdk` repo.
+  - Use `git push --tags` option to push the new `vMAJOR.MINOR+1.0-rc.1` tag.
+
+If any issues need to be fixed before the *MAJOR.MINOR+1.0* version is released:
+
+- [ ] Merge fix PRs to the `master` branch.
+- [ ] Git cherry-pick fix commits to the `release/MAJOR.MINOR+1` branch.
+- [ ] Verify fixes in `release/MAJOR.MINOR+1` branch.
+- [ ] Bump the `release/MAJOR.MINOR+1` branch to `MAJOR.MINOR+1.0-rc.x+1` version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR+1.0-rc.x+1`.
+  - The commit message should be "Bump version to MAJOR.MINOR+1.0-rc.x+1".
+- [ ] Add a tag to the `HEAD` commit in the `release/MAJOR.MINOR+1` branch.
+  - The tag name should be `vMAJOR.MINOR+1.0-rc.x+1`, where x is the current release candidate number.
+  - Use tag message "Release MAJOR.MINOR+1.0 rc.x+1".
+  - Make sure the tag is signed, for extra safety use the explicit `--sign` flag.
+- [ ] Push the new tag to the `bitcoindevkit/bdk` repo.
+  - Use `git push --tags` option to push the new `vMAJOR.MINOR+1.0-rc.x+1` tag.
+
+#### On the day of the release
+
+Tag and publish new release:
+
+- [ ] Bump the `release/MAJOR.MINOR+1` branch to `MAJOR.MINOR+1.0` version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR+1.0`.
+  - The commit message should be "Bump version to MAJOR.MINOR+1.0".
+- [ ] Add a tag to the `HEAD` commit in the `release/MAJOR.MINOR+1` branch.
+  - The tag name should be `vMAJOR.MINOR+1.0`
+  - The first line of the tag message should be "Release MAJOR.MINOR+1.0".
+  - In the body of the tag message put a copy of the **Summary** and **Changelog** for the release.
+  - Make sure the tag is signed, for extra safety use the explicit `--sign` flag.
+- [ ] Wait for the CI to finish one last time.
+- [ ] Push the new tag to the `bitcoindevkit/bdk` repo.
+- [ ] Publish **all** the updated crates to crates.io.
+- [ ] Create the release on GitHub.
+  - Go to "tags", click on the dots on the right and select "Create Release".
+  - Set the title to `Release MAJOR.MINOR+1.0`.
+  - In the release notes body put the **Summary** and **Changelog**.
+  - Use the "+ Auto-generate release notes" button to add details from included PRs.
+  - Until we reach a `1.0.0` release check the "Pre-release" box.
+- [ ] Make sure the new release shows up on [crates.io] and that the docs are built correctly on [docs.rs].
+- [ ] Announce the release, using the **Summary**, on Discord, Twitter and Mastodon.
+- [ ] Celebrate 🎉
+
+[Semantic Versioning]: https://semver.org/
+[crates.io]: https://crates.io/crates/bdk
+[docs.rs]: https://docs.rs/bdk/latest/bdk
+["keep a changelog"]: https://keepachangelog.com/en/1.0.0/

.github/ISSUE_TEMPLATE/patch_release.md

@@ -0,0 +1,71 @@
+---
+name: Patch Release
+about: Create a new patch release [for release managers only]
+title: 'Release MAJOR.MINOR.PATCH+1'
+labels: 'release'
+assignees: ''
+
+---
+
+## Create a new patch release
+
+### Summary
+
+<--release summary to be used in announcements-->
+
+### Commit
+
+<--latest commit ID to include in this release-->
+
+### Changelog
+
+<--add notices from PRs merged since the prior release, see ["keep a changelog"]-->
+
+### Checklist
+
+Release numbering must follow [Semantic Versioning]. These steps assume the current `master`
+branch **development** version is *MAJOR.MINOR.PATCH*.
+
+### On the day of the patch release
+
+Change the `master` branch to the new PATCH+1 version:
+
+- [ ] Switch to the `master` branch.
+- [ ] Create a new PR branch called `bump_dev_MAJOR_MINOR_PATCH+1`, eg. `bump_dev_0_22_1`.
+- [ ] Bump the `bump_dev_MAJOR_MINOR` branch to the next development PATCH+1 version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR.PATCH+1`.
+  - Update the `CHANGELOG.md` file.
+  - The commit message should be "Bump version to MAJOR.MINOR.PATCH+1".
+- [ ] Create PR and merge the `bump_dev_MAJOR_MINOR_PATCH+1` branch to `master`.
+  - Title PR "Bump version to MAJOR.MINOR.PATCH+1".
+
+Cherry-pick, tag and publish new PATCH+1 release:
+
+- [ ] Merge fix PRs to the `master` branch.
+- [ ] Git cherry-pick fix commits to the `release/MAJOR.MINOR` branch to be patched.
+- [ ] Verify fixes in `release/MAJOR.MINOR` branch.
+- [ ] Bump the `release/MAJOR.MINOR.PATCH+1` branch to `MAJOR.MINOR.PATCH+1` version.
+  - Change the `Cargo.toml` version value to `MAJOR.MINOR.MINOR.PATCH+1`.
+  - The commit message should be "Bump version to MAJOR.MINOR.PATCH+1".
+- [ ] Add a tag to the `HEAD` commit in the `release/MAJOR.MINOR` branch.
+  - The tag name should be `vMAJOR.MINOR.PATCH+1`
+  - The first line of the tag message should be "Release MAJOR.MINOR.PATCH+1".
+  - In the body of the tag message put a copy of the **Summary** and **Changelog** for the release.
+  - Make sure the tag is signed, for extra safety use the explicit `--sign` flag.
+- [ ] Wait for the CI to finish one last time.
+- [ ] Push the new tag to the `bitcoindevkit/bdk` repo.
+- [ ] Publish **all** the updated crates to crates.io.
+- [ ] Create the release on GitHub.
+  - Go to "tags", click on the dots on the right and select "Create Release".
+  - Set the title to `Release MAJOR.MINOR.PATCH+1`.
+  - In the release notes body put the **Summary** and **Changelog**.
+  - Use the "+ Auto-generate release notes" button to add details from included PRs.
+  - Until we reach a `1.0.0` release check the "Pre-release" box.
+- [ ] Make sure the new release shows up on [crates.io] and that the docs are built correctly on [docs.rs].
+- [ ] Announce the release, using the **Summary**, on Discord, Twitter and Mastodon.
+- [ ] Celebrate 🎉
+
+[Semantic Versioning]: https://semver.org/
+[crates.io]: https://crates.io/crates/bdk
+[docs.rs]: https://docs.rs/bdk/latest/bdk
+["keep a changelog"]: https://keepachangelog.com/en/1.0.0/

.github/pull_request_template.md

@@ -9,6 +9,11 @@
 <!-- In this section you can include notes directed to the reviewers, like explaining why some parts
 of the PR were done in a specific way -->
 
+### Changelog notice
+
+<!-- Notice the release manager should include in the release tag message changelog -->
+<!-- See https://keepachangelog.com/en/1.0.0/ for examples -->
+
 ### Checklists
 
 #### All Submissions:
@@ -21,7 +26,6 @@ of the PR were done in a specific way -->
 
 * [ ] I've added tests for the new feature
 * [ ] I've added docs for the new feature
-* [ ] I've updated `CHANGELOG.md`
 
 #### Bugfixes:
 

.github/workflows/code_coverage.yml

@@ -1,37 +1,54 @@
-on: [push]
+on: [push, pull_request]
 
 name: Code Coverage
 
 jobs:
-
   Codecov:
     name: Code Coverage
     runs-on: ubuntu-latest
     env:
-      CARGO_INCREMENTAL: '0'
-      RUSTFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off'
-      RUSTDOCFLAGS: '-Zprofile -Ccodegen-units=1 -Cinline-threshold=0 -Clink-dead-code -Coverflow-checks=off'
+      RUSTFLAGS: "-Cinstrument-coverage"
+      RUSTDOCFLAGS: "-Cinstrument-coverage"
+      LLVM_PROFILE_FILE: "report-%p-%m.profraw"
 
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-      - name: Install rustup
-        run: curl https://sh.rustup.rs -sSf | sh -s -- -y
-      - name: Set default toolchain
-        run: rustup default nightly
-      - name: Set profile
-        run: rustup set profile minimal
-      - name: Update toolchain
-        run: rustup update
-      - name: Test
-        run: cargo test --features all-keys,compiler,esplora,ureq,compact_filters --no-default-features
-                    
-      - id: coverage
-        name: Generate coverage
-        uses: actions-rs/grcov@v0.1.5
-
-      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v2
+      - name: Install lcov tools
+        run: sudo apt-get install lcov -y
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
         with:
-          file: ${{ steps.coverage.outputs.report }}
-          directory: ./coverage/reports/
+            toolchain: "1.65.0"
+            override: true
+            profile: minimal
+            components: llvm-tools-preview
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Install grcov
+        run: if [[ ! -e ~/.cargo/bin/grcov ]]; then cargo install grcov; fi
+      - name: Build simulator image
+        run: docker build -t hwi/ledger_emulator ./ci -f ci/Dockerfile.ledger
+      - name: Run simulator image
+        run: docker run --name simulator --network=host hwi/ledger_emulator &
+      - name: Install Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.9'
+      - name: Install python dependencies
+        run: pip install hwi==2.1.1 protobuf==3.20.1
+      - name: Test
+        run: cargo test --all-features
+      - name: Run grcov
+        run: mkdir coverage; grcov . --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore '/*' -o ./coverage/lcov.info
+      - name: Generate HTML coverage report
+        run: genhtml -o coverage-report.html ./coverage/lcov.info
+          #      - name: Coveralls upload
+          #        uses: coverallsapp/github-action@master
+          #        with:
+          #          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Upload artifact
+        uses: actions/upload-artifact@v2
+        with:
+          name: coverage-report
+          path: coverage-report.html

.github/workflows/cont_integration.yml

@@ -10,118 +10,27 @@ jobs:
     strategy:
       matrix:
         rust:
-          - version: 1.60.0 # STABLE
+          - version: stable
             clippy: true
-          - version: 1.56.1 # MSRV
+          - version: 1.57.0 # MSRV
         features:
-          - default
-          - minimal
-          - all-keys
-          - minimal,use-esplora-ureq
-          - key-value-db
-          - electrum
-          - compact_filters
-          - esplora,ureq,key-value-db,electrum
-          - compiler
-          - rpc
-          - verify
-          - async-interface
-          - use-esplora-reqwest
-          - sqlite
-          - sqlite-bundled
+          - --no-default-features
+          - --all-features
     steps:
       - name: checkout
         uses: actions/checkout@v2
-      - name: Generate cache key
-        run: echo "${{ matrix.rust.version }} ${{ matrix.features }}" | tee .cache_key
-      - name: cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('.cache_key') }}-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
-      - name: Set default toolchain
-        run: rustup default ${{ matrix.rust.version }}
-      - name: Set profile
-        run: rustup set profile minimal
-      - name: Add clippy
-        if: ${{ matrix.rust.clippy }}
-        run: rustup component add clippy
-      - name: Update toolchain
-        run: rustup update
-      - name: Build
-        run: cargo build --features ${{ matrix.features }} --no-default-features
-      - name: Clippy
-        if: ${{ matrix.rust.clippy }}
-        run: cargo clippy --all-targets --features ${{ matrix.features }} --no-default-features -- -D warnings
-      - name: Test
-        run: cargo test --features ${{ matrix.features }} --no-default-features
-
-  test-readme-examples:
-    name: Test README.md examples
-    runs-on: ubuntu-latest
-    steps:
-      - name: checkout
-        uses: actions/checkout@v2
-      - name: cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-test-md-docs-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
-      - name: Set default toolchain
-        run: rustup default nightly
-      - name: Set profile
-        run: rustup set profile minimal
-      - name: Update toolchain
-        run: rustup update
-      - name: Test
-        run: cargo test --features test-md-docs --no-default-features -- doctest::ReadmeDoctests
-
-  test-blockchains:
-    name: Blockchain ${{ matrix.blockchain.features }}
-    runs-on: ubuntu-20.04
-    strategy:
-      fail-fast: false
-      matrix:
-        blockchain:
-          - name: electrum
-            testprefix: blockchain::electrum::test
-            features: test-electrum,verify
-          - name: rpc
-            testprefix: blockchain::rpc::test
-            features: test-rpc
-          - name: rpc-legacy
-            testprefix: blockchain::rpc::test
-            features: test-rpc-legacy
-          - name: esplora
-            testprefix: esplora
-            features: test-esplora,use-esplora-reqwest,verify
-          - name: esplora
-            testprefix: esplora
-            features: test-esplora,use-esplora-ureq,verify
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: Cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ github.job }}-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
-      - name: Setup rust toolchain
+      - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
-          override: true
+            toolchain: ${{ matrix.rust.version }}
+            override: true
+            profile: minimal
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Build
+        run: cargo build ${{ matrix.features }}
       - name: Test
-        run: cargo test --no-default-features --features ${{ matrix.blockchain.features }} ${{ matrix.blockchain.testprefix }}::bdk_blockchain_tests
+        run: cargo test ${{ matrix.features }}
 
   check-wasm:
     name: Check WASM
@@ -132,29 +41,26 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-      - name: Cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ github.job }}-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
         # Install a recent version of clang that supports wasm32
       - run: wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add - || exit 1
       - run: sudo apt-add-repository "deb http://apt.llvm.org/focal/ llvm-toolchain-focal-10 main" || exit 1
       - run: sudo apt-get update || exit 1
       - run: sudo apt-get install -y libclang-common-10-dev clang-10 libc6-dev-i386 || exit 1
-      - name: Set default toolchain
-        run: rustup default 1.56.1 # STABLE
-      - name: Set profile
-        run: rustup set profile minimal
-      - name: Add target wasm32
-        run: rustup target add wasm32-unknown-unknown
-      - name: Update toolchain
-        run: rustup update
-      - name: Check
-        run: cargo check --target wasm32-unknown-unknown --features use-esplora-reqwest --no-default-features
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+            override: true
+            profile: minimal
+            target: "wasm32-unknown-unknown"
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Check bdk
+        working-directory: ./crates/bdk
+        run: cargo check --target wasm32-unknown-unknown --features dev-getrandom-wasm
+      - name: Check esplora
+        working-directory: ./crates/esplora
+        run: cargo check --target wasm32-unknown-unknown --features async --no-default-features
 
   fmt:
     name: Rust fmt
@@ -162,13 +68,30 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
-      - name: Set default toolchain
-        run: rustup default nightly
-      - name: Set profile
-        run: rustup set profile minimal
-      - name: Add rustfmt
-        run: rustup component add rustfmt
-      - name: Update toolchain
-        run: rustup update
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: stable
+            override: true
+            profile: minimal
+            components: rustfmt
       - name: Check fmt
         run: cargo fmt --all -- --config format_code_in_doc_comments=true --check
+
+  clippy_check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/toolchain@v1
+        with:
+            # we pin clippy instead of using "stable" so that our CI doesn't break
+            # at each new cargo release
+            toolchain: "1.67.0"
+            components: clippy
+            override: true
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --all-features --all-targets -- -D warnings

.github/workflows/nightly_docs.yml

@@ -9,22 +9,18 @@ jobs:
     steps:
       - name: Checkout sources
         uses: actions/checkout@v2
-      - name: Setup cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: nightly-docs-${{ hashFiles('**/Cargo.toml','**/Cargo.lock') }}
       - name: Set default toolchain
-        run: rustup default nightly-2022-01-25
+        run: rustup default nightly-2022-12-14
       - name: Set profile
         run: rustup set profile minimal
       - name: Update toolchain
         run: rustup update
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
       - name: Build docs
-        run: cargo rustdoc --verbose --features=compiler,electrum,esplora,ureq,compact_filters,key-value-db,all-keys,sqlite -- --cfg docsrs -Dwarnings
+        run: cargo doc --no-deps
+        env:
+          RUSTDOCFLAGS: '--cfg docsrs -Dwarnings'
       - name: Upload artifact
         uses: actions/upload-artifact@v2
         with:

.gitignore

@@ -1,5 +1,6 @@
 /target
 Cargo.lock
+/.vscode
 
 *.swp
 .idea

CHANGELOG.md

@@ -1,31 +1,186 @@
 # Changelog
-All notable changes to this project will be documented in this file.
+
+All notable changes to this project can be found here and in each release's git tag and can be viewed with `git tag -ln100 "v*"`. See also [DEVELOPMENT_CYCLE.md](DEVELOPMENT_CYCLE.md) for more details.
+
+Contributors do not need to change this file but do need to add changelog details in their PR descriptions. The person making the next release will collect changelog details from included PRs and edit this file prior to each release.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+## [v0.27.1]
 
-## [v0.20.0] - [v0.19.0]
+### Summary
+
+Fixes [RUSTSEC-2022-0090], this issue is only applicable if you are using the optional sqlite database feature.
+
+[RUSTSEC-2022-0090]: https://rustsec.org/advisories/RUSTSEC-2022-0090
+
+### Changed
+
+- Update optional sqlite dependency from 0.27.0 to 0.28.0. #867
+
+## [v0.27.0]
+
+### Summary
+
+A maintenance release with a bump in project MSRV to 1.57.0, updated dependence and a few developer oriented improvements. Improvements include  better error formatting, don't default to async/await for wasm32 and adding derived PartialEq and Eq on SyncTime.
+
+### Changed
+
+- Improve display error formatting #814
+- Don't default to use async/await on wasm32 #831
+- Project MSRV changed from 1.56.1 to 1.57.0 #842
+- Update rust-miniscript dependency to latest bug fix release 9.0 #844
+
+### Added
+
+- Derive PartialEq, Eq on SyncTime #837
+
+## [v0.26.0]
+
+### Summary
+
+This release improves Fulcrum electrum server compatibility and fixes public descriptor template key origin paths. We also snuck in small enhancements to configure the electrum client to validate the domain using SSL and sort TransactionDetails by block height and timestamp.
+  
+### Fixed
+  
+- Make electrum blockchain client `save_tx` function order independent to work with Fulcrum servers. #808
+- Fix wrong testnet key origin path in public descriptor templates. #818
+- Make README.md code examples compile without errors. #820
+
+### Changed
+
+- Bump `hwi` dependency to `0.4.0`. #825
+- Bump `esplora-client` dependency to `0.3` #830
+
+### Added
+  
+- For electrum blockchain client, allow user to configure whether to validate the domain using SSL. #805
+- Implement ordering for `TransactionDetails`. #812
+
+## [v0.25.0]
+
+### Summary
+
+This release fixes slow sync time and big script_pubkeys table with SQLite, the wallet rescan height for the FullyNodedExport and setting the network for keys in the KeyMap when using descriptor templates. Also added are new blockchain and mnemonic examples.
+  
+### Fixed
+  
+- Slow sync time and big script_pubkeys table with SQLite.
+- Wallet rescan height for the FullyNodedExport.
+- Setting the network for keys in the KeyMap when using descriptor templates.
+  
+### Added
+  
+- Examples for connecting to Esplora, Electrum Server, Neutrino and Bitcoin Core.
+- Example for using a mnemonic in a descriptors.
+
+## [v0.24.0]
+
+### Summary
+
+This release contains important dependency updates for `rust-bitcoin` to `0.29` and `rust-miniscript` to `8.0`, plus related crates that also depend on the latest version of `rust-bitcoin`. The release also includes a breaking change to the BDK signer which now produces low-R signatures by default, saving one byte. A bug was found in the `get_checksum` and `get_checksum_bytes` functions, which are now deprecated in favor of fixed versions called `calc_checksum` and `calc_checksum_bytes`. And finally a new `hardware-signer` features was added that re-exports the `hwi` crate, along with a new `hardware_signers.rs` example file.
+   
+### Changed
+
+- Updated dependency versions for `rust-bitcoin` to `0.29` and `rust-miniscript` to `8.0`, plus all related crates. @afilini #770
+- BDK Signer now produces low-R signatures by default, saving one byte. If you want to preserve the original behavior, set allow_grinding in the SignOptions to false. @vladimirfomene #779
+- Deprecated `get_checksum`and `get_checksum_bytes` due to bug where they calculates the checksum of a descriptor that already has a checksum.  Use `calc_checksum` and `calc_checksum_bytes` instead. @evanlinjin #765
+- Remove deprecated "address validators". @afilini #770
+  
+### Added
+
+- New `calc_checksum` and `calc_checksum_bytes`, replace deprecated `get_checksum` and `get_checksum_bytes`. @evanlinjin #765
+- Re-export the hwi crate when the feature hardware-signer is on.  @danielabrozzoni #758
+- New examples/hardware_signer.rs. @danielabrozzoni #758
+- Make psbt module public to expose PsbtUtils trait to downstream projects. @notmandatory #782
+
+## [v0.23.0]
+
+### Summary
+
+This release brings new utilities functions on PSBTs like `fee_amount()` and `fee_rate()` and migrates BDK to use our new external esplora client library.
+As always many bug fixes, docs and tests improvement are also included.
+
+### Changed
+
+- Update electrum-client to 0.11.0 by @afilini in https://github.com/bitcoindevkit/bdk/pull/737
+- Change configs for source-base code coverage by @wszdexdrf in https://github.com/bitcoindevkit/bdk/pull/708
+- Improve docs regarding PSBT finalization by @tnull in https://github.com/bitcoindevkit/bdk/pull/753
+- Update compiler example to a Policy example by @rajarshimaitra in https://github.com/bitcoindevkit/bdk/pull/730
+- Fix the release process by @afilini in https://github.com/bitcoindevkit/bdk/pull/754
+- Remove redundant duplicated keys check by @afilini in https://github.com/bitcoindevkit/bdk/pull/761
+- Remove genesis_block lazy initialization by @shobitb in https://github.com/bitcoindevkit/bdk/pull/756
+- Fix `Wallet::descriptor_checksum` to actually return the checksum by @evanlinjin in https://github.com/bitcoindevkit/bdk/pull/763
+- Use the esplora client crate by @afilini in https://github.com/bitcoindevkit/bdk/pull/764
+
+### Added
+
+- Run code coverage on every PR by @danielabrozzoni in https://github.com/bitcoindevkit/bdk/pull/747
+- Add psbt_signer.rs example by @notmandatory in https://github.com/bitcoindevkit/bdk/pull/744
+- Add fee_amount() and fee_rate() functions to PsbtUtils trait by @notmandatory in https://github.com/bitcoindevkit/bdk/pull/728
+- Add tests to improve coverage by @vladimirfomene in https://github.com/bitcoindevkit/bdk/pull/745
+- Enable signing taproot transactions with only `non_witness_utxos` by @afilini in https://github.com/bitcoindevkit/bdk/pull/757
+- Add datatype for is_spent sqlite column by @vladimirfomene in https://github.com/bitcoindevkit/bdk/pull/713
+- Add vscode filter to gitignore by @evanlinjin in https://github.com/bitcoindevkit/bdk/pull/762
+
+## [v0.22.0]
+
+### Summary
+
+This release brings support for hardware signers on desktop through the HWI library.
+It also includes fixes and improvements which are part of our ongoing effort of integrating
+BDK and LDK together.
+
+### Changed
+
+- FeeRate function name as_sat_vb to as_sat_per_vb. #678
+- Verify signatures after signing. #718
+- Dependency electrum-client to 0.11.0. #737
+
+### Added
+  
+- Functions to create FeeRate from sats/kvbytes and sats/kwu. #678
+- Custom hardware wallet signer HwiSigner in wallet::hardwaresigner module. #682
+- Function allow_dust on TxBuilder. #689
+- Implementation of Deref<Target=UrlClient> for EsploraBlockchain. #722
+- Implementation of Deref<Target=Client> for ElectrumBlockchain #705
+- Implementation of Deref<Target=Client> for RpcBlockchain. #731
+
+## [v0.21.0]
+
+- Add `descriptor::checksum::get_checksum_bytes` method.
+- Add `Excess` enum to handle remaining amount after coin selection.
+- Move change creation from `Wallet::create_tx` to `CoinSelectionAlgorithm::coin_select`.
+- Change the interface of `SqliteDatabase::new` to accept any type that implement AsRef<Path>
+- Add the ability to specify which leaves to sign in a taproot transaction through `TapLeavesOptions` in `SignOptions`
+- Add the ability to specify whether a taproot transaction should be signed using the internal key or not, using `sign_with_tap_internal_key` in `SignOptions`
+- Consolidate params `fee_amount` and `amount_needed` in `target_amount` in `CoinSelectionAlgorithm::coin_select` signature.
+- Change the meaning of the `fee_amount` field inside `CoinSelectionResult`: from now on the `fee_amount` will represent only the fees asociated with the utxos in the `selected` field of `CoinSelectionResult`.
+- New `RpcBlockchain` implementation with various fixes.
+- Return balance in separate categories, namely `confirmed`, `trusted_pending`, `untrusted_pending` & `immature`.
+
+## [v0.20.0]
 
 - New MSRV set to `1.56.1`
 - Fee sniping discouraging through nLockTime - if the user specifies a `current_height`, we use that as a nlocktime, otherwise we use the last sync height (or 0 if we never synced)
 - Fix hang when `ElectrumBlockchainConfig::stop_gap` is zero.
 - Set coin type in BIP44, BIP49, and BIP84 templates
-- Get block hash given a block height - A `get_block_hash` method is now defined on the `GetBlockHash` trait and implemented on every blockchain backend. This method expects a block height and returns the corresponding block hash. 
+- Get block hash given a block height - A `get_block_hash` method is now defined on the `GetBlockHash` trait and implemented on every blockchain backend. This method expects a block height and returns the corresponding block hash.
 - Add `remove_partial_sigs` and `try_finalize` to `SignOptions`
 - Deprecate `AddressValidator`
 - Fix Electrum wallet sync potentially causing address index decrement - compare proposed index and current index before applying batch operations during sync.
 
-## [v0.19.0] - [v0.18.0]
+## [v0.19.0]
 
 - added `OldestFirstCoinSelection` impl to `CoinSelectionAlgorithm`
 - New MSRV set to `1.56`
 - Unpinned tokio to `1`
 - Add traits to reuse `Blockchain`s across multiple wallets (`BlockchainFactory` and `StatelessBlockchain`).
 - Upgrade to rust-bitcoin `0.28`
-- If using the `sqlite-db` feature all cached wallet data is deleted due to a possible UTXO inconsistency, a wallet.sync will recreate it  
+- If using the `sqlite-db` feature all cached wallet data is deleted due to a possible UTXO inconsistency, a wallet.sync will recreate it
 - Update `PkOrF` in the policy module to become an enum
 - Add experimental support for Taproot, including:
   - Support for `tr()` descriptors with complex tapscript trees
@@ -34,17 +189,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Support for `tr()` descriptors in the `descriptor!()` macro
 - Add support for Bitcoin Core 23.0 when using the `rpc` blockchain
 
-## [v0.18.0] - [v0.17.0]
+## [v0.18.0]
 
-- Add `sqlite-bundled` feature for deployments that need a bundled version of sqlite, ie. for mobile platforms.
+- Add `sqlite-bundled` feature for deployments that need a bundled version of sqlite, i.e. for mobile platforms.
 - Added `Wallet::get_signers()`, `Wallet::descriptor_checksum()` and `Wallet::get_address_validators()`, exposed the `AsDerived` trait.
 - Deprecate `database::Database::flush()`, the function is only needed for the sled database on mobile, instead for mobile use the sqlite database.
 - Add `keychain: KeychainKind` to `wallet::AddressInfo`.
 - Improve key generation traits
 - Rename `WalletExport` to `FullyNodedExport`, deprecate the former.
-- Bump `miniscript` dependency version to `^6.1`. 
+- Bump `miniscript` dependency version to `^6.1`.
 
-## [v0.17.0] - [v0.16.1]
+## [v0.17.0]
 
 - Removed default verification from `wallet::sync`. sync-time verification is added in `script_sync` and is activated by `verify` feature flag.
 - `verify` flag removed from `TransactionDetails`.
@@ -65,45 +220,45 @@ To decouple the `Wallet` from the `Blockchain` we've made major changes:
 - Removed `max_addresses` sync parameter which determined how many addresses to cache before syncing since this can just be done with `ensure_addresses_cached`.
 - remove `flush` method from the `Database` trait.
 
-## [v0.16.1] - [v0.16.0]
+## [v0.16.1]
 
 - Pin tokio dependency version to ~1.14 to prevent errors due to their new MSRV 1.49.0
 
-## [v0.16.0] - [v0.15.0]
+## [v0.16.0]
 
 - Disable `reqwest` default features.
 - Added `reqwest-default-tls` feature: Use this to restore the TLS defaults of reqwest if you don't want to add a dependency to it in your own manifest.
 - Use dust_value from rust-bitcoin
 - Fixed generating WIF in the correct network format.
 
-## [v0.15.0] - [v0.14.0]
+## [v0.15.0]
 
 - Overhauled sync logic for electrum and esplora.
 - Unify ureq and reqwest esplora backends to have the same configuration parameters. This means reqwest now has a timeout parameter and ureq has a concurrency parameter.
 - Fixed esplora fee estimation.
 
-## [v0.14.0] - [v0.13.0]
+## [v0.14.0]
 
 - BIP39 implementation dependency, in `keys::bip39` changed from tiny-bip39 to rust-bip39.
 - Add new method on the `TxBuilder` to embed data in the transaction via `OP_RETURN`. To allow that a fix to check the dust only on spendable output has been introduced.
 - Update the `Database` trait to store the last sync timestamp and block height
 - Rename `ConfirmationTime` to `BlockTime`
 
-## [v0.13.0] - [v0.12.0]
+## [v0.13.0]
 
 - Exposed `get_tx()` method from `Database` to `Wallet`.
 
-## [v0.12.0] - [v0.11.0]
+## [v0.12.0]
 
 - Activate `miniscript/use-serde` feature to allow consumers of the library to access it via the re-exported `miniscript` crate.
 - Add support for proxies in `EsploraBlockchain`
 - Added `SqliteDatabase` that implements `Database` backed by a sqlite database using `rusqlite` crate.
 
-## [v0.11.0] - [v0.10.0]
+## [v0.11.0]
 
 - Added `flush` method to the `Database` trait to explicitly flush to disk latest changes on the db.
 
-## [v0.10.0] - [v0.9.0]
+## [v0.10.0]
 
 - Added `RpcBlockchain` in the `AnyBlockchain` struct to allow using Rpc backend where `AnyBlockchain` is used (eg `bdk-cli`)
 - Removed hard dependency on `tokio`.
@@ -117,21 +272,21 @@ To decouple the `Wallet` from the `Blockchain` we've made major changes:
 - Removed `stop_gap` from `Blockchain` trait and added it to only `ElectrumBlockchain` and `EsploraBlockchain` structs.
 - Added a `ureq` backend for use when not using feature `async-interface` or target WASM. `ureq` is a blocking HTTP client.
 
-## [v0.9.0] - [v0.8.0]
+## [v0.9.0]
 
 ### Wallet
 
 - Added Bitcoin core RPC added as blockchain backend
 - Added a `verify` feature that can be enable to verify the unconfirmed txs we download against the consensus rules
 
-## [v0.8.0] - [v0.7.0]
+## [v0.8.0]
 
 ### Wallet
 - Added an option that must be explicitly enabled to allow signing using non-`SIGHASH_ALL` sighashes (#350)
 #### Changed
 `get_address` now returns an `AddressInfo` struct that includes the index and derefs to `Address`.
 
-## [v0.7.0] - [v0.6.0]
+## [v0.7.0]
 
 ### Policy
 #### Changed
@@ -146,7 +301,7 @@ Timelocks are considered (optionally) in building the `satisfaction` field
 - Require and validate `non_witness_utxo` for SegWit signatures by default, can be adjusted with `SignOptions`
 - Replace the opt-in builder option `force_non_witness_utxo` with the opposite `only_witness_utxo`. From now on we will provide the `non_witness_utxo`, unless explicitly asked not to.
 
-## [v0.6.0] - [v0.5.1]
+## [v0.6.0]
 
 ### Misc
 #### Changed
@@ -170,13 +325,13 @@ Timelocks are considered (optionally) in building the `satisfaction` field
 #### Fixed
 - Fixed `coin_select` calculation for UTXOs where `value < fee` that caused over-/underflow errors.
 
-## [v0.5.1] - [v0.5.0]
+## [v0.5.1]
 
 ### Misc
 #### Changed
 - Pin `hyper` to `=0.14.4` to make it compile on Rust 1.45
 
-## [v0.5.0] - [v0.4.0]
+## [v0.5.0]
 
 ### Misc
 #### Changed
@@ -186,7 +341,7 @@ Timelocks are considered (optionally) in building the `satisfaction` field
 #### Changed
 - `FeeRate` constructors `from_sat_per_vb` and `default_min_relay_fee` are now `const` functions
 
-## [v0.4.0] - [v0.3.0]
+## [v0.4.0]
 
 ### Keys
 #### Changed
@@ -215,7 +370,7 @@ Timelocks are considered (optionally) in building the `satisfaction` field
 - Removed unneeded `Result<(), PolicyError>` return type for `Satisfaction::finalize()`
 - Removed the `TooManyItemsSelected` policy error (see commit message for more details)
 
-## [v0.3.0] - [v0.2.0]
+## [v0.3.0]
 
 ### Descriptor
 #### Changed
@@ -252,7 +407,7 @@ final transaction is created by calling `finish` on the builder.
 #### Changed
 - Remove `cli.rs` module, `cli-utils` feature and `repl.rs` example; moved to new [`bdk-cli`](https://github.com/bitcoindevkit/bdk-cli) repository
 
-## [v0.2.0] - [0.1.0-beta.1]
+## [v0.2.0]
 
 ### Project
 #### Added
@@ -479,4 +634,12 @@ final transaction is created by calling `finish` on the builder.
 [v0.18.0]: https://github.com/bitcoindevkit/bdk/compare/v0.17.0...v0.18.0
 [v0.19.0]: https://github.com/bitcoindevkit/bdk/compare/v0.18.0...v0.19.0
 [v0.20.0]: https://github.com/bitcoindevkit/bdk/compare/v0.19.0...v0.20.0
-[unreleased]: https://github.com/bitcoindevkit/bdk/compare/v0.20.0...HEAD
+[v0.21.0]: https://github.com/bitcoindevkit/bdk/compare/v0.20.0...v0.21.0
+[v0.22.0]: https://github.com/bitcoindevkit/bdk/compare/v0.21.0...v0.22.0
+[v0.23.0]: https://github.com/bitcoindevkit/bdk/compare/v0.22.0...v0.23.0
+[v0.24.0]: https://github.com/bitcoindevkit/bdk/compare/v0.23.0...v0.24.0
+[v0.25.0]: https://github.com/bitcoindevkit/bdk/compare/v0.24.0...v0.25.0
+[v0.26.0]: https://github.com/bitcoindevkit/bdk/compare/v0.25.0...v0.26.0
+[v0.27.0]: https://github.com/bitcoindevkit/bdk/compare/v0.26.0...v0.27.0
+[v0.27.1]: https://github.com/bitcoindevkit/bdk/compare/v0.27.0...v0.27.1
+[Unreleased]: https://github.com/bitcoindevkit/bdk/compare/v0.27.1...HEAD

Cargo.toml

@@ -1,124 +1,18 @@
-[package]
-name = "bdk"
-version = "0.20.0"
-edition = "2018"
-authors = ["Alekos Filini <alekos.filini@gmail.com>", "Riccardo Casatta <riccardo@casatta.it>"]
-homepage = "https://bitcoindevkit.org"
-repository = "https://github.com/bitcoindevkit/bdk"
-documentation = "https://docs.rs/bdk"
-description = "A modern, lightweight, descriptor-based wallet library"
-keywords = ["bitcoin", "wallet", "descriptor", "psbt"]
-readme = "README.md"
-license = "MIT OR Apache-2.0"
-
-[dependencies]
-bdk-macros = "^0.6"
-log = "^0.4"
-miniscript = { version = "7.0", features = ["use-serde"] }
-bitcoin = { version = "0.28.1", features = ["use-serde", "base64", "rand"] }
-serde = { version = "^1.0", features = ["derive"] }
-serde_json = { version = "^1.0" }
-rand = "^0.7"
-
-# Optional dependencies
-sled = { version = "0.34", optional = true }
-electrum-client = { version = "0.10", optional = true }
-rusqlite = { version = "0.27.0", optional = true }
-ahash = { version = "0.7.6", optional = true }
-reqwest = { version = "0.11", optional = true, default-features = false, features = ["json"] }
-ureq = { version = "~2.2.0", features = ["json"], optional = true }
-futures = { version = "0.3", optional = true }
-async-trait = { version = "0.1", optional = true }
-rocksdb = { version = "0.14", default-features = false, features = ["snappy"], optional = true }
-cc = { version = ">=1.0.64", optional = true }
-socks = { version = "0.3", optional = true }
-lazy_static = { version = "1.4", optional = true }
-
-bip39 = { version = "1.0.1", optional = true }
-bitcoinconsensus = { version = "0.19.0-3", optional = true }
-
-# Needed by bdk_blockchain_tests macro and the `rpc` feature
-bitcoincore-rpc = { version = "0.15", optional = true }
-
-# Platform-specific dependencies
-[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-tokio = { version = "1", features = ["rt"] }
-
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-async-trait = "0.1"
-js-sys = "0.3"
-rand = { version = "^0.7", features = ["wasm-bindgen"] }
-
-[features]
-minimal = []
-compiler = ["miniscript/compiler"]
-verify = ["bitcoinconsensus"]
-default = ["key-value-db", "electrum"]
-sqlite = ["rusqlite", "ahash"]
-sqlite-bundled = ["sqlite", "rusqlite/bundled"]
-compact_filters = ["rocksdb", "socks", "lazy_static", "cc"]
-key-value-db = ["sled"]
-all-keys = ["keys-bip39"]
-keys-bip39 = ["bip39"]
-rpc = ["bitcoincore-rpc"]
-
-# We currently provide mulitple implementations of `Blockchain`, all are
-# blocking except for the `EsploraBlockchain` which can be either async or
-# blocking, depending on the HTTP client in use.
-#
-# - Users wanting asynchronous HTTP calls should enable `async-interface` to get
-#   access to the asynchronous method implementations. Then, if Esplora is wanted,
-#   enable `esplora` AND `reqwest` (`--features=use-esplora-reqwest`).
-# - Users wanting blocking HTTP calls can use any of the other blockchain
-#   implementations (`compact_filters`, `electrum`, or `esplora`). Users wanting to
-#   use Esplora should enable `esplora` AND `ureq`  (`--features=use-esplora-ureq`).
-#
-# WARNING: Please take care with the features below, various combinations will
-# fail to build. We cannot currently build `bdk` with `--all-features`.
-async-interface = ["async-trait"]
-electrum = ["electrum-client"]
-# MUST ALSO USE `--no-default-features`.
-use-esplora-reqwest = ["esplora", "reqwest", "reqwest/socks", "futures"]
-use-esplora-ureq = ["esplora", "ureq", "ureq/socks"]
-# Typical configurations will not need to use `esplora` feature directly.
-esplora = []
-
-# Use below feature with `use-esplora-reqwest` to enable reqwest default TLS support
-reqwest-default-tls = ["reqwest/default-tls"]
-
-# Debug/Test features
-test-blockchains = ["bitcoincore-rpc", "electrum-client"]
-test-electrum = ["electrum", "electrsd/electrs_0_8_10", "electrsd/bitcoind_22_0", "test-blockchains"]
-test-rpc = ["rpc", "electrsd/electrs_0_8_10", "electrsd/bitcoind_22_0", "test-blockchains"]
-test-rpc-legacy = ["rpc", "electrsd/electrs_0_8_10", "electrsd/bitcoind_0_20_0", "test-blockchains"]
-test-esplora = ["electrsd/legacy", "electrsd/esplora_a33e97e1", "electrsd/bitcoind_22_0", "test-blockchains"]
-test-md-docs = ["electrum"]
-
-[dev-dependencies]
-lazy_static = "1.4"
-env_logger = "0.7"
-clap = "2.33"
-electrsd = "0.19.1"
-
-[[example]]
-name = "address_validator"
-[[example]]
-name = "compact_filters_balance"
-required-features = ["compact_filters"]
-
-[[example]]
-name = "miniscriptc"
-path = "examples/compiler.rs"
-required-features = ["compiler"]
-
-[[example]]
-name = "rpcwallet"
-path = "examples/rpcwallet.rs"
-required-features = ["keys-bip39", "key-value-db", "rpc"]
-
 [workspace]
-members = ["macros"]
-[package.metadata.docs.rs]
-features = ["compiler", "electrum", "esplora", "ureq", "compact_filters", "rpc", "key-value-db", "sqlite", "all-keys", "verify"]
-# defines the configuration attribute `docsrs`
-rustdoc-args = ["--cfg", "docsrs"]
+members = [
+    "crates/bdk",
+    "crates/chain",
+    "crates/file_store",
+    "crates/electrum",
+    "example-crates/keychain_tracker_electrum",
+    "example-crates/keychain_tracker_esplora",
+    "example-crates/keychain_tracker_example_cli",
+    "example-crates/wallet_electrum",
+    "example-crates/wallet_esplora",
+    "example-crates/wallet_esplora_async",
+    "nursery/tmp_plan",
+    "nursery/coin_select"
+]
+
+[workspace.package]
+authors = ["Bitcoin Dev Kit Developers"]

DEVELOPMENT_CYCLE.md

@@ -1,46 +1,16 @@
 # Development Cycle
 
-This project follows a regular releasing schedule similar to the one [used by the Rust language](https://doc.rust-lang.org/book/appendix-07-nightly-rust.html). In short, this means that a new release is made at a regular cadence, with all the feature/bugfixes that made it to `master` in time. This ensures that we don't keep delaying releases waiting for "just one more little thing".
+This project follows a regular releasing schedule similar to the one [used by the Rust language]. In short, this means that a new release is made at a regular cadence, with all the feature/bugfixes that made it to `master` in time. This ensures that we don't keep delaying releases waiting for "just one more little thing".
+
+This project uses [Semantic Versioning], but is currently at MAJOR version zero (0.y.z) meaning it is still in initial development. Anything MAY change at any time. The public API SHOULD NOT be considered stable. Until we reach version `1.0.0` we will do our best to document any breaking API changes in the changelog info attached to each release tag.
 
 We decided to maintain a faster release cycle while the library is still in "beta", i.e. before release `1.0.0`: since we are constantly adding new features and, even more importantly, fixing issues, we want developers to have access to those updates as fast as possible. For this reason we will make a release **every 4 weeks**.
 
-Once the project will have reached a more mature state (>= `1.0.0`), we will very likely switch to longer release cycles of **6 weeks**.
+Once the project reaches a more mature state (>= `1.0.0`), we will very likely switch to longer release cycles of **6 weeks**.
 
 The "feature freeze" will happen **one week before the release date**. This means a new branch will be created originating from the `master` tip at that time, and in that branch we will stop adding new features and only focus on ensuring the ones we've added are working properly.
 
-```
-master:           - - - - * - - - * - - - - - - * - - - * ...
-                          |      /              |       |
-release/0.x.0:            * - - #               |       |
-                                                |      /
-release/0.y.0:                                  * - - #
-```
+To create a new release a release manager will create a new issue using the `Release` template and follow the template instructions.
 
-As soon as the release is tagged and published, the `release` branch will be merged back into `master` to update the version in the `Cargo.toml` to apply the new `Cargo.toml` version and all the other fixes made during the feature freeze window.
-
-## Making the Release
-
-What follows are notes and procedures that maintainers can refer to when making releases. All the commits and tags must be signed and, ideally, also [timestamped](https://github.com/opentimestamps/opentimestamps-client/blob/master/doc/git-integration.md).
-
-Pre-`v1.0.0` our "major" releases only affect the "minor" semver value. Accordingly, our "minor" releases will only affect the "patch" value.
-
-1. Create a new branch called `release/x.y.z` from `master`. Double check that your local `master` is up-to-date with the upstream repo before doing so.
-2. Make a commit on the release branch to bump the version to `x.y.z-rc.1`. The message should be "Bump version to x.y.z-rc.1".
-3. Push the new branch to `bitcoindevkit/bdk` on GitHub.
-4. During the one week of feature freeze run additional tests on the release branch.
-5. If a bug is found:
-    - If it's a minor issue you can just fix it in the release branch, since it will be merged back to `master` eventually
-    - For bigger issues you can fix them on `master` and then *cherry-pick* the commit to the release branch
-6. Update the changelog with the new release version.
-7. Update `src/lib.rs` with the new version (line ~43)
-8. On release day, make a commit on the release branch to bump the version to `x.y.z`. The message should be "Bump version to x.y.z".
-9. Add a tag to this commit. The tag name should be `vx.y.z` (for example `v0.5.0`), and the message "Release x.y.z". Make sure the tag is signed, for extra safety use the explicit `--sign` flag.
-10. Push the new commits to the upstream release branch, wait for the CI to finish one last time.
-11. Publish **all** the updated crates to crates.io.
-12. Make a new commit to bump the version value to `x.y.(z+1)-dev`. The message should be "Bump version to x.y.(z+1)-dev".
-13. Merge the release branch back into `master`.
-14. If the `master` branch contains any unreleased changes to the `bdk-macros` crate, change the `bdk` Cargo.toml `[dependencies]` to point to the local path (ie. `bdk-macros = { path = "./macros"}`)
-15. Create the release on GitHub: go to "tags", click on the dots on the right and select "Create Release". Then set the title to `vx.y.z` and write down some brief release notes.
-16. Make sure the new release shows up on crates.io and that the docs are built correctly on docs.rs.
-17. Announce the release on Twitter, Discord and Telegram.
-18. Celebrate :tada:
+[used by the Rust language]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html
+[Semantic Versioning]: https://semver.org/

README.md

@@ -1,3 +1,5 @@
+# The Bitcoin Dev Kit
+
 <div align="center">
   <h1>BDK</h1>
 
@@ -11,9 +13,9 @@
     <a href="https://crates.io/crates/bdk"><img alt="Crate Info" src="https://img.shields.io/crates/v/bdk.svg"/></a>
     <a href="https://github.com/bitcoindevkit/bdk/blob/master/LICENSE"><img alt="MIT or Apache-2.0 Licensed" src="https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg"/></a>
     <a href="https://github.com/bitcoindevkit/bdk/actions?query=workflow%3ACI"><img alt="CI Status" src="https://github.com/bitcoindevkit/bdk/workflows/CI/badge.svg"></a>
-    <a href="https://codecov.io/gh/bitcoindevkit/bdk"><img src="https://codecov.io/gh/bitcoindevkit/bdk/branch/master/graph/badge.svg"/></a>
+    <a href="https://coveralls.io/github/bitcoindevkit/bdk?branch=master"><img src="https://coveralls.io/repos/github/bitcoindevkit/bdk/badge.svg?branch=master"/></a>
     <a href="https://docs.rs/bdk"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-bdk-green"/></a>
-    <a href="https://blog.rust-lang.org/2021/11/01/Rust-1.56.1.html"><img alt="Rustc Version 1.56.1+" src="https://img.shields.io/badge/rustc-1.56.1%2B-lightgrey.svg"/></a>
+    <a href="https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html"><img alt="Rustc Version 1.57.0+" src="https://img.shields.io/badge/rustc-1.57.0%2B-lightgrey.svg"/></a>
     <a href="https://discord.gg/d7NkDKm"><img alt="Chat on Discord" src="https://img.shields.io/discord/753336465005608961?logo=discord"></a>
   </p>
 
@@ -26,162 +28,27 @@
 
 ## About
 
-The `bdk` library aims to be the core building block for Bitcoin wallets of any kind.
+The `bdk` libraries aims to provide well engineered and reviewed components for Bitcoin based applications.
+It is built upon the excellent [`rust-bitcoin`] and [`rust-miniscript`] crates.
 
-* It uses [Miniscript](https://github.com/rust-bitcoin/rust-miniscript) to support descriptors with generalized conditions. This exact same library can be used to build
-  single-sig wallets, multisigs, timelocked contracts and more.
-* It supports multiple blockchain backends and databases, allowing developers to choose exactly what's right for their projects.
-* It's built to be cross-platform: the core logic works on desktop, mobile, and even WebAssembly.
-* It's very easy to extend: developers can implement customized logic for blockchain backends, databases, signers, coin selection, and more, without having to fork and modify this library.
+> ⚠ The Bitcoin Dev Kit developers are in the process of releasing a `v1.0` which is a fundamental re-write of how the library works.
+> See for some background on this project: https://bitcoindevkit.org/blog/road-to-bdk-1/ (ignore the timeline 😁)
+> For a release timeline see the [`bdk_core_staging`] repo where a lot of the component work is being done. The plan is that everything in the `bdk_core_staging` repo will be moved into the `crates` directory here.
 
-## Examples
+## Architecture
 
-### Sync the balance of a descriptor
+The project is split up into several crates in the `/crates` directory:
 
-```rust,no_run
-use bdk::Wallet;
-use bdk::database::MemoryDatabase;
-use bdk::blockchain::ElectrumBlockchain;
-use bdk::SyncOptions;
-use bdk::electrum_client::Client;
-use bdk::bitcoin::Network;
+- [`bdk`](./crates/bdk): Contains the central high level `Wallet` type that is built from the low-level mechanisms provided by the other components
+- [`chain`](./crates/chain): Tools for storing and indexing chain data
+- [`file_store`](./crates/file_store): A (experimental) persistence backend for storing chain data in a single file.
+- [`esplora`](./crates/esplora): Extends the [`esplora-client`] crate with methods to fetch chain data from an esplora HTTP server in the form that [`bdk_chain`] and `Wallet` can consume.
+- [`electrum`](./crates/electrum): Extends the [`electrum-client`] crate with methods to fetch chain data from an electrum server in the form that [`bdk_chain`] and `Wallet` can consume.
 
-fn main() -> Result<(), bdk::Error> {
-    let blockchain = ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?);
-    let wallet = Wallet::new(
-        "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)",
-        Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"),
-        Network::Testnet,
-        MemoryDatabase::default(),
-    )?;
+Fully working examples of how to use these components are in `/example-crates`
 
-    wallet.sync(&blockchain, SyncOptions::default())?;
-
-    println!("Descriptor balance: {} SAT", wallet.get_balance()?);
-
-    Ok(())
-}
-```
-
-### Generate a few addresses
-
-```rust
-use bdk::{Wallet, database::MemoryDatabase};
-use bdk::wallet::AddressIndex::New;
-
-fn main() -> Result<(), bdk::Error> {
-    let wallet = Wallet::new(
-        "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)",
-        Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"),
-        bitcoin::Network::Testnet,
-        MemoryDatabase::default(),
-    )?;
-
-    println!("Address #0: {}", wallet.get_address(New)?);
-    println!("Address #1: {}", wallet.get_address(New)?);
-    println!("Address #2: {}", wallet.get_address(New)?);
-
-    Ok(())
-}
-```
-
-### Create a transaction
-
-```rust,no_run
-use bdk::{FeeRate, Wallet, SyncOptions};
-use bdk::database::MemoryDatabase;
-use bdk::blockchain::ElectrumBlockchain;
-
-use bdk::electrum_client::Client;
-use bdk::wallet::AddressIndex::New;
-
-use bitcoin::consensus::serialize;
-
-fn main() -> Result<(), bdk::Error> {
-    let blockchain = ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?);
-    let wallet = Wallet::new(
-        "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)",
-        Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"),
-        bitcoin::Network::Testnet,
-        MemoryDatabase::default(),
-    )?;
-
-    wallet.sync(&blockchain, SyncOptions::default())?;
-
-    let send_to = wallet.get_address(New)?;
-    let (psbt, details) = {
-        let mut builder = wallet.build_tx();
-        builder
-            .add_recipient(send_to.script_pubkey(), 50_000)
-            .enable_rbf()
-            .do_not_spend_change()
-            .fee_rate(FeeRate::from_sat_per_vb(5.0));
-        builder.finish()?
-    };
-
-    println!("Transaction details: {:#?}", details);
-    println!("Unsigned PSBT: {}", base64::encode(&serialize(&psbt)));
-
-    Ok(())
-}
-```
-
-### Sign a transaction
-
-```rust,no_run
-use bdk::{Wallet, SignOptions, database::MemoryDatabase};
-
-use bitcoin::consensus::deserialize;
-
-fn main() -> Result<(), bdk::Error> {
-    let wallet = Wallet::new(
-        "wpkh([c258d2e4/84h/1h/0h]tprv8griRPhA7342zfRyB6CqeKF8CJDXYu5pgnj1cjL1u2ngKcJha5jjTRimG82ABzJQ4MQe71CV54xfn25BbhCNfEGGJZnxvCDQCd6JkbvxW6h/0/*)",
-        Some("wpkh([c258d2e4/84h/1h/0h]tprv8griRPhA7342zfRyB6CqeKF8CJDXYu5pgnj1cjL1u2ngKcJha5jjTRimG82ABzJQ4MQe71CV54xfn25BbhCNfEGGJZnxvCDQCd6JkbvxW6h/1/*)"),
-        bitcoin::Network::Testnet,
-        MemoryDatabase::default(),
-    )?;
-
-    let psbt = "...";
-    let mut psbt = deserialize(&base64::decode(psbt).unwrap())?;
-
-    let finalized = wallet.sign(&mut psbt, SignOptions::default())?;
-
-    Ok(())
-}
-```
-
-## Testing
-
-### Unit testing
-
-```
-cargo test
-```
-
-### Integration testing
-
-Integration testing require testing features, for example:
-
-```
-cargo test --features test-electrum
-```
-
-The other options are `test-esplora`, `test-rpc` or `test-rpc-legacy` which runs against an older version of Bitcoin Core.
-Note that `electrs` and `bitcoind` binaries are automatically downloaded (on mac and linux), to specify you already have installed binaries you must use `--no-default-features` and provide `BITCOIND_EXE` and `ELECTRS_EXE` as environment variables.
-
-## License
-
-Licensed under either of
-
- * Apache License, Version 2.0
-   ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
- * MIT license
-   ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
-
-at your option.
-
-## Contribution
-
-Unless you explicitly state otherwise, any contribution intentionally submitted
-for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
-dual licensed as above, without any additional terms or conditions.
+[`bdk_core_staging`]: https://github.com/LLFourn/bdk_core_staging
+[`rust-miniscript`]: https://github.com/rust-bitcoin/rust-miniscript
+[`rust-bitcoin`]: https://github.com/rust-bitcoin/rust-bitcoin
+[`esplora-client`]: https://docs.rs/esplora-client/0.3.0/esplora_client/
+[`electrum-client`]: https://docs.rs/electrum-client/0.13.0/electrum_client/

ci/Dockerfile.ledger

@@ -0,0 +1,9 @@
+# Taken from bitcoindevkit/rust-hwi
+FROM ghcr.io/ledgerhq/speculos
+
+RUN apt-get update
+RUN apt-get install wget -y
+RUN wget "https://github.com/LedgerHQ/speculos/blob/master/apps/nanos%23btc%232.1%231c8db8da.elf?raw=true" -O /speculos/btc.elf
+ADD automation.json /speculos/automation.json
+
+ENTRYPOINT ["python", "./speculos.py", "--automation", "file:automation.json", "--model", "nanos", "--display", "headless", "--vnc-port", "41000", "btc.elf"]

ci/automation.json

@@ -0,0 +1,30 @@
+{
+    "version": 1,
+    "rules": [
+        {
+            "regexp": "Address \\(\\d/\\d\\)|Message hash \\(\\d/\\d\\)|Confirm|Fees|Review|Amount",
+            "actions": [
+                [ "button", 2, true ],
+                [ "button", 2, false ]
+            ]
+        },
+        {
+            "text": "Sign",
+            "conditions": [
+                [ "seen", false ]
+            ],
+            "actions": [
+                [ "button", 2, true ],
+                [ "button", 2, false ],
+                [ "setbool", "seen", true ]
+            ]
+        },
+        {
+            "regexp": "Approve|Sign|Accept",
+            "actions": [
+                [ "button", 3, true ],
+                [ "button", 3, false ]
+            ]
+        }
+    ]
+}

clippy.toml

@@ -0,0 +1 @@
+msrv="1.57.0"

codecov.yaml

@@ -1,13 +0,0 @@
-coverage:
-  status:
-    project:
-      default:
-        target: auto
-        threshold: 1%
-        base: auto
-        informational: false
-    patch:
-      default:
-        target: auto
-        threshold: 100%
-        base: auto

crates/bdk/Cargo.toml

@@ -0,0 +1,69 @@
+[package]
+name = "bdk"
+homepage = "https://bitcoindevkit.org"
+version = "1.0.0-alpha.0"
+repository = "https://github.com/bitcoindevkit/bdk"
+documentation = "https://docs.rs/bdk"
+description = "A modern, lightweight, descriptor-based wallet library"
+keywords = ["bitcoin", "wallet", "descriptor", "psbt"]
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+authors = ["Bitcoin Dev Kit Developers"]
+edition = "2021"
+rust-version = "1.57"
+
+[dependencies]
+log = "^0.4"
+rand = "^0.8"
+miniscript = { version = "9", features = ["serde"] }
+bitcoin = { version = "0.29", features = ["serde", "base64", "rand"] }
+serde = { version = "^1.0", features = ["derive"] }
+serde_json = { version = "^1.0" }
+bdk_chain = { path = "../chain", version = "0.4.0", features = ["miniscript", "serde"] }
+
+# Optional dependencies
+hwi = { version = "0.5", optional = true, features = [ "use-miniscript"] }
+bip39 = { version = "1.0.1", optional = true }
+
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+getrandom = "0.2"
+js-sys = "0.3"
+
+
+[features]
+default = ["std"]
+std = []
+compiler = ["miniscript/compiler"]
+all-keys = ["keys-bip39"]
+keys-bip39 = ["bip39"]
+hardware-signer = ["hwi"]
+test-hardware-signer = ["hardware-signer"]
+
+
+# This feature is used to run `cargo check` in our CI targeting wasm. It's not recommended
+# for libraries to explicitly include the "getrandom/js" feature, so we only do it when
+# necessary for running our CI. See: https://docs.rs/getrandom/0.2.8/getrandom/#webassembly-support
+dev-getrandom-wasm = ["getrandom/js"]
+
+[dev-dependencies]
+lazy_static = "1.4"
+env_logger = "0.7"
+# Move back to importing from rust-bitcoin once https://github.com/rust-bitcoin/rust-bitcoin/pull/1342 is released
+base64 = "^0.13"
+assert_matches = "1.5.0"
+
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+
+[[example]]
+name = "mnemonic_to_descriptors"
+path = "examples/mnemonic_to_descriptors.rs"
+required-features = ["all-keys"]
+
+[[example]]
+name = "miniscriptc"
+path = "examples/compiler.rs"
+required-features = ["compiler"]

crates/bdk/README.md

@@ -0,0 +1,227 @@
+<div align="center">
+  <h1>BDK</h1>
+
+  <img src="https://raw.githubusercontent.com/bitcoindevkit/bdk/master/static/bdk.png" width="220" />
+
+  <p>
+    <strong>A modern, lightweight, descriptor-based wallet library written in Rust!</strong>
+  </p>
+
+  <p>
+    <a href="https://crates.io/crates/bdk"><img alt="Crate Info" src="https://img.shields.io/crates/v/bdk.svg"/></a>
+    <a href="https://github.com/bitcoindevkit/bdk/blob/master/LICENSE"><img alt="MIT or Apache-2.0 Licensed" src="https://img.shields.io/badge/license-MIT%2FApache--2.0-blue.svg"/></a>
+    <a href="https://github.com/bitcoindevkit/bdk/actions?query=workflow%3ACI"><img alt="CI Status" src="https://github.com/bitcoindevkit/bdk/workflows/CI/badge.svg"></a>
+    <a href="https://coveralls.io/github/bitcoindevkit/bdk?branch=master"><img src="https://coveralls.io/repos/github/bitcoindevkit/bdk/badge.svg?branch=master"/></a>
+    <a href="https://docs.rs/bdk"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-bdk-green"/></a>
+    <a href="https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html"><img alt="Rustc Version 1.57.0+" src="https://img.shields.io/badge/rustc-1.57.0%2B-lightgrey.svg"/></a>
+    <a href="https://discord.gg/d7NkDKm"><img alt="Chat on Discord" src="https://img.shields.io/discord/753336465005608961?logo=discord"></a>
+  </p>
+
+  <h4>
+    <a href="https://bitcoindevkit.org">Project Homepage</a>
+    <span> | </span>
+    <a href="https://docs.rs/bdk">Documentation</a>
+  </h4>
+</div>
+
+## `bdk`
+
+The `bdk` crate provides the [`Wallet`](`crate::Wallet`) type which is a simple, high-level
+interface built from the low-level components of [`bdk_chain`]. `Wallet` is a good starting point
+for many simple applications as well as a good demonstration of how to use the other mechanisms to
+construct a wallet. It has two keychains (external and internal) which are defined by
+[miniscript descriptors][`rust-miniscript`] and uses them to generate addresses. When you give it
+chain data it also uses the descriptors to find transaction outputs owned by them. From there, you
+can create and sign transactions.
+
+For more information, see the [`Wallet`'s documentation](https://docs.rs/bdk/latest/bdk/wallet/struct.Wallet.html).
+
+### Blockchain data
+
+In order to get blockchain data for `Wallet` to consume, you have to put it into particular form.
+Right now this is [`KeychainScan`] which is defined in [`bdk_chain`].
+
+This can be created manually or from blockchain-scanning crates.
+
+**Blockchain Data Sources**
+
+* [`bdk_esplora`]: Grabs blockchain data from Esplora for updating BDK structures.
+* [`bdk_electrum`]: Grabs blockchain data from Electrum for updating BDK structures.
+
+**Examples**
+
+* [`example-crates/wallet_esplora`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora)
+* [`example-crates/wallet_electrum`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_electrum)
+
+### Persistence
+
+To persist the `Wallet` on disk, `Wallet` needs to be constructed with a
+[`Persist`](https://docs.rs/bdk_chain/latest/bdk_chain/keychain/struct.KeychainPersist.html) implementation.
+
+**Implementations**
+
+* [`bdk_file_store`]: a simple flat-file implementation of `Persist`.
+
+**Example**
+
+```rust
+use bdk::{bitcoin::Network, wallet::{AddressIndex, Wallet}};
+
+fn main() {
+    // a type that implements `Persist`
+    let db = ();
+
+    let descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/0/*)";
+    let mut wallet = Wallet::new(descriptor, None, db, Network::Testnet).expect("should create");
+
+    // get a new address (this increments revealed derivation index)
+    println!("revealed address: {}", wallet.get_address(AddressIndex::New));
+    println!("staged changes: {:?}", wallet.staged());
+    // persist changes
+    wallet.commit().expect("must save");
+}
+```
+
+<!-- ### Sync the balance of a descriptor -->
+
+<!-- ```rust,no_run -->
+<!-- use bdk::Wallet; -->
+<!-- use bdk::blockchain::ElectrumBlockchain; -->
+<!-- use bdk::SyncOptions; -->
+<!-- use bdk::electrum_client::Client; -->
+<!-- use bdk::bitcoin::Network; -->
+
+<!-- fn main() -> Result<(), bdk::Error> { -->
+<!--     let blockchain = ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?); -->
+<!--     let wallet = Wallet::new( -->
+<!--         "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)", -->
+<!--         Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"), -->
+<!--         Network::Testnet, -->
+<!--     )?; -->
+
+<!--     wallet.sync(&blockchain, SyncOptions::default())?; -->
+
+<!--     println!("Descriptor balance: {} SAT", wallet.get_balance()?); -->
+
+<!--     Ok(()) -->
+<!-- } -->
+<!-- ``` -->
+<!-- ### Generate a few addresses -->
+
+<!-- ```rust -->
+<!-- use bdk::Wallet; -->
+<!-- use bdk::wallet::AddressIndex::New; -->
+<!-- use bdk::bitcoin::Network; -->
+
+<!-- fn main() -> Result<(), bdk::Error> { -->
+<!--     let wallet = Wallet::new_no_persist( -->
+<!--         "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)", -->
+<!--         Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"), -->
+<!--         Network::Testnet, -->
+<!--     )?; -->
+
+<!--     println!("Address #0: {}", wallet.get_address(New)); -->
+<!--     println!("Address #1: {}", wallet.get_address(New)); -->
+<!--     println!("Address #2: {}", wallet.get_address(New)); -->
+
+<!--     Ok(()) -->
+<!-- } -->
+<!-- ``` -->
+
+<!-- ### Create a transaction -->
+
+<!-- ```rust,no_run -->
+<!-- use bdk::{FeeRate, Wallet, SyncOptions}; -->
+<!-- use bdk::blockchain::ElectrumBlockchain; -->
+
+<!-- use bdk::electrum_client::Client; -->
+<!-- use bdk::wallet::AddressIndex::New; -->
+
+<!-- use base64; -->
+<!-- use bdk::bitcoin::consensus::serialize; -->
+<!-- use bdk::bitcoin::Network; -->
+
+<!-- fn main() -> Result<(), bdk::Error> { -->
+<!--     let blockchain = ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?); -->
+<!--     let wallet = Wallet::new_no_persist( -->
+<!--         "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)", -->
+<!--         Some("wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/1/*)"), -->
+<!--         Network::Testnet, -->
+<!--     )?; -->
+
+<!--     wallet.sync(&blockchain, SyncOptions::default())?; -->
+
+<!--     let send_to = wallet.get_address(New); -->
+<!--     let (psbt, details) = { -->
+<!--         let mut builder = wallet.build_tx(); -->
+<!--         builder -->
+<!--             .add_recipient(send_to.script_pubkey(), 50_000) -->
+<!--             .enable_rbf() -->
+<!--             .do_not_spend_change() -->
+<!--             .fee_rate(FeeRate::from_sat_per_vb(5.0)); -->
+<!--         builder.finish()? -->
+<!--     }; -->
+
+<!--     println!("Transaction details: {:#?}", details); -->
+<!--     println!("Unsigned PSBT: {}", base64::encode(&serialize(&psbt))); -->
+
+<!--     Ok(()) -->
+<!-- } -->
+<!-- ``` -->
+
+<!-- ### Sign a transaction -->
+
+<!-- ```rust,no_run -->
+<!-- use bdk::{Wallet, SignOptions}; -->
+
+<!-- use base64; -->
+<!-- use bdk::bitcoin::consensus::deserialize; -->
+<!-- use bdk::bitcoin::Network; -->
+
+<!-- fn main() -> Result<(), bdk::Error> { -->
+<!--     let wallet = Wallet::new_no_persist( -->
+<!--         "wpkh([c258d2e4/84h/1h/0h]tprv8griRPhA7342zfRyB6CqeKF8CJDXYu5pgnj1cjL1u2ngKcJha5jjTRimG82ABzJQ4MQe71CV54xfn25BbhCNfEGGJZnxvCDQCd6JkbvxW6h/0/*)", -->
+<!--         Some("wpkh([c258d2e4/84h/1h/0h]tprv8griRPhA7342zfRyB6CqeKF8CJDXYu5pgnj1cjL1u2ngKcJha5jjTRimG82ABzJQ4MQe71CV54xfn25BbhCNfEGGJZnxvCDQCd6JkbvxW6h/1/*)"), -->
+<!--         Network::Testnet, -->
+<!--     )?; -->
+
+<!--     let psbt = "..."; -->
+<!--     let mut psbt = deserialize(&base64::decode(psbt).unwrap())?; -->
+
+<!--     let _finalized = wallet.sign(&mut psbt, SignOptions::default())?; -->
+
+<!--     Ok(()) -->
+<!-- } -->
+<!-- ``` -->
+
+## Testing
+
+### Unit testing
+
+```bash
+cargo test
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0
+   ([LICENSE-APACHE](LICENSE-APACHE) or <https://www.apache.org/licenses/LICENSE-2.0>)
+ * MIT license
+   ([LICENSE-MIT](LICENSE-MIT) or <https://opensource.org/licenses/MIT>)
+
+at your option.
+
+## Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
+
+[`bdk_chain`]: https://docs.rs/bdk_chain/latest
+[`bdk_file_store`]: https://docs.rs/bdk_file_store/latest
+[`bdk_electrum`]: https://docs.rs/bdk_electrum/latest
+[`bdk_esplora`]: https://docs.rs/bdk_esplora/latest
+[`KeychainScan`]: https://docs.rs/bdk_chain/latest/bdk_chain/keychain/struct.KeychainScan.html
+[`rust-miniscript`]: https://docs.rs/miniscript/latest/miniscript/index.html

crates/bdk/examples/compiler.rs

@@ -0,0 +1,73 @@
+// Bitcoin Dev Kit
+// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
+//
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+extern crate bdk;
+extern crate bitcoin;
+extern crate log;
+extern crate miniscript;
+extern crate serde_json;
+
+use std::error::Error;
+use std::str::FromStr;
+
+use log::info;
+
+use bitcoin::Network;
+use miniscript::policy::Concrete;
+use miniscript::Descriptor;
+
+use bdk::wallet::AddressIndex::New;
+use bdk::{KeychainKind, Wallet};
+
+/// Miniscript policy is a high level abstraction of spending conditions. Defined in the
+/// rust-miniscript library here  https://docs.rs/miniscript/7.0.0/miniscript/policy/index.html
+/// rust-miniscript provides a `compile()` function that can be used to compile any miniscript policy
+/// into a descriptor. This descriptor then in turn can be used in bdk a fully functioning wallet
+/// can be derived from the policy.
+///
+/// This example demonstrates the interaction between a bdk wallet and miniscript policy.
+
+fn main() -> Result<(), Box<dyn Error>> {
+    env_logger::init_from_env(
+        env_logger::Env::default().filter_or(env_logger::DEFAULT_FILTER_ENV, "info"),
+    );
+
+    // We start with a generic miniscript policy string
+    let policy_str = "or(10@thresh(4,pk(029ffbe722b147f3035c87cb1c60b9a5947dd49c774cc31e94773478711a929ac0),pk(025f05815e3a1a8a83bfbb03ce016c9a2ee31066b98f567f6227df1d76ec4bd143),pk(025625f41e4a065efc06d5019cbbd56fe8c07595af1231e7cbc03fafb87ebb71ec),pk(02a27c8b850a00f67da3499b60562673dcf5fdfb82b7e17652a7ac54416812aefd),pk(03e618ec5f384d6e19ca9ebdb8e2119e5bef978285076828ce054e55c4daf473e2)),1@and(older(4209713),thresh(2,pk(03deae92101c790b12653231439f27b8897264125ecb2f46f48278603102573165),pk(033841045a531e1adf9910a6ec279589a90b3b8a904ee64ffd692bd08a8996c1aa),pk(02aebf2d10b040eb936a6f02f44ee82f8b34f5c1ccb20ff3949c2b28206b7c1068))))";
+    info!("Compiling policy: \n{}", policy_str);
+
+    // Parse the string as a [`Concrete`] type miniscript policy.
+    let policy = Concrete::<String>::from_str(policy_str)?;
+
+    // Create a `wsh` type descriptor from the policy.
+    // `policy.compile()` returns the resulting miniscript from the policy.
+    let descriptor = Descriptor::new_wsh(policy.compile()?)?;
+
+    info!("Compiled into following Descriptor: \n{}", descriptor);
+
+    // Create a new wallet from this descriptor
+    let mut wallet = Wallet::new_no_persist(&format!("{}", descriptor), None, Network::Regtest)?;
+
+    info!(
+        "First derived address from the descriptor: \n{}",
+        wallet.get_address(New)
+    );
+
+    // BDK also has it's own `Policy` structure to represent the spending condition in a more
+    // human readable json format.
+    let spending_policy = wallet.policies(KeychainKind::External)?;
+    info!(
+        "The BDK spending policy: \n{}",
+        serde_json::to_string_pretty(&spending_policy)?
+    );
+
+    Ok(())
+}

crates/bdk/examples/mnemonic_to_descriptors.rs

@@ -0,0 +1,60 @@
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+use bdk::bitcoin::secp256k1::Secp256k1;
+use bdk::bitcoin::util::bip32::DerivationPath;
+use bdk::bitcoin::Network;
+use bdk::descriptor;
+use bdk::descriptor::IntoWalletDescriptor;
+use bdk::keys::bip39::{Language, Mnemonic, WordCount};
+use bdk::keys::{GeneratableKey, GeneratedKey};
+use bdk::miniscript::Tap;
+use bdk::Error as BDK_Error;
+use std::error::Error;
+use std::str::FromStr;
+
+/// This example demonstrates how to generate a mnemonic phrase
+/// using BDK and use that to generate a descriptor string.
+fn main() -> Result<(), Box<dyn Error>> {
+    let secp = Secp256k1::new();
+
+    // In this example we are generating a 12 words mnemonic phrase
+    // but it is also possible generate 15, 18, 21 and 24 words
+    // using their respective `WordCount` variant.
+    let mnemonic: GeneratedKey<_, Tap> =
+        Mnemonic::generate((WordCount::Words12, Language::English))
+            .map_err(|_| BDK_Error::Generic("Mnemonic generation error".to_string()))?;
+
+    println!("Mnemonic phrase: {}", *mnemonic);
+    let mnemonic_with_passphrase = (mnemonic, None);
+
+    // define external and internal derivation key path
+    let external_path = DerivationPath::from_str("m/86h/0h/0h/0").unwrap();
+    let internal_path = DerivationPath::from_str("m/86h/0h/0h/1").unwrap();
+
+    // generate external and internal descriptor from mnemonic
+    let (external_descriptor, ext_keymap) =
+        descriptor!(tr((mnemonic_with_passphrase.clone(), external_path)))?
+            .into_wallet_descriptor(&secp, Network::Testnet)?;
+    let (internal_descriptor, int_keymap) =
+        descriptor!(tr((mnemonic_with_passphrase, internal_path)))?
+            .into_wallet_descriptor(&secp, Network::Testnet)?;
+
+    println!("tpub external descriptor: {}", external_descriptor);
+    println!("tpub internal descriptor: {}", internal_descriptor);
+    println!(
+        "tprv external descriptor: {}",
+        external_descriptor.to_string_with_secret(&ext_keymap)
+    );
+    println!(
+        "tprv internal descriptor: {}",
+        internal_descriptor.to_string_with_secret(&int_keymap)
+    );
+
+    Ok(())
+}

crates/bdk/examples/policy.rs

@@ -0,0 +1,66 @@
+// Bitcoin Dev Kit
+// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
+//
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+extern crate bdk;
+extern crate env_logger;
+extern crate log;
+use std::error::Error;
+
+use bdk::bitcoin::Network;
+use bdk::descriptor::{policy::BuildSatisfaction, ExtractPolicy, IntoWalletDescriptor};
+use bdk::wallet::signer::SignersContainer;
+
+/// This example describes the use of the BDK's [`bdk::descriptor::policy`] module.
+///
+/// Policy is higher abstraction representation of the wallet descriptor spending condition.
+/// This is useful to express complex miniscript spending conditions into more human readable form.
+/// The resulting `Policy` structure  can be used to derive spending conditions the wallet is capable
+/// to spend from.
+///
+/// This example demos a Policy output for a 2of2 multisig between between 2 parties, where the wallet holds
+/// one of the Extend Private key.
+
+fn main() -> Result<(), Box<dyn Error>> {
+    env_logger::init_from_env(
+        env_logger::Env::default().filter_or(env_logger::DEFAULT_FILTER_ENV, "info"),
+    );
+
+    let secp = bitcoin::secp256k1::Secp256k1::new();
+
+    // The descriptor used in the example
+    // The form is "wsh(multi(2, <privkey>, <pubkey>))"
+    let desc = "wsh(multi(2,tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/*,tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/1/*))";
+
+    // Use the descriptor string to derive the full descriptor and a keymap.
+    // The wallet descriptor can be used to create a new bdk::wallet.
+    // While the `keymap` can be used to create a `SignerContainer`.
+    //
+    // The `SignerContainer` can sign for `PSBT`s.
+    // a bdk::wallet internally uses these to handle transaction signing.
+    // But they can be used as independent tools also.
+    let (wallet_desc, keymap) = desc.into_wallet_descriptor(&secp, Network::Testnet)?;
+
+    log::info!("Example Descriptor for policy analysis : {}", wallet_desc);
+
+    // Create the signer with the keymap and descriptor.
+    let signers_container = SignersContainer::build(keymap, &wallet_desc, &secp);
+
+    // Extract the Policy from the given descriptor and signer.
+    // Note that Policy is a wallet specific structure. It depends on the the descriptor, and
+    // what the concerned wallet with a given signer can sign for.
+    let policy = wallet_desc
+        .extract_policy(&signers_container, BuildSatisfaction::None, &secp)?
+        .expect("We expect a policy");
+
+    log::info!("Derived Policy for the descriptor {:#?}", policy);
+
+    Ok(())
+}

crates/bdk/src/descriptor/checksum.rs

@@ -0,0 +1,182 @@
+// Bitcoin Dev Kit
+// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
+//
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Descriptor checksum
+//!
+//! This module contains a re-implementation of the function used by Bitcoin Core to calculate the
+//! checksum of a descriptor
+
+use crate::descriptor::DescriptorError;
+use alloc::string::String;
+
+const INPUT_CHARSET: &[u8] = b"0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
+const CHECKSUM_CHARSET: &[u8] = b"qpzry9x8gf2tvdw0s3jn54khce6mua7l";
+
+fn poly_mod(mut c: u64, val: u64) -> u64 {
+    let c0 = c >> 35;
+    c = ((c & 0x7ffffffff) << 5) ^ val;
+    if c0 & 1 > 0 {
+        c ^= 0xf5dee51989
+    };
+    if c0 & 2 > 0 {
+        c ^= 0xa9fdca3312
+    };
+    if c0 & 4 > 0 {
+        c ^= 0x1bab10e32d
+    };
+    if c0 & 8 > 0 {
+        c ^= 0x3706b1677a
+    };
+    if c0 & 16 > 0 {
+        c ^= 0x644d626ffd
+    };
+
+    c
+}
+
+/// Computes the checksum bytes of a descriptor.
+/// `exclude_hash = true` ignores all data after the first '#' (inclusive).
+pub(crate) fn calc_checksum_bytes_internal(
+    mut desc: &str,
+    exclude_hash: bool,
+) -> Result<[u8; 8], DescriptorError> {
+    let mut c = 1;
+    let mut cls = 0;
+    let mut clscount = 0;
+
+    let mut original_checksum = None;
+    if exclude_hash {
+        if let Some(split) = desc.split_once('#') {
+            desc = split.0;
+            original_checksum = Some(split.1);
+        }
+    }
+
+    for ch in desc.as_bytes() {
+        let pos = INPUT_CHARSET
+            .iter()
+            .position(|b| b == ch)
+            .ok_or(DescriptorError::InvalidDescriptorCharacter(*ch))? as u64;
+        c = poly_mod(c, pos & 31);
+        cls = cls * 3 + (pos >> 5);
+        clscount += 1;
+        if clscount == 3 {
+            c = poly_mod(c, cls);
+            cls = 0;
+            clscount = 0;
+        }
+    }
+    if clscount > 0 {
+        c = poly_mod(c, cls);
+    }
+    (0..8).for_each(|_| c = poly_mod(c, 0));
+    c ^= 1;
+
+    let mut checksum = [0_u8; 8];
+    for j in 0..8 {
+        checksum[j] = CHECKSUM_CHARSET[((c >> (5 * (7 - j))) & 31) as usize];
+    }
+
+    // if input data already had a checksum, check calculated checksum against original checksum
+    if let Some(original_checksum) = original_checksum {
+        if original_checksum.as_bytes() != checksum {
+            return Err(DescriptorError::InvalidDescriptorChecksum);
+        }
+    }
+
+    Ok(checksum)
+}
+
+/// Compute the checksum bytes of a descriptor, excludes any existing checksum in the descriptor string from the calculation
+pub fn calc_checksum_bytes(desc: &str) -> Result<[u8; 8], DescriptorError> {
+    calc_checksum_bytes_internal(desc, true)
+}
+
+/// Compute the checksum of a descriptor, excludes any existing checksum in the descriptor string from the calculation
+pub fn calc_checksum(desc: &str) -> Result<String, DescriptorError> {
+    // unsafe is okay here as the checksum only uses bytes in `CHECKSUM_CHARSET`
+    calc_checksum_bytes_internal(desc, true)
+        .map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
+}
+
+// TODO in release 0.25.0, remove get_checksum_bytes and get_checksum
+// TODO in release 0.25.0, consolidate calc_checksum_bytes_internal into calc_checksum_bytes
+
+/// Compute the checksum bytes of a descriptor
+#[deprecated(
+    since = "0.24.0",
+    note = "Use new `calc_checksum_bytes` function which excludes any existing checksum in the descriptor string before calculating the checksum hash bytes. See https://github.com/bitcoindevkit/bdk/pull/765."
+)]
+pub fn get_checksum_bytes(desc: &str) -> Result<[u8; 8], DescriptorError> {
+    calc_checksum_bytes_internal(desc, false)
+}
+
+/// Compute the checksum of a descriptor
+#[deprecated(
+    since = "0.24.0",
+    note = "Use new `calc_checksum` function which excludes any existing checksum in the descriptor string before calculating the checksum hash. See https://github.com/bitcoindevkit/bdk/pull/765."
+)]
+pub fn get_checksum(desc: &str) -> Result<String, DescriptorError> {
+    // unsafe is okay here as the checksum only uses bytes in `CHECKSUM_CHARSET`
+    calc_checksum_bytes_internal(desc, false)
+        .map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::descriptor::calc_checksum;
+    use assert_matches::assert_matches;
+
+    // test calc_checksum() function; it should return the same value as Bitcoin Core
+    #[test]
+    fn test_calc_checksum() {
+        let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)";
+        assert_eq!(calc_checksum(desc).unwrap(), "tqz0nc62");
+
+        let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)";
+        assert_eq!(calc_checksum(desc).unwrap(), "lasegmfs");
+    }
+
+    // test calc_checksum() function; it should return the same value as Bitcoin Core even if the
+    // descriptor string includes a checksum hash
+    #[test]
+    fn test_calc_checksum_with_checksum_hash() {
+        let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#tqz0nc62";
+        assert_eq!(calc_checksum(desc).unwrap(), "tqz0nc62");
+
+        let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)#lasegmfs";
+        assert_eq!(calc_checksum(desc).unwrap(), "lasegmfs");
+
+        let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#tqz0nc26";
+        assert_matches!(
+            calc_checksum(desc),
+            Err(DescriptorError::InvalidDescriptorChecksum)
+        );
+
+        let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)#lasegmsf";
+        assert_matches!(
+            calc_checksum(desc),
+            Err(DescriptorError::InvalidDescriptorChecksum)
+        );
+    }
+
+    #[test]
+    fn test_calc_checksum_invalid_character() {
+        let sparkle_heart = unsafe { core::str::from_utf8_unchecked(&[240, 159, 146, 150]) };
+        let invalid_desc = format!("wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcL{}fjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)", sparkle_heart);
+
+        assert_matches!(
+            calc_checksum(&invalid_desc),
+            Err(DescriptorError::InvalidDescriptorCharacter(invalid_char)) if invalid_char == sparkle_heart.as_bytes()[0]
+        );
+    }
+}

crates/bdk/src/descriptor/dsl.rs

@@ -23,7 +23,7 @@ macro_rules! impl_top_level_sh {
     };
 
     ( $inner_struct:ident, $constructor:ident, $sortedmulti_constructor:ident, $ctx:ident, sortedmulti $( $inner:tt )* ) => {{
-        use std::marker::PhantomData;
+        use core::marker::PhantomData;
 
         use $crate::miniscript::descriptor::{$inner_struct, Descriptor, DescriptorPublicKey};
         use $crate::miniscript::$ctx;
@@ -35,7 +35,7 @@ macro_rules! impl_top_level_sh {
         $crate::impl_sortedmulti!(build_desc, sortedmulti $( $inner )*)
     }};
     ( $inner_struct:ident, $constructor:ident, $sortedmulti_constructor:ident, $ctx:ident, sortedmulti_vec $( $inner:tt )* ) => {{
-        use std::marker::PhantomData;
+        use core::marker::PhantomData;
 
         use $crate::miniscript::descriptor::{$inner_struct, Descriptor, DescriptorPublicKey};
         use $crate::miniscript::$ctx;
@@ -203,8 +203,8 @@ macro_rules! impl_node_opcode_two {
                 a_keymap.extend(b_keymap.into_iter());
 
                 let minisc = $crate::miniscript::Miniscript::from_ast($crate::miniscript::miniscript::decode::Terminal::$terminal_variant(
-                    std::sync::Arc::new(a_minisc),
-                    std::sync::Arc::new(b_minisc),
+                    $crate::alloc::sync::Arc::new(a_minisc),
+                    $crate::alloc::sync::Arc::new(b_minisc),
                 ))?;
 
                 minisc.check_miniscript()?;
@@ -234,9 +234,9 @@ macro_rules! impl_node_opcode_three {
                 let networks = $crate::keys::merge_networks(&networks, &c_networks);
 
                 let minisc = $crate::miniscript::Miniscript::from_ast($crate::miniscript::miniscript::decode::Terminal::$terminal_variant(
-                    std::sync::Arc::new(a_minisc),
-                    std::sync::Arc::new(b_minisc),
-                    std::sync::Arc::new(c_minisc),
+                    $crate::alloc::sync::Arc::new(a_minisc),
+                    $crate::alloc::sync::Arc::new(b_minisc),
+                    $crate::alloc::sync::Arc::new(c_minisc),
                 ))?;
 
                 minisc.check_miniscript()?;
@@ -263,7 +263,7 @@ macro_rules! impl_sortedmulti {
             )*
         ];
 
-        keys.into_iter().collect::<Result<Vec<_>, _>>()
+        keys.into_iter().collect::<Result<$crate::alloc::vec::Vec<_>, _>>()
             .map_err($crate::descriptor::DescriptorError::Key)
             .and_then(|keys| $crate::keys::make_sortedmulti($thresh, keys, $build_desc, &secp))
     });
@@ -274,7 +274,7 @@ macro_rules! impl_sortedmulti {
 #[macro_export]
 macro_rules! parse_tap_tree {
     ( @merge $tree_a:expr, $tree_b:expr) => {{
-        use std::sync::Arc;
+        use $crate::alloc::sync::Arc;
         use $crate::miniscript::descriptor::TapTree;
 
         $tree_a
@@ -318,7 +318,7 @@ macro_rules! parse_tap_tree {
 
     // Single leaf
     ( $op:ident ( $( $minisc:tt )* ) ) => {{
-        use std::sync::Arc;
+        use $crate::alloc::sync::Arc;
         use $crate::miniscript::descriptor::TapTree;
 
         $crate::fragment!( $op ( $( $minisc )* ) )
@@ -337,7 +337,7 @@ macro_rules! apply_modifier {
             .and_then(|(minisc, keymap, networks)| {
                 let minisc = $crate::miniscript::Miniscript::from_ast(
                     $crate::miniscript::miniscript::decode::Terminal::$terminal_variant(
-                        std::sync::Arc::new(minisc),
+                        $crate::alloc::sync::Arc::new(minisc),
                     ),
                 )?;
 
@@ -374,8 +374,8 @@ macro_rules! apply_modifier {
         $inner.and_then(|(a_minisc, a_keymap, a_networks)| {
             $crate::impl_leaf_opcode_value_two!(
                 AndV,
-                std::sync::Arc::new(a_minisc),
-                std::sync::Arc::new($crate::fragment!(true).unwrap().0)
+                $crate::alloc::sync::Arc::new(a_minisc),
+                $crate::alloc::sync::Arc::new($crate::fragment!(true).unwrap().0)
             )
             .map(|(minisc, _, _)| (minisc, a_keymap, a_networks))
         })
@@ -384,8 +384,8 @@ macro_rules! apply_modifier {
         $inner.and_then(|(a_minisc, a_keymap, a_networks)| {
             $crate::impl_leaf_opcode_value_two!(
                 OrI,
-                std::sync::Arc::new($crate::fragment!(false).unwrap().0),
-                std::sync::Arc::new(a_minisc)
+                $crate::alloc::sync::Arc::new($crate::fragment!(false).unwrap().0),
+                $crate::alloc::sync::Arc::new(a_minisc)
             )
             .map(|(minisc, _, _)| (minisc, a_keymap, a_networks))
         })
@@ -394,8 +394,8 @@ macro_rules! apply_modifier {
         $inner.and_then(|(a_minisc, a_keymap, a_networks)| {
             $crate::impl_leaf_opcode_value_two!(
                 OrI,
-                std::sync::Arc::new(a_minisc),
-                std::sync::Arc::new($crate::fragment!(false).unwrap().0)
+                $crate::alloc::sync::Arc::new(a_minisc),
+                $crate::alloc::sync::Arc::new($crate::fragment!(false).unwrap().0)
             )
             .map(|(minisc, _, _)| (minisc, a_keymap, a_networks))
         })
@@ -495,6 +495,8 @@ macro_rules! apply_modifier {
 /// let (descriptor, key_map, networks) = bdk::descriptor!(wpkh(my_key))?;
 /// # Ok::<(), Box<dyn std::error::Error>>(())
 /// ```
+///
+/// [`Vec`]: alloc::vec::Vec
 #[macro_export]
 macro_rules! descriptor {
     ( bare ( $( $minisc:tt )* ) ) => ({
@@ -599,7 +601,7 @@ macro_rules! group_multi_keys {
             )*
         ];
 
-        keys.into_iter().collect::<Result<Vec<_>, _>>()
+        keys.into_iter().collect::<Result<$crate::alloc::vec::Vec<_>, _>>()
             .map_err($crate::descriptor::DescriptorError::Key)
     }};
 }
@@ -700,10 +702,10 @@ macro_rules! fragment {
         $crate::keys::make_pkh($key, &secp)
     });
     ( after ( $value:expr ) ) => ({
-        $crate::impl_leaf_opcode_value!(After, $value)
+        $crate::impl_leaf_opcode_value!(After, $crate::bitcoin::PackedLockTime($value)) // TODO!! https://github.com/rust-bitcoin/rust-bitcoin/issues/1302
     });
     ( older ( $value:expr ) ) => ({
-        $crate::impl_leaf_opcode_value!(Older, $value)
+        $crate::impl_leaf_opcode_value!(Older, $crate::bitcoin::Sequence($value)) // TODO!!
     });
     ( sha256 ( $hash:expr ) ) => ({
         $crate::impl_leaf_opcode_value!(Sha256, $hash)
@@ -744,8 +746,8 @@ macro_rules! fragment {
     ( thresh_vec ( $thresh:expr, $items:expr ) ) => ({
         use $crate::miniscript::descriptor::KeyMap;
 
-        let (items, key_maps_networks): (Vec<_>, Vec<_>) = $items.into_iter().map(|(a, b, c)| (a, (b, c))).unzip();
-        let items = items.into_iter().map(std::sync::Arc::new).collect();
+        let (items, key_maps_networks): ($crate::alloc::vec::Vec<_>, $crate::alloc::vec::Vec<_>) = $items.into_iter().map(|(a, b, c)| (a, (b, c))).unzip();
+        let items = items.into_iter().map($crate::alloc::sync::Arc::new).collect();
 
         let (key_maps, valid_networks) = key_maps_networks.into_iter().fold((KeyMap::default(), $crate::keys::any_network()), |(mut keys_acc, net_acc), (key, net)| {
             keys_acc.extend(key.into_iter());
@@ -760,7 +762,7 @@ macro_rules! fragment {
     ( thresh ( $thresh:expr, $( $inner:tt )* ) ) => ({
         let items = $crate::fragment_internal!( @v $( $inner )* );
 
-        items.into_iter().collect::<Result<Vec<_>, _>>()
+        items.into_iter().collect::<Result<$crate::alloc::vec::Vec<_>, _>>()
             .and_then(|items| $crate::fragment!(thresh_vec($thresh, items)))
     });
     ( multi_vec ( $thresh:expr, $keys:expr ) ) => ({
@@ -793,12 +795,13 @@ macro_rules! fragment {
 
 #[cfg(test)]
 mod test {
+    use alloc::string::ToString;
     use bitcoin::hashes::hex::ToHex;
     use bitcoin::secp256k1::Secp256k1;
-    use miniscript::descriptor::{DescriptorPublicKey, DescriptorTrait, KeyMap};
+    use miniscript::descriptor::{DescriptorPublicKey, KeyMap};
     use miniscript::{Descriptor, Legacy, Segwitv0};
 
-    use std::str::FromStr;
+    use core::str::FromStr;
 
     use crate::descriptor::{DescriptorError, DescriptorMeta};
     use crate::keys::{DescriptorKey, IntoDescriptorKey, ValidNetworks};
@@ -806,8 +809,6 @@ mod test {
     use bitcoin::util::bip32;
     use bitcoin::PrivateKey;
 
-    use crate::descriptor::derived::AsDerived;
-
     // test the descriptor!() macro
 
     // verify descriptor generates expected script(s) (if bare or pk) or address(es)
@@ -817,17 +818,15 @@ mod test {
         is_fixed: bool,
         expected: &[&str],
     ) {
-        let secp = Secp256k1::new();
-
         let (desc, _key_map, _networks) = desc.unwrap();
         assert_eq!(desc.is_witness(), is_witness);
-        assert_eq!(!desc.is_deriveable(), is_fixed);
+        assert_eq!(!desc.has_wildcard(), is_fixed);
         for i in 0..expected.len() {
             let index = i as u32;
-            let child_desc = if !desc.is_deriveable() {
-                desc.as_derived_fixed(&secp)
+            let child_desc = if !desc.has_wildcard() {
+                desc.at_derivation_index(0)
             } else {
-                desc.as_derived(index, &secp)
+                desc.at_derivation_index(index)
             };
             let address = child_desc.address(Regtest);
             if let Ok(address) = address {
@@ -839,7 +838,7 @@ mod test {
         }
     }
 
-    // - at least one of each "type" of operator; ie. one modifier, one leaf_opcode, one leaf_opcode_value, etc.
+    // - at least one of each "type" of operator; i.e. one modifier, one leaf_opcode, one leaf_opcode_value, etc.
     // - mixing up key types that implement IntoDescriptorKey in multi() or thresh()
 
     // expected script for pk and bare manually created

crates/bdk/src/descriptor/error.rs

@@ -20,16 +20,14 @@ pub enum Error {
     InvalidDescriptorChecksum,
     /// The descriptor contains hardened derivation steps on public extended keys
     HardenedDerivationXpub,
-    /// The descriptor contains multiple keys with the same BIP32 fingerprint
-    DuplicatedKeys,
 
     /// Error thrown while working with [`keys`](crate::keys)
     Key(crate::keys::KeyError),
     /// Error while extracting and manipulating policies
     Policy(crate::descriptor::policy::PolicyError),
 
-    /// Invalid character found in the descriptor checksum
-    InvalidDescriptorCharacter(char),
+    /// Invalid byte found in the descriptor checksum
+    InvalidDescriptorCharacter(u8),
 
     /// BIP32 error
     Bip32(bitcoin::util::bip32::Error),
@@ -55,10 +53,30 @@ impl From<crate::keys::KeyError> for Error {
 
 impl std::fmt::Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:?}", self)
+        match self {
+            Self::InvalidHdKeyPath => write!(f, "Invalid HD key path"),
+            Self::InvalidDescriptorChecksum => {
+                write!(f, "The provided descriptor doesn't match its checksum")
+            }
+            Self::HardenedDerivationXpub => write!(
+                f,
+                "The descriptor contains hardened derivation steps on public extended keys"
+            ),
+            Self::Key(err) => write!(f, "Key error: {}", err),
+            Self::Policy(err) => write!(f, "Policy error: {}", err),
+            Self::InvalidDescriptorCharacter(char) => {
+                write!(f, "Invalid descriptor character: {}", char)
+            }
+            Self::Bip32(err) => write!(f, "BIP32 error: {}", err),
+            Self::Base58(err) => write!(f, "Base58 error: {}", err),
+            Self::Pk(err) => write!(f, "Key-related error: {}", err),
+            Self::Miniscript(err) => write!(f, "Miniscript error: {}", err),
+            Self::Hex(err) => write!(f, "Hex decoding error: {}", err),
+        }
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for Error {}
 
 impl_error!(bitcoin::util::bip32::Error, Bip32);

crates/bdk/src/descriptor/mod.rs

@@ -14,33 +14,35 @@
 //! This module contains generic utilities to work with descriptors, plus some re-exported types
 //! from [`miniscript`].
 
-use std::collections::{BTreeMap, HashSet};
-use std::ops::Deref;
+use crate::collections::BTreeMap;
+use alloc::string::String;
+use alloc::vec::Vec;
 
 use bitcoin::util::bip32::{ChildNumber, DerivationPath, ExtendedPubKey, Fingerprint, KeySource};
 use bitcoin::util::{psbt, taproot};
 use bitcoin::{secp256k1, PublicKey, XOnlyPublicKey};
-use bitcoin::{Network, Script, TxOut};
+use bitcoin::{Network, TxOut};
 
-use miniscript::descriptor::{DescriptorType, InnerXKey, SinglePubKey};
+use miniscript::descriptor::{
+    DefiniteDescriptorKey, DescriptorSecretKey, DescriptorType, InnerXKey, SinglePubKey,
+};
 pub use miniscript::{
     descriptor::DescriptorXKey, descriptor::KeyMap, descriptor::Wildcard, Descriptor,
     DescriptorPublicKey, Legacy, Miniscript, ScriptContext, Segwitv0,
 };
-use miniscript::{DescriptorTrait, ForEachKey, TranslatePk};
+use miniscript::{ForEachKey, MiniscriptKey, TranslatePk};
 
 use crate::descriptor::policy::BuildSatisfaction;
 
 pub mod checksum;
-pub mod derived;
 #[doc(hidden)]
 pub mod dsl;
 pub mod error;
 pub mod policy;
 pub mod template;
 
-pub use self::checksum::get_checksum;
-pub use self::derived::{AsDerived, DerivedDescriptorKey};
+pub use self::checksum::calc_checksum;
+use self::checksum::calc_checksum_bytes;
 pub use self::error::Error as DescriptorError;
 pub use self::policy::Policy;
 use self::template::DescriptorTemplateOut;
@@ -52,7 +54,7 @@ use crate::wallet::utils::SecpCtx;
 pub type ExtendedDescriptor = Descriptor<DescriptorPublicKey>;
 
 /// Alias for a [`Descriptor`] that contains extended **derived** keys
-pub type DerivedDescriptor<'s> = Descriptor<DerivedDescriptorKey<'s>>;
+pub type DerivedDescriptor = Descriptor<DefiniteDescriptorKey>;
 
 /// Alias for the type of maps that represent derivation paths in a [`psbt::Input`] or
 /// [`psbt::Output`]
@@ -84,19 +86,15 @@ impl IntoWalletDescriptor for &str {
         secp: &SecpCtx,
         network: Network,
     ) -> Result<(ExtendedDescriptor, KeyMap), DescriptorError> {
-        let descriptor = if self.contains('#') {
-            let parts: Vec<&str> = self.splitn(2, '#').collect();
-            if !get_checksum(parts[0])
-                .ok()
-                .map(|computed| computed == parts[1])
-                .unwrap_or(false)
-            {
-                return Err(DescriptorError::InvalidDescriptorChecksum);
+        let descriptor = match self.split_once('#') {
+            Some((desc, original_checksum)) => {
+                let checksum = calc_checksum_bytes(desc)?;
+                if original_checksum.as_bytes() != checksum {
+                    return Err(DescriptorError::InvalidDescriptorChecksum);
+                }
+                desc
             }
-
-            parts[0]
-        } else {
-            self
+            None => self,
         };
 
         ExtendedDescriptor::parse_descriptor(secp, descriptor)?
@@ -132,28 +130,76 @@ impl IntoWalletDescriptor for (ExtendedDescriptor, KeyMap) {
     ) -> Result<(ExtendedDescriptor, KeyMap), DescriptorError> {
         use crate::keys::DescriptorKey;
 
-        let check_key = |pk: &DescriptorPublicKey| {
-            let (pk, _, networks) = if self.0.is_witness() {
-                let descriptor_key: DescriptorKey<miniscript::Segwitv0> =
-                    pk.clone().into_descriptor_key()?;
-                descriptor_key.extract(secp)?
-            } else {
-                let descriptor_key: DescriptorKey<miniscript::Legacy> =
-                    pk.clone().into_descriptor_key()?;
-                descriptor_key.extract(secp)?
-            };
+        struct Translator<'s, 'd> {
+            secp: &'s SecpCtx,
+            descriptor: &'d ExtendedDescriptor,
+            network: Network,
+        }
 
-            if networks.contains(&network) {
-                Ok(pk)
-            } else {
-                Err(DescriptorError::Key(KeyError::InvalidNetwork))
+        impl<'s, 'd>
+            miniscript::Translator<DescriptorPublicKey, miniscript::DummyKey, DescriptorError>
+            for Translator<'s, 'd>
+        {
+            fn pk(
+                &mut self,
+                pk: &DescriptorPublicKey,
+            ) -> Result<miniscript::DummyKey, DescriptorError> {
+                let secp = &self.secp;
+
+                let (_, _, networks) = if self.descriptor.is_taproot() {
+                    let descriptor_key: DescriptorKey<miniscript::Tap> =
+                        pk.clone().into_descriptor_key()?;
+                    descriptor_key.extract(secp)?
+                } else if self.descriptor.is_witness() {
+                    let descriptor_key: DescriptorKey<miniscript::Segwitv0> =
+                        pk.clone().into_descriptor_key()?;
+                    descriptor_key.extract(secp)?
+                } else {
+                    let descriptor_key: DescriptorKey<miniscript::Legacy> =
+                        pk.clone().into_descriptor_key()?;
+                    descriptor_key.extract(secp)?
+                };
+
+                if networks.contains(&self.network) {
+                    Ok(miniscript::DummyKey)
+                } else {
+                    Err(DescriptorError::Key(KeyError::InvalidNetwork))
+                }
             }
-        };
+            fn sha256(
+                &mut self,
+                _sha256: &<DescriptorPublicKey as MiniscriptKey>::Sha256,
+            ) -> Result<miniscript::DummySha256Hash, DescriptorError> {
+                Ok(Default::default())
+            }
+            fn hash256(
+                &mut self,
+                _hash256: &<DescriptorPublicKey as MiniscriptKey>::Hash256,
+            ) -> Result<miniscript::DummyHash256Hash, DescriptorError> {
+                Ok(Default::default())
+            }
+            fn ripemd160(
+                &mut self,
+                _ripemd160: &<DescriptorPublicKey as MiniscriptKey>::Ripemd160,
+            ) -> Result<miniscript::DummyRipemd160Hash, DescriptorError> {
+                Ok(Default::default())
+            }
+            fn hash160(
+                &mut self,
+                _hash160: &<DescriptorPublicKey as MiniscriptKey>::Hash160,
+            ) -> Result<miniscript::DummyHash160Hash, DescriptorError> {
+                Ok(Default::default())
+            }
+        }
 
         // check the network for the keys
-        let translated = self.0.translate_pk(check_key, check_key)?;
+        self.0.translate_pk(&mut Translator {
+            secp,
+            network,
+            descriptor: &self.0,
+        })?;
 
-        Ok((translated, self.1))
+        Ok(self)
     }
 }
 
@@ -163,10 +209,17 @@ impl IntoWalletDescriptor for DescriptorTemplateOut {
         _secp: &SecpCtx,
         network: Network,
     ) -> Result<(ExtendedDescriptor, KeyMap), DescriptorError> {
-        let valid_networks = &self.2;
+        struct Translator {
+            network: Network,
+        }
 
-        let fix_key = |pk: &DescriptorPublicKey| {
-            if valid_networks.contains(&network) {
+        impl miniscript::Translator<DescriptorPublicKey, DescriptorPublicKey, DescriptorError>
+            for Translator
+        {
+            fn pk(
+                &mut self,
+                pk: &DescriptorPublicKey,
+            ) -> Result<DescriptorPublicKey, DescriptorError> {
                 // workaround for xpubs generated by other key types, like bip39: since when the
                 // conversion is made one network has to be chosen, what we generally choose
                 // "mainnet", but then override the set of valid networks to specify that all of
@@ -175,7 +228,7 @@ impl IntoWalletDescriptor for DescriptorTemplateOut {
                 let pk = match pk {
                     DescriptorPublicKey::XPub(ref xpub) => {
                         let mut xpub = xpub.clone();
-                        xpub.xkey.network = network;
+                        xpub.xkey.network = self.network;
 
                         DescriptorPublicKey::XPub(xpub)
                     }
@@ -183,15 +236,42 @@ impl IntoWalletDescriptor for DescriptorTemplateOut {
                 };
 
                 Ok(pk)
-            } else {
-                Err(DescriptorError::Key(KeyError::InvalidNetwork))
             }
-        };
+            miniscript::translate_hash_clone!(
+                DescriptorPublicKey,
+                DescriptorPublicKey,
+                DescriptorError
+            );
+        }
 
-        // fixup the network for keys that need it
-        let translated = self.0.translate_pk(fix_key, fix_key)?;
+        let (desc, keymap, networks) = self;
 
-        Ok((translated, self.1))
+        if !networks.contains(&network) {
+            return Err(DescriptorError::Key(KeyError::InvalidNetwork));
+        }
+
+        // fixup the network for keys that need it in the descriptor
+        let translated = desc.translate_pk(&mut Translator { network })?;
+        // ...and in the key map
+        let fixed_keymap = keymap
+            .into_iter()
+            .map(|(mut k, mut v)| {
+                match (&mut k, &mut v) {
+                    (DescriptorPublicKey::XPub(xpub), DescriptorSecretKey::XPrv(xprv)) => {
+                        xpub.xkey.network = network;
+                        xprv.xkey.network = network;
+                    }
+                    (_, DescriptorSecretKey::Single(key)) => {
+                        key.key.network = network;
+                    }
+                    _ => {}
+                }
+
+                (k, v)
+            })
+            .collect();
+
+        Ok((translated, fixed_keymap))
     }
 }
 
@@ -210,7 +290,7 @@ pub(crate) fn into_wallet_descriptor_checked<T: IntoWalletDescriptor>(
             derivation_path,
             wildcard,
             ..
-        }) = k.as_key()
+        }) = k
         {
             return *wildcard == Wildcard::Hardened
                 || derivation_path.into_iter().any(ChildNumber::is_hardened);
@@ -222,23 +302,9 @@ pub(crate) fn into_wallet_descriptor_checked<T: IntoWalletDescriptor>(
         return Err(DescriptorError::HardenedDerivationXpub);
     }
 
-    // Ensure that there are no duplicated keys
-    let mut found_keys = HashSet::new();
-    let descriptor_contains_duplicated_keys = descriptor.for_any_key(|k| {
-        if let DescriptorPublicKey::XPub(xkey) = k.as_key() {
-            let fingerprint = xkey.root_fingerprint(secp);
-            if found_keys.contains(&fingerprint) {
-                return true;
-            }
-
-            found_keys.insert(fingerprint);
-        }
-
-        false
-    });
-    if descriptor_contains_duplicated_keys {
-        return Err(DescriptorError::DuplicatedKeys);
-    }
+    // Run miniscript's sanity check, which will look for duplicated keys and other potential
+    // issues
+    descriptor.sanity_check()?;
 
     Ok((descriptor, keymap))
 }
@@ -271,7 +337,6 @@ pub trait ExtractPolicy {
 }
 
 pub(crate) trait XKeyUtils {
-    fn full_path(&self, append: &[ChildNumber]) -> DerivationPath;
     fn root_fingerprint(&self, secp: &SecpCtx) -> Fingerprint;
 }
 
@@ -279,27 +344,6 @@ impl<T> XKeyUtils for DescriptorXKey<T>
 where
     T: InnerXKey,
 {
-    fn full_path(&self, append: &[ChildNumber]) -> DerivationPath {
-        let full_path = match self.origin {
-            Some((_, ref path)) => path
-                .into_iter()
-                .chain(self.derivation_path.into_iter())
-                .cloned()
-                .collect(),
-            None => self.derivation_path.clone(),
-        };
-
-        if self.wildcard != Wildcard::None {
-            full_path
-                .into_iter()
-                .chain(append.iter())
-                .cloned()
-                .collect()
-        } else {
-            full_path
-        }
-    }
-
     fn root_fingerprint(&self, secp: &SecpCtx) -> Fingerprint {
         match self.origin {
             Some((fingerprint, _)) => fingerprint,
@@ -308,76 +352,31 @@ where
     }
 }
 
-pub(crate) trait DerivedDescriptorMeta {
-    fn get_hd_keypaths(&self, secp: &SecpCtx) -> HdKeyPaths;
-    fn get_tap_key_origins(&self, secp: &SecpCtx) -> TapKeyOrigins;
-}
-
 pub(crate) trait DescriptorMeta {
     fn is_witness(&self) -> bool;
     fn is_taproot(&self) -> bool;
-    fn get_extended_keys(&self) -> Result<Vec<DescriptorXKey<ExtendedPubKey>>, DescriptorError>;
-    fn derive_from_hd_keypaths<'s>(
+    fn get_extended_keys(&self) -> Vec<DescriptorXKey<ExtendedPubKey>>;
+    fn derive_from_hd_keypaths(
         &self,
         hd_keypaths: &HdKeyPaths,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>>;
-    fn derive_from_tap_key_origins<'s>(
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor>;
+    fn derive_from_tap_key_origins(
         &self,
         tap_key_origins: &TapKeyOrigins,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>>;
-    fn derive_from_psbt_key_origins<'s>(
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor>;
+    fn derive_from_psbt_key_origins(
         &self,
         key_origins: BTreeMap<Fingerprint, (&DerivationPath, SinglePubKey)>,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>>;
-    fn derive_from_psbt_input<'s>(
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor>;
+    fn derive_from_psbt_input(
         &self,
         psbt_input: &psbt::Input,
         utxo: Option<TxOut>,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>>;
-}
-
-pub(crate) trait DescriptorScripts {
-    fn psbt_redeem_script(&self) -> Option<Script>;
-    fn psbt_witness_script(&self) -> Option<Script>;
-}
-
-impl<'s> DescriptorScripts for DerivedDescriptor<'s> {
-    fn psbt_redeem_script(&self) -> Option<Script> {
-        match self.desc_type() {
-            DescriptorType::ShWpkh => Some(self.explicit_script().unwrap()),
-            DescriptorType::ShWsh => Some(self.explicit_script().unwrap().to_v0_p2wsh()),
-            DescriptorType::Sh => Some(self.explicit_script().unwrap()),
-            DescriptorType::Bare => Some(self.explicit_script().unwrap()),
-            DescriptorType::ShSortedMulti => Some(self.explicit_script().unwrap()),
-            DescriptorType::ShWshSortedMulti => Some(self.explicit_script().unwrap().to_v0_p2wsh()),
-            DescriptorType::Pkh
-            | DescriptorType::Wpkh
-            | DescriptorType::Tr
-            | DescriptorType::Wsh
-            | DescriptorType::WshSortedMulti => None,
-        }
-    }
-
-    fn psbt_witness_script(&self) -> Option<Script> {
-        match self.desc_type() {
-            DescriptorType::Wsh => Some(self.explicit_script().unwrap()),
-            DescriptorType::ShWsh => Some(self.explicit_script().unwrap()),
-            DescriptorType::WshSortedMulti | DescriptorType::ShWshSortedMulti => {
-                Some(self.explicit_script().unwrap())
-            }
-            DescriptorType::Bare
-            | DescriptorType::Sh
-            | DescriptorType::Pkh
-            | DescriptorType::Wpkh
-            | DescriptorType::ShSortedMulti
-            | DescriptorType::Tr
-            | DescriptorType::ShWpkh => None,
-        }
-    }
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor>;
 }
 
 impl DescriptorMeta for ExtendedDescriptor {
@@ -397,25 +396,25 @@ impl DescriptorMeta for ExtendedDescriptor {
         self.desc_type() == DescriptorType::Tr
     }
 
-    fn get_extended_keys(&self) -> Result<Vec<DescriptorXKey<ExtendedPubKey>>, DescriptorError> {
+    fn get_extended_keys(&self) -> Vec<DescriptorXKey<ExtendedPubKey>> {
         let mut answer = Vec::new();
 
         self.for_each_key(|pk| {
-            if let DescriptorPublicKey::XPub(xpub) = pk.as_key() {
+            if let DescriptorPublicKey::XPub(xpub) = pk {
                 answer.push(xpub.clone());
             }
 
             true
         });
 
-        Ok(answer)
+        answer
     }
 
-    fn derive_from_psbt_key_origins<'s>(
+    fn derive_from_psbt_key_origins(
         &self,
         key_origins: BTreeMap<Fingerprint, (&DerivationPath, SinglePubKey)>,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>> {
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor> {
         // Ensure that deriving `xpub` with `path` yields `expected`
         let verify_key = |xpub: &DescriptorXKey<ExtendedPubKey>,
                           path: &DerivationPath,
@@ -437,7 +436,7 @@ impl DescriptorMeta for ExtendedDescriptor {
 
         // using `for_any_key` should make this stop as soon as we return `true`
         self.for_any_key(|key| {
-            if let DescriptorPublicKey::XPub(xpub) = key.as_key().deref() {
+            if let DescriptorPublicKey::XPub(xpub) = key {
                 // Check if the key matches one entry in our `key_origins`. If it does, `matches()` will
                 // return the "prefix" that matched, so we remove that prefix from the full path
                 // found in `key_origins` and save it in `derive_path`. We expect this to be a derivation
@@ -495,14 +494,14 @@ impl DescriptorMeta for ExtendedDescriptor {
             false
         });
 
-        path_found.map(|path| self.as_derived(path, secp))
+        path_found.map(|path| self.at_derivation_index(path))
     }
 
-    fn derive_from_hd_keypaths<'s>(
+    fn derive_from_hd_keypaths(
         &self,
         hd_keypaths: &HdKeyPaths,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>> {
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor> {
         // "Convert" an hd_keypaths map to the format required by `derive_from_psbt_key_origins`
         let key_origins = hd_keypaths
             .iter()
@@ -516,11 +515,11 @@ impl DescriptorMeta for ExtendedDescriptor {
         self.derive_from_psbt_key_origins(key_origins, secp)
     }
 
-    fn derive_from_tap_key_origins<'s>(
+    fn derive_from_tap_key_origins(
         &self,
         tap_key_origins: &TapKeyOrigins,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>> {
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor> {
         // "Convert" a tap_key_origins map to the format required by `derive_from_psbt_key_origins`
         let key_origins = tap_key_origins
             .iter()
@@ -529,24 +528,24 @@ impl DescriptorMeta for ExtendedDescriptor {
         self.derive_from_psbt_key_origins(key_origins, secp)
     }
 
-    fn derive_from_psbt_input<'s>(
+    fn derive_from_psbt_input(
         &self,
         psbt_input: &psbt::Input,
         utxo: Option<TxOut>,
-        secp: &'s SecpCtx,
-    ) -> Option<DerivedDescriptor<'s>> {
+        secp: &SecpCtx,
+    ) -> Option<DerivedDescriptor> {
         if let Some(derived) = self.derive_from_hd_keypaths(&psbt_input.bip32_derivation, secp) {
             return Some(derived);
         }
         if let Some(derived) = self.derive_from_tap_key_origins(&psbt_input.tap_key_origins, secp) {
             return Some(derived);
         }
-        if self.is_deriveable() {
+        if self.has_wildcard() {
             // We can't try to bruteforce the derivation index, exit here
             return None;
         }
 
-        let descriptor = self.as_derived_fixed(secp);
+        let descriptor = self.at_derivation_index(0);
         match descriptor.desc_type() {
             // TODO: add pk() here
             DescriptorType::Pkh
@@ -580,90 +579,12 @@ impl DescriptorMeta for ExtendedDescriptor {
     }
 }
 
-impl<'s> DerivedDescriptorMeta for DerivedDescriptor<'s> {
-    fn get_hd_keypaths(&self, secp: &SecpCtx) -> HdKeyPaths {
-        let mut answer = BTreeMap::new();
-        self.for_each_key(|key| {
-            if let DescriptorPublicKey::XPub(xpub) = key.as_key().deref() {
-                let derived_pubkey = xpub
-                    .xkey
-                    .derive_pub(secp, &xpub.derivation_path)
-                    .expect("Derivation can't fail");
-
-                answer.insert(
-                    derived_pubkey.public_key,
-                    (xpub.root_fingerprint(secp), xpub.full_path(&[])),
-                );
-            }
-
-            true
-        });
-
-        answer
-    }
-
-    fn get_tap_key_origins(&self, secp: &SecpCtx) -> TapKeyOrigins {
-        use miniscript::ToPublicKey;
-
-        let mut answer = BTreeMap::new();
-        let mut insert_path = |pk: &DerivedDescriptorKey<'_>, lh| {
-            let key_origin = match pk.deref() {
-                DescriptorPublicKey::XPub(xpub) => {
-                    Some((xpub.root_fingerprint(secp), xpub.full_path(&[])))
-                }
-                DescriptorPublicKey::SinglePub(_) => None,
-            };
-
-            // If this is the internal key, we only insert the key origin if it's not None.
-            // For keys found in the tap tree we always insert a key origin (because the signer
-            // looks for it to know which leaves to sign for), even though it may be None
-            match (lh, key_origin) {
-                (None, Some(ko)) => {
-                    answer
-                        .entry(pk.to_x_only_pubkey())
-                        .or_insert_with(|| (vec![], ko));
-                }
-                (Some(lh), origin) => {
-                    answer
-                        .entry(pk.to_x_only_pubkey())
-                        .or_insert_with(|| (vec![], origin.unwrap_or_default()))
-                        .0
-                        .push(lh);
-                }
-                _ => {}
-            }
-        };
-
-        if let Descriptor::Tr(tr) = &self {
-            // Internal key first, then iterate the scripts
-            insert_path(tr.internal_key(), None);
-
-            for (_, ms) in tr.iter_scripts() {
-                // Assume always the same leaf version
-                let leaf_hash = taproot::TapLeafHash::from_script(
-                    &ms.encode(),
-                    taproot::LeafVersion::TapScript,
-                );
-
-                for key in ms.iter_pk_pkh() {
-                    let key = match key {
-                        miniscript::miniscript::iter::PkPkh::PlainPubkey(pk) => pk,
-                        miniscript::miniscript::iter::PkPkh::HashedPubkey(pk) => pk,
-                    };
-
-                    insert_path(&key, Some(leaf_hash));
-                }
-            }
-        }
-
-        answer
-    }
-}
-
 #[cfg(test)]
 mod test {
-    use std::str::FromStr;
+    use alloc::string::ToString;
+    use core::str::FromStr;
 
+    use assert_matches::assert_matches;
     use bitcoin::consensus::encode::deserialize;
     use bitcoin::hashes::hex::FromHex;
     use bitcoin::secp256k1::Secp256k1;
@@ -787,23 +708,40 @@ mod test {
 
         let secp = Secp256k1::new();
 
-        let xpub = bip32::ExtendedPubKey::from_str("xpub6ERApfZwUNrhLCkDtcHTcxd75RbzS1ed54G1LkBUHQVHQKqhMkhgbmJbZRkrgZw4koxb5JaHWkY4ALHY2grBGRjaDMzQLcgJvLJuZZvRcEL").unwrap();
+        let xprv = bip32::ExtendedPrivKey::from_str("xprv9s21ZrQH143K3c3gF1DUWpWNr2SG2XrG8oYPpqYh7hoWsJy9NjabErnzriJPpnGHyKz5NgdXmq1KVbqS1r4NXdCoKitWg5e86zqXHa8kxyB").unwrap();
         let path = bip32::DerivationPath::from_str("m/0").unwrap();
 
         // here `to_descriptor_key` will set the valid networks for the key to only mainnet, since
         // we are using an "xpub"
-        let key = (xpub, path).into_descriptor_key().unwrap();
+        let key = (xprv, path.clone()).into_descriptor_key().unwrap();
         // override it with any. this happens in some key conversions, like bip39
         let key = key.override_valid_networks(any_network());
 
         // make a descriptor out of it
         let desc = crate::descriptor!(wpkh(key)).unwrap();
         // this should convert the key that supports "any_network" to the right network (testnet)
-        let (wallet_desc, _) = desc
+        let (wallet_desc, keymap) = desc
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
 
-        assert_eq!(wallet_desc.to_string(), "wpkh(tpubDEnoLuPdBep9bzw5LoGYpsxUQYheRQ9gcgrJhJEcdKFB9cWQRyYmkCyRoTqeD4tJYiVVgt6A3rN6rWn9RYhR9sBsGxji29LYWHuKKbdb1ev/0/*)#y8p7e8kk");
+        let mut xprv_testnet = xprv;
+        xprv_testnet.network = Network::Testnet;
+
+        let xpub_testnet = bip32::ExtendedPubKey::from_priv(&secp, &xprv_testnet);
+        let desc_pubkey = DescriptorPublicKey::XPub(DescriptorXKey {
+            xkey: xpub_testnet,
+            origin: None,
+            derivation_path: path,
+            wildcard: Wildcard::Unhardened,
+        });
+
+        assert_eq!(wallet_desc.to_string(), "wpkh(tpubD6NzVbkrYhZ4XtJzoDja5snUjBNQRP5B3f4Hyn1T1x6PVPxzzVjvw6nJx2D8RBCxog9GEVjZoyStfepTz7TtKoBVdkCtnc7VCJh9dD4RAU9/0/*)#a3svx0ha");
+        assert_eq!(
+            keymap
+                .get(&desc_pubkey)
+                .map(|key| key.to_public(&secp).unwrap()),
+            Some(desc_pubkey)
+        );
     }
 
     // test IntoWalletDescriptor trait from &str with and without checksum appended
@@ -829,17 +767,11 @@ mod test {
 
         let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#67ju93jw"
             .into_wallet_descriptor(&secp, Network::Testnet);
-        assert!(matches!(
-            desc.err(),
-            Some(DescriptorError::InvalidDescriptorChecksum)
-        ));
+        assert_matches!(desc, Err(DescriptorError::InvalidDescriptorChecksum));
 
         let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)#67ju93jw"
             .into_wallet_descriptor(&secp, Network::Testnet);
-        assert!(matches!(
-            desc.err(),
-            Some(DescriptorError::InvalidDescriptorChecksum)
-        ));
+        assert_matches!(desc, Err(DescriptorError::InvalidDescriptorChecksum));
     }
 
     // test IntoWalletDescriptor trait from &str with keys from right and wrong network
@@ -873,17 +805,11 @@ mod test {
 
         let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)"
             .into_wallet_descriptor(&secp, Network::Bitcoin);
-        assert!(matches!(
-            desc.err(),
-            Some(DescriptorError::Key(KeyError::InvalidNetwork))
-        ));
+        assert_matches!(desc, Err(DescriptorError::Key(KeyError::InvalidNetwork)));
 
         let desc = "wpkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/1/2/*)"
             .into_wallet_descriptor(&secp, Network::Bitcoin);
-        assert!(matches!(
-            desc.err(),
-            Some(DescriptorError::Key(KeyError::InvalidNetwork))
-        ));
+        assert_matches!(desc, Err(DescriptorError::Key(KeyError::InvalidNetwork)));
     }
 
     // test IntoWalletDescriptor trait from the output of the descriptor!() macro
@@ -917,25 +843,17 @@ mod test {
         let descriptor = "wpkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/0'/1/2/*)";
         let result = into_wallet_descriptor_checked(descriptor, &secp, Network::Testnet);
 
-        assert!(result.is_err());
-        assert!(matches!(
-            result.unwrap_err(),
-            DescriptorError::HardenedDerivationXpub
-        ));
+        assert_matches!(result, Err(DescriptorError::HardenedDerivationXpub));
 
-        let descriptor = "wsh(multi(2,tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/0/*,tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/1/*))";
+        let descriptor = "wsh(multi(2,tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/0/*,tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/0/*))";
         let result = into_wallet_descriptor_checked(descriptor, &secp, Network::Testnet);
 
         assert!(result.is_err());
-        assert!(matches!(
-            result.unwrap_err(),
-            DescriptorError::DuplicatedKeys
-        ));
     }
 
     #[test]
     fn test_sh_wsh_sortedmulti_redeemscript() {
-        use super::{AsDerived, DescriptorScripts};
+        use miniscript::psbt::PsbtInputExt;
 
         let secp = Secp256k1::new();
 
@@ -943,11 +861,16 @@ mod test {
         let (descriptor, _) =
             into_wallet_descriptor_checked(descriptor, &secp, Network::Testnet).unwrap();
 
-        let descriptor = descriptor.as_derived(0, &secp);
+        let descriptor = descriptor.at_derivation_index(0);
 
         let script = Script::from_str("5321022f533b667e2ea3b36e21961c9fe9dca340fbe0af5210173a83ae0337ab20a57621026bb53a98e810bd0ee61a0ed1164ba6c024786d76554e793e202dc6ce9c78c4ea2102d5b8a7d66a41ffdb6f4c53d61994022e886b4f45001fb158b95c9164d45f8ca3210324b75eead2c1f9c60e8adeb5e7009fec7a29afcdb30d829d82d09562fe8bae8521032d34f8932200833487bd294aa219dcbe000b9f9b3d824799541430009f0fa55121037468f8ea99b6c64788398b5ad25480cad08f4b0d65be54ce3a55fd206b5ae4722103f72d3d96663b0ea99b0aeb0d7f273cab11a8de37885f1dddc8d9112adb87169357ae").unwrap();
 
-        assert_eq!(descriptor.psbt_redeem_script(), Some(script.to_v0_p2wsh()));
-        assert_eq!(descriptor.psbt_witness_script(), Some(script));
+        let mut psbt_input = psbt::Input::default();
+        psbt_input
+            .update_with_descriptor_unchecked(&descriptor)
+            .unwrap();
+
+        assert_eq!(psbt_input.redeem_script, Some(script.to_v0_p2wsh()));
+        assert_eq!(psbt_input.witness_script, Some(script));
     }
 }

crates/bdk/src/descriptor/policy.rs

@@ -32,25 +32,30 @@
 //!
 //! let signers = Arc::new(SignersContainer::build(key_map, &extended_desc, &secp));
 //! let policy = extended_desc.extract_policy(&signers, BuildSatisfaction::None, &secp)?;
-//! println!("policy: {}", serde_json::to_string(&policy)?);
+//! println!("policy: {}", serde_json::to_string(&policy).unwrap());
 //! # Ok::<(), bdk::Error>(())
 //! ```
 
-use std::cmp::max;
-use std::collections::{BTreeMap, HashSet, VecDeque};
-use std::fmt;
+use crate::collections::{BTreeMap, HashSet, VecDeque};
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::cmp::max;
+use core::fmt;
 
 use serde::ser::SerializeMap;
 use serde::{Serialize, Serializer};
 
-use bitcoin::hashes::*;
+use bitcoin::hashes::{hash160, ripemd160, sha256};
 use bitcoin::util::bip32::Fingerprint;
-use bitcoin::{PublicKey, XOnlyPublicKey};
+use bitcoin::{LockTime, PublicKey, Sequence, XOnlyPublicKey};
 
 use miniscript::descriptor::{
-    DescriptorPublicKey, DescriptorSinglePub, ShInner, SinglePubKey, SortedMultiVec, WshInner,
+    DescriptorPublicKey, ShInner, SinglePub, SinglePubKey, SortedMultiVec, WshInner,
+};
+use miniscript::hash256;
+use miniscript::{
+    Descriptor, Miniscript, Satisfier, ScriptContext, SigType, Terminal, ToPublicKey,
 };
-use miniscript::{Descriptor, Miniscript, MiniscriptKey, Satisfier, ScriptContext, Terminal};
 
 #[allow(unused_imports)]
 use log::{debug, error, info, trace};
@@ -58,9 +63,9 @@ use log::{debug, error, info, trace};
 use crate::descriptor::ExtractPolicy;
 use crate::keys::ExtScriptContext;
 use crate::wallet::signer::{SignerId, SignersContainer};
-use crate::wallet::utils::{self, After, Older, SecpCtx};
+use crate::wallet::utils::{After, Older, SecpCtx};
 
-use super::checksum::get_checksum;
+use super::checksum::calc_checksum;
 use super::error::Error;
 use super::XKeyUtils;
 use bitcoin::util::psbt::{Input as PsbtInput, PartiallySignedTransaction as Psbt};
@@ -81,11 +86,11 @@ pub enum PkOrF {
 impl PkOrF {
     fn from_key(k: &DescriptorPublicKey, secp: &SecpCtx) -> Self {
         match k {
-            DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+            DescriptorPublicKey::Single(SinglePub {
                 key: SinglePubKey::FullKey(pk),
                 ..
             }) => PkOrF::Pubkey(*pk),
-            DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+            DescriptorPublicKey::Single(SinglePub {
                 key: SinglePubKey::XOnly(pk),
                 ..
             }) => PkOrF::XOnlyPubkey(*pk),
@@ -111,7 +116,7 @@ pub enum SatisfiableItem {
     /// Double SHA256 preimage hash
     Hash256Preimage {
         /// The digest value
-        hash: sha256d::Hash,
+        hash: hash256::Hash,
     },
     /// RIPEMD160 preimage hash
     Ripemd160Preimage {
@@ -125,13 +130,13 @@ pub enum SatisfiableItem {
     },
     /// Absolute timeclock timestamp
     AbsoluteTimelock {
-        /// The timestamp value
-        value: u32,
+        /// The timelock value
+        value: LockTime,
     },
     /// Relative timelock locktime
     RelativeTimelock {
-        /// The locktime value
-        value: u32,
+        /// The timelock value
+        value: Sequence,
     },
     /// Multi-signature public keys with threshold count
     Multisig {
@@ -165,7 +170,7 @@ impl SatisfiableItem {
 
     /// Returns a unique id for the [`SatisfiableItem`]
     pub fn id(&self) -> String {
-        get_checksum(&serde_json::to_string(self).expect("Failed to serialize a SatisfiableItem"))
+        calc_checksum(&serde_json::to_string(self).expect("Failed to serialize a SatisfiableItem"))
             .expect("Failed to compute a SatisfiableItem id")
     }
 }
@@ -438,32 +443,30 @@ pub struct Policy {
 }
 
 /// An extra condition that must be satisfied but that is out of control of the user
-#[derive(Hash, Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Default, Serialize)]
+/// TODO: use `bitcoin::LockTime` and `bitcoin::Sequence`
+#[derive(Hash, Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Default, Serialize)]
 pub struct Condition {
     /// Optional CheckSequenceVerify condition
     #[serde(skip_serializing_if = "Option::is_none")]
-    pub csv: Option<u32>,
+    pub csv: Option<Sequence>,
     /// Optional timelock condition
     #[serde(skip_serializing_if = "Option::is_none")]
-    pub timelock: Option<u32>,
+    pub timelock: Option<LockTime>,
 }
 
 impl Condition {
-    fn merge_nlocktime(a: u32, b: u32) -> Result<u32, PolicyError> {
-        if (a < utils::BLOCKS_TIMELOCK_THRESHOLD) != (b < utils::BLOCKS_TIMELOCK_THRESHOLD) {
+    fn merge_nlocktime(a: LockTime, b: LockTime) -> Result<LockTime, PolicyError> {
+        if !a.is_same_unit(b) {
             Err(PolicyError::MixedTimelockUnits)
+        } else if a > b {
+            Ok(a)
         } else {
-            Ok(max(a, b))
+            Ok(b)
         }
     }
 
-    fn merge_nsequence(a: u32, b: u32) -> Result<u32, PolicyError> {
-        let mask = utils::SEQUENCE_LOCKTIME_TYPE_FLAG | utils::SEQUENCE_LOCKTIME_MASK;
-
-        let a = a & mask;
-        let b = b & mask;
-
-        if (a < utils::SEQUENCE_LOCKTIME_TYPE_FLAG) != (b < utils::SEQUENCE_LOCKTIME_TYPE_FLAG) {
+    fn merge_nsequence(a: Sequence, b: Sequence) -> Result<Sequence, PolicyError> {
+        if a.is_time_locked() != b.is_time_locked() {
             Err(PolicyError::MixedTimelockUnits)
         } else {
             Ok(max(a, b))
@@ -511,10 +514,18 @@ pub enum PolicyError {
 
 impl fmt::Display for PolicyError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self)
+        match self {
+            Self::NotEnoughItemsSelected(err) => write!(f, "Not enought items selected: {}", err),
+            Self::IndexOutOfRange(index) => write!(f, "Index out of range: {}", index),
+            Self::AddOnLeaf => write!(f, "Add on leaf"),
+            Self::AddOnPartialComplete => write!(f, "Add on partial complete"),
+            Self::MixedTimelockUnits => write!(f, "Mixed timelock units"),
+            Self::IncompatibleConditions => write!(f, "Incompatible conditions"),
+        }
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for PolicyError {}
 
 impl Policy {
@@ -720,15 +731,18 @@ impl From<SatisfiableItem> for Policy {
 }
 
 fn signer_id(key: &DescriptorPublicKey, secp: &SecpCtx) -> SignerId {
+    // For consistency we always compute the key hash in "ecdsa" form (with the leading sign
+    // prefix) even if we are in a taproot descriptor. We just want some kind of unique identifier
+    // for a key, so it doesn't really matter how the identifier is computed.
     match key {
-        DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+        DescriptorPublicKey::Single(SinglePub {
             key: SinglePubKey::FullKey(pk),
             ..
-        }) => pk.to_pubkeyhash().into(),
-        DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+        }) => pk.to_pubkeyhash(SigType::Ecdsa).into(),
+        DescriptorPublicKey::Single(SinglePub {
             key: SinglePubKey::XOnly(pk),
             ..
-        }) => pk.to_pubkeyhash().into(),
+        }) => pk.to_pubkeyhash(SigType::Ecdsa).into(),
         DescriptorPublicKey::XPub(xpub) => xpub.root_fingerprint(secp).into(),
     }
 }
@@ -779,7 +793,7 @@ fn generic_sig_in_psbt<
 ) -> bool {
     //TODO check signature validity
     psbt.inputs.iter().all(|input| match key {
-        DescriptorPublicKey::SinglePub(DescriptorSinglePub { key, .. }) => check(input, key),
+        DescriptorPublicKey::Single(SinglePub { key, .. }) => check(input, key),
         DescriptorPublicKey::XPub(xpub) => {
             //TODO check actual derivation matches
             match extract(input, xpub.root_fingerprint(secp)) {
@@ -891,10 +905,13 @@ impl<Ctx: ScriptContext + 'static> ExtractPolicy for Miniscript<DescriptorPublic
                 Some(Ctx::make_signature(pubkey_hash, signers, build_sat, secp))
             }
             Terminal::After(value) => {
-                let mut policy: Policy = SatisfiableItem::AbsoluteTimelock { value: *value }.into();
+                let mut policy: Policy = SatisfiableItem::AbsoluteTimelock {
+                    value: value.into(),
+                }
+                .into();
                 policy.contribution = Satisfaction::Complete {
                     condition: Condition {
-                        timelock: Some(*value),
+                        timelock: Some(value.into()),
                         csv: None,
                     },
                 };
@@ -905,9 +922,11 @@ impl<Ctx: ScriptContext + 'static> ExtractPolicy for Miniscript<DescriptorPublic
                 } = build_sat
                 {
                     let after = After::new(Some(current_height), false);
-                    let after_sat = Satisfier::<bitcoin::PublicKey>::check_after(&after, *value);
-                    let inputs_sat = psbt_inputs_sat(psbt)
-                        .all(|sat| Satisfier::<bitcoin::PublicKey>::check_after(&sat, *value));
+                    let after_sat =
+                        Satisfier::<bitcoin::PublicKey>::check_after(&after, value.into());
+                    let inputs_sat = psbt_inputs_sat(psbt).all(|sat| {
+                        Satisfier::<bitcoin::PublicKey>::check_after(&sat, value.into())
+                    });
                     if after_sat && inputs_sat {
                         policy.satisfaction = policy.contribution.clone();
                     }
@@ -999,6 +1018,9 @@ impl<Ctx: ScriptContext + 'static> ExtractPolicy for Miniscript<DescriptorPublic
 
                 Policy::make_thresh(mapped, threshold)?
             }
+
+            // Unsupported
+            Terminal::RawPkH(_) => None,
         })
     }
 }
@@ -1124,16 +1146,15 @@ mod test {
     use crate::descriptor::{ExtractPolicy, IntoWalletDescriptor};
 
     use super::*;
-    use crate::descriptor::derived::AsDerived;
     use crate::descriptor::policy::SatisfiableItem::{EcdsaSignature, Multisig, Thresh};
     use crate::keys::{DescriptorKey, IntoDescriptorKey};
     use crate::wallet::signer::SignersContainer;
+    use alloc::{string::ToString, sync::Arc};
+    use assert_matches::assert_matches;
     use bitcoin::secp256k1::Secp256k1;
     use bitcoin::util::bip32;
     use bitcoin::Network;
-    use miniscript::DescriptorTrait;
-    use std::str::FromStr;
-    use std::sync::Arc;
+    use core::str::FromStr;
 
     const TPRV0_STR:&str = "tprv8ZgxMBicQKsPdZXrcHNLf5JAJWFAoJ2TrstMRdSKtEggz6PddbuSkvHKM9oKJyFgZV1B7rw8oChspxyYbtmEXYyg1AjfWbL3ho3XHDpHRZf";
     const TPRV1_STR:&str = "tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N";
@@ -1172,8 +1193,8 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint));
-        assert!(matches!(&policy.contribution, Satisfaction::None));
+        assert_matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint);
+        assert_matches!(&policy.contribution, Satisfaction::None);
 
         let desc = descriptor!(wpkh(prvkey)).unwrap();
         let (wallet_desc, keymap) = desc
@@ -1185,10 +1206,8 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint));
-        assert!(
-            matches!(&policy.contribution, Satisfaction::Complete {condition} if condition.csv == None && condition.timelock == None)
-        );
+        assert_matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint);
+        assert_matches!(&policy.contribution, Satisfaction::Complete {condition} if condition.csv.is_none() && condition.timelock.is_none());
     }
 
     // 2 pub keys descriptor, required 2 prv keys
@@ -1207,19 +1226,16 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(&policy.item, Multisig { keys, threshold } if threshold == &2usize
+        assert_matches!(&policy.item, Multisig { keys, threshold } if threshold == &2usize
             && keys[0] == PkOrF::Fingerprint(fingerprint0)
-            && keys[1] == PkOrF::Fingerprint(fingerprint1))
+            && keys[1] == PkOrF::Fingerprint(fingerprint1)
         );
         // TODO should this be "Satisfaction::None" since we have no prv keys?
         // TODO should items and conditions not be empty?
-        assert!(
-            matches!(&policy.contribution, Satisfaction::Partial { n, m, items, conditions, ..} if n == &2usize
+        assert_matches!(&policy.contribution, Satisfaction::Partial { n, m, items, conditions, ..} if n == &2usize
             && m == &2usize
             && items.is_empty()
             && conditions.is_empty()
-            )
         );
     }
 
@@ -1238,18 +1254,15 @@ mod test {
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
-        assert!(
-            matches!(&policy.item, Multisig { keys, threshold } if threshold == &2usize
+        assert_matches!(&policy.item, Multisig { keys, threshold } if threshold == &2usize
             && keys[0] == PkOrF::Fingerprint(fingerprint0)
-            && keys[1] == PkOrF::Fingerprint(fingerprint1))
+            && keys[1] == PkOrF::Fingerprint(fingerprint1)
         );
 
-        assert!(
-            matches!(&policy.contribution, Satisfaction::Partial { n, m, items, conditions, ..} if n == &2usize
+        assert_matches!(&policy.contribution, Satisfaction::Partial { n, m, items, conditions, ..} if n == &2usize
              && m == &2usize
              && items.len() == 1
              && conditions.contains_key(&0)
-            )
         );
     }
 
@@ -1271,18 +1284,15 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(&policy.item, Multisig { keys, threshold } if threshold == &1
+        assert_matches!(&policy.item, Multisig { keys, threshold } if threshold == &1
             && keys[0] == PkOrF::Fingerprint(fingerprint0)
-            && keys[1] == PkOrF::Fingerprint(fingerprint1))
+            && keys[1] == PkOrF::Fingerprint(fingerprint1)
         );
-        assert!(
-            matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &2
+        assert_matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &2
              && m == &1
              && items.len() == 2
              && conditions.contains_key(&vec![0])
              && conditions.contains_key(&vec![1])
-            )
         );
     }
 
@@ -1303,18 +1313,15 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(&policy.item, Multisig { keys, threshold } if threshold == &2
+        assert_matches!(&policy.item, Multisig { keys, threshold } if threshold == &2
             && keys[0] == PkOrF::Fingerprint(fingerprint0)
-            && keys[1] == PkOrF::Fingerprint(fingerprint1))
+            && keys[1] == PkOrF::Fingerprint(fingerprint1)
         );
 
-        assert!(
-            matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &2
+        assert_matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &2
              && m == &2
              && items.len() == 2
              && conditions.contains_key(&vec![0,1])
-            )
         );
     }
 
@@ -1329,31 +1336,27 @@ mod test {
         let (wallet_desc, keymap) = desc
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
-        let single_key = wallet_desc.derive(0);
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = single_key
+        let policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
 
-        assert!(matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint));
-        assert!(matches!(&policy.contribution, Satisfaction::None));
+        assert_matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint);
+        assert_matches!(&policy.contribution, Satisfaction::None);
 
         let desc = descriptor!(wpkh(prvkey)).unwrap();
         let (wallet_desc, keymap) = desc
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
-        let single_key = wallet_desc.derive(0);
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = single_key
+        let policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
 
-        assert!(matches!(&policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == &fingerprint));
-        assert!(
-            matches!(&policy.contribution, Satisfaction::Complete {condition} if condition.csv == None && condition.timelock == None)
-        );
+        assert_matches!(policy.item, EcdsaSignature(PkOrF::Fingerprint(f)) if f == fingerprint);
+        assert_matches!(policy.contribution, Satisfaction::Complete {condition} if condition.csv.is_none() && condition.timelock.is_none());
     }
 
     // single key, 1 prv and 1 pub key descriptor, required 1 prv keys
@@ -1368,25 +1371,21 @@ mod test {
         let (wallet_desc, keymap) = desc
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
-        let single_key = wallet_desc.derive(0);
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = single_key
+        let policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(&policy.item, Multisig { keys, threshold } if threshold == &1
+        assert_matches!(policy.item, Multisig { keys, threshold } if threshold == 1
             && keys[0] == PkOrF::Fingerprint(fingerprint0)
-            && keys[1] == PkOrF::Fingerprint(fingerprint1))
+            && keys[1] == PkOrF::Fingerprint(fingerprint1)
         );
-        assert!(
-            matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &2
-             && m == &1
+        assert_matches!(policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == 2
+             && m == 1
              && items.len() == 2
              && conditions.contains_key(&vec![0])
              && conditions.contains_key(&vec![1])
-            )
         );
     }
 
@@ -1418,18 +1417,14 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(&policy.item, Thresh { items, threshold } if items.len() == 3 && threshold == &2)
-        );
+        assert_matches!(&policy.item, Thresh { items, threshold } if items.len() == 3 && threshold == &2);
 
-        assert!(
-            matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &3
+        assert_matches!(&policy.contribution, Satisfaction::PartialComplete { n, m, items, conditions, .. } if n == &3
              && m == &2
              && items.len() == 3
              && conditions.get(&vec![0,1]).unwrap().iter().next().unwrap().csv.is_none()
-             && conditions.get(&vec![0,2]).unwrap().iter().next().unwrap().csv == Some(sequence)
-             && conditions.get(&vec![1,2]).unwrap().iter().next().unwrap().csv == Some(sequence)
-            )
+             && conditions.get(&vec![0,2]).unwrap().iter().next().unwrap().csv == Some(Sequence(sequence))
+             && conditions.get(&vec![1,2]).unwrap().iter().next().unwrap().csv == Some(Sequence(sequence))
         );
     }
 
@@ -1452,12 +1447,12 @@ mod test {
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = wallet_desc
+        let _policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
-        println!("desc policy = {:?}", policy); // TODO remove
-                                                // TODO how should this fail with mixed timelocks?
+        // println!("desc policy = {:?}", policy); // TODO remove
+        // TODO how should this fail with mixed timelocks?
     }
 
     // - multiple timelocks of the same type should be correctly merged together
@@ -1477,12 +1472,12 @@ mod test {
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = wallet_desc
+        let _policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
-        println!("desc policy = {:?}", policy); // TODO remove
-                                                // TODO how should this merge timelocks?
+        // println!("desc policy = {:?}", policy); // TODO remove
+        // TODO how should this merge timelocks?
         let (prvkey1, _pubkey1, _fingerprint1) = setup_keys(TPRV0_STR, PATH, &secp);
         let locktime_seconds0 = 500000100;
         let locktime_seconds1 = 500000200;
@@ -1495,12 +1490,12 @@ mod test {
             .into_wallet_descriptor(&secp, Network::Testnet)
             .unwrap();
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
-        let policy = wallet_desc
+        let _policy = wallet_desc
             .extract_policy(&signers_container, BuildSatisfaction::None, &secp)
             .unwrap()
             .unwrap();
 
-        println!("desc policy = {:?}", policy); // TODO remove
+        // println!("desc policy = {:?}", policy); // TODO remove
 
         // TODO how should this merge timelocks?
     }
@@ -1574,7 +1569,7 @@ mod test {
             .unwrap();
 
         let addr = wallet_desc
-            .as_derived(0, &secp)
+            .at_derivation_index(0)
             .address(Network::Testnet)
             .unwrap();
         assert_eq!(
@@ -1592,11 +1587,9 @@ mod test {
             .unwrap();
         //println!("{}", serde_json::to_string(&policy_alice_psbt).unwrap());
 
-        assert!(
-            matches!(&policy_alice_psbt.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &2
+        assert_matches!(&policy_alice_psbt.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &2
              && m == &2
              && items == &vec![0]
-            )
         );
 
         let psbt = Psbt::from_str(BOB_SIGNED_PSBT).unwrap();
@@ -1606,11 +1599,9 @@ mod test {
             .unwrap();
         //println!("{}", serde_json::to_string(&policy_bob_psbt).unwrap());
 
-        assert!(
-            matches!(&policy_bob_psbt.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &2
+        assert_matches!(&policy_bob_psbt.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &2
              && m == &2
              && items == &vec![1]
-            )
         );
 
         let psbt = Psbt::from_str(ALICE_BOB_SIGNED_PSBT).unwrap();
@@ -1618,11 +1609,9 @@ mod test {
             .extract_policy(&signers_container, BuildSatisfaction::Psbt(&psbt), &secp)
             .unwrap()
             .unwrap();
-        assert!(
-            matches!(&policy_alice_bob_psbt.satisfaction, Satisfaction::PartialComplete { n, m, items, .. } if n == &2
+        assert_matches!(&policy_alice_bob_psbt.satisfaction, Satisfaction::PartialComplete { n, m, items, .. } if n == &2
              && m == &2
              && items == &vec![0, 1]
-            )
         );
     }
 
@@ -1646,7 +1635,7 @@ mod test {
         let signers_container = Arc::new(SignersContainer::build(keymap, &wallet_desc, &secp));
 
         let addr = wallet_desc
-            .as_derived(0, &secp)
+            .at_derivation_index(0)
             .address(Network::Testnet)
             .unwrap();
         assert_eq!(
@@ -1666,11 +1655,9 @@ mod test {
             .extract_policy(&signers_container, build_sat, &secp)
             .unwrap()
             .unwrap();
-        assert!(
-            matches!(&policy.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &3
+        assert_matches!(&policy.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &3
              && m == &2
              && items.is_empty()
-            )
         );
         //println!("{}", serde_json::to_string(&policy).unwrap());
 
@@ -1684,11 +1671,9 @@ mod test {
             .extract_policy(&signers_container, build_sat_expired, &secp)
             .unwrap()
             .unwrap();
-        assert!(
-            matches!(&policy_expired.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &3
+        assert_matches!(&policy_expired.satisfaction, Satisfaction::Partial { n, m, items, .. } if n == &3
              && m == &2
              && items == &vec![0]
-            )
         );
         //println!("{}", serde_json::to_string(&policy_expired).unwrap());
 
@@ -1704,11 +1689,9 @@ mod test {
             .extract_policy(&signers_container, build_sat_expired_signed, &secp)
             .unwrap()
             .unwrap();
-        assert!(
-            matches!(&policy_expired_signed.satisfaction, Satisfaction::PartialComplete { n, m, items, .. } if n == &3
+        assert_matches!(&policy_expired_signed.satisfaction, Satisfaction::PartialComplete { n, m, items, .. } if n == &3
              && m == &2
              && items == &vec![0, 1]
-            )
         );
         //println!("{}", serde_json::to_string(&policy_expired_signed).unwrap());
     }
@@ -1783,12 +1766,8 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(policy.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2)
-        );
-        assert!(
-            matches!(policy.contribution, Satisfaction::PartialComplete { n: 2, m: 1, items, .. } if items == vec![1])
-        );
+        assert_matches!(policy.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2);
+        assert_matches!(policy.contribution, Satisfaction::PartialComplete { n: 2, m: 1, items, .. } if items == vec![1]);
 
         let alice_sig = SatisfiableItem::SchnorrSignature(PkOrF::Fingerprint(alice_fing));
         let bob_sig = SatisfiableItem::SchnorrSignature(PkOrF::Fingerprint(bob_fing));
@@ -1880,19 +1859,11 @@ mod test {
             .unwrap()
             .unwrap();
 
-        assert!(
-            matches!(policy_unsigned.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2)
-        );
-        assert!(
-            matches!(policy_unsigned.satisfaction, Satisfaction::Partial { n: 2, m: 1, items, .. } if items.is_empty())
-        );
+        assert_matches!(policy_unsigned.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2);
+        assert_matches!(policy_unsigned.satisfaction, Satisfaction::Partial { n: 2, m: 1, items, .. } if items.is_empty());
 
-        assert!(
-            matches!(policy_signed.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2)
-        );
-        assert!(
-            matches!(policy_signed.satisfaction, Satisfaction::PartialComplete { n: 2, m: 1, items, .. } if items == vec![0, 1])
-        );
+        assert_matches!(policy_signed.item, SatisfiableItem::Thresh { ref items, threshold: 1 } if items.len() == 2);
+        assert_matches!(policy_signed.satisfaction, Satisfaction::PartialComplete { n: 2, m: 1, items, .. } if items == vec![0, 1]);
 
         let satisfied_items = match policy_signed.item {
             SatisfiableItem::Thresh { items, .. } => items,

crates/bdk/src/descriptor/template.rs

@@ -73,22 +73,16 @@ impl<T: DescriptorTemplate> IntoWalletDescriptor for T {
 ///
 /// ```
 /// # use bdk::bitcoin::{PrivateKey, Network};
-/// # use bdk::{Wallet};
-/// # use bdk::database::MemoryDatabase;
+/// # use bdk::Wallet;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::P2Pkh;
 ///
 /// let key =
 ///     bitcoin::PrivateKey::from_wif("cTc4vURSzdx6QE6KVynWGomDbLaA75dNALMNyfjh3p8DRRar84Um")?;
-/// let wallet = Wallet::new(
-///     P2Pkh(key),
-///     None,
-///     Network::Testnet,
-///     MemoryDatabase::default(),
-/// )?;
+/// let mut wallet = Wallet::new_no_persist(P2Pkh(key), None, Network::Testnet)?;
 ///
 /// assert_eq!(
-///     wallet.get_address(New)?.to_string(),
+///     wallet.get_address(New).to_string(),
 ///     "mwJ8hxFYW19JLuc65RCTaP4v1rzVU8cVMT"
 /// );
 /// # Ok::<_, Box<dyn std::error::Error>>(())
@@ -107,22 +101,16 @@ impl<K: IntoDescriptorKey<Legacy>> DescriptorTemplate for P2Pkh<K> {
 ///
 /// ```
 /// # use bdk::bitcoin::{PrivateKey, Network};
-/// # use bdk::{Wallet};
-/// # use bdk::database::MemoryDatabase;
-/// # use bdk::wallet::AddressIndex::New;
+/// # use bdk::Wallet;
 /// use bdk::template::P2Wpkh_P2Sh;
+/// use bdk::wallet::AddressIndex;
 ///
 /// let key =
 ///     bitcoin::PrivateKey::from_wif("cTc4vURSzdx6QE6KVynWGomDbLaA75dNALMNyfjh3p8DRRar84Um")?;
-/// let wallet = Wallet::new(
-///     P2Wpkh_P2Sh(key),
-///     None,
-///     Network::Testnet,
-///     MemoryDatabase::default(),
-/// )?;
+/// let mut wallet = Wallet::new_no_persist(P2Wpkh_P2Sh(key), None, Network::Testnet)?;
 ///
 /// assert_eq!(
-///     wallet.get_address(New)?.to_string(),
+///     wallet.get_address(AddressIndex::New).to_string(),
 ///     "2NB4ox5VDRw1ecUv6SnT3VQHPXveYztRqk5"
 /// );
 /// # Ok::<_, Box<dyn std::error::Error>>(())
@@ -143,21 +131,15 @@ impl<K: IntoDescriptorKey<Segwitv0>> DescriptorTemplate for P2Wpkh_P2Sh<K> {
 /// ```
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet};
-/// # use bdk::database::MemoryDatabase;
-/// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::P2Wpkh;
+/// use bdk::wallet::AddressIndex::New;
 ///
 /// let key =
 ///     bitcoin::PrivateKey::from_wif("cTc4vURSzdx6QE6KVynWGomDbLaA75dNALMNyfjh3p8DRRar84Um")?;
-/// let wallet = Wallet::new(
-///     P2Wpkh(key),
-///     None,
-///     Network::Testnet,
-///     MemoryDatabase::default(),
-/// )?;
+/// let mut wallet = Wallet::new_no_persist(P2Wpkh(key), None, Network::Testnet)?;
 ///
 /// assert_eq!(
-///     wallet.get_address(New)?.to_string(),
+///     wallet.get_address(New).to_string(),
 ///     "tb1q4525hmgw265tl3drrl8jjta7ayffu6jf68ltjd"
 /// );
 /// # Ok::<_, Box<dyn std::error::Error>>(())
@@ -182,20 +164,18 @@ impl<K: IntoDescriptorKey<Segwitv0>> DescriptorTemplate for P2Wpkh<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip44;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPrivKey::from_str("tprv8ZgxMBicQKsPeZRHk4rTG6orPS2CRNFX3njhUXx5vj9qGog5ZMH4uGReDWN5kCkY3jmWEtWause41CDvBRXD1shKknAMKxT99o9qUTRVC6m")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip44(key.clone(), KeychainKind::External),
 ///     Some(Bip44(key, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "mmogjc7HJEZkrLqyQYqJmxUqFaC7i4uf89");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "pkh([c55b303f/44'/1'/0']tpubDCuorCpzvYS2LCD75BR46KHE8GdDeg1wsAgNZeNr6DaB5gQK1o14uErKwKLuFmeemkQ6N2m3rNgvctdJLyr7nwu2yia7413Hhg8WWE44cgT/0/*)#5wrnv0xt");
+/// assert_eq!(wallet.get_address(New).to_string(), "mmogjc7HJEZkrLqyQYqJmxUqFaC7i4uf89");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "pkh([c55b303f/44'/1'/0']tpubDCuorCpzvYS2LCD75BR46KHE8GdDeg1wsAgNZeNr6DaB5gQK1o14uErKwKLuFmeemkQ6N2m3rNgvctdJLyr7nwu2yia7413Hhg8WWE44cgT/0/*)#5wrnv0xt");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip44<K: DerivableKey<Legacy>>(pub K, pub KeychainKind);
@@ -221,28 +201,29 @@ impl<K: DerivableKey<Legacy>> DescriptorTemplate for Bip44<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip44Public;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPubKey::from_str("tpubDDDzQ31JkZB7VxUr9bjvBivDdqoFLrDPyLWtLapArAi51ftfmCb2DPxwLQzX65iNcXz1DGaVvyvo6JQ6rTU73r2gqdEo8uov9QKRb7nKCSU")?;
 /// let fingerprint = bitcoin::util::bip32::Fingerprint::from_str("c55b303f")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip44Public(key.clone(), fingerprint, KeychainKind::External),
 ///     Some(Bip44Public(key, fingerprint, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "miNG7dJTzJqNbFS19svRdTCisC65dsubtR");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "pkh([c55b303f/44'/0'/0']tpubDDDzQ31JkZB7VxUr9bjvBivDdqoFLrDPyLWtLapArAi51ftfmCb2DPxwLQzX65iNcXz1DGaVvyvo6JQ6rTU73r2gqdEo8uov9QKRb7nKCSU/0/*)#xgaaevjx");
+/// assert_eq!(wallet.get_address(New).to_string(), "miNG7dJTzJqNbFS19svRdTCisC65dsubtR");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "pkh([c55b303f/44'/1'/0']tpubDDDzQ31JkZB7VxUr9bjvBivDdqoFLrDPyLWtLapArAi51ftfmCb2DPxwLQzX65iNcXz1DGaVvyvo6JQ6rTU73r2gqdEo8uov9QKRb7nKCSU/0/*)#cfhumdqz");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip44Public<K: DerivableKey<Legacy>>(pub K, pub bip32::Fingerprint, pub KeychainKind);
 
 impl<K: DerivableKey<Legacy>> DescriptorTemplate for Bip44Public<K> {
     fn build(self, network: Network) -> Result<DescriptorTemplateOut, DescriptorError> {
-        P2Pkh(legacy::make_bipxx_public(44, self.0, self.1, self.2)?).build(network)
+        P2Pkh(legacy::make_bipxx_public(
+            44, self.0, self.1, self.2, network,
+        )?)
+        .build(network)
     }
 }
 
@@ -258,20 +239,18 @@ impl<K: DerivableKey<Legacy>> DescriptorTemplate for Bip44Public<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip49;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPrivKey::from_str("tprv8ZgxMBicQKsPeZRHk4rTG6orPS2CRNFX3njhUXx5vj9qGog5ZMH4uGReDWN5kCkY3jmWEtWause41CDvBRXD1shKknAMKxT99o9qUTRVC6m")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip49(key.clone(), KeychainKind::External),
 ///     Some(Bip49(key, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "2N4zkWAoGdUv4NXhSsU8DvS5MB36T8nKHEB");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "sh(wpkh([c55b303f/49'/1'/0']tpubDDYr4kdnZgjjShzYNjZUZXUUtpXaofdkMaipyS8ThEh45qFmhT4hKYways7UXmg6V7het1QiFo9kf4kYUXyDvV4rHEyvSpys9pjCB3pukxi/0/*))#s9vxlc8e");
+/// assert_eq!(wallet.get_address(New).to_string(), "2N4zkWAoGdUv4NXhSsU8DvS5MB36T8nKHEB");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "sh(wpkh([c55b303f/49'/1'/0']tpubDDYr4kdnZgjjShzYNjZUZXUUtpXaofdkMaipyS8ThEh45qFmhT4hKYways7UXmg6V7het1QiFo9kf4kYUXyDvV4rHEyvSpys9pjCB3pukxi/0/*))#s9vxlc8e");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip49<K: DerivableKey<Segwitv0>>(pub K, pub KeychainKind);
@@ -284,7 +263,7 @@ impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip49<K> {
 
 /// BIP49 public template. Expands to `sh(wpkh(key/{0,1}/*))`
 ///
-/// This assumes that the key used has already been derived with `m/49'/0'/0'`.
+/// This assumes that the key used has already been derived with `m/49'/0'/0'` for Mainnet or `m/49'/1'/0'` for Testnet.
 ///
 /// This template requires the parent fingerprint to populate correctly the metadata of PSBTs.
 ///
@@ -297,28 +276,29 @@ impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip49<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip49Public;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPubKey::from_str("tpubDC49r947KGK52X5rBWS4BLs5m9SRY3pYHnvRrm7HcybZ3BfdEsGFyzCMzayi1u58eT82ZeyFZwH7DD6Q83E3fM9CpfMtmnTygnLfP59jL9L")?;
 /// let fingerprint = bitcoin::util::bip32::Fingerprint::from_str("c55b303f")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip49Public(key.clone(), fingerprint, KeychainKind::External),
 ///     Some(Bip49Public(key, fingerprint, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "2N3K4xbVAHoiTQSwxkZjWDfKoNC27pLkYnt");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "sh(wpkh([c55b303f/49'/0'/0']tpubDC49r947KGK52X5rBWS4BLs5m9SRY3pYHnvRrm7HcybZ3BfdEsGFyzCMzayi1u58eT82ZeyFZwH7DD6Q83E3fM9CpfMtmnTygnLfP59jL9L/0/*))#gsmdv4xr");
+/// assert_eq!(wallet.get_address(New).to_string(), "2N3K4xbVAHoiTQSwxkZjWDfKoNC27pLkYnt");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "sh(wpkh([c55b303f/49'/1'/0']tpubDC49r947KGK52X5rBWS4BLs5m9SRY3pYHnvRrm7HcybZ3BfdEsGFyzCMzayi1u58eT82ZeyFZwH7DD6Q83E3fM9CpfMtmnTygnLfP59jL9L/0/*))#3tka9g0q");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip49Public<K: DerivableKey<Segwitv0>>(pub K, pub bip32::Fingerprint, pub KeychainKind);
 
 impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip49Public<K> {
     fn build(self, network: Network) -> Result<DescriptorTemplateOut, DescriptorError> {
-        P2Wpkh_P2Sh(segwit_v0::make_bipxx_public(49, self.0, self.1, self.2)?).build(network)
+        P2Wpkh_P2Sh(segwit_v0::make_bipxx_public(
+            49, self.0, self.1, self.2, network,
+        )?)
+        .build(network)
     }
 }
 
@@ -334,20 +314,18 @@ impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip49Public<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip84;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPrivKey::from_str("tprv8ZgxMBicQKsPeZRHk4rTG6orPS2CRNFX3njhUXx5vj9qGog5ZMH4uGReDWN5kCkY3jmWEtWause41CDvBRXD1shKknAMKxT99o9qUTRVC6m")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip84(key.clone(), KeychainKind::External),
 ///     Some(Bip84(key, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "tb1qhl85z42h7r4su5u37rvvw0gk8j2t3n9y7zsg4n");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "wpkh([c55b303f/84'/1'/0']tpubDDc5mum24DekpNw92t6fHGp8Gr2JjF9J7i4TZBtN6Vp8xpAULG5CFaKsfugWa5imhrQQUZKXe261asP5koDHo5bs3qNTmf3U3o4v9SaB8gg/0/*)#6kfecsmr");
+/// assert_eq!(wallet.get_address(New).to_string(), "tb1qhl85z42h7r4su5u37rvvw0gk8j2t3n9y7zsg4n");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "wpkh([c55b303f/84'/1'/0']tpubDDc5mum24DekpNw92t6fHGp8Gr2JjF9J7i4TZBtN6Vp8xpAULG5CFaKsfugWa5imhrQQUZKXe261asP5koDHo5bs3qNTmf3U3o4v9SaB8gg/0/*)#6kfecsmr");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip84<K: DerivableKey<Segwitv0>>(pub K, pub KeychainKind);
@@ -360,7 +338,7 @@ impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip84<K> {
 
 /// BIP84 public template. Expands to `wpkh(key/{0,1}/*)`
 ///
-/// This assumes that the key used has already been derived with `m/84'/0'/0'`.
+/// This assumes that the key used has already been derived with `m/84'/0'/0'` for Mainnet or `m/84'/1'/0'` for Testnet.
 ///
 /// This template requires the parent fingerprint to populate correctly the metadata of PSBTs.
 ///
@@ -373,28 +351,29 @@ impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip84<K> {
 /// # use std::str::FromStr;
 /// # use bdk::bitcoin::{PrivateKey, Network};
 /// # use bdk::{Wallet,  KeychainKind};
-/// # use bdk::database::MemoryDatabase;
 /// # use bdk::wallet::AddressIndex::New;
 /// use bdk::template::Bip84Public;
 ///
 /// let key = bitcoin::util::bip32::ExtendedPubKey::from_str("tpubDC2Qwo2TFsaNC4ju8nrUJ9mqVT3eSgdmy1yPqhgkjwmke3PRXutNGRYAUo6RCHTcVQaDR3ohNU9we59brGHuEKPvH1ags2nevW5opEE9Z5Q")?;
 /// let fingerprint = bitcoin::util::bip32::Fingerprint::from_str("c55b303f")?;
-/// let wallet = Wallet::new(
+/// let mut wallet = Wallet::new_no_persist(
 ///     Bip84Public(key.clone(), fingerprint, KeychainKind::External),
 ///     Some(Bip84Public(key, fingerprint, KeychainKind::Internal)),
 ///     Network::Testnet,
-///     MemoryDatabase::default()
 /// )?;
 ///
-/// assert_eq!(wallet.get_address(New)?.to_string(), "tb1qedg9fdlf8cnnqfd5mks6uz5w4kgpk2pr6y4qc7");
-/// assert_eq!(wallet.public_descriptor(KeychainKind::External)?.unwrap().to_string(), "wpkh([c55b303f/84\'/0\'/0\']tpubDC2Qwo2TFsaNC4ju8nrUJ9mqVT3eSgdmy1yPqhgkjwmke3PRXutNGRYAUo6RCHTcVQaDR3ohNU9we59brGHuEKPvH1ags2nevW5opEE9Z5Q/0/*)#nkk5dtkg");
+/// assert_eq!(wallet.get_address(New).to_string(), "tb1qedg9fdlf8cnnqfd5mks6uz5w4kgpk2pr6y4qc7");
+/// assert_eq!(wallet.public_descriptor(KeychainKind::External).unwrap().to_string(), "wpkh([c55b303f/84'/1'/0']tpubDC2Qwo2TFsaNC4ju8nrUJ9mqVT3eSgdmy1yPqhgkjwmke3PRXutNGRYAUo6RCHTcVQaDR3ohNU9we59brGHuEKPvH1ags2nevW5opEE9Z5Q/0/*)#dhu402yv");
 /// # Ok::<_, Box<dyn std::error::Error>>(())
 /// ```
 pub struct Bip84Public<K: DerivableKey<Segwitv0>>(pub K, pub bip32::Fingerprint, pub KeychainKind);
 
 impl<K: DerivableKey<Segwitv0>> DescriptorTemplate for Bip84Public<K> {
     fn build(self, network: Network) -> Result<DescriptorTemplateOut, DescriptorError> {
-        P2Wpkh(segwit_v0::make_bipxx_public(84, self.0, self.1, self.2)?).build(network)
+        P2Wpkh(segwit_v0::make_bipxx_public(
+            84, self.0, self.1, self.2, network,
+        )?)
+        .build(network)
     }
 }
 
@@ -409,7 +388,7 @@ macro_rules! expand_make_bipxx {
                 keychain: KeychainKind,
                 network: Network,
             ) -> Result<impl IntoDescriptorKey<$ctx>, DescriptorError> {
-                let mut derivation_path = Vec::with_capacity(4);
+                let mut derivation_path = alloc::vec::Vec::with_capacity(4);
                 derivation_path.push(bip32::ChildNumber::from_hardened_idx(bip)?);
 
                 match network {
@@ -440,6 +419,7 @@ macro_rules! expand_make_bipxx {
                 key: K,
                 parent_fingerprint: bip32::Fingerprint,
                 keychain: KeychainKind,
+                network: Network,
             ) -> Result<impl IntoDescriptorKey<$ctx>, DescriptorError> {
                 let derivation_path: bip32::DerivationPath = match keychain {
                     KeychainKind::External => vec![bip32::ChildNumber::from_normal_idx(0)?].into(),
@@ -448,7 +428,10 @@ macro_rules! expand_make_bipxx {
 
                 let source_path = bip32::DerivationPath::from(vec![
                     bip32::ChildNumber::from_hardened_idx(bip)?,
-                    bip32::ChildNumber::from_hardened_idx(0)?,
+                    match network {
+                        Network::Bitcoin => bip32::ChildNumber::from_hardened_idx(0)?,
+                        _ => bip32::ChildNumber::from_hardened_idx(1)?,
+                    },
                     bip32::ChildNumber::from_hardened_idx(0)?,
                 ]);
 
@@ -465,15 +448,15 @@ expand_make_bipxx!(segwit_v0, Segwitv0);
 mod test {
     // test existing descriptor templates, make sure they are expanded to the right descriptors
 
-    use std::str::FromStr;
+    use alloc::{string::ToString, vec::Vec};
+    use core::str::FromStr;
 
     use super::*;
-    use crate::descriptor::derived::AsDerived;
     use crate::descriptor::{DescriptorError, DescriptorMeta};
     use crate::keys::ValidNetworks;
+    use assert_matches::assert_matches;
     use bitcoin::network::constants::Network::Regtest;
-    use bitcoin::secp256k1::Secp256k1;
-    use miniscript::descriptor::{DescriptorPublicKey, DescriptorTrait, KeyMap};
+    use miniscript::descriptor::{DescriptorPublicKey, KeyMap};
     use miniscript::Descriptor;
 
     // BIP44 `pkh(key/44'/{0,1}'/0'/{0,1}/*)`
@@ -490,9 +473,9 @@ mod test {
         if let ExtendedDescriptor::Pkh(pkh) = xdesc.0 {
             let path: Vec<ChildNumber> = pkh.into_inner().full_derivation_path().into();
             let purpose = path.get(0).unwrap();
-            assert!(matches!(purpose, Hardened { index: 44 }));
+            assert_matches!(purpose, Hardened { index: 44 });
             let coin_type = path.get(1).unwrap();
-            assert!(matches!(coin_type, Hardened { index: 0 }));
+            assert_matches!(coin_type, Hardened { index: 0 });
         }
 
         let tprvkey = bitcoin::util::bip32::ExtendedPrivKey::from_str("tprv8ZgxMBicQKsPcx5nBGsR63Pe8KnRUqmbJNENAfGftF3yuXoMMoVJJcYeUw5eVkm9WBPjWYt6HMWYJNesB5HaNVBaFc1M6dRjWSYnmewUMYy").unwrap();
@@ -504,9 +487,9 @@ mod test {
         if let ExtendedDescriptor::Pkh(pkh) = tdesc.0 {
             let path: Vec<ChildNumber> = pkh.into_inner().full_derivation_path().into();
             let purpose = path.get(0).unwrap();
-            assert!(matches!(purpose, Hardened { index: 44 }));
+            assert_matches!(purpose, Hardened { index: 44 });
             let coin_type = path.get(1).unwrap();
-            assert!(matches!(coin_type, Hardened { index: 1 }));
+            assert_matches!(coin_type, Hardened { index: 1 });
         }
     }
 
@@ -517,17 +500,15 @@ mod test {
         is_fixed: bool,
         expected: &[&str],
     ) {
-        let secp = Secp256k1::new();
-
         let (desc, _key_map, _networks) = desc.unwrap();
         assert_eq!(desc.is_witness(), is_witness);
-        assert_eq!(!desc.is_deriveable(), is_fixed);
+        assert_eq!(!desc.has_wildcard(), is_fixed);
         for i in 0..expected.len() {
             let index = i as u32;
-            let child_desc = if !desc.is_deriveable() {
-                desc.as_derived_fixed(&secp)
+            let child_desc = if !desc.has_wildcard() {
+                desc.at_derivation_index(0)
             } else {
-                desc.as_derived(index, &secp)
+                desc.at_derivation_index(index)
             };
             let address = child_desc.address(Regtest).unwrap();
             assert_eq!(address.to_string(), *expected.get(i).unwrap());

crates/bdk/src/error.rs

@@ -9,21 +9,17 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-use std::fmt;
-
 use crate::bitcoin::Network;
-use crate::{descriptor, wallet, wallet::address_validator};
-use bitcoin::OutPoint;
+use crate::{descriptor, wallet};
+use alloc::{string::String, vec::Vec};
+use bitcoin::{OutPoint, Txid};
+use core::fmt;
 
 /// Errors that can be thrown by the [`Wallet`](crate::wallet::Wallet)
 #[derive(Debug)]
 pub enum Error {
-    /// Wrong number of bytes found when trying to convert to u32
-    InvalidU32Bytes(Vec<u8>),
     /// Generic error
     Generic(String),
-    /// This error is thrown when trying to convert Bare and Public key script to address
-    ScriptDoesntHaveAddressForm,
     /// Cannot build a tx without recipients
     NoRecipients,
     /// `manually_selected_only` option is selected but no utxo has been passed
@@ -79,78 +75,94 @@ pub enum Error {
     InvalidPolicyPathError(crate::descriptor::policy::PolicyError),
     /// Signing error
     Signer(crate::wallet::signer::SignerError),
-    /// Invalid network
-    InvalidNetwork {
-        /// requested network, for example what is given as bdk-cli option
-        requested: Network,
-        /// found network, for example the network of the bitcoin node
-        found: Network,
-    },
-    #[cfg(feature = "verify")]
-    /// Transaction verification error
-    Verification(crate::wallet::verify::VerifyError),
-
-    /// Progress value must be between `0.0` (included) and `100.0` (included)
-    InvalidProgressValue(f32),
-    /// Progress update error (maybe the channel has been closed)
-    ProgressUpdateError,
     /// Requested outpoint doesn't exist in the tx (vout greater than available outputs)
     InvalidOutpoint(OutPoint),
-
     /// Error related to the parsing and usage of descriptors
     Descriptor(crate::descriptor::error::Error),
-    /// Error that can be returned to fail the validation of an address
-    AddressValidator(crate::wallet::address_validator::AddressValidatorError),
-    /// Encoding error
-    Encode(bitcoin::consensus::encode::Error),
     /// Miniscript error
     Miniscript(miniscript::Error),
+    /// Miniscript PSBT error
+    MiniscriptPsbt(MiniscriptPsbtError),
     /// BIP32 error
     Bip32(bitcoin::util::bip32::Error),
-    /// An ECDSA error
-    Secp256k1(bitcoin::secp256k1::Error),
-    /// Error serializing or deserializing JSON data
-    Json(serde_json::Error),
-    /// Hex decoding error
-    Hex(bitcoin::hashes::hex::Error),
     /// Partially signed bitcoin transaction error
     Psbt(bitcoin::util::psbt::Error),
-    /// Partially signed bitcoin transaction parse error
-    PsbtParse(bitcoin::util::psbt::PsbtParseError),
-
-    //KeyMismatch(bitcoin::secp256k1::PublicKey, bitcoin::secp256k1::PublicKey),
-    //MissingInputUTXO(usize),
-    //InvalidAddressNetwork(Address),
-    //DifferentTransactions,
-    //DifferentDescriptorStructure,
-    //Uncapable(crate::blockchain::Capability),
-    //MissingCachedAddresses,
-    #[cfg(feature = "electrum")]
-    /// Electrum client error
-    Electrum(electrum_client::Error),
-    #[cfg(feature = "esplora")]
-    /// Esplora client error
-    Esplora(Box<crate::blockchain::esplora::EsploraError>),
-    #[cfg(feature = "compact_filters")]
-    /// Compact filters client error)
-    CompactFilters(crate::blockchain::compact_filters::CompactFiltersError),
-    #[cfg(feature = "key-value-db")]
-    /// Sled database error
-    Sled(sled::Error),
-    #[cfg(feature = "rpc")]
-    /// Rpc client error
-    Rpc(bitcoincore_rpc::Error),
-    #[cfg(feature = "sqlite")]
-    /// Rusqlite client error
-    Rusqlite(rusqlite::Error),
 }
 
-impl fmt::Display for Error {
+/// Errors returned by miniscript when updating inconsistent PSBTs
+#[derive(Debug, Clone)]
+pub enum MiniscriptPsbtError {
+    Conversion(miniscript::descriptor::ConversionError),
+    UtxoUpdate(miniscript::psbt::UtxoUpdateError),
+    OutputUpdate(miniscript::psbt::OutputUpdateError),
+}
+
+impl fmt::Display for MiniscriptPsbtError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self)
+        match self {
+            Self::Conversion(err) => write!(f, "Conversion error: {}", err),
+            Self::UtxoUpdate(err) => write!(f, "UTXO update error: {}", err),
+            Self::OutputUpdate(err) => write!(f, "Output update error: {}", err),
+        }
     }
 }
 
+impl std::error::Error for MiniscriptPsbtError {}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Generic(err) => write!(f, "Generic error: {}", err),
+            Self::NoRecipients => write!(f, "Cannot build tx without recipients"),
+            Self::NoUtxosSelected => write!(f, "No UTXO selected"),
+            Self::OutputBelowDustLimit(limit) => {
+                write!(f, "Output below the dust limit: {}", limit)
+            }
+            Self::InsufficientFunds { needed, available } => write!(
+                f,
+                "Insufficient funds: {} sat available of {} sat needed",
+                available, needed
+            ),
+            Self::BnBTotalTriesExceeded => {
+                write!(f, "Branch and bound coin selection: total tries exceeded")
+            }
+            Self::BnBNoExactMatch => write!(f, "Branch and bound coin selection: not exact match"),
+            Self::UnknownUtxo => write!(f, "UTXO not found in the internal database"),
+            Self::TransactionNotFound => {
+                write!(f, "Transaction not found in the internal database")
+            }
+            Self::TransactionConfirmed => write!(f, "Transaction already confirmed"),
+            Self::IrreplaceableTransaction => write!(f, "Transaction can't be replaced"),
+            Self::FeeRateTooLow { required } => write!(
+                f,
+                "Fee rate too low: required {} sat/vbyte",
+                required.as_sat_per_vb()
+            ),
+            Self::FeeTooLow { required } => write!(f, "Fee to low: required {} sat", required),
+            Self::FeeRateUnavailable => write!(f, "Fee rate unavailable"),
+            Self::MissingKeyOrigin(err) => write!(f, "Missing key origin: {}", err),
+            Self::Key(err) => write!(f, "Key error: {}", err),
+            Self::ChecksumMismatch => write!(f, "Descriptor checksum mismatch"),
+            Self::SpendingPolicyRequired(keychain_kind) => {
+                write!(f, "Spending policy required: {:?}", keychain_kind)
+            }
+            Self::InvalidPolicyPathError(err) => write!(f, "Invalid policy path: {}", err),
+            Self::Signer(err) => write!(f, "Signer error: {}", err),
+            Self::InvalidOutpoint(outpoint) => write!(
+                f,
+                "Requested outpoint doesn't exist in the tx: {}",
+                outpoint
+            ),
+            Self::Descriptor(err) => write!(f, "Descriptor error: {}", err),
+            Self::Miniscript(err) => write!(f, "Miniscript error: {}", err),
+            Self::MiniscriptPsbt(err) => write!(f, "Miniscript PSBT error: {}", err),
+            Self::Bip32(err) => write!(f, "BIP32 error: {}", err),
+            Self::Psbt(err) => write!(f, "PSBT error: {}", err),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
 impl std::error::Error for Error {}
 
 macro_rules! impl_error {
@@ -158,7 +170,7 @@ macro_rules! impl_error {
         impl_error!($from, $to, Error);
     };
     ( $from:ty, $to:ident, $impl_for:ty ) => {
-        impl std::convert::From<$from> for $impl_for {
+        impl core::convert::From<$from> for $impl_for {
             fn from(err: $from) -> Self {
                 <$impl_for>::$to(err)
             }
@@ -167,7 +179,6 @@ macro_rules! impl_error {
 }
 
 impl_error!(descriptor::error::Error, Descriptor);
-impl_error!(address_validator::AddressValidatorError, AddressValidator);
 impl_error!(descriptor::policy::PolicyError, InvalidPolicyPathError);
 impl_error!(wallet::signer::SignerError, Signer);
 
@@ -182,47 +193,7 @@ impl From<crate::keys::KeyError> for Error {
     }
 }
 
-impl_error!(bitcoin::consensus::encode::Error, Encode);
 impl_error!(miniscript::Error, Miniscript);
+impl_error!(MiniscriptPsbtError, MiniscriptPsbt);
 impl_error!(bitcoin::util::bip32::Error, Bip32);
-impl_error!(bitcoin::secp256k1::Error, Secp256k1);
-impl_error!(serde_json::Error, Json);
-impl_error!(bitcoin::hashes::hex::Error, Hex);
 impl_error!(bitcoin::util::psbt::Error, Psbt);
-impl_error!(bitcoin::util::psbt::PsbtParseError, PsbtParse);
-
-#[cfg(feature = "electrum")]
-impl_error!(electrum_client::Error, Electrum);
-#[cfg(feature = "key-value-db")]
-impl_error!(sled::Error, Sled);
-#[cfg(feature = "rpc")]
-impl_error!(bitcoincore_rpc::Error, Rpc);
-#[cfg(feature = "sqlite")]
-impl_error!(rusqlite::Error, Rusqlite);
-
-#[cfg(feature = "compact_filters")]
-impl From<crate::blockchain::compact_filters::CompactFiltersError> for Error {
-    fn from(other: crate::blockchain::compact_filters::CompactFiltersError) -> Self {
-        match other {
-            crate::blockchain::compact_filters::CompactFiltersError::Global(e) => *e,
-            err => Error::CompactFilters(err),
-        }
-    }
-}
-
-#[cfg(feature = "verify")]
-impl From<crate::wallet::verify::VerifyError> for Error {
-    fn from(other: crate::wallet::verify::VerifyError) -> Self {
-        match other {
-            crate::wallet::verify::VerifyError::Global(inner) => *inner,
-            err => Error::Verification(err),
-        }
-    }
-}
-
-#[cfg(feature = "esplora")]
-impl From<crate::blockchain::esplora::EsploraError> for Error {
-    fn from(other: crate::blockchain::esplora::EsploraError) -> Self {
-        Error::Esplora(Box::new(other))
-    }
-}

crates/bdk/src/keys/bip39.rs

@@ -14,6 +14,7 @@
 // TODO: maybe write our own implementation of bip39? Seems stupid to have an extra dependency for
 // something that should be fairly simple to re-implement.
 
+use alloc::string::String;
 use bitcoin::util::bip32;
 use bitcoin::Network;
 
@@ -150,7 +151,8 @@ impl<Ctx: ScriptContext> GeneratableKey<Ctx> for Mnemonic {
 
 #[cfg(test)]
 mod test {
-    use std::str::FromStr;
+    use alloc::string::ToString;
+    use core::str::FromStr;
 
     use bitcoin::util::bip32;
 

crates/bdk/src/keys/mod.rs

@@ -11,11 +11,13 @@
 
 //! Key formats
 
-use std::any::TypeId;
-use std::collections::HashSet;
-use std::marker::PhantomData;
-use std::ops::Deref;
-use std::str::FromStr;
+use crate::collections::HashSet;
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
+use core::any::TypeId;
+use core::marker::PhantomData;
+use core::ops::Deref;
+use core::str::FromStr;
 
 use bitcoin::secp256k1::{self, Secp256k1, Signing};
 
@@ -24,8 +26,8 @@ use bitcoin::{Network, PrivateKey, PublicKey, XOnlyPublicKey};
 
 use miniscript::descriptor::{Descriptor, DescriptorXKey, Wildcard};
 pub use miniscript::descriptor::{
-    DescriptorPublicKey, DescriptorSecretKey, DescriptorSinglePriv, DescriptorSinglePub, KeyMap,
-    SinglePubKey, SortedMultiVec,
+    DescriptorPublicKey, DescriptorSecretKey, KeyMap, SinglePriv, SinglePub, SinglePubKey,
+    SortedMultiVec,
 };
 pub use miniscript::ScriptContext;
 use miniscript::{Miniscript, Terminal};
@@ -40,7 +42,7 @@ pub mod bip39;
 /// Set of valid networks for a key
 pub type ValidNetworks = HashSet<Network>;
 
-/// Create a set containing mainnet, testnet and regtest
+/// Create a set containing mainnet, testnet, signet, and regtest
 pub fn any_network() -> ValidNetworks {
     vec![
         Network::Bitcoin,
@@ -95,7 +97,7 @@ impl<Ctx: ScriptContext> DescriptorKey<Ctx> {
     }
 
     // This method is used internally by `bdk::fragment!` and `bdk::descriptor!`. It has to be
-    // public because it is effectively called by external crates, once the macros are expanded,
+    // public because it is effectively called by external crates once the macros are expanded,
     // but since it is not meant to be part of the public api we hide it from the docs.
     #[doc(hidden)]
     pub fn extract(
@@ -110,7 +112,7 @@ impl<Ctx: ScriptContext> DescriptorKey<Ctx> {
                 let mut key_map = KeyMap::with_capacity(1);
 
                 let public = secret
-                    .as_public(secp)
+                    .to_public(secp)
                     .map_err(|e| miniscript::Error::Unexpected(e.to_string()))?;
                 key_map.insert(public.clone(), secret);
 
@@ -224,8 +226,8 @@ impl<Ctx: ScriptContext + 'static> ExtScriptContext for Ctx {
 /// use bdk::bitcoin::PublicKey;
 ///
 /// use bdk::keys::{
-///     mainnet_network, DescriptorKey, DescriptorPublicKey, DescriptorSinglePub,
-///     IntoDescriptorKey, KeyError, ScriptContext, SinglePubKey,
+///     mainnet_network, DescriptorKey, DescriptorPublicKey, IntoDescriptorKey, KeyError,
+///     ScriptContext, SinglePub, SinglePubKey,
 /// };
 ///
 /// pub struct MyKeyType {
@@ -235,7 +237,7 @@ impl<Ctx: ScriptContext + 'static> ExtScriptContext for Ctx {
 /// impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for MyKeyType {
 ///     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
 ///         Ok(DescriptorKey::from_public(
-///             DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+///             DescriptorPublicKey::Single(SinglePub {
 ///                 origin: None,
 ///                 key: SinglePubKey::FullKey(self.pubkey),
 ///             }),
@@ -277,7 +279,7 @@ impl<Ctx: ScriptContext + 'static> ExtScriptContext for Ctx {
 ///
 /// ```compile_fail
 /// use bdk::bitcoin::PublicKey;
-/// use std::str::FromStr;
+/// use core::str::FromStr;
 ///
 /// use bdk::keys::{DescriptorKey, IntoDescriptorKey, KeyError};
 ///
@@ -375,7 +377,7 @@ impl<Ctx: ScriptContext> From<bip32::ExtendedPrivKey> for ExtendedKey<Ctx> {
 /// `(DerivableKey, KeySource, DerivationPath)` tuples.
 ///
 /// For key types that don't encode any indication about the path to use (like bip39), it's
-/// generally recommended to implemented this trait instead of [`IntoDescriptorKey`]. The same
+/// generally recommended to implement this trait instead of [`IntoDescriptorKey`]. The same
 /// rules regarding script context and valid networks apply.
 ///
 /// ## Examples
@@ -460,12 +462,11 @@ impl<Ctx: ScriptContext> From<bip32::ExtendedPrivKey> for ExtendedKey<Ctx> {
 /// [`ExtendedPubKey`]: (bip32::ExtendedPubKey)
 pub trait DerivableKey<Ctx: ScriptContext = miniscript::Legacy>: Sized {
     /// Consume `self` and turn it into an [`ExtendedKey`]
-    ///
-    /// This can be used to get direct access to `xprv`s and `xpub`s for types that implement this trait,
-    /// like [`Mnemonic`](bip39::Mnemonic) when the `keys-bip39` feature is enabled.
     #[cfg_attr(
         feature = "keys-bip39",
         doc = r##"
+This can be used to get direct access to `xprv`s and `xpub`s for types that implement this trait,
+like [`Mnemonic`](bip39::Mnemonic) when the `keys-bip39` feature is enabled.
 ```rust
 use bdk::bitcoin::Network;
 use bdk::keys::{DerivableKey, ExtendedKey};
@@ -619,7 +620,7 @@ pub trait GeneratableKey<Ctx: ScriptContext>: Sized {
     /// Extra options required by the `generate_with_entropy`
     type Options;
     /// Returned error in case of failure
-    type Error: std::fmt::Debug;
+    type Error: core::fmt::Debug;
 
     /// Generate a key given the extra options and the entropy
     fn generate_with_entropy(
@@ -842,7 +843,7 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for DescriptorKey<Ctx> {
 impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for DescriptorPublicKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
         let networks = match self {
-            DescriptorPublicKey::SinglePub(_) => any_network(),
+            DescriptorPublicKey::Single(_) => any_network(),
             DescriptorPublicKey::XPub(DescriptorXKey { xkey, .. })
                 if xkey.network == Network::Bitcoin =>
             {
@@ -857,7 +858,7 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for DescriptorPublicKey {
 
 impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for PublicKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
-        DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+        DescriptorPublicKey::Single(SinglePub {
             key: SinglePubKey::FullKey(self),
             origin: None,
         })
@@ -867,7 +868,7 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for PublicKey {
 
 impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for XOnlyPublicKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
-        DescriptorPublicKey::SinglePub(DescriptorSinglePub {
+        DescriptorPublicKey::Single(SinglePub {
             key: SinglePubKey::XOnly(self),
             origin: None,
         })
@@ -878,7 +879,7 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for XOnlyPublicKey {
 impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for DescriptorSecretKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
         let networks = match &self {
-            DescriptorSecretKey::SinglePriv(sk) if sk.key.network == Network::Bitcoin => {
+            DescriptorSecretKey::Single(sk) if sk.key.network == Network::Bitcoin => {
                 mainnet_network()
             }
             DescriptorSecretKey::XPrv(DescriptorXKey { xkey, .. })
@@ -903,7 +904,7 @@ impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for &'_ str {
 
 impl<Ctx: ScriptContext> IntoDescriptorKey<Ctx> for PrivateKey {
     fn into_descriptor_key(self) -> Result<DescriptorKey<Ctx>, KeyError> {
-        DescriptorSecretKey::SinglePriv(DescriptorSinglePriv {
+        DescriptorSecretKey::Single(SinglePriv {
             key: self,
             origin: None,
         })
@@ -935,10 +936,18 @@ impl_error!(bitcoin::util::bip32::Error, Bip32, KeyError);
 
 impl std::fmt::Display for KeyError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:?}", self)
+        match self {
+            Self::InvalidScriptContext => write!(f, "Invalid script context"),
+            Self::InvalidNetwork => write!(f, "Invalid network"),
+            Self::InvalidChecksum => write!(f, "Invalid checksum"),
+            Self::Message(err) => write!(f, "{}", err),
+            Self::Bip32(err) => write!(f, "BIP32 error: {}", err),
+            Self::Miniscript(err) => write!(f, "Miniscript error: {}", err),
+        }
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for KeyError {}
 
 #[cfg(test)]

crates/bdk/src/lib.rs

@@ -0,0 +1,46 @@
+#![doc = include_str!("../README.md")]
+#![no_std]
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate std;
+
+#[doc(hidden)]
+#[macro_use]
+pub extern crate alloc;
+
+pub extern crate bitcoin;
+#[cfg(feature = "hardware-signer")]
+pub extern crate hwi;
+extern crate log;
+pub extern crate miniscript;
+extern crate serde;
+extern crate serde_json;
+
+#[cfg(feature = "keys-bip39")]
+extern crate bip39;
+
+#[allow(unused_imports)]
+#[macro_use]
+pub(crate) mod error;
+pub mod descriptor;
+pub mod keys;
+pub mod psbt;
+pub(crate) mod types;
+pub mod wallet;
+
+pub use descriptor::template;
+pub use descriptor::HdKeyPaths;
+pub use error::Error;
+pub use types::*;
+pub use wallet::signer;
+pub use wallet::signer::SignOptions;
+pub use wallet::tx_builder::TxBuilder;
+pub use wallet::Wallet;
+
+/// Get the version of BDK at runtime
+pub fn version() -> &'static str {
+    env!("CARGO_PKG_VERSION", "unknown")
+}
+
+pub use bdk_chain as chain;
+pub(crate) use bdk_chain::collections;

crates/bdk/src/psbt/mod.rs

@@ -0,0 +1,79 @@
+// Bitcoin Dev Kit
+// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
+//
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Additional functions on the `rust-bitcoin` `PartiallySignedTransaction` structure.
+
+use crate::FeeRate;
+use alloc::vec::Vec;
+use bitcoin::util::psbt::PartiallySignedTransaction as Psbt;
+use bitcoin::TxOut;
+
+// TODO upstream the functions here to `rust-bitcoin`?
+
+/// Trait to add functions to extract utxos and calculate fees.
+pub trait PsbtUtils {
+    /// Get the `TxOut` for the specified input index, if it doesn't exist in the PSBT `None` is returned.
+    fn get_utxo_for(&self, input_index: usize) -> Option<TxOut>;
+
+    /// The total transaction fee amount, sum of input amounts minus sum of output amounts, in sats.
+    /// If the PSBT is missing a TxOut for an input returns None.
+    fn fee_amount(&self) -> Option<u64>;
+
+    /// The transaction's fee rate. This value will only be accurate if calculated AFTER the
+    /// `PartiallySignedTransaction` is finalized and all witness/signature data is added to the
+    /// transaction.
+    /// If the PSBT is missing a TxOut for an input returns None.
+    fn fee_rate(&self) -> Option<FeeRate>;
+}
+
+impl PsbtUtils for Psbt {
+    #[allow(clippy::all)] // We want to allow `manual_map` but it is too new.
+    fn get_utxo_for(&self, input_index: usize) -> Option<TxOut> {
+        let tx = &self.unsigned_tx;
+
+        if input_index >= tx.input.len() {
+            return None;
+        }
+
+        if let Some(input) = self.inputs.get(input_index) {
+            if let Some(wit_utxo) = &input.witness_utxo {
+                Some(wit_utxo.clone())
+            } else if let Some(in_tx) = &input.non_witness_utxo {
+                Some(in_tx.output[tx.input[input_index].previous_output.vout as usize].clone())
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    }
+
+    fn fee_amount(&self) -> Option<u64> {
+        let tx = &self.unsigned_tx;
+        let utxos: Option<Vec<TxOut>> = (0..tx.input.len()).map(|i| self.get_utxo_for(i)).collect();
+
+        utxos.map(|inputs| {
+            let input_amount: u64 = inputs.iter().map(|i| i.value).sum();
+            let output_amount: u64 = self.unsigned_tx.output.iter().map(|o| o.value).sum();
+            input_amount
+                .checked_sub(output_amount)
+                .expect("input amount must be greater than output amount")
+        })
+    }
+
+    fn fee_rate(&self) -> Option<FeeRate> {
+        let fee_amount = self.fee_amount();
+        fee_amount.map(|fee| {
+            let weight = self.clone().extract_tx().weight();
+            FeeRate::from_wu(fee, weight)
+        })
+    }
+}

crates/bdk/src/types.rs

@@ -9,16 +9,18 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-use std::convert::AsRef;
-use std::ops::Sub;
+use alloc::boxed::Box;
+use core::convert::AsRef;
+use core::ops::Sub;
 
+use bdk_chain::ConfirmationTime;
 use bitcoin::blockdata::transaction::{OutPoint, Transaction, TxOut};
 use bitcoin::{hash_types::Txid, util::psbt};
 
 use serde::{Deserialize, Serialize};
 
 /// Types of keychains
-#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]
 pub enum KeychainKind {
     /// External
     External = 0,
@@ -51,14 +53,44 @@ impl AsRef<[u8]> for KeychainKind {
 pub struct FeeRate(f32);
 
 impl FeeRate {
+    /// Create a new instance checking the value provided
+    ///
+    /// ## Panics
+    ///
+    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
+    fn new_checked(value: f32) -> Self {
+        assert!(value.is_normal() || value == 0.0);
+        assert!(value.is_sign_positive());
+
+        FeeRate(value)
+    }
+
+    /// Create a new instance of [`FeeRate`] given a float fee rate in sats/kwu
+    pub fn from_sat_per_kwu(sat_per_kwu: f32) -> Self {
+        FeeRate::new_checked(sat_per_kwu / 250.0_f32)
+    }
+
+    /// Create a new instance of [`FeeRate`] given a float fee rate in sats/kvb
+    pub fn from_sat_per_kvb(sat_per_kvb: f32) -> Self {
+        FeeRate::new_checked(sat_per_kvb / 1000.0_f32)
+    }
+
     /// Create a new instance of [`FeeRate`] given a float fee rate in btc/kvbytes
+    ///
+    /// ## Panics
+    ///
+    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
     pub fn from_btc_per_kvb(btc_per_kvb: f32) -> Self {
-        FeeRate(btc_per_kvb * 1e5)
+        FeeRate::new_checked(btc_per_kvb * 1e5)
     }
 
     /// Create a new instance of [`FeeRate`] given a float fee rate in satoshi/vbyte
-    pub const fn from_sat_per_vb(sat_per_vb: f32) -> Self {
-        FeeRate(sat_per_vb)
+    ///
+    /// ## Panics
+    ///
+    /// Panics if the value is not [normal](https://doc.rust-lang.org/std/primitive.f32.html#method.is_normal) (except if it's a positive zero) or negative.
+    pub fn from_sat_per_vb(sat_per_vb: f32) -> Self {
+        FeeRate::new_checked(sat_per_vb)
     }
 
     /// Create a new [`FeeRate`] with the default min relay fee value
@@ -78,7 +110,7 @@ impl FeeRate {
     }
 
     /// Return the value as satoshi/vbyte
-    pub fn as_sat_vb(&self) -> f32 {
+    pub fn as_sat_per_vb(&self) -> f32 {
         self.0
     }
 
@@ -89,11 +121,11 @@ impl FeeRate {
 
     /// Calculate absolute fee in Satoshis using size in virtual bytes.
     pub fn fee_vb(&self, vbytes: usize) -> u64 {
-        (self.as_sat_vb() * vbytes as f32).ceil() as u64
+        (self.as_sat_per_vb() * vbytes as f32).ceil() as u64
     }
 }
 
-impl std::default::Default for FeeRate {
+impl Default for FeeRate {
     fn default() -> Self {
         FeeRate::default_min_relay_fee()
     }
@@ -133,10 +165,14 @@ pub struct LocalUtxo {
     pub keychain: KeychainKind,
     /// Whether this UTXO is spent or not
     pub is_spent: bool,
+    /// The derivation index for the script pubkey in the wallet
+    pub derivation_index: u32,
+    /// The confirmation time for transaction containing this utxo
+    pub confirmation_time: ConfirmationTime,
 }
 
 /// A [`Utxo`] with its `satisfaction_weight`.
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct WeightedUtxo {
     /// The weight of the witness data and `scriptSig` expressed in [weight units]. This is used to
     /// properly maintain the feerate when adding this input to a transaction during coin selection.
@@ -147,7 +183,7 @@ pub struct WeightedUtxo {
     pub utxo: Utxo,
 }
 
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 /// An unspent transaction output (UTXO).
 pub enum Utxo {
     /// A UTXO owned by the local wallet.
@@ -194,51 +230,36 @@ impl Utxo {
 }
 
 /// A wallet transaction
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Default)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 pub struct TransactionDetails {
     /// Optional transaction
     pub transaction: Option<Transaction>,
     /// Transaction id
     pub txid: Txid,
-
     /// Received value (sats)
     /// Sum of owned outputs of this transaction.
     pub received: u64,
     /// Sent value (sats)
     /// Sum of owned inputs of this transaction.
     pub sent: u64,
-    /// Fee value (sats) if available.
-    /// The availability of the fee depends on the backend. It's never `None` with an Electrum
-    /// Server backend, but it could be `None` with a Bitcoin RPC node without txindex that receive
-    /// funds while offline.
+    /// Fee value in sats if it was available.
     pub fee: Option<u64>,
-    /// If the transaction is confirmed, contains height and timestamp of the block containing the
+    /// If the transaction is confirmed, contains height and Unix timestamp of the block containing the
     /// transaction, unconfirmed transaction contains `None`.
-    pub confirmation_time: Option<BlockTime>,
+    pub confirmation_time: ConfirmationTime,
 }
 
-/// Block height and timestamp of a block
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Default)]
-pub struct BlockTime {
-    /// confirmation block height
-    pub height: u32,
-    /// confirmation block timestamp
-    pub timestamp: u64,
+impl PartialOrd for TransactionDetails {
+    fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
 }
 
-/// **DEPRECATED**: Confirmation time of a transaction
-///
-/// The structure has been renamed to `BlockTime`
-#[deprecated(note = "This structure has been renamed to `BlockTime`")]
-pub type ConfirmationTime = BlockTime;
-
-impl BlockTime {
-    /// Returns `Some` `BlockTime` if both `height` and `timestamp` are `Some`
-    pub fn new(height: Option<u32>, timestamp: Option<u64>) -> Option<Self> {
-        match (height, timestamp) {
-            (Some(height), Some(timestamp)) => Some(BlockTime { height, timestamp }),
-            _ => None,
-        }
+impl Ord for TransactionDetails {
+    fn cmp(&self, other: &Self) -> core::cmp::Ordering {
+        self.confirmation_time
+            .cmp(&other.confirmation_time)
+            .then_with(|| self.txid.cmp(&other.txid))
     }
 }
 
@@ -248,7 +269,65 @@ mod tests {
 
     #[test]
     fn can_store_feerate_in_const() {
-        const _MY_RATE: FeeRate = FeeRate::from_sat_per_vb(10.0);
         const _MIN_RELAY: FeeRate = FeeRate::default_min_relay_fee();
     }
+
+    #[test]
+    #[should_panic]
+    fn test_invalid_feerate_neg_zero() {
+        let _ = FeeRate::from_sat_per_vb(-0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_invalid_feerate_neg_value() {
+        let _ = FeeRate::from_sat_per_vb(-5.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_invalid_feerate_nan() {
+        let _ = FeeRate::from_sat_per_vb(f32::NAN);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_invalid_feerate_inf() {
+        let _ = FeeRate::from_sat_per_vb(f32::INFINITY);
+    }
+
+    #[test]
+    fn test_valid_feerate_pos_zero() {
+        let _ = FeeRate::from_sat_per_vb(0.0);
+    }
+
+    #[test]
+    fn test_fee_from_btc_per_kvb() {
+        let fee = FeeRate::from_btc_per_kvb(1e-5);
+        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
+    }
+
+    #[test]
+    fn test_fee_from_sat_per_vbyte() {
+        let fee = FeeRate::from_sat_per_vb(1.0);
+        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
+    }
+
+    #[test]
+    fn test_fee_default_min_relay_fee() {
+        let fee = FeeRate::default_min_relay_fee();
+        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
+    }
+
+    #[test]
+    fn test_fee_from_sat_per_kvb() {
+        let fee = FeeRate::from_sat_per_kvb(1000.0);
+        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
+    }
+
+    #[test]
+    fn test_fee_from_sat_per_kwu() {
+        let fee = FeeRate::from_sat_per_kwu(250.0);
+        assert!((fee.as_sat_per_vb() - 1.0).abs() < f32::EPSILON);
+    }
 }

crates/bdk/src/wallet/export.rs

@@ -20,7 +20,6 @@
 //! ```
 //! # use std::str::FromStr;
 //! # use bitcoin::*;
-//! # use bdk::database::*;
 //! # use bdk::wallet::export::*;
 //! # use bdk::*;
 //! let import = r#"{
@@ -30,43 +29,39 @@
 //! }"#;
 //!
 //! let import = FullyNodedExport::from_str(import)?;
-//! let wallet = Wallet::new(
+//! let wallet = Wallet::new_no_persist(
 //!     &import.descriptor(),
 //!     import.change_descriptor().as_ref(),
 //!     Network::Testnet,
-//!     MemoryDatabase::default(),
 //! )?;
-//! # Ok::<_, bdk::Error>(())
+//! # Ok::<_, Box<dyn std::error::Error>>(())
 //! ```
 //!
 //! ### Export a `Wallet`
 //! ```
 //! # use bitcoin::*;
-//! # use bdk::database::*;
 //! # use bdk::wallet::export::*;
 //! # use bdk::*;
-//! let wallet = Wallet::new(
+//! let wallet = Wallet::new_no_persist(
 //!     "wpkh([c258d2e4/84h/1h/0h]tpubDD3ynpHgJQW8VvWRzQ5WFDCrs4jqVFGHB3vLC3r49XHJSqP8bHKdK4AriuUKLccK68zfzowx7YhmDN8SiSkgCDENUFx9qVw65YyqM78vyVe/0/*)",
 //!     Some("wpkh([c258d2e4/84h/1h/0h]tpubDD3ynpHgJQW8VvWRzQ5WFDCrs4jqVFGHB3vLC3r49XHJSqP8bHKdK4AriuUKLccK68zfzowx7YhmDN8SiSkgCDENUFx9qVw65YyqM78vyVe/1/*)"),
 //!     Network::Testnet,
-//!     MemoryDatabase::default()
 //! )?;
-//! let export = FullyNodedExport::export_wallet(&wallet, "exported wallet", true)
-//!     .map_err(ToString::to_string)
-//!     .map_err(bdk::Error::Generic)?;
+//! let export = FullyNodedExport::export_wallet(&wallet, "exported wallet", true).unwrap();
 //!
 //! println!("Exported: {}", export.to_string());
-//! # Ok::<_, bdk::Error>(())
+//! # Ok::<_, Box<dyn std::error::Error>>(())
 //! ```
 
-use std::str::FromStr;
+use core::str::FromStr;
 
+use alloc::string::{String, ToString};
+use bdk_chain::sparse_chain::ChainPosition;
 use serde::{Deserialize, Serialize};
 
 use miniscript::descriptor::{ShInner, WshInner};
 use miniscript::{Descriptor, ScriptContext, Terminal};
 
-use crate::database::BatchDatabase;
 use crate::types::KeychainKind;
 use crate::wallet::Wallet;
 
@@ -116,7 +111,7 @@ impl FullyNodedExport {
     ///
     /// If the database is empty or `include_blockheight` is false, the `blockheight` field
     /// returned will be `0`.
-    pub fn export_wallet<D: BatchDatabase>(
+    pub fn export_wallet<D>(
         wallet: &Wallet<D>,
         label: &str,
         include_blockheight: bool,
@@ -131,18 +126,14 @@ impl FullyNodedExport {
         let descriptor = remove_checksum(descriptor);
         Self::is_compatible_with_core(&descriptor)?;
 
-        let blockheight = match wallet.database.borrow().iter_txs(false) {
-            _ if !include_blockheight => 0,
-            Err(_) => 0,
-            Ok(txs) => {
-                let mut heights = txs
-                    .into_iter()
-                    .map(|tx| tx.confirmation_time.map(|c| c.height).unwrap_or(0))
-                    .collect::<Vec<_>>();
-                heights.sort_unstable();
-
-                *heights.last().unwrap_or(&0)
-            }
+        let blockheight = if include_blockheight {
+            wallet
+                .transactions()
+                .next()
+                .and_then(|(pos, _)| pos.height().into())
+                .unwrap_or(0)
+        } else {
+            0
         };
 
         let export = FullyNodedExport {
@@ -151,11 +142,7 @@ impl FullyNodedExport {
             blockheight,
         };
 
-        let change_descriptor = match wallet
-            .public_descriptor(KeychainKind::Internal)
-            .map_err(|_| "Invalid change descriptor")?
-            .is_some()
-        {
+        let change_descriptor = match wallet.public_descriptor(KeychainKind::Internal).is_some() {
             false => None,
             true => {
                 let descriptor = wallet
@@ -225,36 +212,43 @@ impl FullyNodedExport {
 
 #[cfg(test)]
 mod test {
-    use std::str::FromStr;
+    use core::str::FromStr;
 
-    use bitcoin::{Network, Txid};
+    use bdk_chain::{BlockId, ConfirmationTime};
+    use bitcoin::hashes::Hash;
+    use bitcoin::{BlockHash, Network, Transaction};
 
     use super::*;
-    use crate::database::{memory::MemoryDatabase, BatchOperations};
-    use crate::types::TransactionDetails;
     use crate::wallet::Wallet;
-    use crate::BlockTime;
 
-    fn get_test_db() -> MemoryDatabase {
-        let mut db = MemoryDatabase::new();
-        db.set_tx(&TransactionDetails {
-            transaction: None,
-            txid: Txid::from_str(
-                "4ddff1fa33af17f377f62b72357b43107c19110a8009b36fb832af505efed98a",
+    fn get_test_wallet(
+        descriptor: &str,
+        change_descriptor: Option<&str>,
+        network: Network,
+    ) -> Wallet<()> {
+        let mut wallet = Wallet::new_no_persist(descriptor, change_descriptor, network).unwrap();
+        let transaction = Transaction {
+            input: vec![],
+            output: vec![],
+            version: 0,
+            lock_time: bitcoin::PackedLockTime::ZERO,
+        };
+        wallet
+            .insert_checkpoint(BlockId {
+                height: 5001,
+                hash: BlockHash::all_zeros(),
+            })
+            .unwrap();
+        wallet
+            .insert_tx(
+                transaction,
+                ConfirmationTime::Confirmed {
+                    height: 5000,
+                    time: 0,
+                },
             )
-            .unwrap(),
-
-            received: 100_000,
-            sent: 0,
-            fee: Some(500),
-            confirmation_time: Some(BlockTime {
-                timestamp: 12345678,
-                height: 5000,
-            }),
-        })
-        .unwrap();
-
-        db
+            .unwrap();
+        wallet
     }
 
     #[test]
@@ -262,13 +256,7 @@ mod test {
         let descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/0/*)";
         let change_descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/1/*)";
 
-        let wallet = Wallet::new(
-            descriptor,
-            Some(change_descriptor),
-            Network::Bitcoin,
-            get_test_db(),
-        )
-        .unwrap();
+        let wallet = get_test_wallet(descriptor, Some(change_descriptor), Network::Bitcoin);
         let export = FullyNodedExport::export_wallet(&wallet, "Test Label", true).unwrap();
 
         assert_eq!(export.descriptor(), descriptor);
@@ -286,7 +274,7 @@ mod test {
 
         let descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/0/*)";
 
-        let wallet = Wallet::new(descriptor, None, Network::Bitcoin, get_test_db()).unwrap();
+        let wallet = get_test_wallet(descriptor, None, Network::Bitcoin);
         FullyNodedExport::export_wallet(&wallet, "Test Label", true).unwrap();
     }
 
@@ -299,13 +287,7 @@ mod test {
         let descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/0/*)";
         let change_descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/50'/0'/1/*)";
 
-        let wallet = Wallet::new(
-            descriptor,
-            Some(change_descriptor),
-            Network::Bitcoin,
-            get_test_db(),
-        )
-        .unwrap();
+        let wallet = get_test_wallet(descriptor, Some(change_descriptor), Network::Bitcoin);
         FullyNodedExport::export_wallet(&wallet, "Test Label", true).unwrap();
     }
 
@@ -322,13 +304,7 @@ mod test {
                                        [c98b1535/48'/0'/0'/2']tpubDCDi5W4sP6zSnzJeowy8rQDVhBdRARaPhK1axABi8V1661wEPeanpEXj4ZLAUEoikVtoWcyK26TKKJSecSfeKxwHCcRrge9k1ybuiL71z4a/1/*\
                                  ))";
 
-        let wallet = Wallet::new(
-            descriptor,
-            Some(change_descriptor),
-            Network::Testnet,
-            get_test_db(),
-        )
-        .unwrap();
+        let wallet = get_test_wallet(descriptor, Some(change_descriptor), Network::Testnet);
         let export = FullyNodedExport::export_wallet(&wallet, "Test Label", true).unwrap();
 
         assert_eq!(export.descriptor(), descriptor);
@@ -342,13 +318,7 @@ mod test {
         let descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/0/*)";
         let change_descriptor = "wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44'/0'/0'/1/*)";
 
-        let wallet = Wallet::new(
-            descriptor,
-            Some(change_descriptor),
-            Network::Bitcoin,
-            get_test_db(),
-        )
-        .unwrap();
+        let wallet = get_test_wallet(descriptor, Some(change_descriptor), Network::Bitcoin);
         let export = FullyNodedExport::export_wallet(&wallet, "Test Label", true).unwrap();
 
         assert_eq!(export.to_string(), "{\"descriptor\":\"wpkh(xprv9s21ZrQH143K4CTb63EaMxja1YiTnSEWKMbn23uoEnAzxjdUJRQkazCAtzxGm4LSoTSVTptoV9RbchnKPW9HxKtZumdyxyikZFDLhogJ5Uj/44\'/0\'/0\'/0/*)\",\"blockheight\":5000,\"label\":\"Test Label\"}");

crates/bdk/src/wallet/hardwaresigner.rs

@@ -0,0 +1,98 @@
+// Bitcoin Dev Kit
+// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
+//
+// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! HWI Signer
+//!
+//! This module contains HWISigner, an implementation of a [TransactionSigner] to be
+//! used with hardware wallets.
+//! ```no_run
+//! # use bdk::bitcoin::Network;
+//! # use bdk::signer::SignerOrdering;
+//! # use bdk::wallet::hardwaresigner::HWISigner;
+//! # use bdk::wallet::AddressIndex::New;
+//! # use bdk::{FeeRate, KeychainKind, SignOptions, Wallet};
+//! # use hwi::{types::HWIChain, HWIClient};
+//! # use std::sync::Arc;
+//! #
+//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! let mut devices = HWIClient::enumerate()?;
+//! if devices.is_empty() {
+//!     panic!("No devices found!");
+//! }
+//! let first_device = devices.remove(0)?;
+//! let custom_signer = HWISigner::from_device(&first_device, HWIChain::Test)?;
+//!
+//! # let mut wallet = Wallet::new_no_persist(
+//! #     "",
+//! #     None,
+//! #     Network::Testnet,
+//! # )?;
+//! #
+//! // Adding the hardware signer to the BDK wallet
+//! wallet.add_signer(
+//!     KeychainKind::External,
+//!     SignerOrdering(200),
+//!     Arc::new(custom_signer),
+//! );
+//!
+//! # Ok(())
+//! # }
+//! ```
+
+use bitcoin::psbt::PartiallySignedTransaction;
+use bitcoin::secp256k1::{All, Secp256k1};
+use bitcoin::util::bip32::Fingerprint;
+
+use hwi::error::Error;
+use hwi::types::{HWIChain, HWIDevice};
+use hwi::HWIClient;
+
+use crate::signer::{SignerCommon, SignerError, SignerId, TransactionSigner};
+
+#[derive(Debug)]
+/// Custom signer for Hardware Wallets
+///
+/// This ignores `sign_options` and leaves the decisions up to the hardware wallet.
+pub struct HWISigner {
+    fingerprint: Fingerprint,
+    client: HWIClient,
+}
+
+impl HWISigner {
+    /// Create a instance from the specified device and chain
+    pub fn from_device(device: &HWIDevice, chain: HWIChain) -> Result<HWISigner, Error> {
+        let client = HWIClient::get_client(device, false, chain)?;
+        Ok(HWISigner {
+            fingerprint: device.fingerprint,
+            client,
+        })
+    }
+}
+
+impl SignerCommon for HWISigner {
+    fn id(&self, _secp: &Secp256k1<All>) -> SignerId {
+        SignerId::Fingerprint(self.fingerprint)
+    }
+}
+
+/// This implementation ignores `sign_options`
+impl TransactionSigner for HWISigner {
+    fn sign_transaction(
+        &self,
+        psbt: &mut PartiallySignedTransaction,
+        _sign_options: &crate::SignOptions,
+        _secp: &crate::wallet::utils::SecpCtx,
+    ) -> Result<(), SignerError> {
+        psbt.combine(self.client.sign_tx(psbt)?.psbt)
+            .expect("Failed to combine HW signed psbt with passed PSBT");
+        Ok(())
+    }
+}

crates/bdk/src/wallet/signer.rs

@@ -15,13 +15,12 @@
 //! through the [`Wallet::add_signer`](super::Wallet::add_signer) function.
 //!
 //! ```
-//! # use std::sync::Arc;
-//! # use std::str::FromStr;
+//! # use alloc::sync::Arc;
+//! # use core::str::FromStr;
 //! # use bitcoin::secp256k1::{Secp256k1, All};
 //! # use bitcoin::*;
 //! # use bitcoin::util::psbt;
 //! # use bdk::signer::*;
-//! # use bdk::database::*;
 //! # use bdk::*;
 //! # #[derive(Debug)]
 //! # struct CustomHSM;
@@ -58,6 +57,7 @@
 //!         &self,
 //!         psbt: &mut psbt::PartiallySignedTransaction,
 //!         input_index: usize,
+//!         _sign_options: &SignOptions,
 //!         _secp: &Secp256k1<All>,
 //!     ) -> Result<(), SignerError> {
 //!         self.device.hsm_sign_input(psbt, input_index)?;
@@ -69,7 +69,7 @@
 //! let custom_signer = CustomSigner::connect();
 //!
 //! let descriptor = "wpkh(tpubD6NzVbkrYhZ4Xferm7Pz4VnjdcDPFyjVu5K4iZXQ4pVN8Cks4pHVowTBXBKRhX64pkRyJZJN5xAKj4UDNnLPb5p2sSKXhewoYx5GbTdUFWq/*)";
-//! let mut wallet = Wallet::new(descriptor, None, Network::Testnet, MemoryDatabase::default())?;
+//! let mut wallet = Wallet::new_no_persist(descriptor, None, Network::Testnet)?;
 //! wallet.add_signer(
 //!     KeychainKind::External,
 //!     SignerOrdering(200),
@@ -79,11 +79,12 @@
 //! # Ok::<_, bdk::Error>(())
 //! ```
 
-use std::cmp::Ordering;
-use std::collections::BTreeMap;
-use std::fmt;
-use std::ops::{Bound::Included, Deref};
-use std::sync::Arc;
+use crate::collections::BTreeMap;
+use alloc::sync::Arc;
+use alloc::vec::Vec;
+use core::cmp::Ordering;
+use core::fmt;
+use core::ops::{Bound::Included, Deref};
 
 use bitcoin::blockdata::opcodes;
 use bitcoin::blockdata::script::Builder as ScriptBuilder;
@@ -95,13 +96,14 @@ use bitcoin::{secp256k1, XOnlyPublicKey};
 use bitcoin::{EcdsaSighashType, PrivateKey, PublicKey, SchnorrSighashType, Script};
 
 use miniscript::descriptor::{
-    Descriptor, DescriptorPublicKey, DescriptorSecretKey, DescriptorSinglePriv, DescriptorXKey,
-    KeyMap, SinglePubKey,
+    Descriptor, DescriptorPublicKey, DescriptorSecretKey, DescriptorXKey, KeyMap, SinglePriv,
+    SinglePubKey,
 };
-use miniscript::{Legacy, MiniscriptKey, Segwitv0, Tap};
+use miniscript::{Legacy, Segwitv0, SigType, Tap, ToPublicKey};
 
 use super::utils::SecpCtx;
 use crate::descriptor::{DescriptorMeta, XKeyUtils};
+use crate::psbt::PsbtUtils;
 
 /// Identifier of a signer in the `SignersContainers`. Used as a key to find the right signer among
 /// multiple of them
@@ -158,6 +160,16 @@ pub enum SignerError {
     InvalidSighash,
     /// Error while computing the hash to sign
     SighashError(sighash::Error),
+    /// Error while signing using hardware wallets
+    #[cfg(feature = "hardware-signer")]
+    HWIError(hwi::error::Error),
+}
+
+#[cfg(feature = "hardware-signer")]
+impl From<hwi::error::Error> for SignerError {
+    fn from(e: hwi::error::Error) -> Self {
+        SignerError::HWIError(e)
+    }
 }
 
 impl From<sighash::Error> for SignerError {
@@ -168,10 +180,26 @@ impl From<sighash::Error> for SignerError {
 
 impl fmt::Display for SignerError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self)
+        match self {
+            Self::MissingKey => write!(f, "Missing private key"),
+            Self::InvalidKey => write!(f, "The private key in use has the right fingerprint but derives differently than expected"),
+            Self::UserCanceled => write!(f, "The user canceled the operation"),
+            Self::InputIndexOutOfRange => write!(f, "Input index out of range"),
+            Self::MissingNonWitnessUtxo => write!(f, "Missing non-witness UTXO"),
+            Self::InvalidNonWitnessUtxo => write!(f, "Invalid non-witness UTXO"),
+            Self::MissingWitnessUtxo => write!(f, "Missing witness UTXO"),
+            Self::MissingWitnessScript => write!(f, "Missing witness script"),
+            Self::MissingHdKeypath => write!(f, "Missing fingerprint and derivation path"),
+            Self::NonStandardSighash => write!(f, "The psbt contains a non standard sighash"),
+            Self::InvalidSighash => write!(f, "Invalid SIGHASH for the signing context in use"),
+            Self::SighashError(err) => write!(f, "Error while computing the hash to sign: {}", err),
+            #[cfg(feature = "hardware-signer")]
+            Self::HWIError(err) => write!(f, "Error while signing using hardware wallets: {}", err),
+        }
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for SignerError {}
 
 /// Signing context
@@ -241,6 +269,7 @@ pub trait InputSigner: SignerCommon {
         &self,
         psbt: &mut psbt::PartiallySignedTransaction,
         input_index: usize,
+        sign_options: &SignOptions,
         secp: &SecpCtx,
     ) -> Result<(), SignerError>;
 }
@@ -254,6 +283,7 @@ pub trait TransactionSigner: SignerCommon {
     fn sign_transaction(
         &self,
         psbt: &mut psbt::PartiallySignedTransaction,
+        sign_options: &SignOptions,
         secp: &SecpCtx,
     ) -> Result<(), SignerError>;
 }
@@ -262,10 +292,11 @@ impl<T: InputSigner> TransactionSigner for T {
     fn sign_transaction(
         &self,
         psbt: &mut psbt::PartiallySignedTransaction,
+        sign_options: &SignOptions,
         secp: &SecpCtx,
     ) -> Result<(), SignerError> {
         for input_index in 0..psbt.inputs.len() {
-            self.sign_input(psbt, input_index, secp)?;
+            self.sign_input(psbt, input_index, sign_options, secp)?;
         }
 
         Ok(())
@@ -287,6 +318,7 @@ impl InputSigner for SignerWrapper<DescriptorXKey<ExtendedPrivKey>> {
         &self,
         psbt: &mut psbt::PartiallySignedTransaction,
         input_index: usize,
+        sign_options: &SignOptions,
         secp: &SecpCtx,
     ) -> Result<(), SignerError> {
         if input_index >= psbt.inputs.len() {
@@ -346,18 +378,18 @@ impl InputSigner for SignerWrapper<DescriptorXKey<ExtendedPrivKey>> {
                 inner: derived_key.private_key,
             };
 
-            SignerWrapper::new(priv_key, self.ctx).sign_input(psbt, input_index, secp)
+            SignerWrapper::new(priv_key, self.ctx).sign_input(psbt, input_index, sign_options, secp)
         }
     }
 }
 
 impl SignerCommon for SignerWrapper<PrivateKey> {
     fn id(&self, secp: &SecpCtx) -> SignerId {
-        SignerId::from(self.public_key(secp).to_pubkeyhash())
+        SignerId::from(self.public_key(secp).to_pubkeyhash(SigType::Ecdsa))
     }
 
     fn descriptor_secret_key(&self) -> Option<DescriptorSecretKey> {
-        Some(DescriptorSecretKey::SinglePriv(DescriptorSinglePriv {
+        Some(DescriptorSecretKey::Single(SinglePriv {
             key: self.signer,
             origin: None,
         }))
@@ -369,6 +401,7 @@ impl InputSigner for SignerWrapper<PrivateKey> {
         &self,
         psbt: &mut psbt::PartiallySignedTransaction,
         input_index: usize,
+        sign_options: &SignOptions,
         secp: &SecpCtx,
     ) -> Result<(), SignerError> {
         if input_index >= psbt.inputs.len() || input_index >= psbt.unsigned_tx.input.len() {
@@ -385,7 +418,10 @@ impl InputSigner for SignerWrapper<PrivateKey> {
         let x_only_pubkey = XOnlyPublicKey::from(pubkey.inner);
 
         if let SignerContext::Tap { is_internal_key } = self.ctx {
-            if is_internal_key && psbt.inputs[input_index].tap_key_sig.is_none() {
+            if is_internal_key
+                && psbt.inputs[input_index].tap_key_sig.is_none()
+                && sign_options.sign_with_tap_internal_key
+            {
                 let (hash, hash_ty) = Tap::sighash(psbt, input_index, None)?;
                 sign_psbt_schnorr(
                     &self.inner,
@@ -404,9 +440,18 @@ impl InputSigner for SignerWrapper<PrivateKey> {
                 let leaf_hashes = leaf_hashes
                     .iter()
                     .filter(|lh| {
-                        !psbt.inputs[input_index]
-                            .tap_script_sigs
-                            .contains_key(&(x_only_pubkey, **lh))
+                        // Removing the leaves we shouldn't sign for
+                        let should_sign = match &sign_options.tap_leaves_options {
+                            TapLeavesOptions::All => true,
+                            TapLeavesOptions::Include(v) => v.contains(lh),
+                            TapLeavesOptions::Exclude(v) => !v.contains(lh),
+                            TapLeavesOptions::None => false,
+                        };
+                        // Filtering out the leaves without our key
+                        should_sign
+                            && !psbt.inputs[input_index]
+                                .tap_script_sigs
+                                .contains_key(&(x_only_pubkey, **lh))
                     })
                     .cloned()
                     .collect::<Vec<_>>();
@@ -443,6 +488,7 @@ impl InputSigner for SignerWrapper<PrivateKey> {
             hash,
             hash_ty,
             secp,
+            sign_options.allow_grinding,
         );
 
         Ok(())
@@ -456,11 +502,16 @@ fn sign_psbt_ecdsa(
     hash: bitcoin::Sighash,
     hash_ty: EcdsaSighashType,
     secp: &SecpCtx,
+    allow_grinding: bool,
 ) {
-    let sig = secp.sign_ecdsa(
-        &Message::from_slice(&hash.into_inner()[..]).unwrap(),
-        secret_key,
-    );
+    let msg = &Message::from_slice(&hash.into_inner()[..]).unwrap();
+    let sig = if allow_grinding {
+        secp.sign_ecdsa_low_r(msg, secret_key)
+    } else {
+        secp.sign_ecdsa(msg, secret_key)
+    };
+    secp.verify_ecdsa(msg, &sig, &pubkey.inner)
+        .expect("invalid or corrupted ecdsa signature");
 
     let final_signature = ecdsa::EcdsaSig { sig, hash_ty };
     psbt_input.partial_sigs.insert(pubkey, final_signature);
@@ -482,14 +533,14 @@ fn sign_psbt_schnorr(
     let keypair = match leaf_hash {
         None => keypair
             .tap_tweak(secp, psbt_input.tap_merkle_root)
-            .into_inner(),
+            .to_inner(),
         Some(_) => keypair, // no tweak for script spend
     };
 
-    let sig = secp.sign_schnorr(
-        &Message::from_slice(&hash.into_inner()[..]).unwrap(),
-        &keypair,
-    );
+    let msg = &Message::from_slice(&hash.into_inner()[..]).unwrap();
+    let sig = secp.sign_schnorr(msg, &keypair);
+    secp.verify_schnorr(&sig, msg, &XOnlyPublicKey::from_keypair(&keypair).0)
+        .expect("invalid or corrupted schnorr signature");
 
     let final_signature = schnorr::SchnorrSig { sig, hash_ty };
 
@@ -510,7 +561,7 @@ fn sign_psbt_schnorr(
 #[derive(Debug, Clone, PartialOrd, PartialEq, Ord, Eq)]
 pub struct SignerOrdering(pub usize);
 
-impl std::default::Default for SignerOrdering {
+impl Default for SignerOrdering {
     fn default() -> Self {
         SignerOrdering(100)
     }
@@ -541,7 +592,7 @@ impl SignersContainer {
         self.0
             .values()
             .filter_map(|signer| signer.descriptor_secret_key())
-            .filter_map(|secret| secret.as_public(secp).ok().map(|public| (public, secret)))
+            .filter_map(|secret| secret.to_public(secp).ok().map(|public| (public, secret)))
             .collect()
     }
 
@@ -566,8 +617,13 @@ impl SignersContainer {
             };
 
             match secret {
-                DescriptorSecretKey::SinglePriv(private_key) => container.add_external(
-                    SignerId::from(private_key.key.public_key(secp).to_pubkeyhash()),
+                DescriptorSecretKey::Single(private_key) => container.add_external(
+                    SignerId::from(
+                        private_key
+                            .key
+                            .public_key(secp)
+                            .to_pubkeyhash(SigType::Ecdsa),
+                    ),
                     SignerOrdering::default(),
                     Arc::new(SignerWrapper::new(private_key.key, ctx)),
                 ),
@@ -668,15 +724,52 @@ pub struct SignOptions {
     /// Defaults to `false` which will only allow signing using `SIGHASH_ALL`.
     pub allow_all_sighashes: bool,
 
-    /// Whether to remove partial_sigs from psbt inputs while finalizing psbt.
+    /// Whether to remove partial signatures from the PSBT inputs while finalizing PSBT.
     ///
-    /// Defaults to `true` which will remove partial_sigs after finalizing.
+    /// Defaults to `true` which will remove partial signatures during finalization.
     pub remove_partial_sigs: bool,
 
-    /// Whether to try finalizing psbt input after the inputs are signed.
+    /// Whether to try finalizing the PSBT after the inputs are signed.
     ///
-    /// Defaults to `true` which will try fianlizing psbt after inputs are signed.
+    /// Defaults to `true` which will try finalizing PSBT after inputs are signed.
     pub try_finalize: bool,
+
+    /// Specifies which Taproot script-spend leaves we should sign for. This option is
+    /// ignored if we're signing a non-taproot PSBT.
+    ///
+    /// Defaults to All, i.e., the wallet will sign all the leaves it has a key for.
+    pub tap_leaves_options: TapLeavesOptions,
+
+    /// Whether we should try to sign a taproot transaction with the taproot internal key
+    /// or not. This option is ignored if we're signing a non-taproot PSBT.
+    ///
+    /// Defaults to `true`, i.e., we always try to sign with the taproot internal key.
+    pub sign_with_tap_internal_key: bool,
+
+    /// Whether we should grind ECDSA signature to ensure signing with low r
+    /// or not.
+    /// Defaults to `true`, i.e., we always grind ECDSA signature to sign with low r.
+    pub allow_grinding: bool,
+}
+
+/// Customize which taproot script-path leaves the signer should sign.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum TapLeavesOptions {
+    /// The signer will sign all the leaves it has a key for.
+    All,
+    /// The signer won't sign leaves other than the ones specified. Note that it could still ignore
+    /// some of the specified leaves, if it doesn't have the right key to sign them.
+    Include(Vec<taproot::TapLeafHash>),
+    /// The signer won't sign the specified leaves.
+    Exclude(Vec<taproot::TapLeafHash>),
+    /// The signer won't sign any leaf.
+    None,
+}
+
+impl Default for TapLeavesOptions {
+    fn default() -> Self {
+        TapLeavesOptions::All
+    }
 }
 
 #[allow(clippy::derivable_impls)]
@@ -688,6 +781,9 @@ impl Default for SignOptions {
             allow_all_sighashes: false,
             remove_partial_sigs: true,
             try_finalize: true,
+            tap_leaves_options: TapLeavesOptions::default(),
+            sign_with_tap_internal_key: true,
+            allow_grinding: true,
         }
     }
 }
@@ -859,11 +955,8 @@ impl ComputeSighash for Tap {
             .unwrap_or_else(|| SchnorrSighashType::Default.into())
             .schnorr_hash_ty()
             .map_err(|_| SignerError::InvalidSighash)?;
-        let witness_utxos = psbt
-            .inputs
-            .iter()
-            .cloned()
-            .map(|i| i.witness_utxo)
+        let witness_utxos = (0..psbt.inputs.len())
+            .map(|i| psbt.get_utxo_for(i))
             .collect::<Vec<_>>();
         let mut all_witness_utxos = vec![];
 
@@ -921,11 +1014,12 @@ mod signers_container_tests {
     use crate::descriptor;
     use crate::descriptor::IntoWalletDescriptor;
     use crate::keys::{DescriptorKey, IntoDescriptorKey};
+    use assert_matches::assert_matches;
     use bitcoin::secp256k1::{All, Secp256k1};
     use bitcoin::util::bip32;
     use bitcoin::Network;
+    use core::str::FromStr;
     use miniscript::ScriptContext;
-    use std::str::FromStr;
 
     fn is_equal(this: &Arc<dyn TransactionSigner>, that: &Arc<DummySigner>) -> bool {
         let secp = Secp256k1::new();
@@ -990,17 +1084,17 @@ mod signers_container_tests {
         signers.add_external(id2.clone(), SignerOrdering(2), signer2.clone());
         signers.add_external(id3.clone(), SignerOrdering(3), signer3.clone());
 
-        assert!(matches!(signers.find(id1), Some(signer) if is_equal(signer, &signer1)));
-        assert!(matches!(signers.find(id2), Some(signer) if is_equal(signer, &signer2)));
-        assert!(matches!(signers.find(id3.clone()), Some(signer) if is_equal(signer, &signer3)));
+        assert_matches!(signers.find(id1), Some(signer) if is_equal(signer, &signer1));
+        assert_matches!(signers.find(id2), Some(signer) if is_equal(signer, &signer2));
+        assert_matches!(signers.find(id3.clone()), Some(signer) if is_equal(signer, &signer3));
 
         // The `signer4` has the same ID as `signer3` but lower ordering.
         // It should be found by `id3` instead of `signer3`.
         signers.add_external(id3.clone(), SignerOrdering(2), signer4.clone());
-        assert!(matches!(signers.find(id3), Some(signer) if is_equal(signer, &signer4)));
+        assert_matches!(signers.find(id3), Some(signer) if is_equal(signer, &signer4));
 
         // Can't find anything with ID that doesn't exist
-        assert!(matches!(signers.find(id_nonexistent), None));
+        assert_matches!(signers.find(id_nonexistent), None);
     }
 
     #[derive(Debug, Clone, Copy)]
@@ -1018,6 +1112,7 @@ mod signers_container_tests {
         fn sign_transaction(
             &self,
             _psbt: &mut psbt::PartiallySignedTransaction,
+            _sign_options: &SignOptions,
             _secp: &SecpCtx,
         ) -> Result<(), SignerError> {
             Ok(())

crates/bdk/src/wallet/tx_builder.rs

@@ -19,7 +19,7 @@
 //! # use bdk::*;
 //! # use bdk::wallet::tx_builder::CreateTx;
 //! # let to_address = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
-//! # let wallet = doctest_wallet!();
+//! # let mut wallet = doctest_wallet!();
 //! // create a TxBuilder from a wallet
 //! let mut tx_builder = wallet.build_tx();
 //!
@@ -36,24 +36,25 @@
 //! # Ok::<(), bdk::Error>(())
 //! ```
 
-use std::collections::BTreeMap;
-use std::collections::HashSet;
-use std::default::Default;
-use std::marker::PhantomData;
+use crate::collections::BTreeMap;
+use crate::collections::HashSet;
+use alloc::{boxed::Box, rc::Rc, string::String, vec::Vec};
+use bdk_chain::ConfirmationTime;
+use core::cell::RefCell;
+use core::marker::PhantomData;
 
 use bitcoin::util::psbt::{self, PartiallySignedTransaction as Psbt};
-use bitcoin::{OutPoint, Script, Transaction};
-
-use miniscript::descriptor::DescriptorTrait;
+use bitcoin::{LockTime, OutPoint, Script, Sequence, Transaction};
 
 use super::coin_selection::{CoinSelectionAlgorithm, DefaultCoinSelectionAlgorithm};
-use crate::{database::BatchDatabase, Error, Utxo, Wallet};
+use super::persist;
 use crate::{
     types::{FeeRate, KeychainKind, LocalUtxo, WeightedUtxo},
     TransactionDetails,
 };
+use crate::{Error, Utxo, Wallet};
 /// Context in which the [`TxBuilder`] is valid
-pub trait TxBuilderContext: std::fmt::Debug + Default + Clone {}
+pub trait TxBuilderContext: core::fmt::Debug + Default + Clone {}
 
 /// Marker type to indicate the [`TxBuilder`] is being used to create a new transaction (as opposed
 /// to bumping the fee of an existing one).
@@ -80,7 +81,7 @@ impl TxBuilderContext for BumpFee {}
 /// # use bdk::wallet::tx_builder::*;
 /// # use bitcoin::*;
 /// # use core::str::FromStr;
-/// # let wallet = doctest_wallet!();
+/// # let mut wallet = doctest_wallet!();
 /// # let addr1 = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
 /// # let addr2 = addr1.clone();
 /// // chaining
@@ -118,7 +119,7 @@ impl TxBuilderContext for BumpFee {}
 /// [`coin_selection`]: Self::coin_selection
 #[derive(Debug)]
 pub struct TxBuilder<'a, D, Cs, Ctx> {
-    pub(crate) wallet: &'a Wallet<D>,
+    pub(crate) wallet: Rc<RefCell<&'a mut Wallet<D>>>,
     pub(crate) params: TxParams,
     pub(crate) coin_selection: Cs,
     pub(crate) phantom: PhantomData<Ctx>,
@@ -139,7 +140,7 @@ pub(crate) struct TxParams {
     pub(crate) manually_selected_only: bool,
     pub(crate) sighash: Option<psbt::PsbtSighashType>,
     pub(crate) ordering: TxOrdering,
-    pub(crate) locktime: Option<u32>,
+    pub(crate) locktime: Option<LockTime>,
     pub(crate) rbf: Option<RbfValue>,
     pub(crate) version: Option<Version>,
     pub(crate) change_policy: ChangeSpendPolicy,
@@ -147,7 +148,8 @@ pub(crate) struct TxParams {
     pub(crate) add_global_xpubs: bool,
     pub(crate) include_output_redeem_witness_script: bool,
     pub(crate) bumping_fee: Option<PreviousFee>,
-    pub(crate) current_height: Option<u32>,
+    pub(crate) current_height: Option<LockTime>,
+    pub(crate) allow_dust: bool,
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -162,16 +164,16 @@ pub(crate) enum FeePolicy {
     FeeAmount(u64),
 }
 
-impl std::default::Default for FeePolicy {
+impl Default for FeePolicy {
     fn default() -> Self {
         FeePolicy::FeeRate(FeeRate::default_min_relay_fee())
     }
 }
 
-impl<'a, Cs: Clone, Ctx, D> Clone for TxBuilder<'a, D, Cs, Ctx> {
+impl<'a, D, Cs: Clone, Ctx> Clone for TxBuilder<'a, D, Cs, Ctx> {
     fn clone(&self) -> Self {
         TxBuilder {
-            wallet: self.wallet,
+            wallet: self.wallet.clone(),
             params: self.params.clone(),
             coin_selection: self.coin_selection.clone(),
             phantom: PhantomData,
@@ -180,9 +182,7 @@ impl<'a, Cs: Clone, Ctx, D> Clone for TxBuilder<'a, D, Cs, Ctx> {
 }
 
 // methods supported by both contexts, for any CoinSelectionAlgorithm
-impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
-    TxBuilder<'a, D, Cs, Ctx>
-{
+impl<'a, D, Cs: CoinSelectionAlgorithm, Ctx: TxBuilderContext> TxBuilder<'a, D, Cs, Ctx> {
     /// Set a custom fee rate
     pub fn fee_rate(&mut self, fee_rate: FeeRate) -> &mut Self {
         self.params.fee_policy = Some(FeePolicy::FeeRate(fee_rate));
@@ -243,7 +243,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     /// # use bitcoin::*;
     /// # use bdk::*;
     /// # let to_address = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
-    /// # let wallet = doctest_wallet!();
+    /// # let mut wallet = doctest_wallet!();
     /// let mut path = BTreeMap::new();
     /// path.insert("aabbccdd".to_string(), vec![0, 1]);
     ///
@@ -275,18 +275,21 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     /// These have priority over the "unspendable" utxos, meaning that if a utxo is present both in
     /// the "utxos" and the "unspendable" list, it will be spent.
     pub fn add_utxos(&mut self, outpoints: &[OutPoint]) -> Result<&mut Self, Error> {
-        let utxos = outpoints
-            .iter()
-            .map(|outpoint| self.wallet.get_utxo(*outpoint)?.ok_or(Error::UnknownUtxo))
-            .collect::<Result<Vec<_>, _>>()?;
+        {
+            let wallet = self.wallet.borrow();
+            let utxos = outpoints
+                .iter()
+                .map(|outpoint| wallet.get_utxo(*outpoint).ok_or(Error::UnknownUtxo))
+                .collect::<Result<Vec<_>, _>>()?;
 
-        for utxo in utxos {
-            let descriptor = self.wallet.get_descriptor_for_keychain(utxo.keychain);
-            let satisfaction_weight = descriptor.max_satisfaction_weight().unwrap();
-            self.params.utxos.push(WeightedUtxo {
-                satisfaction_weight,
-                utxo: Utxo::Local(utxo),
-            });
+            for utxo in utxos {
+                let descriptor = wallet.get_descriptor_for_keychain(utxo.keychain);
+                let satisfaction_weight = descriptor.max_satisfaction_weight().unwrap();
+                self.params.utxos.push(WeightedUtxo {
+                    satisfaction_weight,
+                    utxo: Utxo::Local(utxo),
+                });
+            }
         }
 
         Ok(self)
@@ -425,7 +428,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     /// Use a specific nLockTime while creating the transaction
     ///
     /// This can cause conflicts if the wallet's descriptors contain an "after" (OP_CLTV) operator.
-    pub fn nlocktime(&mut self, locktime: u32) -> &mut Self {
+    pub fn nlocktime(&mut self, locktime: LockTime) -> &mut Self {
         self.params.locktime = Some(locktime);
         self
     }
@@ -504,7 +507,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     /// Overrides the [`DefaultCoinSelectionAlgorithm`](super::coin_selection::DefaultCoinSelectionAlgorithm).
     ///
     /// Note that this function consumes the builder and returns it so it is usually best to put this as the first call on the builder.
-    pub fn coin_selection<P: CoinSelectionAlgorithm<D>>(
+    pub fn coin_selection<P: CoinSelectionAlgorithm>(
         self,
         coin_selection: P,
     ) -> TxBuilder<'a, D, P, Ctx> {
@@ -516,13 +519,18 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
         }
     }
 
-    /// Finish the building the transaction.
+    /// Finish building the transaction.
     ///
     /// Returns the [`BIP174`] "PSBT" and summary details about the transaction.
     ///
     /// [`BIP174`]: https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki
-    pub fn finish(self) -> Result<(Psbt, TransactionDetails), Error> {
-        self.wallet.create_tx(self.coin_selection, self.params)
+    pub fn finish(self) -> Result<(Psbt, TransactionDetails), Error>
+    where
+        D: persist::PersistBackend<KeychainKind, ConfirmationTime>,
+    {
+        self.wallet
+            .borrow_mut()
+            .create_tx(self.coin_selection, self.params)
     }
 
     /// Enable signaling RBF
@@ -540,7 +548,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     ///
     /// If the `nsequence` is higher than `0xFFFFFFFD` an error will be thrown, since it would not
     /// be a valid nSequence to signal RBF.
-    pub fn enable_rbf_with_sequence(&mut self, nsequence: u32) -> &mut Self {
+    pub fn enable_rbf_with_sequence(&mut self, nsequence: Sequence) -> &mut Self {
         self.params.rbf = Some(RbfValue::Value(nsequence));
         self
     }
@@ -557,12 +565,20 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>, Ctx: TxBuilderContext>
     ///
     /// In both cases, if you don't provide a current height, we use the last sync height.
     pub fn current_height(&mut self, height: u32) -> &mut Self {
-        self.params.current_height = Some(height);
+        self.params.current_height = Some(LockTime::from_height(height).expect("Invalid height"));
+        self
+    }
+
+    /// Set whether or not the dust limit is checked.
+    ///
+    /// **Note**: by avoiding a dust limit check you may end up with a transaction that is non-standard.
+    pub fn allow_dust(&mut self, allow_dust: bool) -> &mut Self {
+        self.params.allow_dust = allow_dust;
         self
     }
 }
 
-impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>> TxBuilder<'a, D, Cs, CreateTx> {
+impl<'a, D, Cs: CoinSelectionAlgorithm> TxBuilder<'a, D, Cs, CreateTx> {
     /// Replace the recipients already added with a new list
     pub fn set_recipients(&mut self, recipients: Vec<(Script, u64)>) -> &mut Self {
         self.params.recipients = recipients;
@@ -608,7 +624,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>> TxBuilder<'a, D, Cs, C
     /// # use bdk::*;
     /// # use bdk::wallet::tx_builder::CreateTx;
     /// # let to_address = Address::from_str("2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt").unwrap();
-    /// # let wallet = doctest_wallet!();
+    /// # let mut wallet = doctest_wallet!();
     /// let mut tx_builder = wallet.build_tx();
     ///
     /// tx_builder
@@ -633,7 +649,7 @@ impl<'a, D: BatchDatabase, Cs: CoinSelectionAlgorithm<D>> TxBuilder<'a, D, Cs, C
 }
 
 // methods supported only by bump_fee
-impl<'a, D: BatchDatabase> TxBuilder<'a, D, DefaultCoinSelectionAlgorithm, BumpFee> {
+impl<'a, D> TxBuilder<'a, D, DefaultCoinSelectionAlgorithm, BumpFee> {
     /// Explicitly tells the wallet that it is allowed to reduce the amount of the output matching this
     /// `script_pubkey` in order to bump the transaction fee. Without specifying this the wallet
     /// will attempt to find a change output to shrink instead.
@@ -688,14 +704,8 @@ impl TxOrdering {
             TxOrdering::Untouched => {}
             TxOrdering::Shuffle => {
                 use rand::seq::SliceRandom;
-                #[cfg(test)]
-                use rand::SeedableRng;
-
-                #[cfg(not(test))]
                 let mut rng = rand::thread_rng();
-                #[cfg(test)]
-                let mut rng = rand::rngs::StdRng::seed_from_u64(0);
-
+                tx.input.shuffle(&mut rng);
                 tx.output.shuffle(&mut rng);
             }
             TxOrdering::Bip69Lexicographic => {
@@ -727,13 +737,13 @@ impl Default for Version {
 #[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
 pub(crate) enum RbfValue {
     Default,
-    Value(u32),
+    Value(Sequence),
 }
 
 impl RbfValue {
-    pub(crate) fn get_value(&self) -> u32 {
+    pub(crate) fn get_value(&self) -> Sequence {
         match self {
-            RbfValue::Default => 0xFFFFFFFD,
+            RbfValue::Default => Sequence::ENABLE_RBF_NO_LOCKTIME,
             RbfValue::Value(v) => *v,
         }
     }
@@ -781,6 +791,7 @@ mod test {
         };
     }
 
+    use bdk_chain::ConfirmationTime;
     use bitcoin::consensus::deserialize;
     use bitcoin::hashes::hex::FromHex;
 
@@ -806,15 +817,25 @@ mod test {
         let original_tx = ordering_test_tx!();
         let mut tx = original_tx.clone();
 
-        TxOrdering::Shuffle.sort_tx(&mut tx);
+        (0..40)
+            .find(|_| {
+                TxOrdering::Shuffle.sort_tx(&mut tx);
+                original_tx.input != tx.input
+            })
+            .expect("it should have moved the inputs at least once");
 
-        assert_eq!(original_tx.input, tx.input);
-        assert_ne!(original_tx.output, tx.output);
+        let mut tx = original_tx.clone();
+        (0..40)
+            .find(|_| {
+                TxOrdering::Shuffle.sort_tx(&mut tx);
+                original_tx.output != tx.output
+            })
+            .expect("it should have moved the outputs at least once");
     }
 
     #[test]
     fn test_output_ordering_bip69() {
-        use std::str::FromStr;
+        use core::str::FromStr;
 
         let original_tx = ordering_test_tx!();
         let mut tx = original_tx;
@@ -849,24 +870,33 @@ mod test {
     }
 
     fn get_test_utxos() -> Vec<LocalUtxo> {
+        use bitcoin::hashes::Hash;
+
         vec![
             LocalUtxo {
                 outpoint: OutPoint {
-                    txid: Default::default(),
+                    txid: bitcoin::Txid::from_inner([0; 32]),
                     vout: 0,
                 },
                 txout: Default::default(),
                 keychain: KeychainKind::External,
                 is_spent: false,
+                confirmation_time: ConfirmationTime::Unconfirmed,
+                derivation_index: 0,
             },
             LocalUtxo {
                 outpoint: OutPoint {
-                    txid: Default::default(),
+                    txid: bitcoin::Txid::from_inner([0; 32]),
                     vout: 1,
                 },
                 txout: Default::default(),
                 keychain: KeychainKind::Internal,
                 is_spent: false,
+                confirmation_time: ConfirmationTime::Confirmed {
+                    height: 32,
+                    time: 42,
+                },
+                derivation_index: 1,
             },
         ]
     }

crates/bdk/src/wallet/utils.rs

@@ -9,23 +9,11 @@
 // You may not use this file except in accordance with one or both of these
 // licenses.
 
-use bitcoin::blockdata::script::Script;
 use bitcoin::secp256k1::{All, Secp256k1};
+use bitcoin::{LockTime, Script, Sequence};
 
 use miniscript::{MiniscriptKey, Satisfier, ToPublicKey};
 
-// MSB of the nSequence. If set there's no consensus-constraint, so it must be disabled when
-// spending using CSV in order to enforce CSV rules
-pub(crate) const SEQUENCE_LOCKTIME_DISABLE_FLAG: u32 = 1 << 31;
-// When nSequence is lower than this flag the timelock is interpreted as block-height-based,
-// otherwise it's time-based
-pub(crate) const SEQUENCE_LOCKTIME_TYPE_FLAG: u32 = 1 << 22;
-// Mask for the bits used to express the timelock
-pub(crate) const SEQUENCE_LOCKTIME_MASK: u32 = 0x0000FFFF;
-
-// Threshold for nLockTime to be considered a block-height-based timelock rather than time-based
-pub(crate) const BLOCKS_TIMELOCK_THRESHOLD: u32 = 500000000;
-
 /// Trait to check if a value is below the dust limit.
 /// We are performing dust value calculation for a given script public key using rust-bitcoin to
 /// keep it compatible with network dust rate
@@ -38,7 +26,7 @@ pub trait IsDust {
 
 impl IsDust for u64 {
     fn is_dust(&self, script: &Script) -> bool {
-        *self < script.dust_value().as_sat()
+        *self < script.dust_value().to_sat()
     }
 }
 
@@ -56,19 +44,15 @@ impl After {
     }
 }
 
-pub(crate) fn check_nsequence_rbf(rbf: u32, csv: u32) -> bool {
-    // This flag cannot be set in the nSequence when spending using OP_CSV
-    if rbf & SEQUENCE_LOCKTIME_DISABLE_FLAG != 0 {
+pub(crate) fn check_nsequence_rbf(rbf: Sequence, csv: Sequence) -> bool {
+    // The RBF value must enable relative timelocks
+    if !rbf.is_relative_lock_time() {
         return false;
     }
 
-    let mask = SEQUENCE_LOCKTIME_TYPE_FLAG | SEQUENCE_LOCKTIME_MASK;
-    let rbf = rbf & mask;
-    let csv = csv & mask;
-
     // Both values should be represented in the same unit (either time-based or
     // block-height based)
-    if (rbf < SEQUENCE_LOCKTIME_TYPE_FLAG) != (csv < SEQUENCE_LOCKTIME_TYPE_FLAG) {
+    if rbf.is_time_locked() != csv.is_time_locked() {
         return false;
     }
 
@@ -80,24 +64,10 @@ pub(crate) fn check_nsequence_rbf(rbf: u32, csv: u32) -> bool {
     true
 }
 
-pub(crate) fn check_nlocktime(nlocktime: u32, required: u32) -> bool {
-    // Both values should be expressed in the same unit
-    if (nlocktime < BLOCKS_TIMELOCK_THRESHOLD) != (required < BLOCKS_TIMELOCK_THRESHOLD) {
-        return false;
-    }
-
-    // The value should be at least `required`
-    if nlocktime < required {
-        return false;
-    }
-
-    true
-}
-
 impl<Pk: MiniscriptKey + ToPublicKey> Satisfier<Pk> for After {
-    fn check_after(&self, n: u32) -> bool {
+    fn check_after(&self, n: LockTime) -> bool {
         if let Some(current_height) = self.current_height {
-            current_height >= n
+            current_height >= n.to_consensus_u32()
         } else {
             self.assume_height_reached
         }
@@ -125,10 +95,15 @@ impl Older {
 }
 
 impl<Pk: MiniscriptKey + ToPublicKey> Satisfier<Pk> for Older {
-    fn check_older(&self, n: u32) -> bool {
+    fn check_older(&self, n: Sequence) -> bool {
         if let Some(current_height) = self.current_height {
             // TODO: test >= / >
-            current_height as u64 >= self.create_height.unwrap_or(0) as u64 + n as u64
+            current_height
+                >= self
+                    .create_height
+                    .unwrap_or(0)
+                    .checked_add(n.to_consensus_u32())
+                    .expect("Overflowing addition")
         } else {
             self.assume_height_reached
         }
@@ -139,13 +114,13 @@ pub(crate) type SecpCtx = Secp256k1<All>;
 
 #[cfg(test)]
 mod test {
-    use super::{
-        check_nlocktime, check_nsequence_rbf, IsDust, BLOCKS_TIMELOCK_THRESHOLD,
-        SEQUENCE_LOCKTIME_TYPE_FLAG,
-    };
-    use crate::bitcoin::Address;
-    use crate::types::FeeRate;
-    use std::str::FromStr;
+    // When nSequence is lower than this flag the timelock is interpreted as block-height-based,
+    // otherwise it's time-based
+    pub(crate) const SEQUENCE_LOCKTIME_TYPE_FLAG: u32 = 1 << 22;
+
+    use super::{check_nsequence_rbf, IsDust};
+    use crate::bitcoin::{Address, Sequence};
+    use core::str::FromStr;
 
     #[test]
     fn test_is_dust() {
@@ -164,86 +139,42 @@ mod test {
         assert!(!294.is_dust(&script_p2wpkh));
     }
 
-    #[test]
-    fn test_fee_from_btc_per_kb() {
-        let fee = FeeRate::from_btc_per_kvb(1e-5);
-        assert!((fee.as_sat_vb() - 1.0).abs() < 0.0001);
-    }
-
-    #[test]
-    fn test_fee_from_sats_vbyte() {
-        let fee = FeeRate::from_sat_per_vb(1.0);
-        assert!((fee.as_sat_vb() - 1.0).abs() < 0.0001);
-    }
-
-    #[test]
-    fn test_fee_default_min_relay_fee() {
-        let fee = FeeRate::default_min_relay_fee();
-        assert!((fee.as_sat_vb() - 1.0).abs() < 0.0001);
-    }
-
     #[test]
     fn test_check_nsequence_rbf_msb_set() {
-        let result = check_nsequence_rbf(0x80000000, 5000);
+        let result = check_nsequence_rbf(Sequence(0x80000000), Sequence(5000));
         assert!(!result);
     }
 
     #[test]
     fn test_check_nsequence_rbf_lt_csv() {
-        let result = check_nsequence_rbf(4000, 5000);
+        let result = check_nsequence_rbf(Sequence(4000), Sequence(5000));
         assert!(!result);
     }
 
     #[test]
     fn test_check_nsequence_rbf_different_unit() {
-        let result = check_nsequence_rbf(SEQUENCE_LOCKTIME_TYPE_FLAG + 5000, 5000);
+        let result =
+            check_nsequence_rbf(Sequence(SEQUENCE_LOCKTIME_TYPE_FLAG + 5000), Sequence(5000));
         assert!(!result);
     }
 
     #[test]
     fn test_check_nsequence_rbf_mask() {
-        let result = check_nsequence_rbf(0x3f + 10_000, 5000);
+        let result = check_nsequence_rbf(Sequence(0x3f + 10_000), Sequence(5000));
         assert!(result);
     }
 
     #[test]
     fn test_check_nsequence_rbf_same_unit_blocks() {
-        let result = check_nsequence_rbf(10_000, 5000);
+        let result = check_nsequence_rbf(Sequence(10_000), Sequence(5000));
         assert!(result);
     }
 
     #[test]
     fn test_check_nsequence_rbf_same_unit_time() {
         let result = check_nsequence_rbf(
-            SEQUENCE_LOCKTIME_TYPE_FLAG + 10_000,
-            SEQUENCE_LOCKTIME_TYPE_FLAG + 5000,
-        );
-        assert!(result);
-    }
-
-    #[test]
-    fn test_check_nlocktime_lt_cltv() {
-        let result = check_nlocktime(4000, 5000);
-        assert!(!result);
-    }
-
-    #[test]
-    fn test_check_nlocktime_different_unit() {
-        let result = check_nlocktime(BLOCKS_TIMELOCK_THRESHOLD + 5000, 5000);
-        assert!(!result);
-    }
-
-    #[test]
-    fn test_check_nlocktime_same_unit_blocks() {
-        let result = check_nlocktime(10_000, 5000);
-        assert!(result);
-    }
-
-    #[test]
-    fn test_check_nlocktime_same_unit_time() {
-        let result = check_nlocktime(
-            BLOCKS_TIMELOCK_THRESHOLD + 10_000,
-            BLOCKS_TIMELOCK_THRESHOLD + 5000,
+            Sequence(SEQUENCE_LOCKTIME_TYPE_FLAG + 10_000),
+            Sequence(SEQUENCE_LOCKTIME_TYPE_FLAG + 5000),
         );
         assert!(result);
     }

crates/bdk/tests/common.rs

@@ -0,0 +1,93 @@
+#![allow(unused)]
+use bdk::{wallet::AddressIndex, Wallet};
+use bdk_chain::{BlockId, ConfirmationTime};
+use bitcoin::hashes::Hash;
+use bitcoin::{BlockHash, Network, Transaction, TxOut};
+
+/// Return a fake wallet that appears to be funded for testing.
+pub fn get_funded_wallet_with_change(
+    descriptor: &str,
+    change: Option<&str>,
+) -> (Wallet, bitcoin::Txid) {
+    let mut wallet = Wallet::new_no_persist(descriptor, change, Network::Regtest).unwrap();
+    let address = wallet.get_address(AddressIndex::New).address;
+
+    let tx = Transaction {
+        version: 1,
+        lock_time: bitcoin::PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 50_000,
+            script_pubkey: address.script_pubkey(),
+        }],
+    };
+
+    wallet
+        .insert_checkpoint(BlockId {
+            height: 1_000,
+            hash: BlockHash::all_zeros(),
+        })
+        .unwrap();
+    wallet
+        .insert_tx(
+            tx.clone(),
+            ConfirmationTime::Confirmed {
+                height: 1_000,
+                time: 100,
+            },
+        )
+        .unwrap();
+
+    (wallet, tx.txid())
+}
+
+pub fn get_funded_wallet(descriptor: &str) -> (Wallet, bitcoin::Txid) {
+    get_funded_wallet_with_change(descriptor, None)
+}
+
+pub fn get_test_wpkh() -> &'static str {
+    "wpkh(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW)"
+}
+
+pub fn get_test_single_sig_csv() -> &'static str {
+    // and(pk(Alice),older(6))
+    "wsh(and_v(v:pk(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW),older(6)))"
+}
+
+pub fn get_test_a_or_b_plus_csv() -> &'static str {
+    // or(pk(Alice),and(pk(Bob),older(144)))
+    "wsh(or_d(pk(cRjo6jqfVNP33HhSS76UhXETZsGTZYx8FMFvR9kpbtCSV1PmdZdu),and_v(v:pk(cMnkdebixpXMPfkcNEjjGin7s94hiehAH4mLbYkZoh9KSiNNmqC8),older(144))))"
+}
+
+pub fn get_test_single_sig_cltv() -> &'static str {
+    // and(pk(Alice),after(100000))
+    "wsh(and_v(v:pk(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW),after(100000)))"
+}
+
+pub fn get_test_tr_single_sig() -> &'static str {
+    "tr(cNJmN3fH9DDbDt131fQNkVakkpzawJBSeybCUNmP1BovpmGQ45xG)"
+}
+
+pub fn get_test_tr_with_taptree() -> &'static str {
+    "tr(b511bd5771e47ee27558b1765e87b541668304ec567721c7b880edc0a010da55,{pk(cPZzKuNmpuUjD1e8jUU4PVzy2b5LngbSip8mBsxf4e7rSFZVb4Uh),pk(8aee2b8120a5f157f1223f72b5e62b825831a27a9fdf427db7cc697494d4a642)})"
+}
+
+pub fn get_test_tr_with_taptree_both_priv() -> &'static str {
+    "tr(b511bd5771e47ee27558b1765e87b541668304ec567721c7b880edc0a010da55,{pk(cPZzKuNmpuUjD1e8jUU4PVzy2b5LngbSip8mBsxf4e7rSFZVb4Uh),pk(cNaQCDwmmh4dS9LzCgVtyy1e1xjCJ21GUDHe9K98nzb689JvinGV)})"
+}
+
+pub fn get_test_tr_repeated_key() -> &'static str {
+    "tr(b511bd5771e47ee27558b1765e87b541668304ec567721c7b880edc0a010da55,{and_v(v:pk(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW),after(100)),and_v(v:pk(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW),after(200))})"
+}
+
+pub fn get_test_tr_single_sig_xprv() -> &'static str {
+    "tr(tprv8ZgxMBicQKsPdDArR4xSAECuVxeX1jwwSXR4ApKbkYgZiziDc4LdBy2WvJeGDfUSE4UT4hHhbgEwbdq8ajjUHiKDegkwrNU6V55CxcxonVN/*)"
+}
+
+pub fn get_test_tr_with_taptree_xprv() -> &'static str {
+    "tr(cNJmN3fH9DDbDt131fQNkVakkpzawJBSeybCUNmP1BovpmGQ45xG,{pk(tprv8ZgxMBicQKsPdDArR4xSAECuVxeX1jwwSXR4ApKbkYgZiziDc4LdBy2WvJeGDfUSE4UT4hHhbgEwbdq8ajjUHiKDegkwrNU6V55CxcxonVN/*),pk(8aee2b8120a5f157f1223f72b5e62b825831a27a9fdf427db7cc697494d4a642)})"
+}
+
+pub fn get_test_tr_dup_keys() -> &'static str {
+    "tr(cNJmN3fH9DDbDt131fQNkVakkpzawJBSeybCUNmP1BovpmGQ45xG,{pk(8aee2b8120a5f157f1223f72b5e62b825831a27a9fdf427db7cc697494d4a642),pk(8aee2b8120a5f157f1223f72b5e62b825831a27a9fdf427db7cc697494d4a642)})"
+}

crates/bdk/tests/psbt.rs

@@ -0,0 +1,158 @@
+use bdk::bitcoin::TxIn;
+use bdk::wallet::AddressIndex;
+use bdk::wallet::AddressIndex::New;
+use bdk::{psbt, FeeRate, SignOptions};
+use bitcoin::util::psbt::PartiallySignedTransaction as Psbt;
+use core::str::FromStr;
+mod common;
+use common::*;
+
+// from bip 174
+const PSBT_STR: &str = "cHNidP8BAKACAAAAAqsJSaCMWvfEm4IS9Bfi8Vqz9cM9zxU4IagTn4d6W3vkAAAAAAD+////qwlJoIxa98SbghL0F+LxWrP1wz3PFTghqBOfh3pbe+QBAAAAAP7///8CYDvqCwAAAAAZdqkUdopAu9dAy+gdmI5x3ipNXHE5ax2IrI4kAAAAAAAAGXapFG9GILVT+glechue4O/p+gOcykWXiKwAAAAAAAEHakcwRAIgR1lmF5fAGwNrJZKJSGhiGDR9iYZLcZ4ff89X0eURZYcCIFMJ6r9Wqk2Ikf/REf3xM286KdqGbX+EhtdVRs7tr5MZASEDXNxh/HupccC1AaZGoqg7ECy0OIEhfKaC3Ibi1z+ogpIAAQEgAOH1BQAAAAAXqRQ1RebjO4MsRwUPJNPuuTycA5SLx4cBBBYAFIXRNTfy4mVAWjTbr6nj3aAfuCMIAAAA";
+
+#[test]
+#[should_panic(expected = "InputIndexOutOfRange")]
+fn test_psbt_malformed_psbt_input_legacy() {
+    let psbt_bip = Psbt::from_str(PSBT_STR).unwrap();
+    let (mut wallet, _) = get_funded_wallet(get_test_wpkh());
+    let send_to = wallet.get_address(AddressIndex::New);
+    let mut builder = wallet.build_tx();
+    builder.add_recipient(send_to.script_pubkey(), 10_000);
+    let (mut psbt, _) = builder.finish().unwrap();
+    psbt.inputs.push(psbt_bip.inputs[0].clone());
+    let options = SignOptions {
+        trust_witness_utxo: true,
+        ..Default::default()
+    };
+    let _ = wallet.sign(&mut psbt, options).unwrap();
+}
+
+#[test]
+#[should_panic(expected = "InputIndexOutOfRange")]
+fn test_psbt_malformed_psbt_input_segwit() {
+    let psbt_bip = Psbt::from_str(PSBT_STR).unwrap();
+    let (mut wallet, _) = get_funded_wallet(get_test_wpkh());
+    let send_to = wallet.get_address(AddressIndex::New);
+    let mut builder = wallet.build_tx();
+    builder.add_recipient(send_to.script_pubkey(), 10_000);
+    let (mut psbt, _) = builder.finish().unwrap();
+    psbt.inputs.push(psbt_bip.inputs[1].clone());
+    let options = SignOptions {
+        trust_witness_utxo: true,
+        ..Default::default()
+    };
+    let _ = wallet.sign(&mut psbt, options).unwrap();
+}
+
+#[test]
+#[should_panic(expected = "InputIndexOutOfRange")]
+fn test_psbt_malformed_tx_input() {
+    let (mut wallet, _) = get_funded_wallet(get_test_wpkh());
+    let send_to = wallet.get_address(AddressIndex::New);
+    let mut builder = wallet.build_tx();
+    builder.add_recipient(send_to.script_pubkey(), 10_000);
+    let (mut psbt, _) = builder.finish().unwrap();
+    psbt.unsigned_tx.input.push(TxIn::default());
+    let options = SignOptions {
+        trust_witness_utxo: true,
+        ..Default::default()
+    };
+    let _ = wallet.sign(&mut psbt, options).unwrap();
+}
+
+#[test]
+fn test_psbt_sign_with_finalized() {
+    let psbt_bip = Psbt::from_str(PSBT_STR).unwrap();
+    let (mut wallet, _) = get_funded_wallet(get_test_wpkh());
+    let send_to = wallet.get_address(AddressIndex::New);
+    let mut builder = wallet.build_tx();
+    builder.add_recipient(send_to.script_pubkey(), 10_000);
+    let (mut psbt, _) = builder.finish().unwrap();
+
+    // add a finalized input
+    psbt.inputs.push(psbt_bip.inputs[0].clone());
+    psbt.unsigned_tx
+        .input
+        .push(psbt_bip.unsigned_tx.input[0].clone());
+
+    let _ = wallet.sign(&mut psbt, SignOptions::default()).unwrap();
+}
+
+#[test]
+fn test_psbt_fee_rate_with_witness_utxo() {
+    use psbt::PsbtUtils;
+
+    let expected_fee_rate = 1.2345;
+
+    let (mut wallet, _) = get_funded_wallet("wpkh(tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)");
+    let addr = wallet.get_address(New);
+    let mut builder = wallet.build_tx();
+    builder.drain_to(addr.script_pubkey()).drain_wallet();
+    builder.fee_rate(FeeRate::from_sat_per_vb(expected_fee_rate));
+    let (mut psbt, _) = builder.finish().unwrap();
+    let fee_amount = psbt.fee_amount();
+    assert!(fee_amount.is_some());
+
+    let unfinalized_fee_rate = psbt.fee_rate().unwrap();
+
+    let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
+    assert!(finalized);
+
+    let finalized_fee_rate = psbt.fee_rate().unwrap();
+    assert!(finalized_fee_rate.as_sat_per_vb() >= expected_fee_rate);
+    assert!(finalized_fee_rate.as_sat_per_vb() < unfinalized_fee_rate.as_sat_per_vb());
+}
+
+#[test]
+fn test_psbt_fee_rate_with_nonwitness_utxo() {
+    use psbt::PsbtUtils;
+
+    let expected_fee_rate = 1.2345;
+
+    let (mut wallet, _) = get_funded_wallet("pkh(tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)");
+    let addr = wallet.get_address(New);
+    let mut builder = wallet.build_tx();
+    builder.drain_to(addr.script_pubkey()).drain_wallet();
+    builder.fee_rate(FeeRate::from_sat_per_vb(expected_fee_rate));
+    let (mut psbt, _) = builder.finish().unwrap();
+    let fee_amount = psbt.fee_amount();
+    assert!(fee_amount.is_some());
+    let unfinalized_fee_rate = psbt.fee_rate().unwrap();
+
+    let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
+    assert!(finalized);
+
+    let finalized_fee_rate = psbt.fee_rate().unwrap();
+    assert!(finalized_fee_rate.as_sat_per_vb() >= expected_fee_rate);
+    assert!(finalized_fee_rate.as_sat_per_vb() < unfinalized_fee_rate.as_sat_per_vb());
+}
+
+#[test]
+fn test_psbt_fee_rate_with_missing_txout() {
+    use psbt::PsbtUtils;
+
+    let expected_fee_rate = 1.2345;
+
+    let (mut wpkh_wallet,  _) = get_funded_wallet("wpkh(tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)");
+    let addr = wpkh_wallet.get_address(New);
+    let mut builder = wpkh_wallet.build_tx();
+    builder.drain_to(addr.script_pubkey()).drain_wallet();
+    builder.fee_rate(FeeRate::from_sat_per_vb(expected_fee_rate));
+    let (mut wpkh_psbt, _) = builder.finish().unwrap();
+
+    wpkh_psbt.inputs[0].witness_utxo = None;
+    wpkh_psbt.inputs[0].non_witness_utxo = None;
+    assert!(wpkh_psbt.fee_amount().is_none());
+    assert!(wpkh_psbt.fee_rate().is_none());
+
+    let (mut pkh_wallet,  _) = get_funded_wallet("pkh(tprv8ZgxMBicQKsPd3EupYiPRhaMooHKUHJxNsTfYuScep13go8QFfHdtkG9nRkFGb7busX4isf6X9dURGCoKgitaApQ6MupRhZMcELAxTBRJgS/*)");
+    let addr = pkh_wallet.get_address(New);
+    let mut builder = pkh_wallet.build_tx();
+    builder.drain_to(addr.script_pubkey()).drain_wallet();
+    builder.fee_rate(FeeRate::from_sat_per_vb(expected_fee_rate));
+    let (mut pkh_psbt, _) = builder.finish().unwrap();
+
+    pkh_psbt.inputs[0].non_witness_utxo = None;
+    assert!(pkh_psbt.fee_amount().is_none());
+    assert!(pkh_psbt.fee_rate().is_none());
+}

crates/chain/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "bdk_chain"
+version = "0.4.0"
+edition = "2021"
+rust-version = "1.57"
+homepage = "https://bitcoindevkit.org"
+repository = "https://github.com/bitcoindevkit/bdk"
+documentation = "https://docs.rs/bdk_chain"
+description = "Collection of core structures for Bitcoin Dev Kit."
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bitcoin = { version = "0.29" }
+serde_crate = { package = "serde", version = "1", optional = true, features = ["derive"] }
+
+# Use hashbrown as a feature flag to have HashSet and HashMap from it.
+# note version 0.13 breaks outs MSRV.
+hashbrown = { version = "0.12", optional = true,  features = ["serde"] }
+miniscript = { version = "9.0.0", optional = true  }
+
+[dev-dependencies]
+rand = "0.8"
+
+[features]
+default = ["std", "miniscript"]
+std = []
+serde = ["serde_crate", "bitcoin/serde" ]

crates/chain/README.md

@@ -0,0 +1,3 @@
+# BDK Chain
+
+BDK keychain tracker, tools for storing and indexing chain data.

crates/chain/src/chain_data.rs

@@ -0,0 +1,218 @@
+use bitcoin::{hashes::Hash, BlockHash, OutPoint, TxOut, Txid};
+
+use crate::{
+    sparse_chain::{self, ChainPosition},
+    COINBASE_MATURITY,
+};
+
+/// Represents the height at which a transaction is confirmed.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(crate = "serde_crate")
+)]
+pub enum TxHeight {
+    Confirmed(u32),
+    Unconfirmed,
+}
+
+impl Default for TxHeight {
+    fn default() -> Self {
+        Self::Unconfirmed
+    }
+}
+
+impl core::fmt::Display for TxHeight {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Confirmed(h) => core::write!(f, "confirmed_at({})", h),
+            Self::Unconfirmed => core::write!(f, "unconfirmed"),
+        }
+    }
+}
+
+impl From<Option<u32>> for TxHeight {
+    fn from(opt: Option<u32>) -> Self {
+        match opt {
+            Some(h) => Self::Confirmed(h),
+            None => Self::Unconfirmed,
+        }
+    }
+}
+
+impl From<TxHeight> for Option<u32> {
+    fn from(height: TxHeight) -> Self {
+        match height {
+            TxHeight::Confirmed(h) => Some(h),
+            TxHeight::Unconfirmed => None,
+        }
+    }
+}
+
+impl crate::sparse_chain::ChainPosition for TxHeight {
+    fn height(&self) -> TxHeight {
+        *self
+    }
+
+    fn max_ord_of_height(height: TxHeight) -> Self {
+        height
+    }
+
+    fn min_ord_of_height(height: TxHeight) -> Self {
+        height
+    }
+}
+
+impl TxHeight {
+    pub fn is_confirmed(&self) -> bool {
+        matches!(self, Self::Confirmed(_))
+    }
+}
+
+/// Block height and timestamp at which a transaction is confirmed.
+#[derive(Debug, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(crate = "serde_crate")
+)]
+pub enum ConfirmationTime {
+    Confirmed { height: u32, time: u64 },
+    Unconfirmed,
+}
+
+impl sparse_chain::ChainPosition for ConfirmationTime {
+    fn height(&self) -> TxHeight {
+        match self {
+            ConfirmationTime::Confirmed { height, .. } => TxHeight::Confirmed(*height),
+            ConfirmationTime::Unconfirmed => TxHeight::Unconfirmed,
+        }
+    }
+
+    fn max_ord_of_height(height: TxHeight) -> Self {
+        match height {
+            TxHeight::Confirmed(height) => Self::Confirmed {
+                height,
+                time: u64::MAX,
+            },
+            TxHeight::Unconfirmed => Self::Unconfirmed,
+        }
+    }
+
+    fn min_ord_of_height(height: TxHeight) -> Self {
+        match height {
+            TxHeight::Confirmed(height) => Self::Confirmed {
+                height,
+                time: u64::MIN,
+            },
+            TxHeight::Unconfirmed => Self::Unconfirmed,
+        }
+    }
+}
+
+impl ConfirmationTime {
+    pub fn is_confirmed(&self) -> bool {
+        matches!(self, Self::Confirmed { .. })
+    }
+}
+
+/// A reference to a block in the canonical chain.
+#[derive(Debug, Clone, PartialEq, Eq, Copy, PartialOrd, Ord)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(crate = "serde_crate")
+)]
+pub struct BlockId {
+    /// The height of the block.
+    pub height: u32,
+    /// The hash of the block.
+    pub hash: BlockHash,
+}
+
+impl Default for BlockId {
+    fn default() -> Self {
+        Self {
+            height: Default::default(),
+            hash: BlockHash::from_inner([0u8; 32]),
+        }
+    }
+}
+
+impl From<(u32, BlockHash)> for BlockId {
+    fn from((height, hash): (u32, BlockHash)) -> Self {
+        Self { height, hash }
+    }
+}
+
+impl From<BlockId> for (u32, BlockHash) {
+    fn from(block_id: BlockId) -> Self {
+        (block_id.height, block_id.hash)
+    }
+}
+
+impl From<(&u32, &BlockHash)> for BlockId {
+    fn from((height, hash): (&u32, &BlockHash)) -> Self {
+        Self {
+            height: *height,
+            hash: *hash,
+        }
+    }
+}
+
+/// A `TxOut` with as much data as we can retrieve about it
+#[derive(Debug, Clone, PartialEq)]
+pub struct FullTxOut<I> {
+    /// The location of the `TxOut`.
+    pub outpoint: OutPoint,
+    /// The `TxOut`.
+    pub txout: TxOut,
+    /// The position of the transaction in `outpoint` in the overall chain.
+    pub chain_position: I,
+    /// The txid and chain position of the transaction (if any) that has spent this output.
+    pub spent_by: Option<(I, Txid)>,
+    /// Whether this output is on a coinbase transaction.
+    pub is_on_coinbase: bool,
+}
+
+impl<I: ChainPosition> FullTxOut<I> {
+    /// Whether the utxo is/was/will be spendable at `height`.
+    ///
+    /// It is spendable if it is not an immature coinbase output and no spending tx has been
+    /// confirmed by that height.
+    pub fn is_spendable_at(&self, height: u32) -> bool {
+        if !self.is_mature(height) {
+            return false;
+        }
+
+        if self.chain_position.height() > TxHeight::Confirmed(height) {
+            return false;
+        }
+
+        match &self.spent_by {
+            Some((spending_height, _)) => spending_height.height() > TxHeight::Confirmed(height),
+            None => true,
+        }
+    }
+
+    pub fn is_mature(&self, height: u32) -> bool {
+        if self.is_on_coinbase {
+            let tx_height = match self.chain_position.height() {
+                TxHeight::Confirmed(tx_height) => tx_height,
+                TxHeight::Unconfirmed => {
+                    debug_assert!(false, "coinbase tx can never be unconfirmed");
+                    return false;
+                }
+            };
+            let age = height.saturating_sub(tx_height);
+            if age + 1 < COINBASE_MATURITY {
+                return false;
+            }
+        }
+
+        true
+    }
+}
+
+// TODO: make test

crates/chain/src/chain_graph.rs

@@ -0,0 +1,639 @@
+//! Module for structures that combine the features of [`sparse_chain`] and [`tx_graph`].
+use crate::{
+    collections::HashSet,
+    sparse_chain::{self, ChainPosition, SparseChain},
+    tx_graph::{self, TxGraph},
+    BlockId, ForEachTxOut, FullTxOut, TxHeight,
+};
+use alloc::{string::ToString, vec::Vec};
+use bitcoin::{OutPoint, Transaction, TxOut, Txid};
+use core::fmt::Debug;
+
+/// A consistent combination of a [`SparseChain<P>`] and a [`TxGraph<T>`].
+///
+/// `SparseChain` only keeps track of transaction ids and their position in the chain, but you often
+/// want to store the full transactions as well. Additionally, you want to make sure that everything
+/// in the chain is consistent with the full transaction data. `ChainGraph` enforces these two
+/// invariants:
+///
+/// 1. Every transaction that is in the chain is also in the graph (you always have the full
+/// transaction).
+/// 2. No transactions in the chain conflict with each other, i.e., they don't double spend each
+/// other or have ancestors that double spend each other.
+///
+/// Note that the `ChainGraph` guarantees a 1:1 mapping between transactions in the `chain` and
+/// `graph` but not the other way around. Transactions may fall out of the *chain* (via re-org or
+/// mempool eviction) but will remain in the *graph*.
+#[derive(Clone, Debug, PartialEq)]
+pub struct ChainGraph<P = TxHeight> {
+    chain: SparseChain<P>,
+    graph: TxGraph,
+}
+
+impl<P> Default for ChainGraph<P> {
+    fn default() -> Self {
+        Self {
+            chain: Default::default(),
+            graph: Default::default(),
+        }
+    }
+}
+
+impl<P> AsRef<SparseChain<P>> for ChainGraph<P> {
+    fn as_ref(&self) -> &SparseChain<P> {
+        &self.chain
+    }
+}
+
+impl<P> AsRef<TxGraph> for ChainGraph<P> {
+    fn as_ref(&self) -> &TxGraph {
+        &self.graph
+    }
+}
+
+impl<P> AsRef<ChainGraph<P>> for ChainGraph<P> {
+    fn as_ref(&self) -> &ChainGraph<P> {
+        self
+    }
+}
+
+impl<P> ChainGraph<P> {
+    /// Returns a reference to the internal [`SparseChain`].
+    pub fn chain(&self) -> &SparseChain<P> {
+        &self.chain
+    }
+
+    /// Returns a reference to the internal [`TxGraph`].
+    pub fn graph(&self) -> &TxGraph {
+        &self.graph
+    }
+}
+
+impl<P> ChainGraph<P>
+where
+    P: ChainPosition,
+{
+    /// Create a new chain graph from a `chain` and a `graph`.
+    ///
+    /// There are two reasons this can return an `Err`:
+    ///
+    /// 1. There is a transaction in the `chain` that does not have its corresponding full
+    /// transaction in `graph`.
+    /// 2. The `chain` has two transactions that are allegedly in it, but they conflict in the `graph`
+    /// (so could not possibly be in the same chain).
+    pub fn new(chain: SparseChain<P>, graph: TxGraph) -> Result<Self, NewError<P>> {
+        let mut missing = HashSet::default();
+        for (pos, txid) in chain.txids() {
+            if let Some(tx) = graph.get_tx(*txid) {
+                let conflict = graph
+                    .walk_conflicts(tx, |_, txid| Some((chain.tx_position(txid)?.clone(), txid)))
+                    .next();
+                if let Some((conflict_pos, conflict)) = conflict {
+                    return Err(NewError::Conflict {
+                        a: (pos.clone(), *txid),
+                        b: (conflict_pos, conflict),
+                    });
+                }
+            } else {
+                missing.insert(*txid);
+            }
+        }
+
+        if !missing.is_empty() {
+            return Err(NewError::Missing(missing));
+        }
+
+        Ok(Self { chain, graph })
+    }
+
+    /// Take an update in the form of a [`SparseChain<P>`][`SparseChain`] and attempt to turn it
+    /// into a chain graph by filling in full transactions from `self` and from `new_txs`. This
+    /// returns a `ChainGraph<P, Cow<T>>` where the [`Cow<'a, T>`] will borrow the transaction if it
+    /// got it from `self`.
+    ///
+    /// This is useful when interacting with services like an electrum server which returns a list
+    /// of txids and heights when calling [`script_get_history`], which can easily be inserted into a
+    /// [`SparseChain<TxHeight>`][`SparseChain`]. From there, you need to figure out which full
+    /// transactions you are missing in your chain graph and form `new_txs`. You then use
+    /// `inflate_update` to turn this into an update `ChainGraph<P, Cow<Transaction>>` and finally
+    /// use [`determine_changeset`] to generate the changeset from it.
+    ///
+    /// [`SparseChain`]: crate::sparse_chain::SparseChain
+    /// [`Cow<'a, T>`]: std::borrow::Cow
+    /// [`script_get_history`]: https://docs.rs/electrum-client/latest/electrum_client/trait.ElectrumApi.html#tymethod.script_get_history
+    /// [`determine_changeset`]: Self::determine_changeset
+    pub fn inflate_update(
+        &self,
+        update: SparseChain<P>,
+        new_txs: impl IntoIterator<Item = Transaction>,
+    ) -> Result<ChainGraph<P>, NewError<P>> {
+        let mut inflated_chain = SparseChain::default();
+        let mut inflated_graph = TxGraph::default();
+
+        for (height, hash) in update.checkpoints().clone().into_iter() {
+            let _ = inflated_chain
+                .insert_checkpoint(BlockId { height, hash })
+                .expect("must insert");
+        }
+
+        // [TODO] @evanlinjin: These need better comments
+        // - copy transactions that have changed positions into the graph
+        // - add new transactions to an inflated chain
+        for (pos, txid) in update.txids() {
+            match self.chain.tx_position(*txid) {
+                Some(original_pos) => {
+                    if original_pos != pos {
+                        let tx = self
+                            .graph
+                            .get_tx(*txid)
+                            .expect("tx must exist as it is referenced in sparsechain")
+                            .clone();
+                        let _ = inflated_chain
+                            .insert_tx(*txid, pos.clone())
+                            .expect("must insert since this was already in update");
+                        let _ = inflated_graph.insert_tx(tx);
+                    }
+                }
+                None => {
+                    let _ = inflated_chain
+                        .insert_tx(*txid, pos.clone())
+                        .expect("must insert since this was already in update");
+                }
+            }
+        }
+
+        for tx in new_txs {
+            let _ = inflated_graph.insert_tx(tx);
+        }
+
+        ChainGraph::new(inflated_chain, inflated_graph)
+    }
+
+    /// Gets the checkpoint limit.
+    ///
+    /// Refer to [`SparseChain::checkpoint_limit`] for more.
+    pub fn checkpoint_limit(&self) -> Option<usize> {
+        self.chain.checkpoint_limit()
+    }
+
+    /// Sets the checkpoint limit.
+    ///
+    /// Refer to [`SparseChain::set_checkpoint_limit`] for more.
+    pub fn set_checkpoint_limit(&mut self, limit: Option<usize>) {
+        self.chain.set_checkpoint_limit(limit)
+    }
+
+    /// Determines the changes required to invalidate checkpoints `from_height` (inclusive) and
+    /// above. Displaced transactions will have their positions moved to [`TxHeight::Unconfirmed`].
+    pub fn invalidate_checkpoints_preview(&self, from_height: u32) -> ChangeSet<P> {
+        ChangeSet {
+            chain: self.chain.invalidate_checkpoints_preview(from_height),
+            ..Default::default()
+        }
+    }
+
+    /// Invalidate checkpoints `from_height` (inclusive) and above. Displaced transactions will be
+    /// re-positioned to [`TxHeight::Unconfirmed`].
+    ///
+    /// This is equivalent to calling [`Self::invalidate_checkpoints_preview`] and
+    /// [`Self::apply_changeset`] in sequence.
+    pub fn invalidate_checkpoints(&mut self, from_height: u32) -> ChangeSet<P>
+    where
+        ChangeSet<P>: Clone,
+    {
+        let changeset = self.invalidate_checkpoints_preview(from_height);
+        self.apply_changeset(changeset.clone());
+        changeset
+    }
+
+    /// Get a transaction currently in the underlying [`SparseChain`].
+    ///
+    /// This does not necessarily mean that it is *confirmed* in the blockchain; it might just be in
+    /// the unconfirmed transaction list within the [`SparseChain`].
+    pub fn get_tx_in_chain(&self, txid: Txid) -> Option<(&P, &Transaction)> {
+        let position = self.chain.tx_position(txid)?;
+        let full_tx = self.graph.get_tx(txid).expect("must exist");
+        Some((position, full_tx))
+    }
+
+    /// Determines the changes required to insert a transaction into the inner [`ChainGraph`] and
+    /// [`SparseChain`] at the given `position`.
+    ///
+    /// If inserting it into the chain `position` will result in conflicts, the returned
+    /// [`ChangeSet`] should evict conflicting transactions.
+    pub fn insert_tx_preview(
+        &self,
+        tx: Transaction,
+        pos: P,
+    ) -> Result<ChangeSet<P>, InsertTxError<P>> {
+        let mut changeset = ChangeSet {
+            chain: self.chain.insert_tx_preview(tx.txid(), pos)?,
+            graph: self.graph.insert_tx_preview(tx),
+        };
+        self.fix_conflicts(&mut changeset)?;
+        Ok(changeset)
+    }
+
+    /// Inserts [`Transaction`] at the given chain position.
+    ///
+    /// This is equivalent to calling [`Self::insert_tx_preview`] and [`Self::apply_changeset`] in
+    /// sequence.
+    pub fn insert_tx(&mut self, tx: Transaction, pos: P) -> Result<ChangeSet<P>, InsertTxError<P>> {
+        let changeset = self.insert_tx_preview(tx, pos)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Determines the changes required to insert a [`TxOut`] into the internal [`TxGraph`].
+    pub fn insert_txout_preview(&self, outpoint: OutPoint, txout: TxOut) -> ChangeSet<P> {
+        ChangeSet {
+            chain: Default::default(),
+            graph: self.graph.insert_txout_preview(outpoint, txout),
+        }
+    }
+
+    /// Inserts a [`TxOut`] into the internal [`TxGraph`].
+    ///
+    /// This is equivalent to calling [`Self::insert_txout_preview`] and [`Self::apply_changeset`]
+    /// in sequence.
+    pub fn insert_txout(&mut self, outpoint: OutPoint, txout: TxOut) -> ChangeSet<P> {
+        let changeset = self.insert_txout_preview(outpoint, txout);
+        self.apply_changeset(changeset.clone());
+        changeset
+    }
+
+    /// Determines the changes required to insert a `block_id` (a height and block hash) into the
+    /// chain.
+    ///
+    /// If a checkpoint with a different hash already exists at that height, this will return an error.
+    pub fn insert_checkpoint_preview(
+        &self,
+        block_id: BlockId,
+    ) -> Result<ChangeSet<P>, InsertCheckpointError> {
+        self.chain
+            .insert_checkpoint_preview(block_id)
+            .map(|chain_changeset| ChangeSet {
+                chain: chain_changeset,
+                ..Default::default()
+            })
+    }
+
+    /// Inserts checkpoint into [`Self`].
+    ///
+    /// This is equivalent to calling [`Self::insert_checkpoint_preview`] and
+    /// [`Self::apply_changeset`] in sequence.
+    pub fn insert_checkpoint(
+        &mut self,
+        block_id: BlockId,
+    ) -> Result<ChangeSet<P>, InsertCheckpointError> {
+        let changeset = self.insert_checkpoint_preview(block_id)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Calculates the difference between self and `update` in the form of a [`ChangeSet`].
+    pub fn determine_changeset(
+        &self,
+        update: &ChainGraph<P>,
+    ) -> Result<ChangeSet<P>, UpdateError<P>> {
+        let chain_changeset = self
+            .chain
+            .determine_changeset(&update.chain)
+            .map_err(UpdateError::Chain)?;
+
+        let mut changeset = ChangeSet {
+            chain: chain_changeset,
+            graph: self.graph.determine_additions(&update.graph),
+        };
+
+        self.fix_conflicts(&mut changeset)?;
+        Ok(changeset)
+    }
+
+    /// Given a transaction, return an iterator of `txid`s that conflict with it (spends at least
+    /// one of the same inputs). This iterator includes all descendants of conflicting transactions.
+    ///
+    /// This method only returns conflicts that exist in the [`SparseChain`] as transactions that
+    /// are not included in [`SparseChain`] are already considered as evicted.
+    pub fn tx_conflicts_in_chain<'a>(
+        &'a self,
+        tx: &'a Transaction,
+    ) -> impl Iterator<Item = (&'a P, Txid)> + 'a {
+        self.graph.walk_conflicts(tx, move |_, conflict_txid| {
+            self.chain
+                .tx_position(conflict_txid)
+                .map(|conflict_pos| (conflict_pos, conflict_txid))
+        })
+    }
+
+    /// Fix changeset conflicts.
+    ///
+    /// **WARNING:** If there are any missing full txs, conflict resolution will not be complete. In
+    /// debug mode, this will result in panic.
+    fn fix_conflicts(&self, changeset: &mut ChangeSet<P>) -> Result<(), UnresolvableConflict<P>> {
+        let mut chain_conflicts = vec![];
+
+        for (&txid, pos_change) in &changeset.chain.txids {
+            let pos = match pos_change {
+                Some(pos) => {
+                    // Ignore txs that are still in the chain -- we only care about new ones
+                    if self.chain.tx_position(txid).is_some() {
+                        continue;
+                    }
+                    pos
+                }
+                // Ignore txids that are being deleted by the change (they can't conflict)
+                None => continue,
+            };
+
+            let mut full_tx = self.graph.get_tx(txid);
+
+            if full_tx.is_none() {
+                full_tx = changeset.graph.tx.iter().find(|tx| tx.txid() == txid)
+            }
+
+            debug_assert!(full_tx.is_some(), "should have full tx at this point");
+
+            let full_tx = match full_tx {
+                Some(full_tx) => full_tx,
+                None => continue,
+            };
+
+            for (conflict_pos, conflict_txid) in self.tx_conflicts_in_chain(full_tx) {
+                chain_conflicts.push((pos.clone(), txid, conflict_pos, conflict_txid))
+            }
+        }
+
+        for (update_pos, update_txid, conflicting_pos, conflicting_txid) in chain_conflicts {
+            // We have found a tx that conflicts with our update txid. Only allow this when the
+            // conflicting tx will be positioned as "unconfirmed" after the update is applied.
+            // If so, we will modify the changeset to evict the conflicting txid.
+
+            // determine the position of the conflicting txid after the current changeset is applied
+            let conflicting_new_pos = changeset
+                .chain
+                .txids
+                .get(&conflicting_txid)
+                .map(Option::as_ref)
+                .unwrap_or(Some(conflicting_pos));
+
+            match conflicting_new_pos {
+                None => {
+                    // conflicting txid will be deleted, can ignore
+                }
+                Some(existing_new_pos) => match existing_new_pos.height() {
+                    TxHeight::Confirmed(_) => {
+                        // the new position of the conflicting tx is "confirmed", therefore cannot be
+                        // evicted, return error
+                        return Err(UnresolvableConflict {
+                            already_confirmed_tx: (conflicting_pos.clone(), conflicting_txid),
+                            update_tx: (update_pos, update_txid),
+                        });
+                    }
+                    TxHeight::Unconfirmed => {
+                        // the new position of the conflicting tx is "unconfirmed", therefore it can
+                        // be evicted
+                        changeset.chain.txids.insert(conflicting_txid, None);
+                    }
+                },
+            };
+        }
+
+        Ok(())
+    }
+
+    /// Applies `changeset` to `self`.
+    ///
+    /// **Warning** this method assumes that the changeset is correctly formed. If it is not, the
+    /// chain graph may behave incorrectly in the future and panic unexpectedly.
+    pub fn apply_changeset(&mut self, changeset: ChangeSet<P>) {
+        self.chain.apply_changeset(changeset.chain);
+        self.graph.apply_additions(changeset.graph);
+    }
+
+    /// Applies the `update` chain graph. Note this is shorthand for calling
+    /// [`Self::determine_changeset()`] and [`Self::apply_changeset()`] in sequence.
+    pub fn apply_update(&mut self, update: ChainGraph<P>) -> Result<ChangeSet<P>, UpdateError<P>> {
+        let changeset = self.determine_changeset(&update)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Get the full transaction output at an outpoint if it exists in the chain and the graph.
+    pub fn full_txout(&self, outpoint: OutPoint) -> Option<FullTxOut<P>> {
+        self.chain.full_txout(&self.graph, outpoint)
+    }
+
+    /// Iterate over the full transactions and their position in the chain ordered by their position
+    /// in ascending order.
+    pub fn transactions_in_chain(&self) -> impl DoubleEndedIterator<Item = (&P, &Transaction)> {
+        self.chain
+            .txids()
+            .map(move |(pos, txid)| (pos, self.graph.get_tx(*txid).expect("must exist")))
+    }
+
+    /// Find the transaction in the chain that spends `outpoint`.
+    ///
+    /// This uses the input/output relationships in the internal `graph`. Note that the transaction
+    /// which includes `outpoint` does not need to be in the `graph` or the `chain` for this to
+    /// return `Some(_)`.
+    pub fn spent_by(&self, outpoint: OutPoint) -> Option<(&P, Txid)> {
+        self.chain.spent_by(&self.graph, outpoint)
+    }
+
+    /// Whether the chain graph contains any data whatsoever.
+    pub fn is_empty(&self) -> bool {
+        self.chain.is_empty() && self.graph.is_empty()
+    }
+}
+
+/// Represents changes to [`ChainGraph`].
+///
+/// This is essentially a combination of [`sparse_chain::ChangeSet`] and [`tx_graph::Additions`].
+#[derive(Debug, Clone, PartialEq)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(
+        crate = "serde_crate",
+        bound(
+            deserialize = "P: serde::Deserialize<'de>",
+            serialize = "P: serde::Serialize"
+        )
+    )
+)]
+#[must_use]
+pub struct ChangeSet<P> {
+    pub chain: sparse_chain::ChangeSet<P>,
+    pub graph: tx_graph::Additions,
+}
+
+impl<P> ChangeSet<P> {
+    /// Returns `true` if this [`ChangeSet`] records no changes.
+    pub fn is_empty(&self) -> bool {
+        self.chain.is_empty() && self.graph.is_empty()
+    }
+
+    /// Returns `true` if this [`ChangeSet`] contains transaction evictions.
+    pub fn contains_eviction(&self) -> bool {
+        self.chain
+            .txids
+            .iter()
+            .any(|(_, new_pos)| new_pos.is_none())
+    }
+
+    /// Appends the changes in `other` into self such that applying `self` afterward has the same
+    /// effect as sequentially applying the original `self` and `other`.
+    pub fn append(&mut self, other: ChangeSet<P>)
+    where
+        P: ChainPosition,
+    {
+        self.chain.append(other.chain);
+        self.graph.append(other.graph);
+    }
+}
+
+impl<P> Default for ChangeSet<P> {
+    fn default() -> Self {
+        Self {
+            chain: Default::default(),
+            graph: Default::default(),
+        }
+    }
+}
+
+impl<P> ForEachTxOut for ChainGraph<P> {
+    fn for_each_txout(&self, f: impl FnMut((OutPoint, &TxOut))) {
+        self.graph.for_each_txout(f)
+    }
+}
+
+impl<P> ForEachTxOut for ChangeSet<P> {
+    fn for_each_txout(&self, f: impl FnMut((OutPoint, &TxOut))) {
+        self.graph.for_each_txout(f)
+    }
+}
+
+/// Error that may occur when calling [`ChainGraph::new`].
+#[derive(Clone, Debug, PartialEq)]
+pub enum NewError<P> {
+    /// Two transactions within the sparse chain conflicted with each other
+    Conflict { a: (P, Txid), b: (P, Txid) },
+    /// One or more transactions in the chain were not in the graph
+    Missing(HashSet<Txid>),
+}
+
+impl<P: core::fmt::Debug> core::fmt::Display for NewError<P> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            NewError::Conflict { a, b } => write!(
+                f,
+                "Unable to inflate sparse chain to chain graph since transactions {:?} and {:?}",
+                a, b
+            ),
+            NewError::Missing(missing) => write!(
+                f,
+                "missing full transactions for {}",
+                missing
+                    .iter()
+                    .map(|txid| txid.to_string())
+                    .collect::<Vec<_>>()
+                    .join(", ")
+            ),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl<P: core::fmt::Debug> std::error::Error for NewError<P> {}
+
+/// Error that may occur when inserting a transaction.
+///
+/// Refer to [`ChainGraph::insert_tx_preview`] and [`ChainGraph::insert_tx`].
+#[derive(Clone, Debug, PartialEq)]
+pub enum InsertTxError<P> {
+    Chain(sparse_chain::InsertTxError<P>),
+    UnresolvableConflict(UnresolvableConflict<P>),
+}
+
+impl<P: core::fmt::Debug> core::fmt::Display for InsertTxError<P> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            InsertTxError::Chain(inner) => core::fmt::Display::fmt(inner, f),
+            InsertTxError::UnresolvableConflict(inner) => core::fmt::Display::fmt(inner, f),
+        }
+    }
+}
+
+impl<P> From<sparse_chain::InsertTxError<P>> for InsertTxError<P> {
+    fn from(inner: sparse_chain::InsertTxError<P>) -> Self {
+        Self::Chain(inner)
+    }
+}
+
+#[cfg(feature = "std")]
+impl<P: core::fmt::Debug> std::error::Error for InsertTxError<P> {}
+
+/// A nice alias of [`sparse_chain::InsertCheckpointError`].
+pub type InsertCheckpointError = sparse_chain::InsertCheckpointError;
+
+/// Represents an update failure.
+#[derive(Clone, Debug, PartialEq)]
+pub enum UpdateError<P> {
+    /// The update chain was inconsistent with the existing chain
+    Chain(sparse_chain::UpdateError<P>),
+    /// A transaction in the update spent the same input as an already confirmed transaction
+    UnresolvableConflict(UnresolvableConflict<P>),
+}
+
+impl<P: core::fmt::Debug> core::fmt::Display for UpdateError<P> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            UpdateError::Chain(inner) => core::fmt::Display::fmt(inner, f),
+            UpdateError::UnresolvableConflict(inner) => core::fmt::Display::fmt(inner, f),
+        }
+    }
+}
+
+impl<P> From<sparse_chain::UpdateError<P>> for UpdateError<P> {
+    fn from(inner: sparse_chain::UpdateError<P>) -> Self {
+        Self::Chain(inner)
+    }
+}
+
+#[cfg(feature = "std")]
+impl<P: core::fmt::Debug> std::error::Error for UpdateError<P> {}
+
+/// Represents an unresolvable conflict between an update's transaction and an
+/// already-confirmed transaction.
+#[derive(Clone, Debug, PartialEq)]
+pub struct UnresolvableConflict<P> {
+    pub already_confirmed_tx: (P, Txid),
+    pub update_tx: (P, Txid),
+}
+
+impl<P: core::fmt::Debug> core::fmt::Display for UnresolvableConflict<P> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        let Self {
+            already_confirmed_tx,
+            update_tx,
+        } = self;
+        write!(f, "update transaction {} at height {:?} conflicts with an already confirmed transaction {} at height {:?}",
+            update_tx.1, update_tx.0, already_confirmed_tx.1, already_confirmed_tx.0)
+    }
+}
+
+impl<P> From<UnresolvableConflict<P>> for UpdateError<P> {
+    fn from(inner: UnresolvableConflict<P>) -> Self {
+        Self::UnresolvableConflict(inner)
+    }
+}
+
+impl<P> From<UnresolvableConflict<P>> for InsertTxError<P> {
+    fn from(inner: UnresolvableConflict<P>) -> Self {
+        Self::UnresolvableConflict(inner)
+    }
+}
+
+#[cfg(feature = "std")]
+impl<P: core::fmt::Debug> std::error::Error for UnresolvableConflict<P> {}

crates/chain/src/descriptor_ext.rs

@@ -0,0 +1,16 @@
+use crate::miniscript::{Descriptor, DescriptorPublicKey};
+
+/// A trait to extend the functionality of a miniscript descriptor.
+pub trait DescriptorExt {
+    /// Returns the minimum value (in satoshis) at which an output is broadcastable.
+    fn dust_value(&self) -> u64;
+}
+
+impl DescriptorExt for Descriptor<DescriptorPublicKey> {
+    fn dust_value(&self) -> u64 {
+        self.at_derivation_index(0)
+            .script_pubkey()
+            .dust_value()
+            .to_sat()
+    }
+}

crates/chain/src/example_utils.rs

@@ -0,0 +1,30 @@
+#![allow(unused)]
+use alloc::vec::Vec;
+use bitcoin::{
+    consensus,
+    hashes::{hex::FromHex, Hash},
+    Transaction,
+};
+
+use crate::BlockId;
+
+pub const RAW_TX_1: &str = "0200000000010116d6174da7183d70d0a7d4dc314d517a7d135db79ad63515028b293a76f4f9d10000000000feffffff023a21fc8350060000160014531c405e1881ef192294b8813631e258bf98ea7a1027000000000000225120a60869f0dbcf1dc659c9cecbaf8050135ea9e8cdc487053f1dc6880949dc684c024730440220591b1a172a122da49ba79a3e79f98aaa03fd7a372f9760da18890b6a327e6010022013e82319231da6c99abf8123d7c07e13cf9bd8d76e113e18dc452e5024db156d012102318a2d558b2936c52e320decd6d92a88d7f530be91b6fe0af5caf41661e77da3ef2e0100";
+pub const RAW_TX_2: &str = "02000000000101a688607020cfae91a61e7c516b5ef1264d5d77f17200c3866826c6c808ebf1620000000000feffffff021027000000000000225120a60869f0dbcf1dc659c9cecbaf8050135ea9e8cdc487053f1dc6880949dc684c20fd48ff530600001600146886c525e41d4522042bd0b159dfbade2504a6bb024730440220740ff7e665cd20565d4296b549df8d26b941be3f1e3af89a0b60e50c0dbeb69a02206213ab7030cf6edc6c90d4ccf33010644261e029950a688dc0b1a9ebe6ddcc5a012102f2ac6b396a97853cb6cd62242c8ae4842024742074475023532a51e9c53194253e760100";
+pub const RAW_TX_3: &str = "0200000000010135d67ee47b557e68b8c6223958f597381965ed719f1207ee2b9e20432a24a5dc0100000000feffffff021027000000000000225120a82f29944d65b86ae6b5e5cc75e294ead6c59391a1edc5e016e3498c67fc7bbb62215a5055060000160014070df7671dea67a50c4799a744b5c9be8f4bac690247304402207ebf8d29f71fd03e7e6977b3ea78ca5fcc5c49a42ae822348fc401862fdd766c02201d7e4ff0684ecb008b6142f36ead1b0b4d615524c4f58c261113d361f4427e25012103e6a75e2fab85e5ecad641afc4ffba7222f998649d9f18cac92f0fcc8618883b3ee760100";
+pub const RAW_TX_4: &str = "02000000000101d00e8f76ed313e19b339ee293c0f52b0325c95e24c8f3966fa353fb2bedbcf580100000000feffffff021027000000000000225120882d74e5d0572d5a816cef0041a96b6c1de832f6f9676d9605c44d5e9a97d3dc9cda55fe53060000160014852b5864b8edd42fab4060c87f818e50780865ff0247304402201dccbb9bed7fba924b6d249c5837cc9b37470c0e3d8fbea77cb59baba3efe6fa0220700cc170916913b9bfc2bc0fefb6af776e8b542c561702f136cddc1c7aa43141012103acec3fc79dbbca745815c2a807dc4e81010c80e308e84913f59cb42a275dad97f3760100";
+
+pub fn tx_from_hex(s: &str) -> Transaction {
+    let raw = Vec::from_hex(s).expect("data must be in hex");
+    consensus::deserialize(raw.as_slice()).expect("must deserialize")
+}
+
+pub fn new_hash<H: Hash>(s: &str) -> H {
+    <H as bitcoin::hashes::Hash>::hash(s.as_bytes())
+}
+
+pub fn new_block_id(height: u32, hash: &str) -> BlockId {
+    BlockId {
+        height,
+        hash: new_hash(hash),
+    }
+}

crates/chain/src/keychain.rs

@@ -0,0 +1,309 @@
+//! Module for keychain related structures.
+//!
+//! A keychain here is a set of application-defined indexes for a miniscript descriptor where we can
+//! derive script pubkeys at a particular derivation index. The application's index is simply
+//! anything that implements `Ord`.
+//!
+//! [`KeychainTxOutIndex`] indexes script pubkeys of keychains and scans in relevant outpoints (that
+//! has a `txout` containing an indexed script pubkey). Internally, this uses [`SpkTxOutIndex`], but
+//! also maintains "revealed" and "lookahead" index counts per keychain.
+//!
+//! [`KeychainTracker`] combines [`ChainGraph`] and [`KeychainTxOutIndex`] and enforces atomic
+//! changes between both these structures. [`KeychainScan`] is a structure used to update to
+//! [`KeychainTracker`] and changes made on a [`KeychainTracker`] are reported by
+//! [`KeychainChangeSet`]s.
+//!
+//! [`SpkTxOutIndex`]: crate::SpkTxOutIndex
+use crate::{
+    chain_graph::{self, ChainGraph},
+    collections::BTreeMap,
+    sparse_chain::ChainPosition,
+    tx_graph::TxGraph,
+    ForEachTxOut,
+};
+
+#[cfg(feature = "miniscript")]
+pub mod persist;
+#[cfg(feature = "miniscript")]
+pub use persist::*;
+#[cfg(feature = "miniscript")]
+mod tracker;
+#[cfg(feature = "miniscript")]
+pub use tracker::*;
+#[cfg(feature = "miniscript")]
+mod txout_index;
+#[cfg(feature = "miniscript")]
+pub use txout_index::*;
+
+/// Represents updates to the derivation index of a [`KeychainTxOutIndex`].
+///
+/// It can be applied to [`KeychainTxOutIndex`] with [`apply_additions`]. [`DerivationAdditions] are
+/// monotone in that they will never decrease the revealed derivation index.
+///
+/// [`KeychainTxOutIndex`]: crate::keychain::KeychainTxOutIndex
+/// [`apply_additions`]: crate::keychain::KeychainTxOutIndex::apply_additions
+#[derive(Clone, Debug, PartialEq)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(
+        crate = "serde_crate",
+        bound(
+            deserialize = "K: Ord + serde::Deserialize<'de>",
+            serialize = "K: Ord + serde::Serialize"
+        )
+    )
+)]
+#[must_use]
+pub struct DerivationAdditions<K>(pub BTreeMap<K, u32>);
+
+impl<K> DerivationAdditions<K> {
+    /// Returns whether the additions are empty.
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    /// Get the inner map of the keychain to its new derivation index.
+    pub fn as_inner(&self) -> &BTreeMap<K, u32> {
+        &self.0
+    }
+}
+
+impl<K: Ord> DerivationAdditions<K> {
+    /// Append another [`DerivationAdditions`] into self.
+    ///
+    /// If the keychain already exists, increase the index when the other's index > self's index.
+    /// If the keychain did not exist, append the new keychain.
+    pub fn append(&mut self, mut other: Self) {
+        self.0.iter_mut().for_each(|(key, index)| {
+            if let Some(other_index) = other.0.remove(key) {
+                *index = other_index.max(*index);
+            }
+        });
+
+        self.0.append(&mut other.0);
+    }
+}
+
+impl<K> Default for DerivationAdditions<K> {
+    fn default() -> Self {
+        Self(Default::default())
+    }
+}
+
+impl<K> AsRef<BTreeMap<K, u32>> for DerivationAdditions<K> {
+    fn as_ref(&self) -> &BTreeMap<K, u32> {
+        &self.0
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+/// An update that includes the last active indexes of each keychain.
+pub struct KeychainScan<K, P> {
+    /// The update data in the form of a chain that could be applied
+    pub update: ChainGraph<P>,
+    /// The last active indexes of each keychain
+    pub last_active_indices: BTreeMap<K, u32>,
+}
+
+impl<K, P> Default for KeychainScan<K, P> {
+    fn default() -> Self {
+        Self {
+            update: Default::default(),
+            last_active_indices: Default::default(),
+        }
+    }
+}
+
+impl<K, P> From<ChainGraph<P>> for KeychainScan<K, P> {
+    fn from(update: ChainGraph<P>) -> Self {
+        KeychainScan {
+            update,
+            last_active_indices: Default::default(),
+        }
+    }
+}
+
+/// Represents changes to a [`KeychainTracker`].
+///
+/// This is essentially a combination of [`DerivationAdditions`] and [`chain_graph::ChangeSet`].
+#[derive(Clone, Debug)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(
+        crate = "serde_crate",
+        bound(
+            deserialize = "K: Ord + serde::Deserialize<'de>, P: serde::Deserialize<'de>",
+            serialize = "K: Ord + serde::Serialize, P: serde::Serialize"
+        )
+    )
+)]
+#[must_use]
+pub struct KeychainChangeSet<K, P> {
+    /// The changes in local keychain derivation indices
+    pub derivation_indices: DerivationAdditions<K>,
+    /// The changes that have occurred in the blockchain
+    pub chain_graph: chain_graph::ChangeSet<P>,
+}
+
+impl<K, P> Default for KeychainChangeSet<K, P> {
+    fn default() -> Self {
+        Self {
+            chain_graph: Default::default(),
+            derivation_indices: Default::default(),
+        }
+    }
+}
+
+impl<K, P> KeychainChangeSet<K, P> {
+    /// Returns whether the [`KeychainChangeSet`] is empty (no changes recorded).
+    pub fn is_empty(&self) -> bool {
+        self.chain_graph.is_empty() && self.derivation_indices.is_empty()
+    }
+
+    /// Appends the changes in `other` into `self` such that applying `self` afterward has the same
+    /// effect as sequentially applying the original `self` and `other`.
+    ///
+    /// Note the derivation indices cannot be decreased, so `other` will only change the derivation
+    /// index for a keychain, if it's value is higher than the one in `self`.
+    pub fn append(&mut self, other: KeychainChangeSet<K, P>)
+    where
+        K: Ord,
+        P: ChainPosition,
+    {
+        self.derivation_indices.append(other.derivation_indices);
+        self.chain_graph.append(other.chain_graph);
+    }
+}
+
+impl<K, P> From<chain_graph::ChangeSet<P>> for KeychainChangeSet<K, P> {
+    fn from(changeset: chain_graph::ChangeSet<P>) -> Self {
+        Self {
+            chain_graph: changeset,
+            ..Default::default()
+        }
+    }
+}
+
+impl<K, P> From<DerivationAdditions<K>> for KeychainChangeSet<K, P> {
+    fn from(additions: DerivationAdditions<K>) -> Self {
+        Self {
+            derivation_indices: additions,
+            ..Default::default()
+        }
+    }
+}
+
+impl<K, P> AsRef<TxGraph> for KeychainScan<K, P> {
+    fn as_ref(&self) -> &TxGraph {
+        self.update.graph()
+    }
+}
+
+impl<K, P> ForEachTxOut for KeychainChangeSet<K, P> {
+    fn for_each_txout(&self, f: impl FnMut((bitcoin::OutPoint, &bitcoin::TxOut))) {
+        self.chain_graph.for_each_txout(f)
+    }
+}
+
+/// Balance, differentiated into various categories.
+#[derive(Debug, PartialEq, Eq, Clone, Default)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(crate = "serde_crate",)
+)]
+pub struct Balance {
+    /// All coinbase outputs not yet matured
+    pub immature: u64,
+    /// Unconfirmed UTXOs generated by a wallet tx
+    pub trusted_pending: u64,
+    /// Unconfirmed UTXOs received from an external wallet
+    pub untrusted_pending: u64,
+    /// Confirmed and immediately spendable balance
+    pub confirmed: u64,
+}
+
+impl Balance {
+    /// Get sum of trusted_pending and confirmed coins.
+    ///
+    /// This is the balance you can spend right now that shouldn't get cancelled via another party
+    /// double spending it.
+    pub fn trusted_spendable(&self) -> u64 {
+        self.confirmed + self.trusted_pending
+    }
+
+    /// Get the whole balance visible to the wallet.
+    pub fn total(&self) -> u64 {
+        self.confirmed + self.trusted_pending + self.untrusted_pending + self.immature
+    }
+}
+
+impl core::fmt::Display for Balance {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(
+            f,
+            "{{ immature: {}, trusted_pending: {}, untrusted_pending: {}, confirmed: {} }}",
+            self.immature, self.trusted_pending, self.untrusted_pending, self.confirmed
+        )
+    }
+}
+
+impl core::ops::Add for Balance {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        Self {
+            immature: self.immature + other.immature,
+            trusted_pending: self.trusted_pending + other.trusted_pending,
+            untrusted_pending: self.untrusted_pending + other.untrusted_pending,
+            confirmed: self.confirmed + other.confirmed,
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::TxHeight;
+
+    use super::*;
+    #[test]
+    fn append_keychain_derivation_indices() {
+        #[derive(Ord, PartialOrd, Eq, PartialEq, Clone, Debug)]
+        enum Keychain {
+            One,
+            Two,
+            Three,
+            Four,
+        }
+        let mut lhs_di = BTreeMap::<Keychain, u32>::default();
+        let mut rhs_di = BTreeMap::<Keychain, u32>::default();
+        lhs_di.insert(Keychain::One, 7);
+        lhs_di.insert(Keychain::Two, 0);
+        rhs_di.insert(Keychain::One, 3);
+        rhs_di.insert(Keychain::Two, 5);
+        lhs_di.insert(Keychain::Three, 3);
+        rhs_di.insert(Keychain::Four, 4);
+        let mut lhs = KeychainChangeSet {
+            derivation_indices: DerivationAdditions(lhs_di),
+            chain_graph: chain_graph::ChangeSet::<TxHeight>::default(),
+        };
+
+        let rhs = KeychainChangeSet {
+            derivation_indices: DerivationAdditions(rhs_di),
+            chain_graph: chain_graph::ChangeSet::<TxHeight>::default(),
+        };
+
+        lhs.append(rhs);
+
+        // Exiting index doesn't update if the new index in `other` is lower than `self`.
+        assert_eq!(lhs.derivation_indices.0.get(&Keychain::One), Some(&7));
+        // Existing index updates if the new index in `other` is higher than `self`.
+        assert_eq!(lhs.derivation_indices.0.get(&Keychain::Two), Some(&5));
+        // Existing index is unchanged if keychain doesn't exist in `other`.
+        assert_eq!(lhs.derivation_indices.0.get(&Keychain::Three), Some(&3));
+        // New keychain gets added if the keychain is in `other` but not in `self`.
+        assert_eq!(lhs.derivation_indices.0.get(&Keychain::Four), Some(&4));
+    }
+}

crates/chain/src/keychain/persist.rs

@@ -0,0 +1,108 @@
+//! Persistence for changes made to a [`KeychainTracker`].
+//!
+//! BDK's [`KeychainTracker`] needs somewhere to persist changes it makes during operation.
+//! Operations like giving out a new address are crucial to persist so that next time the
+//! application is loaded, it can find transactions related to that address.
+//!
+//! Note that the [`KeychainTracker`] does not read this persisted data during operation since it
+//! always has a copy in memory.
+//!
+//! [`KeychainTracker`]: crate::keychain::KeychainTracker
+
+use crate::{keychain, sparse_chain::ChainPosition};
+
+/// `Persist` wraps a [`PersistBackend`] to create a convenient staging area for changes before they
+/// are persisted. Not all changes made to the [`KeychainTracker`] need to be written to disk right
+/// away so you can use [`Persist::stage`] to *stage* it first and then [`Persist::commit`] to
+/// finally, write it to disk.
+///
+/// [`KeychainTracker`]: keychain::KeychainTracker
+#[derive(Debug)]
+pub struct Persist<K, P, B> {
+    backend: B,
+    stage: keychain::KeychainChangeSet<K, P>,
+}
+
+impl<K, P, B> Persist<K, P, B> {
+    /// Create a new `Persist` from a [`PersistBackend`].
+    pub fn new(backend: B) -> Self {
+        Self {
+            backend,
+            stage: Default::default(),
+        }
+    }
+
+    /// Stage a `changeset` to later persistence with [`commit`].
+    ///
+    /// [`commit`]: Self::commit
+    pub fn stage(&mut self, changeset: keychain::KeychainChangeSet<K, P>)
+    where
+        K: Ord,
+        P: ChainPosition,
+    {
+        self.stage.append(changeset)
+    }
+
+    /// Get the changes that haven't been committed yet
+    pub fn staged(&self) -> &keychain::KeychainChangeSet<K, P> {
+        &self.stage
+    }
+
+    /// Commit the staged changes to the underlying persistence backend.
+    ///
+    /// Returns a backend-defined error if this fails.
+    pub fn commit(&mut self) -> Result<(), B::WriteError>
+    where
+        B: PersistBackend<K, P>,
+    {
+        self.backend.append_changeset(&self.stage)?;
+        self.stage = Default::default();
+        Ok(())
+    }
+}
+
+/// A persistence backend for [`Persist`].
+pub trait PersistBackend<K, P> {
+    /// The error the backend returns when it fails to write.
+    type WriteError: core::fmt::Debug;
+
+    /// The error the backend returns when it fails to load.
+    type LoadError: core::fmt::Debug;
+
+    /// Appends a new changeset to the persistent backend.
+    ///
+    /// It is up to the backend what it does with this. It could store every changeset in a list or
+    /// it inserts the actual changes into a more structured database. All it needs to guarantee is
+    /// that [`load_into_keychain_tracker`] restores a keychain tracker to what it should be if all
+    /// changesets had been applied sequentially.
+    ///
+    /// [`load_into_keychain_tracker`]: Self::load_into_keychain_tracker
+    fn append_changeset(
+        &mut self,
+        changeset: &keychain::KeychainChangeSet<K, P>,
+    ) -> Result<(), Self::WriteError>;
+
+    /// Applies all the changesets the backend has received to `tracker`.
+    fn load_into_keychain_tracker(
+        &mut self,
+        tracker: &mut keychain::KeychainTracker<K, P>,
+    ) -> Result<(), Self::LoadError>;
+}
+
+impl<K, P> PersistBackend<K, P> for () {
+    type WriteError = ();
+    type LoadError = ();
+
+    fn append_changeset(
+        &mut self,
+        _changeset: &keychain::KeychainChangeSet<K, P>,
+    ) -> Result<(), Self::WriteError> {
+        Ok(())
+    }
+    fn load_into_keychain_tracker(
+        &mut self,
+        _tracker: &mut keychain::KeychainTracker<K, P>,
+    ) -> Result<(), Self::LoadError> {
+        Ok(())
+    }
+}

crates/chain/src/keychain/tracker.rs

@@ -0,0 +1,308 @@
+use bitcoin::Transaction;
+use miniscript::{Descriptor, DescriptorPublicKey};
+
+use crate::{
+    chain_graph::{self, ChainGraph},
+    collections::*,
+    keychain::{KeychainChangeSet, KeychainScan, KeychainTxOutIndex},
+    sparse_chain::{self, SparseChain},
+    tx_graph::TxGraph,
+    BlockId, FullTxOut, TxHeight,
+};
+
+use super::{Balance, DerivationAdditions};
+
+/// A convenient combination of a [`KeychainTxOutIndex`] and a [`ChainGraph`].
+///
+/// The [`KeychainTracker`] atomically updates its [`KeychainTxOutIndex`] whenever new chain data is
+/// incorporated into its internal [`ChainGraph`].
+#[derive(Clone, Debug)]
+pub struct KeychainTracker<K, P> {
+    /// Index between script pubkeys to transaction outputs
+    pub txout_index: KeychainTxOutIndex<K>,
+    chain_graph: ChainGraph<P>,
+}
+
+impl<K, P> KeychainTracker<K, P>
+where
+    P: sparse_chain::ChainPosition,
+    K: Ord + Clone + core::fmt::Debug,
+{
+    /// Add a keychain to the tracker's `txout_index` with a descriptor to derive addresses.
+    /// This is just shorthand for calling [`KeychainTxOutIndex::add_keychain`] on the internal
+    /// `txout_index`.
+    ///
+    /// Adding a keychain means you will be able to derive new script pubkeys under that keychain
+    /// and the tracker will discover transaction outputs with those script pubkeys.
+    pub fn add_keychain(&mut self, keychain: K, descriptor: Descriptor<DescriptorPublicKey>) {
+        self.txout_index.add_keychain(keychain, descriptor)
+    }
+
+    /// Get the internal map of keychains to their descriptors. This is just shorthand for calling
+    /// [`KeychainTxOutIndex::keychains`] on the internal `txout_index`.
+    pub fn keychains(&mut self) -> &BTreeMap<K, Descriptor<DescriptorPublicKey>> {
+        self.txout_index.keychains()
+    }
+
+    /// Get the checkpoint limit of the internal [`SparseChain`].
+    ///
+    /// Refer to [`SparseChain::checkpoint_limit`] for more.
+    pub fn checkpoint_limit(&self) -> Option<usize> {
+        self.chain_graph.checkpoint_limit()
+    }
+
+    /// Set the checkpoint limit of the internal [`SparseChain`].
+    ///
+    /// Refer to [`SparseChain::set_checkpoint_limit`] for more.
+    pub fn set_checkpoint_limit(&mut self, limit: Option<usize>) {
+        self.chain_graph.set_checkpoint_limit(limit)
+    }
+
+    /// Determines the resultant [`KeychainChangeSet`] if the given [`KeychainScan`] is applied.
+    ///
+    /// Internally, we call [`ChainGraph::determine_changeset`] and also determine the additions of
+    /// [`KeychainTxOutIndex`].
+    pub fn determine_changeset(
+        &self,
+        scan: &KeychainScan<K, P>,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::UpdateError<P>> {
+        // TODO: `KeychainTxOutIndex::determine_additions`
+        let mut derivation_indices = scan.last_active_indices.clone();
+        derivation_indices.retain(|keychain, index| {
+            match self.txout_index.last_revealed_index(keychain) {
+                Some(existing) => *index > existing,
+                None => true,
+            }
+        });
+
+        Ok(KeychainChangeSet {
+            derivation_indices: DerivationAdditions(derivation_indices),
+            chain_graph: self.chain_graph.determine_changeset(&scan.update)?,
+        })
+    }
+
+    /// Directly applies a [`KeychainScan`] on [`KeychainTracker`].
+    ///
+    /// This is equivalent to calling [`determine_changeset`] and [`apply_changeset`] in sequence.
+    ///
+    /// [`determine_changeset`]: Self::determine_changeset
+    /// [`apply_changeset`]: Self::apply_changeset
+    pub fn apply_update(
+        &mut self,
+        scan: KeychainScan<K, P>,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::UpdateError<P>> {
+        let changeset = self.determine_changeset(&scan)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Applies the changes in `changeset` to [`KeychainTracker`].
+    ///
+    /// Internally, this calls [`KeychainTxOutIndex::apply_additions`] and
+    /// [`ChainGraph::apply_changeset`] in sequence.
+    pub fn apply_changeset(&mut self, changeset: KeychainChangeSet<K, P>) {
+        let KeychainChangeSet {
+            derivation_indices,
+            chain_graph,
+        } = changeset;
+        self.txout_index.apply_additions(derivation_indices);
+        let _ = self.txout_index.scan(&chain_graph);
+        self.chain_graph.apply_changeset(chain_graph)
+    }
+
+    /// Iterates through [`FullTxOut`]s that are considered to exist in our representation of the
+    /// blockchain/mempool.
+    ///
+    /// In other words, these are `txout`s of confirmed and in-mempool transactions, based on our
+    /// view of the blockchain/mempool.
+    pub fn full_txouts(&self) -> impl Iterator<Item = (&(K, u32), FullTxOut<P>)> + '_ {
+        self.txout_index
+            .txouts()
+            .filter_map(move |(spk_i, op, _)| Some((spk_i, self.chain_graph.full_txout(op)?)))
+    }
+
+    /// Iterates through [`FullTxOut`]s that are unspent outputs.
+    ///
+    /// Refer to [`full_txouts`] for more.
+    ///
+    /// [`full_txouts`]: Self::full_txouts
+    pub fn full_utxos(&self) -> impl Iterator<Item = (&(K, u32), FullTxOut<P>)> + '_ {
+        self.full_txouts()
+            .filter(|(_, txout)| txout.spent_by.is_none())
+    }
+
+    /// Returns a reference to the internal [`ChainGraph`].
+    pub fn chain_graph(&self) -> &ChainGraph<P> {
+        &self.chain_graph
+    }
+
+    /// Returns a reference to the internal [`TxGraph`] (which is part of the [`ChainGraph`]).
+    pub fn graph(&self) -> &TxGraph {
+        self.chain_graph().graph()
+    }
+
+    /// Returns a reference to the internal [`SparseChain`] (which is part of the [`ChainGraph`]).
+    pub fn chain(&self) -> &SparseChain<P> {
+        self.chain_graph().chain()
+    }
+
+    /// Determines the changes as a result of inserting `block_id` (a height and block hash) into the
+    /// tracker.
+    ///
+    /// The caller is responsible for guaranteeing that a block exists at that height. If a
+    /// checkpoint already exists at that height with a different hash; this will return an error.
+    /// Otherwise it will return `Ok(true)` if the checkpoint didn't already exist or `Ok(false)`
+    /// if it did.
+    ///
+    /// **Warning**: This function modifies the internal state of the tracker. You are responsible
+    /// for persisting these changes to disk if you need to restore them.
+    pub fn insert_checkpoint_preview(
+        &self,
+        block_id: BlockId,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::InsertCheckpointError> {
+        Ok(KeychainChangeSet {
+            chain_graph: self.chain_graph.insert_checkpoint_preview(block_id)?,
+            ..Default::default()
+        })
+    }
+
+    /// Directly insert a `block_id` into the tracker.
+    ///
+    /// This is equivalent of calling [`insert_checkpoint_preview`] and [`apply_changeset`] in
+    /// sequence.
+    ///
+    /// [`insert_checkpoint_preview`]: Self::insert_checkpoint_preview
+    /// [`apply_changeset`]: Self::apply_changeset
+    pub fn insert_checkpoint(
+        &mut self,
+        block_id: BlockId,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::InsertCheckpointError> {
+        let changeset = self.insert_checkpoint_preview(block_id)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Determines the changes as a result of inserting a transaction into the inner [`ChainGraph`]
+    /// and optionally into the inner chain at `position`.
+    ///
+    /// **Warning**: This function modifies the internal state of the chain graph. You are
+    /// responsible for persisting these changes to disk if you need to restore them.
+    pub fn insert_tx_preview(
+        &self,
+        tx: Transaction,
+        pos: P,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::InsertTxError<P>> {
+        Ok(KeychainChangeSet {
+            chain_graph: self.chain_graph.insert_tx_preview(tx, pos)?,
+            ..Default::default()
+        })
+    }
+
+    /// Directly insert a transaction into the inner [`ChainGraph`] and optionally into the inner
+    /// chain at `position`.
+    ///
+    /// This is equivalent of calling [`insert_tx_preview`] and [`apply_changeset`] in sequence.
+    ///
+    /// [`insert_tx_preview`]: Self::insert_tx_preview
+    /// [`apply_changeset`]: Self::apply_changeset
+    pub fn insert_tx(
+        &mut self,
+        tx: Transaction,
+        pos: P,
+    ) -> Result<KeychainChangeSet<K, P>, chain_graph::InsertTxError<P>> {
+        let changeset = self.insert_tx_preview(tx, pos)?;
+        self.apply_changeset(changeset.clone());
+        Ok(changeset)
+    }
+
+    /// Returns the *balance* of the keychain, i.e., the value of unspent transaction outputs tracked.
+    ///
+    /// The caller provides a `should_trust` predicate which must decide whether the value of
+    /// unconfirmed outputs on this keychain are guaranteed to be realized or not. For example:
+    ///
+    /// - For an *internal* (change) keychain, `should_trust` should generally be `true` since even if
+    /// you lose an internal output due to eviction, you will always gain back the value from whatever output the
+    /// unconfirmed transaction was spending (since that output is presumably from your wallet).
+    /// - For an *external* keychain, you might want `should_trust` to return  `false` since someone may cancel (by double spending)
+    /// a payment made to addresses on that keychain.
+    ///
+    /// When in doubt set `should_trust` to return false. This doesn't do anything other than change
+    /// where the unconfirmed output's value is accounted for in `Balance`.
+    pub fn balance(&self, mut should_trust: impl FnMut(&K) -> bool) -> Balance {
+        let mut immature = 0;
+        let mut trusted_pending = 0;
+        let mut untrusted_pending = 0;
+        let mut confirmed = 0;
+        let last_sync_height = self.chain().latest_checkpoint().map(|latest| latest.height);
+        for ((keychain, _), utxo) in self.full_utxos() {
+            let chain_position = &utxo.chain_position;
+
+            match chain_position.height() {
+                TxHeight::Confirmed(_) => {
+                    if utxo.is_on_coinbase {
+                        if utxo.is_mature(
+                            last_sync_height
+                                .expect("since it's confirmed we must have a checkpoint"),
+                        ) {
+                            confirmed += utxo.txout.value;
+                        } else {
+                            immature += utxo.txout.value;
+                        }
+                    } else {
+                        confirmed += utxo.txout.value;
+                    }
+                }
+                TxHeight::Unconfirmed => {
+                    if should_trust(keychain) {
+                        trusted_pending += utxo.txout.value;
+                    } else {
+                        untrusted_pending += utxo.txout.value;
+                    }
+                }
+            }
+        }
+
+        Balance {
+            immature,
+            trusted_pending,
+            untrusted_pending,
+            confirmed,
+        }
+    }
+
+    /// Returns the balance of all spendable confirmed unspent outputs of this tracker at a
+    /// particular height.
+    pub fn balance_at(&self, height: u32) -> u64 {
+        self.full_txouts()
+            .filter(|(_, full_txout)| full_txout.is_spendable_at(height))
+            .map(|(_, full_txout)| full_txout.txout.value)
+            .sum()
+    }
+}
+
+impl<K, P> Default for KeychainTracker<K, P> {
+    fn default() -> Self {
+        Self {
+            txout_index: Default::default(),
+            chain_graph: Default::default(),
+        }
+    }
+}
+
+impl<K, P> AsRef<SparseChain<P>> for KeychainTracker<K, P> {
+    fn as_ref(&self) -> &SparseChain<P> {
+        self.chain_graph.chain()
+    }
+}
+
+impl<K, P> AsRef<TxGraph> for KeychainTracker<K, P> {
+    fn as_ref(&self) -> &TxGraph {
+        self.chain_graph.graph()
+    }
+}
+
+impl<K, P> AsRef<ChainGraph<P>> for KeychainTracker<K, P> {
+    fn as_ref(&self) -> &ChainGraph<P> {
+        &self.chain_graph
+    }
+}

crates/chain/src/keychain/txout_index.rs

@@ -0,0 +1,590 @@
+use crate::{
+    collections::*,
+    miniscript::{Descriptor, DescriptorPublicKey},
+    ForEachTxOut, SpkTxOutIndex,
+};
+use alloc::{borrow::Cow, vec::Vec};
+use bitcoin::{secp256k1::Secp256k1, OutPoint, Script, TxOut};
+use core::{fmt::Debug, ops::Deref};
+
+use super::DerivationAdditions;
+
+/// Maximum [BIP32](https://bips.xyz/32) derivation index.
+pub const BIP32_MAX_INDEX: u32 = (1 << 31) - 1;
+
+/// A convenient wrapper around [`SpkTxOutIndex`] that relates script pubkeys to miniscript public
+/// [`Descriptor`]s.
+///
+/// Descriptors are referenced by the provided keychain generic (`K`).
+///
+/// Script pubkeys for a descriptor are revealed chronologically from index 0. I.e., If the last
+/// revealed index of a descriptor is 5; scripts of indices 0 to 4 are guaranteed to be already
+/// revealed. In addition to revealed scripts, we have a `lookahead` parameter for each keychain,
+/// which defines the number of script pubkeys to store ahead of the last revealed index.
+///
+/// Methods that could update the last revealed index will return [`DerivationAdditions`] to report
+/// these changes. This can be persisted for future recovery.
+///
+/// ## Synopsis
+///
+/// ```
+/// use bdk_chain::keychain::KeychainTxOutIndex;
+/// # use bdk_chain::{ miniscript::{Descriptor, DescriptorPublicKey} };
+/// # use core::str::FromStr;
+///
+/// // imagine our service has internal and external addresses but also addresses for users
+/// #[derive(Clone, Debug, PartialEq, Eq, Ord, PartialOrd)]
+/// enum MyKeychain {
+///     External,
+///     Internal,
+///     MyAppUser {
+///         user_id: u32
+///     }
+/// }
+///
+/// let mut txout_index = KeychainTxOutIndex::<MyKeychain>::default();
+///
+/// # let secp = bdk_chain::bitcoin::secp256k1::Secp256k1::signing_only();
+/// # let (external_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
+/// # let (internal_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/1/*)").unwrap();
+/// # let descriptor_for_user_42 = external_descriptor.clone();
+/// txout_index.add_keychain(MyKeychain::External, external_descriptor);
+/// txout_index.add_keychain(MyKeychain::Internal, internal_descriptor);
+/// txout_index.add_keychain(MyKeychain::MyAppUser { user_id: 42 }, descriptor_for_user_42);
+///
+/// let new_spk_for_user = txout_index.reveal_next_spk(&MyKeychain::MyAppUser{ user_id: 42 });
+/// ```
+///
+/// [`Ord`]: core::cmp::Ord
+/// [`SpkTxOutIndex`]: crate::spk_txout_index::SpkTxOutIndex
+/// [`Descriptor`]: crate::miniscript::Descriptor
+#[derive(Clone, Debug)]
+pub struct KeychainTxOutIndex<K> {
+    inner: SpkTxOutIndex<(K, u32)>,
+    // descriptors of each keychain
+    keychains: BTreeMap<K, Descriptor<DescriptorPublicKey>>,
+    // last revealed indexes
+    last_revealed: BTreeMap<K, u32>,
+    // lookahead settings for each keychain
+    lookahead: BTreeMap<K, u32>,
+}
+
+impl<K> Default for KeychainTxOutIndex<K> {
+    fn default() -> Self {
+        Self {
+            inner: SpkTxOutIndex::default(),
+            keychains: BTreeMap::default(),
+            last_revealed: BTreeMap::default(),
+            lookahead: BTreeMap::default(),
+        }
+    }
+}
+
+impl<K> Deref for KeychainTxOutIndex<K> {
+    type Target = SpkTxOutIndex<(K, u32)>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
+    /// Scans an object for relevant outpoints, which are stored and indexed internally.
+    ///
+    /// If the matched script pubkey is part of the lookahead, the last stored index is updated for
+    /// the script pubkey's keychain and the [`DerivationAdditions`] returned will reflect the
+    /// change.
+    ///
+    /// Typically, this method is used in two situations:
+    ///
+    /// 1. After loading transaction data from the disk, you may scan over all the txouts to restore all
+    /// your txouts.
+    /// 2. When getting new data from the chain, you usually scan it before incorporating it into
+    /// your chain state (i.e., `SparseChain`, `ChainGraph`).
+    ///
+    /// See [`ForEachTxout`] for the types that support this.
+    ///
+    /// [`ForEachTxout`]: crate::ForEachTxOut
+    pub fn scan(&mut self, txouts: &impl ForEachTxOut) -> DerivationAdditions<K> {
+        let mut additions = DerivationAdditions::<K>::default();
+        txouts.for_each_txout(|(op, txout)| additions.append(self.scan_txout(op, txout)));
+        additions
+    }
+
+    /// Scan a single outpoint for a matching script pubkey.
+    ///
+    /// If it matches, this will store and index it.
+    pub fn scan_txout(&mut self, op: OutPoint, txout: &TxOut) -> DerivationAdditions<K> {
+        match self.inner.scan_txout(op, txout).cloned() {
+            Some((keychain, index)) => self.reveal_to_target(&keychain, index).1,
+            None => DerivationAdditions::default(),
+        }
+    }
+
+    /// Return a reference to the internal [`SpkTxOutIndex`].
+    pub fn inner(&self) -> &SpkTxOutIndex<(K, u32)> {
+        &self.inner
+    }
+
+    /// Return a reference to the internal map of the keychain to descriptors.
+    pub fn keychains(&self) -> &BTreeMap<K, Descriptor<DescriptorPublicKey>> {
+        &self.keychains
+    }
+
+    /// Add a keychain to the tracker's `txout_index` with a descriptor to derive addresses.
+    ///
+    /// Adding a keychain means you will be able to derive new script pubkeys under that keychain
+    /// and the txout index will discover transaction outputs with those script pubkeys.
+    ///
+    /// # Panics
+    ///
+    /// This will panic if a different `descriptor` is introduced to the same `keychain`.
+    pub fn add_keychain(&mut self, keychain: K, descriptor: Descriptor<DescriptorPublicKey>) {
+        let old_descriptor = &*self.keychains.entry(keychain).or_insert(descriptor.clone());
+        assert_eq!(
+            &descriptor, old_descriptor,
+            "keychain already contains a different descriptor"
+        );
+    }
+
+    /// Return the lookahead setting for each keychain.
+    ///
+    /// Refer to [`set_lookahead`] for a deeper explanation of the `lookahead`.
+    ///
+    /// [`set_lookahead`]: Self::set_lookahead
+    pub fn lookaheads(&self) -> &BTreeMap<K, u32> {
+        &self.lookahead
+    }
+
+    /// Convenience method to call [`set_lookahead`] for all keychains.
+    ///
+    /// [`set_lookahead`]: Self::set_lookahead
+    pub fn set_lookahead_for_all(&mut self, lookahead: u32) {
+        for keychain in &self.keychains.keys().cloned().collect::<Vec<_>>() {
+            self.lookahead.insert(keychain.clone(), lookahead);
+            self.replenish_lookahead(keychain);
+        }
+    }
+
+    /// Set the lookahead count for `keychain`.
+    ///
+    /// The lookahead is the number of scripts to cache ahead of the last stored script index. This
+    /// is useful during a scan via [`scan`] or [`scan_txout`].
+    ///
+    /// # Panics
+    ///
+    /// This will panic if the `keychain` does not exist.
+    ///
+    /// [`scan`]: Self::scan
+    /// [`scan_txout`]: Self::scan_txout
+    pub fn set_lookahead(&mut self, keychain: &K, lookahead: u32) {
+        self.lookahead.insert(keychain.clone(), lookahead);
+        self.replenish_lookahead(keychain);
+    }
+
+    /// Convenience method to call [`lookahead_to_target`] for multiple keychains.
+    ///
+    /// [`lookahead_to_target`]: Self::lookahead_to_target
+    pub fn lookahead_to_target_multi(&mut self, target_indexes: BTreeMap<K, u32>) {
+        for (keychain, target_index) in target_indexes {
+            self.lookahead_to_target(&keychain, target_index)
+        }
+    }
+
+    /// Store lookahead scripts until `target_index`.
+    ///
+    /// This does not change the `lookahead` setting.
+    pub fn lookahead_to_target(&mut self, keychain: &K, target_index: u32) {
+        let next_index = self.next_store_index(keychain);
+        if let Some(temp_lookahead) = target_index.checked_sub(next_index).filter(|&v| v > 0) {
+            let old_lookahead = self.lookahead.insert(keychain.clone(), temp_lookahead);
+            self.replenish_lookahead(keychain);
+
+            // revert
+            match old_lookahead {
+                Some(lookahead) => self.lookahead.insert(keychain.clone(), lookahead),
+                None => self.lookahead.remove(keychain),
+            };
+        }
+    }
+
+    fn replenish_lookahead(&mut self, keychain: &K) {
+        let descriptor = self.keychains.get(keychain).expect("keychain must exist");
+        let next_store_index = self.next_store_index(keychain);
+        let next_reveal_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
+        let lookahead = self.lookahead.get(keychain).map_or(0, |v| *v);
+
+        for (new_index, new_spk) in range_descriptor_spks(
+            Cow::Borrowed(descriptor),
+            next_store_index..next_reveal_index + lookahead,
+        ) {
+            let _inserted = self
+                .inner
+                .insert_spk((keychain.clone(), new_index), new_spk);
+            debug_assert!(_inserted, "replenish lookahead: must not have existing spk: keychain={:?}, lookahead={}, next_store_index={}, next_reveal_index={}", keychain, lookahead, next_store_index, next_reveal_index);
+        }
+    }
+
+    fn next_store_index(&self, keychain: &K) -> u32 {
+        self.inner()
+            .all_spks()
+            .range((keychain.clone(), u32::MIN)..(keychain.clone(), u32::MAX))
+            .last()
+            .map_or(0, |((_, v), _)| *v + 1)
+    }
+
+    /// Generates script pubkey iterators for every `keychain`. The iterators iterate over all
+    /// derivable script pubkeys.
+    pub fn spks_of_all_keychains(
+        &self,
+    ) -> BTreeMap<K, impl Iterator<Item = (u32, Script)> + Clone> {
+        self.keychains
+            .iter()
+            .map(|(keychain, descriptor)| {
+                (
+                    keychain.clone(),
+                    range_descriptor_spks(Cow::Owned(descriptor.clone()), 0..),
+                )
+            })
+            .collect()
+    }
+
+    /// Generates a script pubkey iterator for the given `keychain`'s descriptor (if it exists). The
+    /// iterator iterates over all derivable scripts of the keychain's descriptor.
+    ///
+    /// # Panics
+    ///
+    /// This will panic if the `keychain` does not exist.
+    pub fn spks_of_keychain(&self, keychain: &K) -> impl Iterator<Item = (u32, Script)> + Clone {
+        let descriptor = self
+            .keychains
+            .get(keychain)
+            .expect("keychain must exist")
+            .clone();
+        range_descriptor_spks(Cow::Owned(descriptor), 0..)
+    }
+
+    /// Convenience method to get [`revealed_spks_of_keychain`] of all keychains.
+    ///
+    /// [`revealed_spks_of_keychain`]: Self::revealed_spks_of_keychain
+    pub fn revealed_spks_of_all_keychains(
+        &self,
+    ) -> BTreeMap<K, impl Iterator<Item = (u32, &Script)> + Clone> {
+        self.keychains
+            .keys()
+            .map(|keychain| (keychain.clone(), self.revealed_spks_of_keychain(keychain)))
+            .collect()
+    }
+
+    /// Iterates over the script pubkeys revealed by this index under `keychain`.
+    pub fn revealed_spks_of_keychain(
+        &self,
+        keychain: &K,
+    ) -> impl DoubleEndedIterator<Item = (u32, &Script)> + Clone {
+        let next_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
+        self.inner
+            .all_spks()
+            .range((keychain.clone(), u32::MIN)..(keychain.clone(), next_index))
+            .map(|((_, derivation_index), spk)| (*derivation_index, spk))
+    }
+
+    /// Get the next derivation index for `keychain`. The next index is the index after the last revealed
+    /// derivation index.
+    ///
+    /// The second field in the returned tuple represents whether the next derivation index is new.
+    /// There are two scenarios where the next derivation index is reused (not new):
+    ///
+    /// 1. The keychain's descriptor has no wildcard, and a script has already been revealed.
+    /// 2. The number of revealed scripts has already reached 2^31 (refer to BIP-32).
+    ///
+    /// Not checking the second field of the tuple may result in address reuse.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the `keychain` does not exist.
+    pub fn next_index(&self, keychain: &K) -> (u32, bool) {
+        let descriptor = self.keychains.get(keychain).expect("keychain must exist");
+        let last_index = self.last_revealed.get(keychain).cloned();
+
+        // we can only get the next index if the wildcard exists.
+        let has_wildcard = descriptor.has_wildcard();
+
+        match last_index {
+            // if there is no index, next_index is always 0.
+            None => (0, true),
+            // descriptors without wildcards can only have one index.
+            Some(_) if !has_wildcard => (0, false),
+            // derivation index must be < 2^31 (BIP-32).
+            Some(index) if index > BIP32_MAX_INDEX => {
+                unreachable!("index is out of bounds")
+            }
+            Some(index) if index == BIP32_MAX_INDEX => (index, false),
+            // get the next derivation index.
+            Some(index) => (index + 1, true),
+        }
+    }
+
+    /// Get the last derivation index that is revealed for each keychain.
+    ///
+    /// Keychains with no revealed indices will not be included in the returned [`BTreeMap`].
+    pub fn last_revealed_indices(&self) -> &BTreeMap<K, u32> {
+        &self.last_revealed
+    }
+
+    /// Get the last derivation index revealed for `keychain`.
+    pub fn last_revealed_index(&self, keychain: &K) -> Option<u32> {
+        self.last_revealed.get(keychain).cloned()
+    }
+
+    /// Convenience method to call [`Self::reveal_to_target`] on multiple keychains.
+    pub fn reveal_to_target_multi(
+        &mut self,
+        keychains: &BTreeMap<K, u32>,
+    ) -> (
+        BTreeMap<K, impl Iterator<Item = (u32, Script)>>,
+        DerivationAdditions<K>,
+    ) {
+        let mut additions = DerivationAdditions::default();
+        let mut spks = BTreeMap::new();
+
+        for (keychain, &index) in keychains {
+            let (new_spks, new_additions) = self.reveal_to_target(keychain, index);
+            if !new_additions.is_empty() {
+                spks.insert(keychain.clone(), new_spks);
+                additions.append(new_additions);
+            }
+        }
+
+        (spks, additions)
+    }
+
+    /// Reveals script pubkeys of the `keychain`'s descriptor **up to and including** the
+    /// `target_index`.
+    ///
+    /// If the `target_index` cannot be reached (due to the descriptor having no wildcard and/or
+    /// the `target_index` is in the hardened index range), this method will make a best-effort and
+    /// reveal up to the last possible index.
+    ///
+    /// This returns an iterator of newly revealed indices (alongside their scripts) and a
+    /// [`DerivationAdditions`], which reports updates to the latest revealed index. If no new script
+    /// pubkeys are revealed, then both of these will be empty.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `keychain` does not exist.
+    pub fn reveal_to_target(
+        &mut self,
+        keychain: &K,
+        target_index: u32,
+    ) -> (impl Iterator<Item = (u32, Script)>, DerivationAdditions<K>) {
+        let descriptor = self.keychains.get(keychain).expect("keychain must exist");
+        let has_wildcard = descriptor.has_wildcard();
+
+        let target_index = if has_wildcard { target_index } else { 0 };
+        let next_reveal_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
+        let lookahead = self.lookahead.get(keychain).map_or(0, |v| *v);
+
+        debug_assert_eq!(
+            next_reveal_index + lookahead,
+            self.next_store_index(keychain)
+        );
+
+        // if we need to reveal new indices, the latest revealed index goes here
+        let mut reveal_to_index = None;
+
+        // if the target is not yet revealed, but is already stored (due to lookahead), we need to
+        // set the `reveal_to_index` as target here (as the `for` loop below only updates
+        // `reveal_to_index` for indexes that are NOT stored)
+        if next_reveal_index <= target_index && target_index < next_reveal_index + lookahead {
+            reveal_to_index = Some(target_index);
+        }
+
+        // we range over indexes that are not stored
+        let range = next_reveal_index + lookahead..=target_index + lookahead;
+        for (new_index, new_spk) in range_descriptor_spks(Cow::Borrowed(descriptor), range) {
+            let _inserted = self
+                .inner
+                .insert_spk((keychain.clone(), new_index), new_spk);
+            debug_assert!(_inserted, "must not have existing spk",);
+
+            // everything after `target_index` is stored for lookahead only
+            if new_index <= target_index {
+                reveal_to_index = Some(new_index);
+            }
+        }
+
+        match reveal_to_index {
+            Some(index) => {
+                let _old_index = self.last_revealed.insert(keychain.clone(), index);
+                debug_assert!(_old_index < Some(index));
+                (
+                    range_descriptor_spks(
+                        Cow::Owned(descriptor.clone()),
+                        next_reveal_index..index + 1,
+                    ),
+                    DerivationAdditions(core::iter::once((keychain.clone(), index)).collect()),
+                )
+            }
+            None => (
+                range_descriptor_spks(
+                    Cow::Owned(descriptor.clone()),
+                    next_reveal_index..next_reveal_index,
+                ),
+                DerivationAdditions::default(),
+            ),
+        }
+    }
+
+    /// Attempts to reveal the next script pubkey for `keychain`.
+    ///
+    /// Returns the derivation index of the revealed script pubkey, the revealed script pubkey and a
+    /// [`DerivationAdditions`] which represents changes in the last revealed index (if any).
+    ///
+    /// When a new script cannot be revealed, we return the last revealed script and an empty
+    /// [`DerivationAdditions`]. There are two scenarios when a new script pubkey cannot be derived:
+    ///
+    ///  1. The descriptor has no wildcard and already has one script revealed.
+    ///  2. The descriptor has already revealed scripts up to the numeric bound.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the `keychain` does not exist.
+    pub fn reveal_next_spk(&mut self, keychain: &K) -> ((u32, &Script), DerivationAdditions<K>) {
+        let (next_index, _) = self.next_index(keychain);
+        let additions = self.reveal_to_target(keychain, next_index).1;
+        let script = self
+            .inner
+            .spk_at_index(&(keychain.clone(), next_index))
+            .expect("script must already be stored");
+        ((next_index, script), additions)
+    }
+
+    /// Gets the next unused script pubkey in the keychain. I.e., the script pubkey with the lowest
+    /// index that has not been used yet.
+    ///
+    /// This will derive and reveal a new script pubkey if no more unused script pubkeys exist.
+    ///
+    /// If the descriptor has no wildcard and already has a used script pubkey or if a descriptor
+    /// has used all scripts up to the derivation bounds, then the last derived script pubkey will be
+    /// returned.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `keychain` has never been added to the index
+    pub fn next_unused_spk(&mut self, keychain: &K) -> ((u32, &Script), DerivationAdditions<K>) {
+        let need_new = self.unused_spks_of_keychain(keychain).next().is_none();
+        // this rather strange branch is needed because of some lifetime issues
+        if need_new {
+            self.reveal_next_spk(keychain)
+        } else {
+            (
+                self.unused_spks_of_keychain(keychain)
+                    .next()
+                    .expect("we already know next exists"),
+                DerivationAdditions::default(),
+            )
+        }
+    }
+
+    /// Marks the script pubkey at `index` as used even though the tracker hasn't seen an output with it.
+    /// This only has an effect when the `index` had been added to `self` already and was unused.
+    ///
+    /// Returns whether the `index` was initially present as `unused`.
+    ///
+    /// This is useful when you want to reserve a script pubkey for something but don't want to add
+    /// the transaction output using it to the index yet. Other callers will consider `index` on
+    /// `keychain` used until you call [`unmark_used`].
+    ///
+    /// [`unmark_used`]: Self::unmark_used
+    pub fn mark_used(&mut self, keychain: &K, index: u32) -> bool {
+        self.inner.mark_used(&(keychain.clone(), index))
+    }
+
+    /// Undoes the effect of [`mark_used`]. Returns whether the `index` is inserted back into
+    /// `unused`.
+    ///
+    /// Note that if `self` has scanned an output with this script pubkey, then this will have no
+    /// effect.
+    ///
+    /// [`mark_used`]: Self::mark_used
+    pub fn unmark_used(&mut self, keychain: &K, index: u32) -> bool {
+        self.inner.unmark_used(&(keychain.clone(), index))
+    }
+
+    /// Iterates over all unused script pubkeys for a `keychain` stored in the index.
+    pub fn unused_spks_of_keychain(
+        &self,
+        keychain: &K,
+    ) -> impl DoubleEndedIterator<Item = (u32, &Script)> {
+        let next_index = self.last_revealed.get(keychain).map_or(0, |&v| v + 1);
+        let range = (keychain.clone(), u32::MIN)..(keychain.clone(), next_index);
+        self.inner
+            .unused_spks(range)
+            .map(|((_, i), script)| (*i, script))
+    }
+
+    /// Iterates over all the [`OutPoint`] that have a `TxOut` with a script pubkey derived from
+    /// `keychain`.
+    pub fn txouts_of_keychain(
+        &self,
+        keychain: &K,
+    ) -> impl DoubleEndedIterator<Item = (u32, OutPoint)> + '_ {
+        self.inner
+            .outputs_in_range((keychain.clone(), u32::MIN)..(keychain.clone(), u32::MAX))
+            .map(|((_, i), op)| (*i, op))
+    }
+
+    /// Returns the highest derivation index of the `keychain` where [`KeychainTxOutIndex`] has
+    /// found a [`TxOut`] with it's script pubkey.
+    pub fn last_used_index(&self, keychain: &K) -> Option<u32> {
+        self.txouts_of_keychain(keychain).last().map(|(i, _)| i)
+    }
+
+    /// Returns the highest derivation index of each keychain that [`KeychainTxOutIndex`] has found
+    /// a [`TxOut`] with it's script pubkey.
+    pub fn last_used_indices(&self) -> BTreeMap<K, u32> {
+        self.keychains
+            .iter()
+            .filter_map(|(keychain, _)| {
+                self.last_used_index(keychain)
+                    .map(|index| (keychain.clone(), index))
+            })
+            .collect()
+    }
+
+    /// Applies the derivation additions to the [`KeychainTxOutIndex`], extending the number of
+    /// derived scripts per keychain, as specified in the `additions`.
+    pub fn apply_additions(&mut self, additions: DerivationAdditions<K>) {
+        let _ = self.reveal_to_target_multi(&additions.0);
+    }
+}
+
+fn range_descriptor_spks<'a, R>(
+    descriptor: Cow<'a, Descriptor<DescriptorPublicKey>>,
+    range: R,
+) -> impl Iterator<Item = (u32, Script)> + Clone + Send + 'a
+where
+    R: Iterator<Item = u32> + Clone + Send + 'a,
+{
+    let secp = Secp256k1::verification_only();
+    let has_wildcard = descriptor.has_wildcard();
+    range
+        .into_iter()
+        // non-wildcard descriptors can only have one derivation index (0)
+        .take_while(move |&index| has_wildcard || index == 0)
+        // we can only iterate over non-hardened indices
+        .take_while(|&index| index <= BIP32_MAX_INDEX)
+        .map(
+            move |index| -> Result<_, miniscript::descriptor::ConversionError> {
+                Ok((
+                    index,
+                    descriptor
+                        .at_derivation_index(index)
+                        .derived_descriptor(&secp)?
+                        .script_pubkey(),
+                ))
+            },
+        )
+        .take_while(Result::is_ok)
+        .map(Result::unwrap)
+}

crates/chain/src/lib.rs

@@ -0,0 +1,89 @@
+//! This crate is a collection of core structures for [Bitcoin Dev Kit] (alpha release).
+//!
+//! The goal of this crate is to give wallets the mechanisms needed to:
+//!
+//! 1. Figure out what data they need to fetch.
+//! 2. Process the data in a way that never leads to inconsistent states.
+//! 3. Fully index that data and expose it to be consumed without friction.
+//!
+//! Our design goals for these mechanisms are:
+//!
+//! 1. Data source agnostic -- nothing in `bdk_chain` cares about where you get data from or whether
+//!    you do it synchronously or asynchronously. If you know a fact about the blockchain, you can just
+//!    tell `bdk_chain`'s APIs about it, and that information will be integrated, if it can be done
+//!    consistently.
+//! 2. Error-free APIs.
+//! 3. Data persistence agnostic -- `bdk_chain` does not care where you cache on-chain data, what you
+//!    cache or how you fetch it.
+//!
+//! [Bitcoin Dev Kit]: https://bitcoindevkit.org/
+#![no_std]
+pub use bitcoin;
+pub mod chain_graph;
+mod spk_txout_index;
+pub use spk_txout_index::*;
+mod chain_data;
+pub use chain_data::*;
+pub mod keychain;
+pub mod sparse_chain;
+mod tx_data_traits;
+pub mod tx_graph;
+pub use tx_data_traits::*;
+
+#[doc(hidden)]
+pub mod example_utils;
+
+#[cfg(feature = "miniscript")]
+pub use miniscript;
+#[cfg(feature = "miniscript")]
+mod descriptor_ext;
+#[cfg(feature = "miniscript")]
+pub use descriptor_ext::DescriptorExt;
+
+#[allow(unused_imports)]
+#[macro_use]
+extern crate alloc;
+
+#[cfg(feature = "serde")]
+pub extern crate serde_crate as serde;
+
+#[cfg(feature = "bincode")]
+extern crate bincode;
+
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate std;
+
+#[cfg(all(not(feature = "std"), feature = "hashbrown"))]
+extern crate hashbrown;
+
+// When no-std use `alloc`'s Hash collections. This is activated by default
+#[cfg(all(not(feature = "std"), not(feature = "hashbrown")))]
+#[doc(hidden)]
+pub mod collections {
+    #![allow(dead_code)]
+    pub type HashSet<K> = alloc::collections::BTreeSet<K>;
+    pub type HashMap<K, V> = alloc::collections::BTreeMap<K, V>;
+    pub use alloc::collections::{btree_map as hash_map, *};
+}
+
+// When we have std, use `std`'s all collections
+#[cfg(all(feature = "std", not(feature = "hashbrown")))]
+#[doc(hidden)]
+pub mod collections {
+    pub use std::collections::{hash_map, *};
+}
+
+// With this special feature `hashbrown`, use `hashbrown`'s hash collections, and else from `alloc`.
+#[cfg(feature = "hashbrown")]
+#[doc(hidden)]
+pub mod collections {
+    #![allow(dead_code)]
+    pub type HashSet<K> = hashbrown::HashSet<K>;
+    pub type HashMap<K, V> = hashbrown::HashMap<K, V>;
+    pub use alloc::collections::*;
+    pub use hashbrown::hash_map;
+}
+
+/// How many confirmations are needed f or a coinbase output to be spent.
+pub const COINBASE_MATURITY: u32 = 100;

crates/chain/src/spk_txout_index.rs

@@ -0,0 +1,309 @@
+use core::ops::RangeBounds;
+
+use crate::{
+    collections::{hash_map::Entry, BTreeMap, BTreeSet, HashMap},
+    ForEachTxOut,
+};
+use bitcoin::{self, OutPoint, Script, Transaction, TxOut, Txid};
+
+/// An index storing [`TxOut`]s that have a script pubkey that matches those in a list.
+///
+/// The basic idea is that you insert script pubkeys you care about into the index with
+/// [`insert_spk`] and then when you call [`scan`], the index will look at any txouts you pass in and
+/// store and index any txouts matching one of its script pubkeys.
+///
+/// Each script pubkey is associated with an application-defined index script index `I`, which must be
+/// [`Ord`]. Usually, this is used to associate the derivation index of the script pubkey or even a
+/// combination of `(keychain, derivation_index)`.
+///
+/// Note there is no harm in scanning transactions that disappear from the blockchain or were never
+/// in there in the first place. `SpkTxOutIndex` is intentionally *monotone* -- you cannot delete or
+/// modify txouts that have been indexed. To find out which txouts from the index are actually in the
+/// chain or unspent, you must use other sources of information like a [`SparseChain`].
+///
+/// [`TxOut`]: bitcoin::TxOut
+/// [`insert_spk`]: Self::insert_spk
+/// [`Ord`]: core::cmp::Ord
+/// [`scan`]: Self::scan
+/// [`SparseChain`]: crate::sparse_chain::SparseChain
+#[derive(Clone, Debug)]
+pub struct SpkTxOutIndex<I> {
+    /// script pubkeys ordered by index
+    spks: BTreeMap<I, Script>,
+    /// A reverse lookup from spk to spk index
+    spk_indices: HashMap<Script, I>,
+    /// The set of unused indexes.
+    unused: BTreeSet<I>,
+    /// Lookup index and txout by outpoint.
+    txouts: BTreeMap<OutPoint, (I, TxOut)>,
+    /// Lookup from spk index to outpoints that had that spk
+    spk_txouts: BTreeSet<(I, OutPoint)>,
+}
+
+impl<I> Default for SpkTxOutIndex<I> {
+    fn default() -> Self {
+        Self {
+            txouts: Default::default(),
+            spks: Default::default(),
+            spk_indices: Default::default(),
+            spk_txouts: Default::default(),
+            unused: Default::default(),
+        }
+    }
+}
+
+/// This macro is used instead of a member function of `SpkTxOutIndex`, which would result in a
+/// compiler error[E0521]: "borrowed data escapes out of closure" when we attempt to take a
+/// reference out of the `ForEachTxOut` closure during scanning.
+macro_rules! scan_txout {
+    ($self:ident, $op:expr, $txout:expr) => {{
+        let spk_i = $self.spk_indices.get(&$txout.script_pubkey);
+        if let Some(spk_i) = spk_i {
+            $self.txouts.insert($op, (spk_i.clone(), $txout.clone()));
+            $self.spk_txouts.insert((spk_i.clone(), $op));
+            $self.unused.remove(&spk_i);
+        }
+        spk_i
+    }};
+}
+
+impl<I: Clone + Ord> SpkTxOutIndex<I> {
+    /// Scans an object containing many txouts.
+    ///
+    /// Typically, this is used in two situations:
+    ///
+    /// 1. After loading transaction data from the disk, you may scan over all the txouts to restore all
+    /// your txouts.
+    /// 2. When getting new data from the chain, you usually scan it before incorporating it into your chain state.
+    ///
+    /// See [`ForEachTxout`] for the types that support this.
+    ///
+    /// [`ForEachTxout`]: crate::ForEachTxOut
+    pub fn scan(&mut self, txouts: &impl ForEachTxOut) -> BTreeSet<I> {
+        let mut scanned_indices = BTreeSet::new();
+
+        txouts.for_each_txout(|(op, txout)| {
+            if let Some(spk_i) = scan_txout!(self, op, txout) {
+                scanned_indices.insert(spk_i.clone());
+            }
+        });
+
+        scanned_indices
+    }
+
+    /// Scan a single `TxOut` for a matching script pubkey and returns the index that matches the
+    /// script pubkey (if any).
+    pub fn scan_txout(&mut self, op: OutPoint, txout: &TxOut) -> Option<&I> {
+        scan_txout!(self, op, txout)
+    }
+
+    /// Iterate over all known txouts that spend to tracked script pubkeys.
+    pub fn txouts(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = (&I, OutPoint, &TxOut)> + ExactSizeIterator {
+        self.txouts
+            .iter()
+            .map(|(op, (index, txout))| (index, *op, txout))
+    }
+
+    /// Finds all txouts on a transaction that has previously been scanned and indexed.
+    pub fn txouts_in_tx(
+        &self,
+        txid: Txid,
+    ) -> impl DoubleEndedIterator<Item = (&I, OutPoint, &TxOut)> {
+        self.txouts
+            .range(OutPoint::new(txid, u32::MIN)..=OutPoint::new(txid, u32::MAX))
+            .map(|(op, (index, txout))| (index, *op, txout))
+    }
+
+    /// Iterates over all the outputs with script pubkeys in an index range.
+    pub fn outputs_in_range(
+        &self,
+        range: impl RangeBounds<I>,
+    ) -> impl DoubleEndedIterator<Item = (&I, OutPoint)> {
+        use bitcoin::hashes::Hash;
+        use core::ops::Bound::*;
+        let min_op = OutPoint {
+            txid: Txid::from_inner([0x00; 32]),
+            vout: u32::MIN,
+        };
+        let max_op = OutPoint {
+            txid: Txid::from_inner([0xff; 32]),
+            vout: u32::MAX,
+        };
+
+        let start = match range.start_bound() {
+            Included(index) => Included((index.clone(), min_op)),
+            Excluded(index) => Excluded((index.clone(), max_op)),
+            Unbounded => Unbounded,
+        };
+
+        let end = match range.end_bound() {
+            Included(index) => Included((index.clone(), max_op)),
+            Excluded(index) => Excluded((index.clone(), min_op)),
+            Unbounded => Unbounded,
+        };
+
+        self.spk_txouts.range((start, end)).map(|(i, op)| (i, *op))
+    }
+
+    /// Returns the txout and script pubkey index of the `TxOut` at `OutPoint`.
+    ///
+    /// Returns `None` if the `TxOut` hasn't been scanned or if nothing matching was found there.
+    pub fn txout(&self, outpoint: OutPoint) -> Option<(&I, &TxOut)> {
+        self.txouts
+            .get(&outpoint)
+            .map(|(spk_i, txout)| (spk_i, txout))
+    }
+
+    /// Returns the script that has been inserted at the `index`.
+    ///
+    /// If that index hasn't been inserted yet, it will return `None`.
+    pub fn spk_at_index(&self, index: &I) -> Option<&Script> {
+        self.spks.get(index)
+    }
+
+    /// The script pubkeys that are being tracked by the index.
+    pub fn all_spks(&self) -> &BTreeMap<I, Script> {
+        &self.spks
+    }
+
+    /// Adds a script pubkey to scan for. Returns `false` and does nothing if spk already exists in the map
+    ///
+    /// the index will look for outputs spending to this spk whenever it scans new data.
+    pub fn insert_spk(&mut self, index: I, spk: Script) -> bool {
+        match self.spk_indices.entry(spk.clone()) {
+            Entry::Vacant(value) => {
+                value.insert(index.clone());
+                self.spks.insert(index.clone(), spk);
+                self.unused.insert(index);
+                true
+            }
+            Entry::Occupied(_) => false,
+        }
+    }
+
+    /// Iterates over all unused script pubkeys in an index range.
+    ///
+    /// Here, "unused" means that after the script pubkey was stored in the index, the index has
+    /// never scanned a transaction output with it.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # use bdk_chain::SpkTxOutIndex;
+    ///
+    /// // imagine our spks are indexed like (keychain, derivation_index).
+    /// let txout_index = SpkTxOutIndex::<(u32, u32)>::default();
+    /// let all_unused_spks = txout_index.unused_spks(..);
+    /// let change_index = 1;
+    /// let unused_change_spks =
+    ///     txout_index.unused_spks((change_index, u32::MIN)..(change_index, u32::MAX));
+    /// ```
+    pub fn unused_spks<R>(&self, range: R) -> impl DoubleEndedIterator<Item = (&I, &Script)>
+    where
+        R: RangeBounds<I>,
+    {
+        self.unused
+            .range(range)
+            .map(move |index| (index, self.spk_at_index(index).expect("must exist")))
+    }
+
+    /// Returns whether the script pubkey at `index` has been used or not.
+    ///
+    /// Here, "unused" means that after the script pubkey was stored in the index, the index has
+    /// never scanned a transaction output with it.
+    pub fn is_used(&self, index: &I) -> bool {
+        self.unused.get(index).is_none()
+    }
+
+    /// Marks the script pubkey at `index` as used even though it hasn't seen an output spending to it.
+    /// This only affects when the `index` had already been added to `self` and was unused.
+    ///
+    /// Returns whether the `index` was initially present as `unused`.
+    ///
+    /// This is useful when you want to reserve a script pubkey for something but don't want to add
+    /// the transaction output using it to the index yet. Other callers will consider the `index` used
+    /// until you call [`unmark_used`].
+    ///
+    /// [`unmark_used`]: Self::unmark_used
+    pub fn mark_used(&mut self, index: &I) -> bool {
+        self.unused.remove(index)
+    }
+
+    /// Undoes the effect of [`mark_used`]. Returns whether the `index` is inserted back into
+    /// `unused`.
+    ///
+    /// Note that if `self` has scanned an output with this script pubkey then this will have no
+    /// effect.
+    ///
+    /// [`mark_used`]: Self::mark_used
+    pub fn unmark_used(&mut self, index: &I) -> bool {
+        // we cannot set the index as unused when it does not exist
+        if !self.spks.contains_key(index) {
+            return false;
+        }
+        // we cannot set the index as unused when txouts are indexed under it
+        if self.outputs_in_range(index..=index).next().is_some() {
+            return false;
+        }
+        self.unused.insert(index.clone())
+    }
+
+    /// Returns the index associated with the script pubkey.
+    pub fn index_of_spk(&self, script: &Script) -> Option<&I> {
+        self.spk_indices.get(script)
+    }
+
+    /// Computes total input value going from script pubkeys in the index (sent) and the total output
+    /// value going to script pubkeys in the index (received) in `tx`. For the `sent` to be computed
+    /// correctly, the output being spent must have already been scanned by the index. Calculating
+    /// received just uses the transaction outputs directly, so it will be correct even if it has not
+    /// been scanned.
+    pub fn sent_and_received(&self, tx: &Transaction) -> (u64, u64) {
+        let mut sent = 0;
+        let mut received = 0;
+
+        for txin in &tx.input {
+            if let Some((_, txout)) = self.txout(txin.previous_output) {
+                sent += txout.value;
+            }
+        }
+        for txout in &tx.output {
+            if self.index_of_spk(&txout.script_pubkey).is_some() {
+                received += txout.value;
+            }
+        }
+
+        (sent, received)
+    }
+
+    /// Computes the net value that this transaction gives to the script pubkeys in the index and
+    /// *takes* from the transaction outputs in the index. Shorthand for calling
+    /// [`sent_and_received`] and subtracting sent from received.
+    ///
+    /// [`sent_and_received`]: Self::sent_and_received
+    pub fn net_value(&self, tx: &Transaction) -> i64 {
+        let (sent, received) = self.sent_and_received(tx);
+        received as i64 - sent as i64
+    }
+
+    /// Whether any of the inputs of this transaction spend a txout tracked or whether any output
+    /// matches one of our script pubkeys.
+    ///
+    /// It is easily possible to misuse this method and get false negatives by calling it before you
+    /// have scanned the `TxOut`s the transaction is spending. For example, if you want to filter out
+    /// all the transactions in a block that are irrelevant, you **must first scan all the
+    /// transactions in the block** and only then use this method.
+    pub fn is_relevant(&self, tx: &Transaction) -> bool {
+        let input_matches = tx
+            .input
+            .iter()
+            .any(|input| self.txouts.contains_key(&input.previous_output));
+        let output_matches = tx
+            .output
+            .iter()
+            .any(|output| self.spk_indices.contains_key(&output.script_pubkey));
+        input_matches || output_matches
+    }
+}

crates/chain/src/tx_data_traits.rs

@@ -0,0 +1,33 @@
+use bitcoin::{Block, OutPoint, Transaction, TxOut};
+
+/// Trait to do something with every txout contained in a structure.
+///
+/// We would prefer to just work with things that can give us an `Iterator<Item=(OutPoint, &TxOut)>`
+/// here, but rust's type system makes it extremely hard to do this (without trait objects).
+pub trait ForEachTxOut {
+    /// The provided closure `f` will be called with each `outpoint/txout` pair.
+    fn for_each_txout(&self, f: impl FnMut((OutPoint, &TxOut)));
+}
+
+impl ForEachTxOut for Block {
+    fn for_each_txout(&self, mut f: impl FnMut((OutPoint, &TxOut))) {
+        for tx in self.txdata.iter() {
+            tx.for_each_txout(&mut f)
+        }
+    }
+}
+
+impl ForEachTxOut for Transaction {
+    fn for_each_txout(&self, mut f: impl FnMut((OutPoint, &TxOut))) {
+        let txid = self.txid();
+        for (i, txout) in self.output.iter().enumerate() {
+            f((
+                OutPoint {
+                    txid,
+                    vout: i as u32,
+                },
+                txout,
+            ))
+        }
+    }
+}

crates/chain/src/tx_graph.rs

@@ -0,0 +1,581 @@
+//! Module for structures that store and traverse transactions.
+//!
+//! [`TxGraph`] is a monotone structure that inserts transactions and indexes the spends. The
+//! [`Additions`] structure reports changes of [`TxGraph`] but can also be applied to a
+//! [`TxGraph`] as well. Lastly, [`TxDescendants`] is an [`Iterator`] that traverses descendants of
+//! a given transaction.
+//!
+//! Conflicting transactions are allowed to coexist within a [`TxGraph`]. This is useful for
+//! identifying and traversing conflicts and descendants of a given transaction.
+//!
+//! # Previewing and applying changes
+//!
+//! Methods that either preview or apply changes to [`TxGraph`] will return [`Additions`].
+//! [`Additions`] can be applied back to a [`TxGraph`] or be used to inform persistent storage
+//! of the changes to [`TxGraph`].
+//!
+//! ```
+//! # use bdk_chain::tx_graph::TxGraph;
+//! # use bdk_chain::example_utils::*;
+//! # use bitcoin::Transaction;
+//! # let tx_a = tx_from_hex(RAW_TX_1);
+//! # let tx_b = tx_from_hex(RAW_TX_2);
+//! let mut graph = TxGraph::default();
+//!
+//! // preview a transaction insertion (not actually inserted)
+//! let additions = graph.insert_tx_preview(tx_a);
+//! // apply the insertion
+//! graph.apply_additions(additions);
+//!
+//! // you can also insert a transaction directly
+//! let already_applied_additions = graph.insert_tx(tx_b);
+//! ```
+//!
+//! A [`TxGraph`] can also be updated with another [`TxGraph`].
+//!
+//! ```
+//! # use bdk_chain::tx_graph::TxGraph;
+//! # use bdk_chain::example_utils::*;
+//! # use bitcoin::Transaction;
+//! # let tx_a = tx_from_hex(RAW_TX_1);
+//! # let tx_b = tx_from_hex(RAW_TX_2);
+//! let mut graph = TxGraph::default();
+//! let update = TxGraph::new(vec![tx_a, tx_b]);
+//!
+//! // preview additions as the result of the update
+//! let additions = graph.determine_additions(&update);
+//! // apply the additions
+//! graph.apply_additions(additions);
+//!
+//! // we can also apply the update graph directly
+//! // the additions will be empty as we have already applied the same update above
+//! let additions = graph.apply_update(update);
+//! assert!(additions.is_empty());
+//! ```
+use crate::{collections::*, ForEachTxOut};
+use alloc::vec::Vec;
+use bitcoin::{OutPoint, Transaction, TxOut, Txid};
+use core::ops::RangeInclusive;
+
+/// A graph of transactions and spends.
+///
+/// See the [module-level documentation] for more.
+///
+/// [module-level documentation]: crate::tx_graph
+#[derive(Clone, Debug, PartialEq, Default)]
+pub struct TxGraph {
+    txs: HashMap<Txid, TxNode>,
+    spends: BTreeMap<OutPoint, HashSet<Txid>>,
+
+    // This atrocity exists so that `TxGraph::outspends()` can return a reference.
+    // FIXME: This can be removed once `HashSet::new` is a const fn.
+    empty_outspends: HashSet<Txid>,
+}
+
+/// Node of a [`TxGraph`]. This can either be a whole transaction, or a partial transaction (where
+/// we only have select outputs).
+#[derive(Clone, Debug, PartialEq)]
+enum TxNode {
+    Whole(Transaction),
+    Partial(BTreeMap<u32, TxOut>),
+}
+
+impl Default for TxNode {
+    fn default() -> Self {
+        Self::Partial(BTreeMap::new())
+    }
+}
+
+impl TxGraph {
+    /// Iterate over all tx outputs known by [`TxGraph`].
+    pub fn all_txouts(&self) -> impl Iterator<Item = (OutPoint, &TxOut)> {
+        self.txs.iter().flat_map(|(txid, tx)| match tx {
+            TxNode::Whole(tx) => tx
+                .output
+                .iter()
+                .enumerate()
+                .map(|(vout, txout)| (OutPoint::new(*txid, vout as _), txout))
+                .collect::<Vec<_>>(),
+            TxNode::Partial(txouts) => txouts
+                .iter()
+                .map(|(vout, txout)| (OutPoint::new(*txid, *vout as _), txout))
+                .collect::<Vec<_>>(),
+        })
+    }
+
+    /// Iterate over all full transactions in the graph.
+    pub fn full_transactions(&self) -> impl Iterator<Item = &Transaction> {
+        self.txs.iter().filter_map(|(_, tx)| match tx {
+            TxNode::Whole(tx) => Some(tx),
+            TxNode::Partial(_) => None,
+        })
+    }
+
+    /// Get a transaction by txid. This only returns `Some` for full transactions.
+    ///
+    /// Refer to [`get_txout`] for getting a specific [`TxOut`].
+    ///
+    /// [`get_txout`]: Self::get_txout
+    pub fn get_tx(&self, txid: Txid) -> Option<&Transaction> {
+        match self.txs.get(&txid)? {
+            TxNode::Whole(tx) => Some(tx),
+            TxNode::Partial(_) => None,
+        }
+    }
+
+    /// Obtains a single tx output (if any) at the specified outpoint.
+    pub fn get_txout(&self, outpoint: OutPoint) -> Option<&TxOut> {
+        match self.txs.get(&outpoint.txid)? {
+            TxNode::Whole(tx) => tx.output.get(outpoint.vout as usize),
+            TxNode::Partial(txouts) => txouts.get(&outpoint.vout),
+        }
+    }
+
+    /// Returns a [`BTreeMap`] of vout to output of the provided `txid`.
+    pub fn txouts(&self, txid: Txid) -> Option<BTreeMap<u32, &TxOut>> {
+        Some(match self.txs.get(&txid)? {
+            TxNode::Whole(tx) => tx
+                .output
+                .iter()
+                .enumerate()
+                .map(|(vout, txout)| (vout as u32, txout))
+                .collect::<BTreeMap<_, _>>(),
+            TxNode::Partial(txouts) => txouts
+                .iter()
+                .map(|(vout, txout)| (*vout, txout))
+                .collect::<BTreeMap<_, _>>(),
+        })
+    }
+
+    /// Calculates the fee of a given transaction. Returns 0 if `tx` is a coinbase transaction.
+    /// Returns `Some(_)` if we have all the `TxOut`s being spent by `tx` in the graph (either as
+    /// the full transactions or individual txouts). If the returned value is negative, then the
+    /// transaction is invalid according to the graph.
+    ///
+    /// Returns `None` if we're missing an input for the tx in the graph.
+    ///
+    /// Note `tx` does not have to be in the graph for this to work.
+    pub fn calculate_fee(&self, tx: &Transaction) -> Option<i64> {
+        if tx.is_coin_base() {
+            return Some(0);
+        }
+        let inputs_sum = tx
+            .input
+            .iter()
+            .map(|txin| {
+                self.get_txout(txin.previous_output)
+                    .map(|txout| txout.value as i64)
+            })
+            .sum::<Option<i64>>()?;
+
+        let outputs_sum = tx
+            .output
+            .iter()
+            .map(|txout| txout.value as i64)
+            .sum::<i64>();
+
+        Some(inputs_sum - outputs_sum)
+    }
+}
+
+impl TxGraph {
+    /// Construct a new [`TxGraph`] from a list of transactions.
+    pub fn new(txs: impl IntoIterator<Item = Transaction>) -> Self {
+        let mut new = Self::default();
+        for tx in txs.into_iter() {
+            let _ = new.insert_tx(tx);
+        }
+        new
+    }
+    /// Inserts the given [`TxOut`] at [`OutPoint`].
+    ///
+    /// Note this will ignore the action if we already have the full transaction that the txout is
+    /// alleged to be on (even if it doesn't match it!).
+    pub fn insert_txout(&mut self, outpoint: OutPoint, txout: TxOut) -> Additions {
+        let additions = self.insert_txout_preview(outpoint, txout);
+        self.apply_additions(additions.clone());
+        additions
+    }
+
+    /// Inserts the given transaction into [`TxGraph`].
+    ///
+    /// The [`Additions`] returned will be empty if `tx` already exists.
+    pub fn insert_tx(&mut self, tx: Transaction) -> Additions {
+        let additions = self.insert_tx_preview(tx);
+        self.apply_additions(additions.clone());
+        additions
+    }
+
+    /// Extends this graph with another so that `self` becomes the union of the two sets of
+    /// transactions.
+    ///
+    /// The returned [`Additions`] is the set difference between `update` and `self` (transactions that
+    /// exist in `update` but not in `self`).
+    pub fn apply_update(&mut self, update: TxGraph) -> Additions {
+        let additions = self.determine_additions(&update);
+        self.apply_additions(additions.clone());
+        additions
+    }
+
+    /// Applies [`Additions`] to [`TxGraph`].
+    pub fn apply_additions(&mut self, additions: Additions) {
+        for tx in additions.tx {
+            let txid = tx.txid();
+
+            tx.input
+                .iter()
+                .map(|txin| txin.previous_output)
+                // coinbase spends are not to be counted
+                .filter(|outpoint| !outpoint.is_null())
+                // record spend as this tx has spent this outpoint
+                .for_each(|outpoint| {
+                    self.spends.entry(outpoint).or_default().insert(txid);
+                });
+
+            if let Some(TxNode::Whole(old_tx)) = self.txs.insert(txid, TxNode::Whole(tx)) {
+                debug_assert_eq!(
+                    old_tx.txid(),
+                    txid,
+                    "old tx of the same txid should not be different."
+                );
+            }
+        }
+
+        for (outpoint, txout) in additions.txout {
+            let tx_entry = self
+                .txs
+                .entry(outpoint.txid)
+                .or_insert_with(TxNode::default);
+
+            match tx_entry {
+                TxNode::Whole(_) => { /* do nothing since we already have full tx */ }
+                TxNode::Partial(txouts) => {
+                    txouts.insert(outpoint.vout, txout);
+                }
+            }
+        }
+    }
+
+    /// Previews the resultant [`Additions`] when [`Self`] is updated against the `update` graph.
+    ///
+    /// The [`Additions`] would be the set difference between `update` and `self` (transactions that
+    /// exist in `update` but not in `self`).
+    pub fn determine_additions(&self, update: &TxGraph) -> Additions {
+        let mut additions = Additions::default();
+
+        for (&txid, update_tx) in &update.txs {
+            if self.get_tx(txid).is_some() {
+                continue;
+            }
+
+            match update_tx {
+                TxNode::Whole(tx) => {
+                    if matches!(self.txs.get(&txid), None | Some(TxNode::Partial(_))) {
+                        additions.tx.insert(tx.clone());
+                    }
+                }
+                TxNode::Partial(partial) => {
+                    for (&vout, update_txout) in partial {
+                        let outpoint = OutPoint::new(txid, vout);
+
+                        if self.get_txout(outpoint) != Some(update_txout) {
+                            additions.txout.insert(outpoint, update_txout.clone());
+                        }
+                    }
+                }
+            }
+        }
+
+        additions
+    }
+
+    /// Returns the resultant [`Additions`] if the given transaction is inserted. Does not actually
+    /// mutate [`Self`].
+    ///
+    /// The [`Additions`] result will be empty if `tx` already exists in `self`.
+    pub fn insert_tx_preview(&self, tx: Transaction) -> Additions {
+        let mut update = Self::default();
+        update.txs.insert(tx.txid(), TxNode::Whole(tx));
+        self.determine_additions(&update)
+    }
+
+    /// Returns the resultant [`Additions`] if the given `txout` is inserted at `outpoint`. Does not
+    /// mutate `self`.
+    ///
+    /// The [`Additions`] result will be empty if the `outpoint` (or a full transaction containing
+    /// the `outpoint`) already existed in `self`.
+    pub fn insert_txout_preview(&self, outpoint: OutPoint, txout: TxOut) -> Additions {
+        let mut update = Self::default();
+        update.txs.insert(
+            outpoint.txid,
+            TxNode::Partial([(outpoint.vout, txout)].into()),
+        );
+        self.determine_additions(&update)
+    }
+}
+
+impl TxGraph {
+    /// The transactions spending from this output.
+    ///
+    /// `TxGraph` allows conflicting transactions within the graph. Obviously the transactions in
+    /// the returned set will never be in the same active-chain.
+    pub fn outspends(&self, outpoint: OutPoint) -> &HashSet<Txid> {
+        self.spends.get(&outpoint).unwrap_or(&self.empty_outspends)
+    }
+
+    /// Iterates over the transactions spending from `txid`.
+    ///
+    /// The iterator item is a union of `(vout, txid-set)` where:
+    ///
+    /// - `vout` is the provided `txid`'s outpoint that is being spent
+    /// - `txid-set` is the set of txids spending the `vout`.
+    pub fn tx_outspends(
+        &self,
+        txid: Txid,
+    ) -> impl DoubleEndedIterator<Item = (u32, &HashSet<Txid>)> + '_ {
+        let start = OutPoint { txid, vout: 0 };
+        let end = OutPoint {
+            txid,
+            vout: u32::MAX,
+        };
+        self.spends
+            .range(start..=end)
+            .map(|(outpoint, spends)| (outpoint.vout, spends))
+    }
+
+    /// Iterate over all partial transactions (outputs only) in the graph.
+    pub fn partial_transactions(&self) -> impl Iterator<Item = (Txid, &BTreeMap<u32, TxOut>)> {
+        self.txs.iter().filter_map(|(txid, tx)| match tx {
+            TxNode::Whole(_) => None,
+            TxNode::Partial(partial) => Some((*txid, partial)),
+        })
+    }
+
+    /// Creates an iterator that filters and maps descendants from the starting `txid`.
+    ///
+    /// The supplied closure takes in two inputs `(depth, descendant_txid)`:
+    ///
+    /// * `depth` is the distance between the starting `txid` and the `descendant_txid`. I.e., if the
+    ///     descendant is spending an output of the starting `txid`; the `depth` will be 1.
+    /// * `descendant_txid` is the descendant's txid which we are considering to walk.
+    ///
+    /// The supplied closure returns an `Option<T>`, allowing the caller to map each node it vists
+    /// and decide whether to visit descendants.
+    pub fn walk_descendants<'g, F, O>(&'g self, txid: Txid, walk_map: F) -> TxDescendants<F>
+    where
+        F: FnMut(usize, Txid) -> Option<O> + 'g,
+    {
+        TxDescendants::new_exclude_root(self, txid, walk_map)
+    }
+
+    /// Creates an iterator that both filters and maps conflicting transactions (this includes
+    /// descendants of directly-conflicting transactions, which are also considered conflicts).
+    ///
+    /// Refer to [`Self::walk_descendants`] for `walk_map` usage.
+    pub fn walk_conflicts<'g, F, O>(&'g self, tx: &'g Transaction, walk_map: F) -> TxDescendants<F>
+    where
+        F: FnMut(usize, Txid) -> Option<O> + 'g,
+    {
+        let txids = self.direct_conflicts_of_tx(tx).map(|(_, txid)| txid);
+        TxDescendants::from_multiple_include_root(self, txids, walk_map)
+    }
+
+    /// Given a transaction, return an iterator of txids that directly conflict with the given
+    /// transaction's inputs (spends). The conflicting txids are returned with the given
+    /// transaction's vin (in which it conflicts).
+    ///
+    /// Note that this only returns directly conflicting txids and does not include descendants of
+    /// those txids (which are technically also conflicting).
+    pub fn direct_conflicts_of_tx<'g>(
+        &'g self,
+        tx: &'g Transaction,
+    ) -> impl Iterator<Item = (usize, Txid)> + '_ {
+        let txid = tx.txid();
+        tx.input
+            .iter()
+            .enumerate()
+            .filter_map(move |(vin, txin)| self.spends.get(&txin.previous_output).zip(Some(vin)))
+            .flat_map(|(spends, vin)| core::iter::repeat(vin).zip(spends.iter().cloned()))
+            .filter(move |(_, conflicting_txid)| *conflicting_txid != txid)
+    }
+
+    /// Whether the graph has any transactions or outputs in it.
+    pub fn is_empty(&self) -> bool {
+        self.txs.is_empty()
+    }
+}
+
+/// A structure that represents changes to a [`TxGraph`].
+///
+/// It is named "additions" because [`TxGraph`] is monotone, so transactions can only be added and
+/// not removed.
+///
+/// Refer to [module-level documentation] for more.
+///
+/// [module-level documentation]: crate::tx_graph
+#[derive(Debug, Clone, PartialEq, Default)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(crate = "serde_crate")
+)]
+#[must_use]
+pub struct Additions {
+    pub tx: BTreeSet<Transaction>,
+    pub txout: BTreeMap<OutPoint, TxOut>,
+}
+
+impl Additions {
+    /// Returns true if the [`Additions`] is empty (no transactions or txouts).
+    pub fn is_empty(&self) -> bool {
+        self.tx.is_empty() && self.txout.is_empty()
+    }
+
+    /// Iterates over all outpoints contained within [`Additions`].
+    pub fn txouts(&self) -> impl Iterator<Item = (OutPoint, &TxOut)> {
+        self.tx
+            .iter()
+            .flat_map(|tx| {
+                tx.output
+                    .iter()
+                    .enumerate()
+                    .map(move |(vout, txout)| (OutPoint::new(tx.txid(), vout as _), txout))
+            })
+            .chain(self.txout.iter().map(|(op, txout)| (*op, txout)))
+    }
+
+    /// Appends the changes in `other` into self such that applying `self` afterward has the same
+    /// effect as sequentially applying the original `self` and `other`.
+    pub fn append(&mut self, mut other: Additions) {
+        self.tx.append(&mut other.tx);
+        self.txout.append(&mut other.txout);
+    }
+}
+
+impl AsRef<TxGraph> for TxGraph {
+    fn as_ref(&self) -> &TxGraph {
+        self
+    }
+}
+
+impl ForEachTxOut for Additions {
+    fn for_each_txout(&self, f: impl FnMut((OutPoint, &TxOut))) {
+        self.txouts().for_each(f)
+    }
+}
+
+impl ForEachTxOut for TxGraph {
+    fn for_each_txout(&self, f: impl FnMut((OutPoint, &TxOut))) {
+        self.all_txouts().for_each(f)
+    }
+}
+
+/// An iterator that traverses transaction descendants.
+///
+/// This `struct` is created by the [`walk_descendants`] method of [`TxGraph`].
+///
+/// [`walk_descendants`]: TxGraph::walk_descendants
+pub struct TxDescendants<'g, F> {
+    graph: &'g TxGraph,
+    visited: HashSet<Txid>,
+    stack: Vec<(usize, Txid)>,
+    filter_map: F,
+}
+
+impl<'g, F> TxDescendants<'g, F> {
+    /// Creates a `TxDescendants` that includes the starting `txid` when iterating.
+    #[allow(unused)]
+    pub(crate) fn new_include_root(graph: &'g TxGraph, txid: Txid, filter_map: F) -> Self {
+        Self {
+            graph,
+            visited: Default::default(),
+            stack: [(0, txid)].into(),
+            filter_map,
+        }
+    }
+
+    /// Creates a `TxDescendants` that excludes the starting `txid` when iterating.
+    pub(crate) fn new_exclude_root(graph: &'g TxGraph, txid: Txid, filter_map: F) -> Self {
+        let mut descendants = Self {
+            graph,
+            visited: Default::default(),
+            stack: Default::default(),
+            filter_map,
+        };
+        descendants.populate_stack(1, txid);
+        descendants
+    }
+
+    /// Creates a `TxDescendants` from multiple starting transactions that include the starting
+    /// `txid`s when iterating.
+    pub(crate) fn from_multiple_include_root<I>(graph: &'g TxGraph, txids: I, filter_map: F) -> Self
+    where
+        I: IntoIterator<Item = Txid>,
+    {
+        Self {
+            graph,
+            visited: Default::default(),
+            stack: txids.into_iter().map(|txid| (0, txid)).collect(),
+            filter_map,
+        }
+    }
+
+    /// Creates a `TxDescendants` from multiple starting transactions that excludes the starting
+    /// `txid`s when iterating.
+    #[allow(unused)]
+    pub(crate) fn from_multiple_exclude_root<I>(graph: &'g TxGraph, txids: I, filter_map: F) -> Self
+    where
+        I: IntoIterator<Item = Txid>,
+    {
+        let mut descendants = Self {
+            graph,
+            visited: Default::default(),
+            stack: Default::default(),
+            filter_map,
+        };
+        for txid in txids {
+            descendants.populate_stack(1, txid);
+        }
+        descendants
+    }
+}
+
+impl<'g, F> TxDescendants<'g, F> {
+    fn populate_stack(&mut self, depth: usize, txid: Txid) {
+        let spend_paths = self
+            .graph
+            .spends
+            .range(tx_outpoint_range(txid))
+            .flat_map(|(_, spends)| spends)
+            .map(|&txid| (depth, txid));
+        self.stack.extend(spend_paths);
+    }
+}
+
+impl<'g, F, O> Iterator for TxDescendants<'g, F>
+where
+    F: FnMut(usize, Txid) -> Option<O>,
+{
+    type Item = O;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let (op_spends, txid, item) = loop {
+            // we have exhausted all paths when stack is empty
+            let (op_spends, txid) = self.stack.pop()?;
+            // we do not want to visit the same transaction twice
+            if self.visited.insert(txid) {
+                // ignore paths when user filters them out
+                if let Some(item) = (self.filter_map)(op_spends, txid) {
+                    break (op_spends, txid, item);
+                }
+            }
+        };
+
+        self.populate_stack(op_spends + 1, txid);
+        Some(item)
+    }
+}
+
+fn tx_outpoint_range(txid: Txid) -> RangeInclusive<OutPoint> {
+    OutPoint::new(txid, u32::MIN)..=OutPoint::new(txid, u32::MAX)
+}

crates/chain/tests/common/mod.rs

@@ -0,0 +1,60 @@
+#[allow(unused_macros)]
+macro_rules! h {
+    ($index:literal) => {{
+        bitcoin::hashes::Hash::hash($index.as_bytes())
+    }};
+}
+
+#[allow(unused_macros)]
+macro_rules! chain {
+    ($([$($tt:tt)*]),*) => { chain!( checkpoints: [$([$($tt)*]),*] ) };
+    (checkpoints: $($tail:tt)*) => { chain!( index: TxHeight, checkpoints: $($tail)*) };
+    (index: $ind:ty, checkpoints: [ $([$height:expr, $block_hash:expr]),* ] $(,txids: [$(($txid:expr, $tx_height:expr)),*])?) => {{
+        #[allow(unused_mut)]
+        let mut chain = bdk_chain::sparse_chain::SparseChain::<$ind>::from_checkpoints([$(($height, $block_hash).into()),*]);
+
+        $(
+            $(
+                let _ = chain.insert_tx($txid, $tx_height).expect("should succeed");
+            )*
+        )?
+
+        chain
+    }};
+}
+
+#[allow(unused_macros)]
+macro_rules! changeset {
+    (checkpoints: $($tail:tt)*) => { changeset!(index: TxHeight, checkpoints: $($tail)*) };
+    (
+        index: $ind:ty,
+        checkpoints: [ $(( $height:expr, $cp_to:expr )),* ]
+        $(,txids: [ $(( $txid:expr, $tx_to:expr )),* ])?
+    ) => {{
+        use bdk_chain::collections::BTreeMap;
+
+        #[allow(unused_mut)]
+        bdk_chain::sparse_chain::ChangeSet::<$ind> {
+            checkpoints: {
+                let mut changes = BTreeMap::default();
+                $(changes.insert($height, $cp_to);)*
+                changes
+            },
+            txids: {
+                let mut changes = BTreeMap::default();
+                $($(changes.insert($txid, $tx_to.map(|h: TxHeight| h.into()));)*)?
+                changes
+            }
+        }
+    }};
+}
+
+#[allow(unused)]
+pub fn new_tx(lt: u32) -> bitcoin::Transaction {
+    bitcoin::Transaction {
+        version: 0x00,
+        lock_time: bitcoin::PackedLockTime(lt),
+        input: vec![],
+        output: vec![],
+    }
+}

crates/chain/tests/test_chain_graph.rs

@@ -0,0 +1,653 @@
+#[macro_use]
+mod common;
+
+use bdk_chain::{
+    chain_graph::*,
+    collections::HashSet,
+    sparse_chain,
+    tx_graph::{self, TxGraph},
+    BlockId, TxHeight,
+};
+use bitcoin::{OutPoint, PackedLockTime, Script, Sequence, Transaction, TxIn, TxOut, Witness};
+
+#[test]
+fn test_spent_by() {
+    let tx1 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let op = OutPoint {
+        txid: tx1.txid(),
+        vout: 0,
+    };
+
+    let tx2 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: op,
+            ..Default::default()
+        }],
+        output: vec![],
+    };
+    let tx3 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(42),
+        input: vec![TxIn {
+            previous_output: op,
+            ..Default::default()
+        }],
+        output: vec![],
+    };
+
+    let mut cg1 = ChainGraph::default();
+    let _ = cg1
+        .insert_tx(tx1, TxHeight::Unconfirmed)
+        .expect("should insert");
+    let mut cg2 = cg1.clone();
+    let _ = cg1
+        .insert_tx(tx2.clone(), TxHeight::Unconfirmed)
+        .expect("should insert");
+    let _ = cg2
+        .insert_tx(tx3.clone(), TxHeight::Unconfirmed)
+        .expect("should insert");
+
+    assert_eq!(cg1.spent_by(op), Some((&TxHeight::Unconfirmed, tx2.txid())));
+    assert_eq!(cg2.spent_by(op), Some((&TxHeight::Unconfirmed, tx3.txid())));
+}
+
+#[test]
+fn update_evicts_conflicting_tx() {
+    let cp_a = BlockId {
+        height: 0,
+        hash: h!("A"),
+    };
+    let cp_b = BlockId {
+        height: 1,
+        hash: h!("B"),
+    };
+    let cp_b2 = BlockId {
+        height: 1,
+        hash: h!("B'"),
+    };
+
+    let tx_a = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let tx_b = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_a.txid(), 0),
+            script_sig: Script::new(),
+            sequence: Sequence::default(),
+            witness: Witness::new(),
+        }],
+        output: vec![TxOut::default()],
+    };
+
+    let tx_b2 = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_a.txid(), 0),
+            script_sig: Script::new(),
+            sequence: Sequence::default(),
+            witness: Witness::new(),
+        }],
+        output: vec![TxOut::default(), TxOut::default()],
+    };
+    {
+        let mut cg1 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg.insert_checkpoint(cp_a).expect("should insert cp");
+            let _ = cg
+                .insert_tx(tx_a.clone(), TxHeight::Confirmed(0))
+                .expect("should insert tx");
+            let _ = cg
+                .insert_tx(tx_b.clone(), TxHeight::Unconfirmed)
+                .expect("should insert tx");
+            cg
+        };
+        let cg2 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg
+                .insert_tx(tx_b2.clone(), TxHeight::Unconfirmed)
+                .expect("should insert tx");
+            cg
+        };
+
+        let changeset = ChangeSet::<TxHeight> {
+            chain: sparse_chain::ChangeSet {
+                checkpoints: Default::default(),
+                txids: [
+                    (tx_b.txid(), None),
+                    (tx_b2.txid(), Some(TxHeight::Unconfirmed)),
+                ]
+                .into(),
+            },
+            graph: tx_graph::Additions {
+                tx: [tx_b2.clone()].into(),
+                txout: [].into(),
+            },
+        };
+        assert_eq!(
+            cg1.determine_changeset(&cg2),
+            Ok(changeset.clone()),
+            "tx should be evicted from mempool"
+        );
+
+        cg1.apply_changeset(changeset);
+    }
+
+    {
+        let cg1 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg.insert_checkpoint(cp_a).expect("should insert cp");
+            let _ = cg.insert_checkpoint(cp_b).expect("should insert cp");
+            let _ = cg
+                .insert_tx(tx_a.clone(), TxHeight::Confirmed(0))
+                .expect("should insert tx");
+            let _ = cg
+                .insert_tx(tx_b.clone(), TxHeight::Confirmed(1))
+                .expect("should insert tx");
+            cg
+        };
+        let cg2 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg
+                .insert_tx(tx_b2.clone(), TxHeight::Unconfirmed)
+                .expect("should insert tx");
+            cg
+        };
+        assert_eq!(
+            cg1.determine_changeset(&cg2),
+            Err(UpdateError::UnresolvableConflict(UnresolvableConflict {
+                already_confirmed_tx: (TxHeight::Confirmed(1), tx_b.txid()),
+                update_tx: (TxHeight::Unconfirmed, tx_b2.txid()),
+            })),
+            "fail if tx is evicted from valid block"
+        );
+    }
+
+    {
+        // Given 2 blocks `{A, B}`, and an update that invalidates block B with
+        // `{A, B'}`, we expect txs that exist in `B` that conflicts with txs
+        // introduced in the update to be successfully evicted.
+        let mut cg1 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg.insert_checkpoint(cp_a).expect("should insert cp");
+            let _ = cg.insert_checkpoint(cp_b).expect("should insert cp");
+            let _ = cg
+                .insert_tx(tx_a, TxHeight::Confirmed(0))
+                .expect("should insert tx");
+            let _ = cg
+                .insert_tx(tx_b.clone(), TxHeight::Confirmed(1))
+                .expect("should insert tx");
+            cg
+        };
+        let cg2 = {
+            let mut cg = ChainGraph::default();
+            let _ = cg.insert_checkpoint(cp_a).expect("should insert cp");
+            let _ = cg.insert_checkpoint(cp_b2).expect("should insert cp");
+            let _ = cg
+                .insert_tx(tx_b2.clone(), TxHeight::Unconfirmed)
+                .expect("should insert tx");
+            cg
+        };
+
+        let changeset = ChangeSet::<TxHeight> {
+            chain: sparse_chain::ChangeSet {
+                checkpoints: [(1, Some(h!("B'")))].into(),
+                txids: [
+                    (tx_b.txid(), None),
+                    (tx_b2.txid(), Some(TxHeight::Unconfirmed)),
+                ]
+                .into(),
+            },
+            graph: tx_graph::Additions {
+                tx: [tx_b2].into(),
+                txout: [].into(),
+            },
+        };
+        assert_eq!(
+            cg1.determine_changeset(&cg2),
+            Ok(changeset.clone()),
+            "tx should be evicted from B",
+        );
+
+        cg1.apply_changeset(changeset);
+    }
+}
+
+#[test]
+fn chain_graph_new_missing() {
+    let tx_a = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+    let tx_b = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let update = chain!(
+        index: TxHeight,
+        checkpoints: [[0, h!("A")]],
+        txids: [
+            (tx_a.txid(), TxHeight::Confirmed(0)),
+            (tx_b.txid(), TxHeight::Confirmed(0))
+        ]
+    );
+    let mut graph = TxGraph::default();
+
+    let mut expected_missing = HashSet::new();
+    expected_missing.insert(tx_a.txid());
+    expected_missing.insert(tx_b.txid());
+
+    assert_eq!(
+        ChainGraph::new(update.clone(), graph.clone()),
+        Err(NewError::Missing(expected_missing.clone()))
+    );
+
+    let _ = graph.insert_tx(tx_b.clone());
+    expected_missing.remove(&tx_b.txid());
+
+    assert_eq!(
+        ChainGraph::new(update.clone(), graph.clone()),
+        Err(NewError::Missing(expected_missing.clone()))
+    );
+
+    let _ = graph.insert_txout(
+        OutPoint {
+            txid: tx_a.txid(),
+            vout: 0,
+        },
+        tx_a.output[0].clone(),
+    );
+
+    assert_eq!(
+        ChainGraph::new(update.clone(), graph.clone()),
+        Err(NewError::Missing(expected_missing)),
+        "inserting an output instead of full tx doesn't satisfy constraint"
+    );
+
+    let _ = graph.insert_tx(tx_a.clone());
+
+    let new_graph = ChainGraph::new(update.clone(), graph.clone()).unwrap();
+    let expected_graph = {
+        let mut cg = ChainGraph::<TxHeight>::default();
+        let _ = cg
+            .insert_checkpoint(update.latest_checkpoint().unwrap())
+            .unwrap();
+        let _ = cg.insert_tx(tx_a, TxHeight::Confirmed(0)).unwrap();
+        let _ = cg.insert_tx(tx_b, TxHeight::Confirmed(0)).unwrap();
+        cg
+    };
+
+    assert_eq!(new_graph, expected_graph);
+}
+
+#[test]
+fn chain_graph_new_conflicts() {
+    let tx_a = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let tx_b = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_a.txid(), 0),
+            script_sig: Script::new(),
+            sequence: Sequence::default(),
+            witness: Witness::new(),
+        }],
+        output: vec![TxOut::default()],
+    };
+
+    let tx_b2 = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_a.txid(), 0),
+            script_sig: Script::new(),
+            sequence: Sequence::default(),
+            witness: Witness::new(),
+        }],
+        output: vec![TxOut::default(), TxOut::default()],
+    };
+
+    let chain = chain!(
+        index: TxHeight,
+        checkpoints: [[5, h!("A")]],
+        txids: [
+            (tx_a.txid(), TxHeight::Confirmed(1)),
+            (tx_b.txid(), TxHeight::Confirmed(2)),
+            (tx_b2.txid(), TxHeight::Confirmed(3))
+        ]
+    );
+
+    let graph = TxGraph::new([tx_a, tx_b, tx_b2]);
+
+    assert!(matches!(
+        ChainGraph::new(chain, graph),
+        Err(NewError::Conflict { .. })
+    ));
+}
+
+#[test]
+fn test_get_tx_in_chain() {
+    let mut cg = ChainGraph::default();
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let _ = cg.insert_tx(tx.clone(), TxHeight::Unconfirmed).unwrap();
+    assert_eq!(
+        cg.get_tx_in_chain(tx.txid()),
+        Some((&TxHeight::Unconfirmed, &tx))
+    );
+}
+
+#[test]
+fn test_iterate_transactions() {
+    let mut cg = ChainGraph::default();
+    let txs = (0..3)
+        .map(|i| Transaction {
+            version: i,
+            lock_time: PackedLockTime(0),
+            input: vec![],
+            output: vec![TxOut::default()],
+        })
+        .collect::<Vec<_>>();
+    let _ = cg
+        .insert_checkpoint(BlockId {
+            height: 1,
+            hash: h!("A"),
+        })
+        .unwrap();
+    let _ = cg
+        .insert_tx(txs[0].clone(), TxHeight::Confirmed(1))
+        .unwrap();
+    let _ = cg.insert_tx(txs[1].clone(), TxHeight::Unconfirmed).unwrap();
+    let _ = cg
+        .insert_tx(txs[2].clone(), TxHeight::Confirmed(0))
+        .unwrap();
+
+    assert_eq!(
+        cg.transactions_in_chain().collect::<Vec<_>>(),
+        vec![
+            (&TxHeight::Confirmed(0), &txs[2]),
+            (&TxHeight::Confirmed(1), &txs[0]),
+            (&TxHeight::Unconfirmed, &txs[1]),
+        ]
+    );
+}
+
+/// Start with: block1, block2a, tx1, tx2a
+///   Update 1: block2a -> block2b , tx2a -> tx2b
+///   Update 2: block2b -> block2c , tx2b -> tx2a
+#[test]
+fn test_apply_changes_reintroduce_tx() {
+    let block1 = BlockId {
+        height: 1,
+        hash: h!("block 1"),
+    };
+    let block2a = BlockId {
+        height: 2,
+        hash: h!("block 2a"),
+    };
+    let block2b = BlockId {
+        height: 2,
+        hash: h!("block 2b"),
+    };
+    let block2c = BlockId {
+        height: 2,
+        hash: h!("block 2c"),
+    };
+
+    let tx1 = Transaction {
+        version: 0,
+        lock_time: PackedLockTime(1),
+        input: Vec::new(),
+        output: [TxOut {
+            value: 1,
+            script_pubkey: Script::new(),
+        }]
+        .into(),
+    };
+
+    let tx2a = Transaction {
+        version: 0,
+        lock_time: PackedLockTime('a'.into()),
+        input: [TxIn {
+            previous_output: OutPoint::new(tx1.txid(), 0),
+            ..Default::default()
+        }]
+        .into(),
+        output: [TxOut {
+            value: 0,
+            ..Default::default()
+        }]
+        .into(),
+    };
+
+    let tx2b = Transaction {
+        lock_time: PackedLockTime('b'.into()),
+        ..tx2a.clone()
+    };
+
+    // block1, block2a, tx1, tx2a
+    let mut cg = {
+        let mut cg = ChainGraph::default();
+        let _ = cg.insert_checkpoint(block1).unwrap();
+        let _ = cg.insert_checkpoint(block2a).unwrap();
+        let _ = cg.insert_tx(tx1, TxHeight::Confirmed(1)).unwrap();
+        let _ = cg.insert_tx(tx2a.clone(), TxHeight::Confirmed(2)).unwrap();
+        cg
+    };
+
+    // block2a -> block2b , tx2a -> tx2b
+    let update = {
+        let mut update = ChainGraph::default();
+        let _ = update.insert_checkpoint(block1).unwrap();
+        let _ = update.insert_checkpoint(block2b).unwrap();
+        let _ = update
+            .insert_tx(tx2b.clone(), TxHeight::Confirmed(2))
+            .unwrap();
+        update
+    };
+    assert_eq!(
+        cg.apply_update(update).expect("should update"),
+        ChangeSet {
+            chain: changeset! {
+                checkpoints: [(2, Some(block2b.hash))],
+                txids: [(tx2a.txid(), None), (tx2b.txid(), Some(TxHeight::Confirmed(2)))]
+            },
+            graph: tx_graph::Additions {
+                tx: [tx2b.clone()].into(),
+                ..Default::default()
+            },
+        }
+    );
+
+    // block2b -> block2c , tx2b -> tx2a
+    let update = {
+        let mut update = ChainGraph::default();
+        let _ = update.insert_checkpoint(block1).unwrap();
+        let _ = update.insert_checkpoint(block2c).unwrap();
+        let _ = update
+            .insert_tx(tx2a.clone(), TxHeight::Confirmed(2))
+            .unwrap();
+        update
+    };
+    assert_eq!(
+        cg.apply_update(update).expect("should update"),
+        ChangeSet {
+            chain: changeset! {
+                checkpoints: [(2, Some(block2c.hash))],
+                txids: [(tx2b.txid(), None), (tx2a.txid(), Some(TxHeight::Confirmed(2)))]
+            },
+            ..Default::default()
+        }
+    );
+}
+
+#[test]
+fn test_evict_descendants() {
+    let block_1 = BlockId {
+        height: 1,
+        hash: h!("block 1"),
+    };
+
+    let block_2a = BlockId {
+        height: 2,
+        hash: h!("block 2 a"),
+    };
+
+    let block_2b = BlockId {
+        height: 2,
+        hash: h!("block 2 b"),
+    };
+
+    let tx_1 = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(h!("fake tx"), 0),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: 10_000,
+            script_pubkey: Script::new(),
+        }],
+        ..common::new_tx(1)
+    };
+    let tx_2 = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_1.txid(), 0),
+            ..Default::default()
+        }],
+        output: vec![
+            TxOut {
+                value: 20_000,
+                script_pubkey: Script::new(),
+            },
+            TxOut {
+                value: 30_000,
+                script_pubkey: Script::new(),
+            },
+        ],
+        ..common::new_tx(2)
+    };
+    let tx_3 = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_2.txid(), 0),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: 40_000,
+            script_pubkey: Script::new(),
+        }],
+        ..common::new_tx(3)
+    };
+    let tx_4 = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_2.txid(), 1),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: 40_000,
+            script_pubkey: Script::new(),
+        }],
+        ..common::new_tx(4)
+    };
+    let tx_5 = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_4.txid(), 0),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: 40_000,
+            script_pubkey: Script::new(),
+        }],
+        ..common::new_tx(5)
+    };
+
+    let tx_conflict = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_1.txid(), 0),
+            ..Default::default()
+        }],
+        output: vec![TxOut {
+            value: 12345,
+            script_pubkey: Script::new(),
+        }],
+        ..common::new_tx(6)
+    };
+
+    // 1 is spent by 2, 2 is spent by 3 and 4, 4 is spent by 5
+    let _txid_1 = tx_1.txid();
+    let txid_2 = tx_2.txid();
+    let txid_3 = tx_3.txid();
+    let txid_4 = tx_4.txid();
+    let txid_5 = tx_5.txid();
+
+    // this tx conflicts with 2
+    let txid_conflict = tx_conflict.txid();
+
+    let cg = {
+        let mut cg = ChainGraph::<TxHeight>::default();
+        let _ = cg.insert_checkpoint(block_1);
+        let _ = cg.insert_checkpoint(block_2a);
+        let _ = cg.insert_tx(tx_1, TxHeight::Confirmed(1));
+        let _ = cg.insert_tx(tx_2, TxHeight::Confirmed(2));
+        let _ = cg.insert_tx(tx_3, TxHeight::Confirmed(2));
+        let _ = cg.insert_tx(tx_4, TxHeight::Confirmed(2));
+        let _ = cg.insert_tx(tx_5, TxHeight::Confirmed(2));
+        cg
+    };
+
+    let update = {
+        let mut cg = ChainGraph::<TxHeight>::default();
+        let _ = cg.insert_checkpoint(block_1);
+        let _ = cg.insert_checkpoint(block_2b);
+        let _ = cg.insert_tx(tx_conflict.clone(), TxHeight::Confirmed(2));
+        cg
+    };
+
+    assert_eq!(
+        cg.determine_changeset(&update),
+        Ok(ChangeSet {
+            chain: changeset! {
+                checkpoints: [(2, Some(block_2b.hash))],
+                txids: [(txid_2, None), (txid_3, None), (txid_4, None), (txid_5, None), (txid_conflict, Some(TxHeight::Confirmed(2)))]
+            },
+            graph: tx_graph::Additions {
+                tx: [tx_conflict.clone()].into(),
+                ..Default::default()
+            }
+        })
+    );
+
+    let err = cg
+        .insert_tx_preview(tx_conflict, TxHeight::Unconfirmed)
+        .expect_err("must fail due to conflicts");
+    assert!(matches!(err, InsertTxError::UnresolvableConflict(_)));
+}

crates/chain/tests/test_keychain_tracker.rs

@@ -0,0 +1,239 @@
+#![cfg(feature = "miniscript")]
+#[macro_use]
+mod common;
+use bdk_chain::{
+    keychain::{Balance, KeychainTracker},
+    miniscript::{
+        bitcoin::{secp256k1::Secp256k1, OutPoint, PackedLockTime, Transaction, TxOut},
+        Descriptor,
+    },
+    BlockId, ConfirmationTime, TxHeight,
+};
+use bitcoin::TxIn;
+
+#[test]
+fn test_insert_tx() {
+    let mut tracker = KeychainTracker::default();
+    let secp = Secp256k1::new();
+    let (descriptor, _) = Descriptor::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
+    tracker.add_keychain((), descriptor.clone());
+    let txout = TxOut {
+        value: 100_000,
+        script_pubkey: descriptor.at_derivation_index(5).script_pubkey(),
+    };
+
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![txout],
+    };
+
+    let _ = tracker.txout_index.reveal_to_target(&(), 5);
+
+    let changeset = tracker
+        .insert_tx_preview(tx.clone(), ConfirmationTime::Unconfirmed)
+        .unwrap();
+    tracker.apply_changeset(changeset);
+    assert_eq!(
+        tracker
+            .chain_graph()
+            .transactions_in_chain()
+            .collect::<Vec<_>>(),
+        vec![(&ConfirmationTime::Unconfirmed, &tx)]
+    );
+
+    assert_eq!(
+        tracker
+            .txout_index
+            .txouts_of_keychain(&())
+            .collect::<Vec<_>>(),
+        vec![(
+            5,
+            OutPoint {
+                txid: tx.txid(),
+                vout: 0
+            }
+        )]
+    );
+}
+
+#[test]
+fn test_balance() {
+    use core::str::FromStr;
+    #[derive(Debug, Clone, PartialEq, Eq, Ord, PartialOrd)]
+    enum Keychain {
+        One,
+        Two,
+    }
+    let mut tracker = KeychainTracker::<Keychain, TxHeight>::default();
+    let one = Descriptor::from_str("tr([73c5da0a/86'/0'/0']xpub6BgBgsespWvERF3LHQu6CnqdvfEvtMcQjYrcRzx53QJjSxarj2afYWcLteoGVky7D3UKDP9QyrLprQ3VCECoY49yfdDEHGCtMMj92pReUsQ/0/*)#rg247h69").unwrap();
+    let two = Descriptor::from_str("tr([73c5da0a/86'/0'/0']xpub6BgBgsespWvERF3LHQu6CnqdvfEvtMcQjYrcRzx53QJjSxarj2afYWcLteoGVky7D3UKDP9QyrLprQ3VCECoY49yfdDEHGCtMMj92pReUsQ/1/*)#ju05rz2a").unwrap();
+    tracker.add_keychain(Keychain::One, one);
+    tracker.add_keychain(Keychain::Two, two);
+
+    let tx1 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 13_000,
+            script_pubkey: tracker
+                .txout_index
+                .reveal_next_spk(&Keychain::One)
+                .0
+                 .1
+                .clone(),
+        }],
+    };
+
+    let tx2 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 7_000,
+            script_pubkey: tracker
+                .txout_index
+                .reveal_next_spk(&Keychain::Two)
+                .0
+                 .1
+                .clone(),
+        }],
+    };
+
+    let tx_coinbase = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn::default()],
+        output: vec![TxOut {
+            value: 11_000,
+            script_pubkey: tracker
+                .txout_index
+                .reveal_next_spk(&Keychain::Two)
+                .0
+                 .1
+                .clone(),
+        }],
+    };
+
+    assert!(tx_coinbase.is_coin_base());
+
+    let _ = tracker
+        .insert_checkpoint(BlockId {
+            height: 5,
+            hash: h!("1"),
+        })
+        .unwrap();
+
+    let should_trust = |keychain: &Keychain| match *keychain {
+        Keychain::One => false,
+        Keychain::Two => true,
+    };
+
+    assert_eq!(tracker.balance(should_trust), Balance::default());
+
+    let _ = tracker
+        .insert_tx(tx1.clone(), TxHeight::Unconfirmed)
+        .unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            untrusted_pending: 13_000,
+            ..Default::default()
+        }
+    );
+
+    let _ = tracker
+        .insert_tx(tx2.clone(), TxHeight::Unconfirmed)
+        .unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 7_000,
+            untrusted_pending: 13_000,
+            ..Default::default()
+        }
+    );
+
+    let _ = tracker
+        .insert_tx(tx_coinbase, TxHeight::Confirmed(0))
+        .unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 7_000,
+            untrusted_pending: 13_000,
+            immature: 11_000,
+            ..Default::default()
+        }
+    );
+
+    let _ = tracker.insert_tx(tx1, TxHeight::Confirmed(1)).unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 7_000,
+            untrusted_pending: 0,
+            immature: 11_000,
+            confirmed: 13_000,
+        }
+    );
+
+    let _ = tracker.insert_tx(tx2, TxHeight::Confirmed(2)).unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 0,
+            untrusted_pending: 0,
+            immature: 11_000,
+            confirmed: 20_000,
+        }
+    );
+
+    let _ = tracker
+        .insert_checkpoint(BlockId {
+            height: 98,
+            hash: h!("98"),
+        })
+        .unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 0,
+            untrusted_pending: 0,
+            immature: 11_000,
+            confirmed: 20_000,
+        }
+    );
+
+    let _ = tracker
+        .insert_checkpoint(BlockId {
+            height: 99,
+            hash: h!("99"),
+        })
+        .unwrap();
+
+    assert_eq!(
+        tracker.balance(should_trust),
+        Balance {
+            trusted_pending: 0,
+            untrusted_pending: 0,
+            immature: 0,
+            confirmed: 31_000,
+        }
+    );
+
+    assert_eq!(tracker.balance_at(0), 0);
+    assert_eq!(tracker.balance_at(1), 13_000);
+    assert_eq!(tracker.balance_at(2), 20_000);
+    assert_eq!(tracker.balance_at(98), 20_000);
+    assert_eq!(tracker.balance_at(99), 31_000);
+    assert_eq!(tracker.balance_at(100), 31_000);
+}

crates/chain/tests/test_keychain_txout_index.rs

@@ -0,0 +1,369 @@
+#![cfg(feature = "miniscript")]
+
+#[macro_use]
+mod common;
+use bdk_chain::{
+    collections::BTreeMap,
+    keychain::{DerivationAdditions, KeychainTxOutIndex},
+};
+
+use bitcoin::{secp256k1::Secp256k1, OutPoint, Script, Transaction, TxOut};
+use miniscript::{Descriptor, DescriptorPublicKey};
+
+#[derive(Clone, Debug, PartialEq, Eq, Ord, PartialOrd)]
+enum TestKeychain {
+    External,
+    Internal,
+}
+
+fn init_txout_index() -> (
+    bdk_chain::keychain::KeychainTxOutIndex<TestKeychain>,
+    Descriptor<DescriptorPublicKey>,
+    Descriptor<DescriptorPublicKey>,
+) {
+    let mut txout_index = bdk_chain::keychain::KeychainTxOutIndex::<TestKeychain>::default();
+
+    let secp = bdk_chain::bitcoin::secp256k1::Secp256k1::signing_only();
+    let (external_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
+    let (internal_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/1/*)").unwrap();
+
+    txout_index.add_keychain(TestKeychain::External, external_descriptor.clone());
+    txout_index.add_keychain(TestKeychain::Internal, internal_descriptor.clone());
+
+    (txout_index, external_descriptor, internal_descriptor)
+}
+
+fn spk_at_index(descriptor: &Descriptor<DescriptorPublicKey>, index: u32) -> Script {
+    descriptor
+        .derived_descriptor(&Secp256k1::verification_only(), index)
+        .expect("must derive")
+        .script_pubkey()
+}
+
+#[test]
+fn test_set_all_derivation_indices() {
+    let (mut txout_index, _, _) = init_txout_index();
+    let derive_to: BTreeMap<_, _> =
+        [(TestKeychain::External, 12), (TestKeychain::Internal, 24)].into();
+    assert_eq!(
+        txout_index.reveal_to_target_multi(&derive_to).1.as_inner(),
+        &derive_to
+    );
+    assert_eq!(txout_index.last_revealed_indices(), &derive_to);
+    assert_eq!(
+        txout_index.reveal_to_target_multi(&derive_to).1,
+        DerivationAdditions::default(),
+        "no changes if we set to the same thing"
+    );
+}
+
+#[test]
+fn test_lookahead() {
+    let (mut txout_index, external_desc, internal_desc) = init_txout_index();
+
+    // ensure it does not break anything if lookahead is set multiple times
+    (0..=10).for_each(|lookahead| txout_index.set_lookahead(&TestKeychain::External, lookahead));
+    (0..=20)
+        .filter(|v| v % 2 == 0)
+        .for_each(|lookahead| txout_index.set_lookahead(&TestKeychain::Internal, lookahead));
+
+    assert_eq!(txout_index.inner().all_spks().len(), 30);
+
+    // given:
+    // - external lookahead set to 10
+    // - internal lookahead set to 20
+    // when:
+    // - set external derivation index to value higher than last, but within the lookahead value
+    // expect:
+    // - scripts cached in spk_txout_index should increase correctly
+    // - stored scripts of external keychain should be of expected counts
+    for index in (0..20).skip_while(|i| i % 2 == 1) {
+        let (revealed_spks, revealed_additions) =
+            txout_index.reveal_to_target(&TestKeychain::External, index);
+        assert_eq!(
+            revealed_spks.collect::<Vec<_>>(),
+            vec![(index, spk_at_index(&external_desc, index))],
+        );
+        assert_eq!(
+            revealed_additions.as_inner(),
+            &[(TestKeychain::External, index)].into()
+        );
+
+        assert_eq!(
+            txout_index.inner().all_spks().len(),
+            10 /* external lookahead */ +
+            20 /* internal lookahead */ +
+            index as usize + 1 /* `derived` count */
+        );
+        assert_eq!(
+            txout_index
+                .revealed_spks_of_keychain(&TestKeychain::External)
+                .count(),
+            index as usize + 1,
+        );
+        assert_eq!(
+            txout_index
+                .revealed_spks_of_keychain(&TestKeychain::Internal)
+                .count(),
+            0,
+        );
+        assert_eq!(
+            txout_index
+                .unused_spks_of_keychain(&TestKeychain::External)
+                .count(),
+            index as usize + 1,
+        );
+        assert_eq!(
+            txout_index
+                .unused_spks_of_keychain(&TestKeychain::Internal)
+                .count(),
+            0,
+        );
+    }
+
+    // given:
+    // - internal lookahead is 20
+    // - internal derivation index is `None`
+    // when:
+    // - derivation index is set ahead of current derivation index + lookahead
+    // expect:
+    // - scripts cached in spk_txout_index should increase correctly, a.k.a. no scripts are skipped
+    let (revealed_spks, revealed_additions) =
+        txout_index.reveal_to_target(&TestKeychain::Internal, 24);
+    assert_eq!(
+        revealed_spks.collect::<Vec<_>>(),
+        (0..=24)
+            .map(|index| (index, spk_at_index(&internal_desc, index)))
+            .collect::<Vec<_>>(),
+    );
+    assert_eq!(
+        revealed_additions.as_inner(),
+        &[(TestKeychain::Internal, 24)].into()
+    );
+    assert_eq!(
+        txout_index.inner().all_spks().len(),
+        10 /* external lookahead */ +
+        20 /* internal lookahead */ +
+        20 /* external stored index count */ +
+        25 /* internal stored index count */
+    );
+    assert_eq!(
+        txout_index
+            .revealed_spks_of_keychain(&TestKeychain::Internal)
+            .count(),
+        25,
+    );
+
+    // ensure derivation indices are expected for each keychain
+    let last_external_index = txout_index
+        .last_revealed_index(&TestKeychain::External)
+        .expect("already derived");
+    let last_internal_index = txout_index
+        .last_revealed_index(&TestKeychain::Internal)
+        .expect("already derived");
+    assert_eq!(last_external_index, 19);
+    assert_eq!(last_internal_index, 24);
+
+    // when:
+    // - scanning txouts with spks within stored indexes
+    // expect:
+    // - no changes to stored index counts
+    let external_iter = 0..=last_external_index;
+    let internal_iter = last_internal_index - last_external_index..=last_internal_index;
+    for (external_index, internal_index) in external_iter.zip(internal_iter) {
+        let tx = Transaction {
+            output: vec![
+                TxOut {
+                    script_pubkey: external_desc
+                        .at_derivation_index(external_index)
+                        .script_pubkey(),
+                    value: 10_000,
+                },
+                TxOut {
+                    script_pubkey: internal_desc
+                        .at_derivation_index(internal_index)
+                        .script_pubkey(),
+                    value: 10_000,
+                },
+            ],
+            ..common::new_tx(external_index)
+        };
+        assert_eq!(txout_index.scan(&tx), DerivationAdditions::default());
+        assert_eq!(
+            txout_index.last_revealed_index(&TestKeychain::External),
+            Some(last_external_index)
+        );
+        assert_eq!(
+            txout_index.last_revealed_index(&TestKeychain::Internal),
+            Some(last_internal_index)
+        );
+        assert_eq!(
+            txout_index
+                .revealed_spks_of_keychain(&TestKeychain::External)
+                .count(),
+            last_external_index as usize + 1,
+        );
+        assert_eq!(
+            txout_index
+                .revealed_spks_of_keychain(&TestKeychain::Internal)
+                .count(),
+            last_internal_index as usize + 1,
+        );
+    }
+}
+
+// when:
+// - scanning txouts with spks above last stored index
+// expect:
+// - last revealed index should increase as expected
+// - last used index should change as expected
+#[test]
+fn test_scan_with_lookahead() {
+    let (mut txout_index, external_desc, _) = init_txout_index();
+    txout_index.set_lookahead_for_all(10);
+
+    let spks: BTreeMap<u32, Script> = [0, 10, 20, 30]
+        .into_iter()
+        .map(|i| (i, external_desc.at_derivation_index(i).script_pubkey()))
+        .collect();
+
+    for (&spk_i, spk) in &spks {
+        let op = OutPoint::new(h!("fake tx"), spk_i);
+        let txout = TxOut {
+            script_pubkey: spk.clone(),
+            value: 0,
+        };
+
+        let additions = txout_index.scan_txout(op, &txout);
+        assert_eq!(
+            additions.as_inner(),
+            &[(TestKeychain::External, spk_i)].into()
+        );
+        assert_eq!(
+            txout_index.last_revealed_index(&TestKeychain::External),
+            Some(spk_i)
+        );
+        assert_eq!(
+            txout_index.last_used_index(&TestKeychain::External),
+            Some(spk_i)
+        );
+    }
+
+    // now try with index 41 (lookahead surpassed), we expect that the txout to not be indexed
+    let spk_41 = external_desc.at_derivation_index(41).script_pubkey();
+    let op = OutPoint::new(h!("fake tx"), 41);
+    let txout = TxOut {
+        script_pubkey: spk_41,
+        value: 0,
+    };
+    let additions = txout_index.scan_txout(op, &txout);
+    assert!(additions.is_empty());
+}
+
+#[test]
+fn test_wildcard_derivations() {
+    let (mut txout_index, external_desc, _) = init_txout_index();
+    let external_spk_0 = external_desc.at_derivation_index(0).script_pubkey();
+    let external_spk_16 = external_desc.at_derivation_index(16).script_pubkey();
+    let external_spk_26 = external_desc.at_derivation_index(26).script_pubkey();
+    let external_spk_27 = external_desc.at_derivation_index(27).script_pubkey();
+
+    // - nothing is derived
+    // - unused list is also empty
+    //
+    // - next_derivation_index() == (0, true)
+    // - derive_new() == ((0, <spk>), DerivationAdditions)
+    // - next_unused() == ((0, <spk>), DerivationAdditions:is_empty())
+    assert_eq!(txout_index.next_index(&TestKeychain::External), (0, true));
+    let (spk, changeset) = txout_index.reveal_next_spk(&TestKeychain::External);
+    assert_eq!(spk, (0_u32, &external_spk_0));
+    assert_eq!(changeset.as_inner(), &[(TestKeychain::External, 0)].into());
+    let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
+    assert_eq!(spk, (0_u32, &external_spk_0));
+    assert_eq!(changeset.as_inner(), &[].into());
+
+    // - derived till 25
+    // - used all spks till 15.
+    // - used list : [0..=15, 17, 20, 23]
+    // - unused list: [16, 18, 19, 21, 22, 24, 25]
+
+    // - next_derivation_index() = (26, true)
+    // - derive_new() = ((26, <spk>), DerivationAdditions)
+    // - next_unused() == ((16, <spk>), DerivationAdditions::is_empty())
+    let _ = txout_index.reveal_to_target(&TestKeychain::External, 25);
+
+    (0..=15)
+        .into_iter()
+        .chain(vec![17, 20, 23].into_iter())
+        .for_each(|index| assert!(txout_index.mark_used(&TestKeychain::External, index)));
+
+    assert_eq!(txout_index.next_index(&TestKeychain::External), (26, true));
+
+    let (spk, changeset) = txout_index.reveal_next_spk(&TestKeychain::External);
+    assert_eq!(spk, (26, &external_spk_26));
+
+    assert_eq!(changeset.as_inner(), &[(TestKeychain::External, 26)].into());
+
+    let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
+    assert_eq!(spk, (16, &external_spk_16));
+    assert_eq!(changeset.as_inner(), &[].into());
+
+    // - Use all the derived till 26.
+    // - next_unused() = ((27, <spk>), DerivationAdditions)
+    (0..=26).into_iter().for_each(|index| {
+        txout_index.mark_used(&TestKeychain::External, index);
+    });
+
+    let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
+    assert_eq!(spk, (27, &external_spk_27));
+    assert_eq!(changeset.as_inner(), &[(TestKeychain::External, 27)].into());
+}
+
+#[test]
+fn test_non_wildcard_derivations() {
+    let mut txout_index = KeychainTxOutIndex::<TestKeychain>::default();
+
+    let secp = bitcoin::secp256k1::Secp256k1::signing_only();
+    let (no_wildcard_descriptor, _) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "wpkh([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/1/0)").unwrap();
+    let external_spk = no_wildcard_descriptor
+        .at_derivation_index(0)
+        .script_pubkey();
+
+    txout_index.add_keychain(TestKeychain::External, no_wildcard_descriptor);
+
+    // given:
+    // - `txout_index` with no stored scripts
+    // expect:
+    // - next derivation index should be new
+    // - when we derive a new script, script @ index 0
+    // - when we get the next unused script, script @ index 0
+    assert_eq!(txout_index.next_index(&TestKeychain::External), (0, true));
+    let (spk, changeset) = txout_index.reveal_next_spk(&TestKeychain::External);
+    assert_eq!(spk, (0, &external_spk));
+    assert_eq!(changeset.as_inner(), &[(TestKeychain::External, 0)].into());
+
+    let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
+    assert_eq!(spk, (0, &external_spk));
+    assert_eq!(changeset.as_inner(), &[].into());
+
+    // given:
+    // - the non-wildcard descriptor already has a stored and used script
+    // expect:
+    // - next derivation index should not be new
+    // - derive new and next unused should return the old script
+    // - store_up_to should not panic and return empty additions
+    assert_eq!(txout_index.next_index(&TestKeychain::External), (0, false));
+    txout_index.mark_used(&TestKeychain::External, 0);
+
+    let (spk, changeset) = txout_index.reveal_next_spk(&TestKeychain::External);
+    assert_eq!(spk, (0, &external_spk));
+    assert_eq!(changeset.as_inner(), &[].into());
+
+    let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
+    assert_eq!(spk, (0, &external_spk));
+    assert_eq!(changeset.as_inner(), &[].into());
+    let (revealed_spks, revealed_additions) =
+        txout_index.reveal_to_target(&TestKeychain::External, 200);
+    assert_eq!(revealed_spks.count(), 0);
+    assert!(revealed_additions.is_empty());
+}

crates/chain/tests/test_sparse_chain.rs

@@ -0,0 +1,773 @@
+#[macro_use]
+mod common;
+
+use bdk_chain::{collections::BTreeSet, sparse_chain::*, BlockId, TxHeight};
+use bitcoin::{hashes::Hash, Txid};
+use core::ops::Bound;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash)]
+pub struct TestIndex(TxHeight, u32);
+
+impl ChainPosition for TestIndex {
+    fn height(&self) -> TxHeight {
+        self.0
+    }
+
+    fn max_ord_of_height(height: TxHeight) -> Self {
+        Self(height, u32::MAX)
+    }
+
+    fn min_ord_of_height(height: TxHeight) -> Self {
+        Self(height, u32::MIN)
+    }
+}
+
+impl TestIndex {
+    pub fn new<H>(height: H, ext: u32) -> Self
+    where
+        H: Into<TxHeight>,
+    {
+        Self(height.into(), ext)
+    }
+}
+
+#[test]
+fn add_first_checkpoint() {
+    let chain = SparseChain::default();
+    assert_eq!(
+        chain.determine_changeset(&chain!([0, h!("A")])),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A")))],
+            txids: []
+        },),
+        "add first tip"
+    );
+}
+
+#[test]
+fn add_second_tip() {
+    let chain = chain!([0, h!("A")]);
+    assert_eq!(
+        chain.determine_changeset(&chain!([0, h!("A")], [1, h!("B")])),
+        Ok(changeset! {
+            checkpoints: [(1, Some(h!("B")))],
+            txids: []
+        },),
+        "extend tip by one"
+    );
+}
+
+#[test]
+fn two_disjoint_chains_cannot_merge() {
+    let chain1 = chain!([0, h!("A")]);
+    let chain2 = chain!([1, h!("B")]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Err(UpdateError::NotConnected(0))
+    );
+}
+
+#[test]
+fn duplicate_chains_should_merge() {
+    let chain1 = chain!([0, h!("A")]);
+    let chain2 = chain!([0, h!("A")]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(ChangeSet::default())
+    );
+}
+
+#[test]
+fn duplicate_chains_with_txs_should_merge() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(ChangeSet::default())
+    );
+}
+
+#[test]
+fn duplicate_chains_with_different_txs_should_merge() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx1"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [],
+            txids: [(h!("tx1"), Some(TxHeight::Confirmed(0)))]
+        })
+    );
+}
+
+#[test]
+fn invalidate_first_and_only_checkpoint_without_tx_changes() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A'")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A'")))],
+            txids: []
+        },)
+    );
+}
+
+#[test]
+fn invalidate_first_and_only_checkpoint_with_tx_move_forward() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A'")],[1, h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(1))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A'"))), (1, Some(h!("B")))],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(1)))]
+        },)
+    );
+}
+
+#[test]
+fn invalidate_first_and_only_checkpoint_with_tx_move_backward() {
+    let chain1 = chain!(checkpoints: [[1,h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(1))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A")],[1, h!("B'")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A"))), (1, Some(h!("B'")))],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(0)))]
+        },)
+    );
+}
+
+#[test]
+fn invalidate_a_checkpoint_and_try_and_move_tx_when_it_wasnt_within_invalidation() {
+    let chain1 = chain!(checkpoints: [[0, h!("A")], [1, h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0, h!("A")], [1, h!("B'")]], txids: [(h!("tx0"), TxHeight::Confirmed(1))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Err(UpdateError::TxInconsistent {
+            txid: h!("tx0"),
+            original_pos: TxHeight::Confirmed(0),
+            update_pos: TxHeight::Confirmed(1),
+        })
+    );
+}
+
+/// This test doesn't make much sense. We're invalidating a block at height 1 and moving it to
+/// height 0. It should be impossible for it to be at height 1 at any point if it was at height 0
+/// all along.
+#[test]
+fn move_invalidated_tx_into_earlier_checkpoint() {
+    let chain1 = chain!(checkpoints: [[0, h!("A")], [1, h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(1))]);
+    let chain2 = chain!(checkpoints: [[0, h!("A")], [1, h!("B'")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(1, Some(h!("B'")))],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(0)))]
+        },)
+    );
+}
+
+#[test]
+fn invalidate_first_and_only_checkpoint_with_tx_move_to_mempool() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    let chain2 = chain!(checkpoints: [[0,h!("A'")]], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A'")))],
+            txids: [(h!("tx0"), Some(TxHeight::Unconfirmed))]
+        },)
+    );
+}
+
+#[test]
+fn confirm_tx_without_extending_chain() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+    let chain2 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(0)))]
+        },)
+    );
+}
+
+#[test]
+fn confirm_tx_backwards_while_extending_chain() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+    let chain2 = chain!(checkpoints: [[0,h!("A")],[1,h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(0))]);
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(1, Some(h!("B")))],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(0)))]
+        },)
+    );
+}
+
+#[test]
+fn confirm_tx_in_new_block() {
+    let chain1 = chain!(checkpoints: [[0,h!("A")]], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+    let chain2 = chain! {
+        checkpoints: [[0,h!("A")], [1,h!("B")]],
+        txids: [(h!("tx0"), TxHeight::Confirmed(1))]
+    };
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(1, Some(h!("B")))],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(1)))]
+        },)
+    );
+}
+
+#[test]
+fn merging_mempool_of_empty_chains_doesnt_fail() {
+    let chain1 = chain!(checkpoints: [], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+    let chain2 = chain!(checkpoints: [], txids: [(h!("tx1"), TxHeight::Unconfirmed)]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [],
+            txids: [(h!("tx1"), Some(TxHeight::Unconfirmed))]
+        },)
+    );
+}
+
+#[test]
+fn cannot_insert_confirmed_tx_without_checkpoints() {
+    let chain = SparseChain::default();
+    assert_eq!(
+        chain.insert_tx_preview(h!("A"), TxHeight::Confirmed(0)),
+        Err(InsertTxError::TxTooHigh {
+            txid: h!("A"),
+            tx_height: 0,
+            tip_height: None
+        })
+    );
+}
+
+#[test]
+fn empty_chain_can_add_unconfirmed_transactions() {
+    let chain1 = chain!(checkpoints: [[0, h!("A")]], txids: []);
+    let chain2 = chain!(checkpoints: [], txids: [(h!("tx0"), TxHeight::Unconfirmed)]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [],
+            txids: [ (h!("tx0"), Some(TxHeight::Unconfirmed)) ]
+        },)
+    );
+}
+
+#[test]
+fn can_update_with_shorter_chain() {
+    let chain1 = chain!(checkpoints: [[1, h!("B")],[2, h!("C")]], txids: []);
+    let chain2 = chain!(checkpoints: [[1, h!("B")]], txids: [(h!("tx0"), TxHeight::Confirmed(1))]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [],
+            txids: [(h!("tx0"), Some(TxHeight::Confirmed(1)))]
+        },)
+    )
+}
+
+#[test]
+fn can_introduce_older_checkpoints() {
+    let chain1 = chain!(checkpoints: [[2, h!("C")], [3, h!("D")]], txids: []);
+    let chain2 = chain!(checkpoints: [[1, h!("B")], [2, h!("C")]], txids: []);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(1, Some(h!("B")))],
+            txids: []
+        },)
+    );
+}
+
+#[test]
+fn fix_blockhash_before_agreement_point() {
+    let chain1 = chain!([0, h!("im-wrong")], [1, h!("we-agree")]);
+    let chain2 = chain!([0, h!("fix")], [1, h!("we-agree")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("fix")))],
+            txids: []
+        },)
+    )
+}
+
+// TODO: Use macro
+#[test]
+fn cannot_change_ext_index_of_confirmed_tx() {
+    let chain1 = chain!(
+        index: TestIndex,
+        checkpoints: [[1, h!("A")]],
+        txids: [(h!("tx0"), TestIndex(TxHeight::Confirmed(1), 10))]
+    );
+    let chain2 = chain!(
+        index: TestIndex,
+        checkpoints: [[1, h!("A")]],
+        txids: [(h!("tx0"), TestIndex(TxHeight::Confirmed(1), 20))]
+    );
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Err(UpdateError::TxInconsistent {
+            txid: h!("tx0"),
+            original_pos: TestIndex(TxHeight::Confirmed(1), 10),
+            update_pos: TestIndex(TxHeight::Confirmed(1), 20),
+        }),
+    )
+}
+
+#[test]
+fn can_change_index_of_unconfirmed_tx() {
+    let chain1 = chain!(
+        index: TestIndex,
+        checkpoints: [[1, h!("A")]],
+        txids: [(h!("tx1"), TestIndex(TxHeight::Unconfirmed, 10))]
+    );
+    let chain2 = chain!(
+        index: TestIndex,
+        checkpoints: [[1, h!("A")]],
+        txids: [(h!("tx1"), TestIndex(TxHeight::Unconfirmed, 20))]
+    );
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(ChangeSet {
+            checkpoints: [].into(),
+            txids: [(h!("tx1"), Some(TestIndex(TxHeight::Unconfirmed, 20)),)].into()
+        },),
+    )
+}
+
+/// B and C are in both chain and update
+/// ```
+///        | 0 | 1 | 2 | 3 | 4
+/// chain  |     B   C
+/// update | A   B   C   D
+/// ```
+/// This should succeed with the point of agreement being C and A should be added in addition.
+#[test]
+fn two_points_of_agreement() {
+    let chain1 = chain!([1, h!("B")], [2, h!("C")]);
+    let chain2 = chain!([0, h!("A")], [1, h!("B")], [2, h!("C")], [3, h!("D")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [(0, Some(h!("A"))), (3, Some(h!("D")))]
+        },),
+    );
+}
+
+/// Update and chain does not connect:
+/// ```
+///        | 0 | 1 | 2 | 3 | 4
+/// chain  |     B   C
+/// update | A   B       D
+/// ```
+/// This should fail as we cannot figure out whether C & D are on the same chain
+#[test]
+fn update_and_chain_does_not_connect() {
+    let chain1 = chain!([1, h!("B")], [2, h!("C")]);
+    let chain2 = chain!([0, h!("A")], [1, h!("B")], [3, h!("D")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Err(UpdateError::NotConnected(2)),
+    );
+}
+
+/// Transient invalidation:
+/// ```
+///        | 0 | 1 | 2 | 3 | 4 | 5
+/// chain  | A       B   C       E
+/// update | A       B'  C'  D
+/// ```
+/// This should succeed and invalidate B,C and E with point of agreement being A.
+/// It should also invalidate transactions at height 1.
+#[test]
+fn transitive_invalidation_applies_to_checkpoints_higher_than_invalidation() {
+    let chain1 = chain! {
+        checkpoints: [[0, h!("A")], [2, h!("B")], [3, h!("C")], [5, h!("E")]],
+        txids: [
+            (h!("a"), TxHeight::Confirmed(0)),
+            (h!("b1"), TxHeight::Confirmed(1)),
+            (h!("b2"), TxHeight::Confirmed(2)),
+            (h!("d"), TxHeight::Confirmed(3)),
+            (h!("e"), TxHeight::Confirmed(5))
+        ]
+    };
+    let chain2 = chain! {
+        checkpoints: [[0, h!("A")], [2, h!("B'")], [3, h!("C'")], [4, h!("D")]],
+        txids: [(h!("b1"), TxHeight::Confirmed(4)), (h!("b2"), TxHeight::Confirmed(3))]
+    };
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [
+                (2, Some(h!("B'"))),
+                (3, Some(h!("C'"))),
+                (4, Some(h!("D"))),
+                (5, None)
+            ],
+            txids: [
+                (h!("b1"), Some(TxHeight::Confirmed(4))),
+                (h!("b2"), Some(TxHeight::Confirmed(3))),
+                (h!("d"), Some(TxHeight::Unconfirmed)),
+                (h!("e"), Some(TxHeight::Unconfirmed))
+            ]
+        },)
+    );
+}
+
+/// Transient invalidation:
+/// ```
+///        | 0 | 1 | 2 | 3 | 4
+/// chain  |     B   C       E
+/// update |     B'  C'  D
+/// ```
+///
+/// This should succeed and invalidate B, C and E with no point of agreement
+#[test]
+fn transitive_invalidation_applies_to_checkpoints_higher_than_invalidation_no_point_of_agreement() {
+    let chain1 = chain!([1, h!("B")], [2, h!("C")], [4, h!("E")]);
+    let chain2 = chain!([1, h!("B'")], [2, h!("C'")], [3, h!("D")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [
+                (1, Some(h!("B'"))),
+                (2, Some(h!("C'"))),
+                (3, Some(h!("D"))),
+                (4, None)
+            ]
+        },)
+    )
+}
+
+/// Transient invalidation:
+/// ```
+///        | 0 | 1 | 2 | 3 | 4
+/// chain  | A   B   C       E
+/// update |     B'  C'  D
+/// ```
+///
+/// This should fail since although it tells us that B and C are invalid it doesn't tell us whether
+/// A was invalid.
+#[test]
+fn invalidation_but_no_connection() {
+    let chain1 = chain!([0, h!("A")], [1, h!("B")], [2, h!("C")], [4, h!("E")]);
+    let chain2 = chain!([1, h!("B'")], [2, h!("C'")], [3, h!("D")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Err(UpdateError::NotConnected(0))
+    )
+}
+
+#[test]
+fn checkpoint_limit_is_respected() {
+    let mut chain1 = SparseChain::default();
+    let _ = chain1
+        .apply_update(chain!(
+            [1, h!("A")],
+            [2, h!("B")],
+            [3, h!("C")],
+            [4, h!("D")],
+            [5, h!("E")]
+        ))
+        .unwrap();
+
+    assert_eq!(chain1.checkpoints().len(), 5);
+    chain1.set_checkpoint_limit(Some(4));
+    assert_eq!(chain1.checkpoints().len(), 4);
+
+    let _ = chain1
+        .insert_checkpoint(BlockId {
+            height: 6,
+            hash: h!("F"),
+        })
+        .unwrap();
+    assert_eq!(chain1.checkpoints().len(), 4);
+
+    let changeset = chain1.determine_changeset(&chain!([6, h!("F")], [7, h!("G")]));
+    assert_eq!(changeset, Ok(changeset!(checkpoints: [(7, Some(h!("G")))])));
+
+    chain1.apply_changeset(changeset.unwrap());
+
+    assert_eq!(chain1.checkpoints().len(), 4);
+}
+
+#[test]
+fn range_txids_by_height() {
+    let mut chain = chain!(index: TestIndex, checkpoints: [[1, h!("block 1")], [2, h!("block 2")]]);
+
+    let txids: [(TestIndex, Txid); 4] = [
+        (
+            TestIndex(TxHeight::Confirmed(1), u32::MIN),
+            Txid::from_inner([0x00; 32]),
+        ),
+        (
+            TestIndex(TxHeight::Confirmed(1), u32::MAX),
+            Txid::from_inner([0xfe; 32]),
+        ),
+        (
+            TestIndex(TxHeight::Confirmed(2), u32::MIN),
+            Txid::from_inner([0x01; 32]),
+        ),
+        (
+            TestIndex(TxHeight::Confirmed(2), u32::MAX),
+            Txid::from_inner([0xff; 32]),
+        ),
+    ];
+
+    // populate chain with txids
+    for (index, txid) in txids {
+        let _ = chain.insert_tx(txid, index).expect("should succeed");
+    }
+
+    // inclusive start
+    assert_eq!(
+        chain
+            .range_txids_by_height(TxHeight::Confirmed(1)..)
+            .collect::<Vec<_>>(),
+        txids.iter().collect::<Vec<_>>(),
+    );
+
+    // exclusive start
+    assert_eq!(
+        chain
+            .range_txids_by_height((Bound::Excluded(TxHeight::Confirmed(1)), Bound::Unbounded,))
+            .collect::<Vec<_>>(),
+        txids[2..].iter().collect::<Vec<_>>(),
+    );
+
+    // inclusive end
+    assert_eq!(
+        chain
+            .range_txids_by_height((Bound::Unbounded, Bound::Included(TxHeight::Confirmed(2))))
+            .collect::<Vec<_>>(),
+        txids[..4].iter().collect::<Vec<_>>(),
+    );
+
+    // exclusive end
+    assert_eq!(
+        chain
+            .range_txids_by_height(..TxHeight::Confirmed(2))
+            .collect::<Vec<_>>(),
+        txids[..2].iter().collect::<Vec<_>>(),
+    );
+}
+
+#[test]
+fn range_txids_by_index() {
+    let mut chain = chain!(index: TestIndex, checkpoints: [[1, h!("block 1")],[2, h!("block 2")]]);
+
+    let txids: [(TestIndex, Txid); 4] = [
+        (TestIndex(TxHeight::Confirmed(1), u32::MIN), h!("tx 1 min")),
+        (TestIndex(TxHeight::Confirmed(1), u32::MAX), h!("tx 1 max")),
+        (TestIndex(TxHeight::Confirmed(2), u32::MIN), h!("tx 2 min")),
+        (TestIndex(TxHeight::Confirmed(2), u32::MAX), h!("tx 2 max")),
+    ];
+
+    // populate chain with txids
+    for (index, txid) in txids {
+        let _ = chain.insert_tx(txid, index).expect("should succeed");
+    }
+
+    // inclusive start
+    assert_eq!(
+        chain
+            .range_txids_by_position(TestIndex(TxHeight::Confirmed(1), u32::MIN)..)
+            .collect::<Vec<_>>(),
+        txids.iter().collect::<Vec<_>>(),
+    );
+    assert_eq!(
+        chain
+            .range_txids_by_position(TestIndex(TxHeight::Confirmed(1), u32::MAX)..)
+            .collect::<Vec<_>>(),
+        txids[1..].iter().collect::<Vec<_>>(),
+    );
+
+    // exclusive start
+    assert_eq!(
+        chain
+            .range_txids_by_position((
+                Bound::Excluded(TestIndex(TxHeight::Confirmed(1), u32::MIN)),
+                Bound::Unbounded
+            ))
+            .collect::<Vec<_>>(),
+        txids[1..].iter().collect::<Vec<_>>(),
+    );
+    assert_eq!(
+        chain
+            .range_txids_by_position((
+                Bound::Excluded(TestIndex(TxHeight::Confirmed(1), u32::MAX)),
+                Bound::Unbounded
+            ))
+            .collect::<Vec<_>>(),
+        txids[2..].iter().collect::<Vec<_>>(),
+    );
+
+    // inclusive end
+    assert_eq!(
+        chain
+            .range_txids_by_position((
+                Bound::Unbounded,
+                Bound::Included(TestIndex(TxHeight::Confirmed(2), u32::MIN))
+            ))
+            .collect::<Vec<_>>(),
+        txids[..3].iter().collect::<Vec<_>>(),
+    );
+    assert_eq!(
+        chain
+            .range_txids_by_position((
+                Bound::Unbounded,
+                Bound::Included(TestIndex(TxHeight::Confirmed(2), u32::MAX))
+            ))
+            .collect::<Vec<_>>(),
+        txids[..4].iter().collect::<Vec<_>>(),
+    );
+
+    // exclusive end
+    assert_eq!(
+        chain
+            .range_txids_by_position(..TestIndex(TxHeight::Confirmed(2), u32::MIN))
+            .collect::<Vec<_>>(),
+        txids[..2].iter().collect::<Vec<_>>(),
+    );
+    assert_eq!(
+        chain
+            .range_txids_by_position(..TestIndex(TxHeight::Confirmed(2), u32::MAX))
+            .collect::<Vec<_>>(),
+        txids[..3].iter().collect::<Vec<_>>(),
+    );
+}
+
+#[test]
+fn range_txids() {
+    let mut chain = SparseChain::default();
+
+    let txids = (0..100)
+        .map(|v| Txid::hash(v.to_string().as_bytes()))
+        .collect::<BTreeSet<Txid>>();
+
+    // populate chain
+    for txid in &txids {
+        let _ = chain
+            .insert_tx(*txid, TxHeight::Unconfirmed)
+            .expect("should succeed");
+    }
+
+    for txid in &txids {
+        assert_eq!(
+            chain
+                .range_txids((TxHeight::Unconfirmed, *txid)..)
+                .map(|(_, txid)| txid)
+                .collect::<Vec<_>>(),
+            txids.range(*txid..).collect::<Vec<_>>(),
+            "range with inclusive start should succeed"
+        );
+
+        assert_eq!(
+            chain
+                .range_txids((
+                    Bound::Excluded((TxHeight::Unconfirmed, *txid)),
+                    Bound::Unbounded,
+                ))
+                .map(|(_, txid)| txid)
+                .collect::<Vec<_>>(),
+            txids
+                .range((Bound::Excluded(*txid), Bound::Unbounded,))
+                .collect::<Vec<_>>(),
+            "range with exclusive start should succeed"
+        );
+
+        assert_eq!(
+            chain
+                .range_txids(..(TxHeight::Unconfirmed, *txid))
+                .map(|(_, txid)| txid)
+                .collect::<Vec<_>>(),
+            txids.range(..*txid).collect::<Vec<_>>(),
+            "range with exclusive end should succeed"
+        );
+
+        assert_eq!(
+            chain
+                .range_txids((
+                    Bound::Included((TxHeight::Unconfirmed, *txid)),
+                    Bound::Unbounded,
+                ))
+                .map(|(_, txid)| txid)
+                .collect::<Vec<_>>(),
+            txids
+                .range((Bound::Included(*txid), Bound::Unbounded,))
+                .collect::<Vec<_>>(),
+            "range with inclusive end should succeed"
+        );
+    }
+}
+
+#[test]
+fn invalidated_txs_move_to_unconfirmed() {
+    let chain1 = chain! {
+        checkpoints: [[0, h!("A")], [1, h!("B")], [2, h!("C")]],
+        txids: [
+            (h!("a"), TxHeight::Confirmed(0)),
+            (h!("b"), TxHeight::Confirmed(1)),
+            (h!("c"), TxHeight::Confirmed(2)),
+            (h!("d"), TxHeight::Unconfirmed)
+        ]
+    };
+
+    let chain2 = chain!([0, h!("A")], [1, h!("B'")]);
+
+    assert_eq!(
+        chain1.determine_changeset(&chain2),
+        Ok(changeset! {
+            checkpoints: [
+                (1, Some(h!("B'"))),
+                (2, None)
+            ],
+            txids: [
+                (h!("b"), Some(TxHeight::Unconfirmed)),
+                (h!("c"), Some(TxHeight::Unconfirmed))
+            ]
+        },)
+    );
+}
+
+#[test]
+fn change_tx_position_from_unconfirmed_to_confirmed() {
+    let mut chain = SparseChain::<TxHeight>::default();
+    let txid = h!("txid");
+
+    let _ = chain.insert_tx(txid, TxHeight::Unconfirmed).unwrap();
+
+    assert_eq!(chain.tx_position(txid), Some(&TxHeight::Unconfirmed));
+    let _ = chain
+        .insert_checkpoint(BlockId {
+            height: 0,
+            hash: h!("0"),
+        })
+        .unwrap();
+    let _ = chain.insert_tx(txid, TxHeight::Confirmed(0)).unwrap();
+
+    assert_eq!(chain.tx_position(txid), Some(&TxHeight::Confirmed(0)));
+}

crates/chain/tests/test_spk_txout_index.rs

@@ -0,0 +1,100 @@
+use bdk_chain::SpkTxOutIndex;
+use bitcoin::{hashes::hex::FromHex, OutPoint, PackedLockTime, Script, Transaction, TxIn, TxOut};
+
+#[test]
+fn spk_txout_sent_and_received() {
+    let spk1 = Script::from_hex("001404f1e52ce2bab3423c6a8c63b7cd730d8f12542c").unwrap();
+    let spk2 = Script::from_hex("00142b57404ae14f08c3a0c903feb2af7830605eb00f").unwrap();
+
+    let mut index = SpkTxOutIndex::default();
+    index.insert_spk(0, spk1.clone());
+    index.insert_spk(1, spk2.clone());
+
+    let tx1 = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 42_000,
+            script_pubkey: spk1.clone(),
+        }],
+    };
+
+    assert_eq!(index.sent_and_received(&tx1), (0, 42_000));
+    assert_eq!(index.net_value(&tx1), 42_000);
+    index.scan(&tx1);
+    assert_eq!(
+        index.sent_and_received(&tx1),
+        (0, 42_000),
+        "shouldn't change after scanning"
+    );
+
+    let tx2 = Transaction {
+        version: 0x1,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint {
+                txid: tx1.txid(),
+                vout: 0,
+            },
+            ..Default::default()
+        }],
+        output: vec![
+            TxOut {
+                value: 20_000,
+                script_pubkey: spk2,
+            },
+            TxOut {
+                script_pubkey: spk1,
+                value: 30_000,
+            },
+        ],
+    };
+
+    assert_eq!(index.sent_and_received(&tx2), (42_000, 50_000));
+    assert_eq!(index.net_value(&tx2), 8_000);
+}
+
+#[test]
+fn mark_used() {
+    let spk1 = Script::from_hex("001404f1e52ce2bab3423c6a8c63b7cd730d8f12542c").unwrap();
+    let spk2 = Script::from_hex("00142b57404ae14f08c3a0c903feb2af7830605eb00f").unwrap();
+
+    let mut spk_index = SpkTxOutIndex::default();
+    spk_index.insert_spk(1, spk1.clone());
+    spk_index.insert_spk(2, spk2);
+
+    assert!(!spk_index.is_used(&1));
+    spk_index.mark_used(&1);
+    assert!(spk_index.is_used(&1));
+    spk_index.unmark_used(&1);
+    assert!(!spk_index.is_used(&1));
+    spk_index.mark_used(&1);
+    assert!(spk_index.is_used(&1));
+
+    let tx1 = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 42_000,
+            script_pubkey: spk1,
+        }],
+    };
+
+    spk_index.scan(&tx1);
+    spk_index.unmark_used(&1);
+    assert!(
+        spk_index.is_used(&1),
+        "even though we unmark_used it doesn't matter because there was a tx scanned that used it"
+    );
+}
+
+#[test]
+fn unmark_used_does_not_result_in_invalid_representation() {
+    let mut spk_index = SpkTxOutIndex::default();
+    assert!(!spk_index.unmark_used(&0));
+    assert!(!spk_index.unmark_used(&1));
+    assert!(!spk_index.unmark_used(&2));
+    assert!(spk_index.unused_spks(..).collect::<Vec<_>>().is_empty());
+}

crates/chain/tests/test_tx_graph.rs

@@ -0,0 +1,512 @@
+#[macro_use]
+mod common;
+use bdk_chain::{
+    collections::*,
+    tx_graph::{Additions, TxGraph},
+};
+use bitcoin::{hashes::Hash, OutPoint, PackedLockTime, Script, Transaction, TxIn, TxOut, Txid};
+use core::iter;
+
+#[test]
+fn insert_txouts() {
+    let original_ops = [
+        (
+            OutPoint::new(h!("tx1"), 1),
+            TxOut {
+                value: 10_000,
+                script_pubkey: Script::new(),
+            },
+        ),
+        (
+            OutPoint::new(h!("tx1"), 2),
+            TxOut {
+                value: 20_000,
+                script_pubkey: Script::new(),
+            },
+        ),
+    ];
+
+    let update_ops = [(
+        OutPoint::new(h!("tx2"), 0),
+        TxOut {
+            value: 20_000,
+            script_pubkey: Script::new(),
+        },
+    )];
+
+    let mut graph = {
+        let mut graph = TxGraph::default();
+        for (outpoint, txout) in &original_ops {
+            assert_eq!(
+                graph.insert_txout(*outpoint, txout.clone()),
+                Additions {
+                    txout: [(*outpoint, txout.clone())].into(),
+                    ..Default::default()
+                }
+            );
+        }
+        graph
+    };
+
+    let update = {
+        let mut graph = TxGraph::default();
+        for (outpoint, txout) in &update_ops {
+            assert_eq!(
+                graph.insert_txout(*outpoint, txout.clone()),
+                Additions {
+                    txout: [(*outpoint, txout.clone())].into(),
+                    ..Default::default()
+                }
+            );
+        }
+        graph
+    };
+
+    let additions = graph.determine_additions(&update);
+
+    assert_eq!(
+        additions,
+        Additions {
+            tx: [].into(),
+            txout: update_ops.into(),
+        }
+    );
+
+    graph.apply_additions(additions);
+    assert_eq!(graph.all_txouts().count(), 3);
+    assert_eq!(graph.full_transactions().count(), 0);
+    assert_eq!(graph.partial_transactions().count(), 2);
+}
+
+#[test]
+fn insert_tx_graph_doesnt_count_coinbase_as_spent() {
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::null(),
+            ..Default::default()
+        }],
+        output: vec![],
+    };
+
+    let mut graph = TxGraph::default();
+    let _ = graph.insert_tx(tx);
+    assert!(graph.outspends(OutPoint::null()).is_empty());
+    assert!(graph.tx_outspends(Txid::all_zeros()).next().is_none());
+}
+
+#[test]
+fn insert_tx_graph_keeps_track_of_spend() {
+    let tx1 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut::default()],
+    };
+
+    let op = OutPoint {
+        txid: tx1.txid(),
+        vout: 0,
+    };
+
+    let tx2 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: op,
+            ..Default::default()
+        }],
+        output: vec![],
+    };
+
+    let mut graph1 = TxGraph::default();
+    let mut graph2 = TxGraph::default();
+
+    // insert in different order
+    let _ = graph1.insert_tx(tx1.clone());
+    let _ = graph1.insert_tx(tx2.clone());
+
+    let _ = graph2.insert_tx(tx2.clone());
+    let _ = graph2.insert_tx(tx1);
+
+    assert_eq!(
+        graph1.outspends(op),
+        &iter::once(tx2.txid()).collect::<HashSet<_>>()
+    );
+    assert_eq!(graph2.outspends(op), graph1.outspends(op));
+}
+
+#[test]
+fn insert_tx_can_retrieve_full_tx_from_graph() {
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::null(),
+            ..Default::default()
+        }],
+        output: vec![TxOut::default()],
+    };
+
+    let mut graph = TxGraph::default();
+    let _ = graph.insert_tx(tx.clone());
+    assert_eq!(graph.get_tx(tx.txid()), Some(&tx));
+}
+
+#[test]
+fn insert_tx_displaces_txouts() {
+    let mut tx_graph = TxGraph::default();
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 42_000,
+            script_pubkey: Script::default(),
+        }],
+    };
+
+    let _ = tx_graph.insert_txout(
+        OutPoint {
+            txid: tx.txid(),
+            vout: 0,
+        },
+        TxOut {
+            value: 1_337_000,
+            script_pubkey: Script::default(),
+        },
+    );
+
+    let _ = tx_graph.insert_txout(
+        OutPoint {
+            txid: tx.txid(),
+            vout: 0,
+        },
+        TxOut {
+            value: 1_000_000_000,
+            script_pubkey: Script::default(),
+        },
+    );
+
+    let _additions = tx_graph.insert_tx(tx.clone());
+
+    assert_eq!(
+        tx_graph
+            .get_txout(OutPoint {
+                txid: tx.txid(),
+                vout: 0
+            })
+            .unwrap()
+            .value,
+        42_000
+    );
+    assert_eq!(
+        tx_graph.get_txout(OutPoint {
+            txid: tx.txid(),
+            vout: 1
+        }),
+        None
+    );
+}
+
+#[test]
+fn insert_txout_does_not_displace_tx() {
+    let mut tx_graph = TxGraph::default();
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 42_000,
+            script_pubkey: Script::default(),
+        }],
+    };
+
+    let _additions = tx_graph.insert_tx(tx.clone());
+
+    let _ = tx_graph.insert_txout(
+        OutPoint {
+            txid: tx.txid(),
+            vout: 0,
+        },
+        TxOut {
+            value: 1_337_000,
+            script_pubkey: Script::default(),
+        },
+    );
+
+    let _ = tx_graph.insert_txout(
+        OutPoint {
+            txid: tx.txid(),
+            vout: 0,
+        },
+        TxOut {
+            value: 1_000_000_000,
+            script_pubkey: Script::default(),
+        },
+    );
+
+    assert_eq!(
+        tx_graph
+            .get_txout(OutPoint {
+                txid: tx.txid(),
+                vout: 0
+            })
+            .unwrap()
+            .value,
+        42_000
+    );
+    assert_eq!(
+        tx_graph.get_txout(OutPoint {
+            txid: tx.txid(),
+            vout: 1
+        }),
+        None
+    );
+}
+
+#[test]
+fn test_calculate_fee() {
+    let mut graph = TxGraph::default();
+    let intx1 = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 100,
+            ..Default::default()
+        }],
+    };
+    let intx2 = Transaction {
+        version: 0x02,
+        lock_time: PackedLockTime(0),
+        input: vec![],
+        output: vec![TxOut {
+            value: 200,
+            ..Default::default()
+        }],
+    };
+
+    let intxout1 = (
+        OutPoint {
+            txid: h!("dangling output"),
+            vout: 0,
+        },
+        TxOut {
+            value: 300,
+            ..Default::default()
+        },
+    );
+
+    let _ = graph.insert_tx(intx1.clone());
+    let _ = graph.insert_tx(intx2.clone());
+    let _ = graph.insert_txout(intxout1.0, intxout1.1);
+
+    let mut tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![
+            TxIn {
+                previous_output: OutPoint {
+                    txid: intx1.txid(),
+                    vout: 0,
+                },
+                ..Default::default()
+            },
+            TxIn {
+                previous_output: OutPoint {
+                    txid: intx2.txid(),
+                    vout: 0,
+                },
+                ..Default::default()
+            },
+            TxIn {
+                previous_output: intxout1.0,
+                ..Default::default()
+            },
+        ],
+        output: vec![TxOut {
+            value: 500,
+            ..Default::default()
+        }],
+    };
+
+    assert_eq!(graph.calculate_fee(&tx), Some(100));
+
+    tx.input.remove(2);
+
+    // fee would be negative
+    assert_eq!(graph.calculate_fee(&tx), Some(-200));
+
+    // If we have an unknown outpoint, fee should return None.
+    tx.input.push(TxIn {
+        previous_output: OutPoint {
+            txid: h!("unknown_txid"),
+            vout: 0,
+        },
+        ..Default::default()
+    });
+    assert_eq!(graph.calculate_fee(&tx), None);
+}
+
+#[test]
+fn test_calculate_fee_on_coinbase() {
+    let tx = Transaction {
+        version: 0x01,
+        lock_time: PackedLockTime(0),
+        input: vec![TxIn {
+            previous_output: OutPoint::null(),
+            ..Default::default()
+        }],
+        output: vec![TxOut::default()],
+    };
+
+    let graph = TxGraph::default();
+
+    assert_eq!(graph.calculate_fee(&tx), Some(0));
+}
+
+#[test]
+fn test_conflicting_descendants() {
+    let previous_output = OutPoint::new(h!("op"), 2);
+
+    // tx_a spends previous_output
+    let tx_a = Transaction {
+        input: vec![TxIn {
+            previous_output,
+            ..TxIn::default()
+        }],
+        output: vec![TxOut::default()],
+        ..common::new_tx(0)
+    };
+
+    // tx_a2 spends previous_output and conflicts with tx_a
+    let tx_a2 = Transaction {
+        input: vec![TxIn {
+            previous_output,
+            ..TxIn::default()
+        }],
+        output: vec![TxOut::default(), TxOut::default()],
+        ..common::new_tx(1)
+    };
+
+    // tx_b spends tx_a
+    let tx_b = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_a.txid(), 0),
+            ..TxIn::default()
+        }],
+        output: vec![TxOut::default()],
+        ..common::new_tx(2)
+    };
+
+    let txid_a = tx_a.txid();
+    let txid_b = tx_b.txid();
+
+    let mut graph = TxGraph::default();
+    let _ = graph.insert_tx(tx_a);
+    let _ = graph.insert_tx(tx_b);
+
+    assert_eq!(
+        graph
+            .walk_conflicts(&tx_a2, |depth, txid| Some((depth, txid)))
+            .collect::<Vec<_>>(),
+        vec![(0_usize, txid_a), (1_usize, txid_b),],
+    );
+}
+
+#[test]
+fn test_descendants_no_repeat() {
+    let tx_a = Transaction {
+        output: vec![TxOut::default(), TxOut::default(), TxOut::default()],
+        ..common::new_tx(0)
+    };
+
+    let txs_b = (0..3)
+        .map(|vout| Transaction {
+            input: vec![TxIn {
+                previous_output: OutPoint::new(tx_a.txid(), vout),
+                ..TxIn::default()
+            }],
+            output: vec![TxOut::default()],
+            ..common::new_tx(1)
+        })
+        .collect::<Vec<_>>();
+
+    let txs_c = (0..2)
+        .map(|vout| Transaction {
+            input: vec![TxIn {
+                previous_output: OutPoint::new(txs_b[vout as usize].txid(), vout),
+                ..TxIn::default()
+            }],
+            output: vec![TxOut::default()],
+            ..common::new_tx(2)
+        })
+        .collect::<Vec<_>>();
+
+    let tx_d = Transaction {
+        input: vec![
+            TxIn {
+                previous_output: OutPoint::new(txs_c[0].txid(), 0),
+                ..TxIn::default()
+            },
+            TxIn {
+                previous_output: OutPoint::new(txs_c[1].txid(), 0),
+                ..TxIn::default()
+            },
+        ],
+        output: vec![TxOut::default()],
+        ..common::new_tx(3)
+    };
+
+    let tx_e = Transaction {
+        input: vec![TxIn {
+            previous_output: OutPoint::new(tx_d.txid(), 0),
+            ..TxIn::default()
+        }],
+        output: vec![TxOut::default()],
+        ..common::new_tx(4)
+    };
+
+    let txs_not_connected = (10..20)
+        .map(|v| Transaction {
+            input: vec![TxIn {
+                previous_output: OutPoint::new(h!("tx_does_not_exist"), v),
+                ..TxIn::default()
+            }],
+            output: vec![TxOut::default()],
+            ..common::new_tx(v)
+        })
+        .collect::<Vec<_>>();
+
+    let mut graph = TxGraph::default();
+    let mut expected_txids = BTreeSet::new();
+
+    // these are NOT descendants of `tx_a`
+    for tx in txs_not_connected {
+        let _ = graph.insert_tx(tx.clone());
+    }
+
+    // these are the expected descendants of `tx_a`
+    for tx in txs_b
+        .iter()
+        .chain(&txs_c)
+        .chain(core::iter::once(&tx_d))
+        .chain(core::iter::once(&tx_e))
+    {
+        let _ = graph.insert_tx(tx.clone());
+        assert!(expected_txids.insert(tx.txid()));
+    }
+
+    let descendants = graph
+        .walk_descendants(tx_a.txid(), |_, txid| Some(txid))
+        .collect::<Vec<_>>();
+
+    assert_eq!(descendants.len(), expected_txids.len());
+
+    for txid in descendants {
+        assert!(expected_txids.remove(&txid));
+    }
+    assert!(expected_txids.is_empty());
+}

crates/electrum/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "bdk_electrum"
+version = "0.2.0"
+edition = "2021"
+homepage = "https://bitcoindevkit.org"
+repository = "https://github.com/bitcoindevkit/bdk"
+documentation = "https://docs.rs/bdk_electrum"
+description = "Fetch data from electrum in the form BDK accepts"
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk_chain = { path = "../chain", version = "0.4.0", features = ["serde", "miniscript"] }
+electrum-client = { version = "0.12" }

crates/electrum/README.md

@@ -0,0 +1,3 @@
+# BDK Electrum
+
+BDK Electrum client library for updating the keychain tracker.

crates/electrum/src/lib.rs

@@ -0,0 +1,588 @@
+//! This crate is used for updating structures of the [`bdk_chain`] crate with data from electrum.
+//!
+//! The star of the show is the [`ElectrumExt::scan`] method, which scans for relevant blockchain
+//! data (via electrum) and outputs an [`ElectrumUpdate`].
+//!
+//! An [`ElectrumUpdate`] only includes `txid`s and no full transactions. The caller is responsible
+//! for obtaining full transactions before applying. This can be done with
+//! these steps:
+//!
+//! 1. Determine which full transactions are missing. The method [`missing_full_txs`] of
+//! [`ElectrumUpdate`] can be used.
+//!
+//! 2. Obtaining the full transactions. To do this via electrum, the method
+//! [`batch_transaction_get`] can be used.
+//!
+//! Refer to [`bdk_electrum_example`] for a complete example.
+//!
+//! [`ElectrumClient::scan`]: ElectrumClient::scan
+//! [`missing_full_txs`]: ElectrumUpdate::missing_full_txs
+//! [`batch_transaction_get`]: ElectrumApi::batch_transaction_get
+//! [`bdk_electrum_example`]: https://github.com/LLFourn/bdk_core_staging/tree/master/bdk_electrum_example
+
+use std::{
+    collections::{BTreeMap, HashMap},
+    fmt::Debug,
+};
+
+pub use bdk_chain;
+use bdk_chain::{
+    bitcoin::{hashes::hex::FromHex, BlockHash, OutPoint, Script, Transaction, Txid},
+    chain_graph::{self, ChainGraph},
+    keychain::KeychainScan,
+    sparse_chain::{self, ChainPosition, SparseChain},
+    tx_graph::TxGraph,
+    BlockId, ConfirmationTime, TxHeight,
+};
+pub use electrum_client;
+use electrum_client::{Client, ElectrumApi, Error};
+
+/// Trait to extend [`electrum_client::Client`] functionality.
+///
+/// Refer to [crate-level documentation] for more.
+///
+/// [crate-level documentation]: crate
+pub trait ElectrumExt {
+    /// Fetch the latest block height.
+    fn get_tip(&self) -> Result<(u32, BlockHash), Error>;
+
+    /// Scan the blockchain (via electrum) for the data specified. This returns a [`ElectrumUpdate`]
+    /// which can be transformed into a [`KeychainScan`] after we find all the missing full
+    /// transactions.
+    ///
+    /// - `local_chain`: the most recent block hashes present locally
+    /// - `keychain_spks`: keychains that we want to scan transactions for
+    /// - `txids`: transactions for which we want the updated [`ChainPosition`]s
+    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to included in the update
+    fn scan<K: Ord + Clone>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        stop_gap: usize,
+        batch_size: usize,
+    ) -> Result<ElectrumUpdate<K, TxHeight>, Error>;
+
+    /// Convenience method to call [`scan`] without requiring a keychain.
+    ///
+    /// [`scan`]: ElectrumExt::scan
+    fn scan_without_keychain(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        misc_spks: impl IntoIterator<Item = Script>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        batch_size: usize,
+    ) -> Result<SparseChain, Error> {
+        let spk_iter = misc_spks
+            .into_iter()
+            .enumerate()
+            .map(|(i, spk)| (i as u32, spk));
+
+        self.scan(
+            local_chain,
+            [((), spk_iter)].into(),
+            txids,
+            outpoints,
+            usize::MAX,
+            batch_size,
+        )
+        .map(|u| u.chain_update)
+    }
+}
+
+impl ElectrumExt for Client {
+    fn get_tip(&self) -> Result<(u32, BlockHash), Error> {
+        // TODO: unsubscribe when added to the client, or is there a better call to use here?
+        self.block_headers_subscribe()
+            .map(|data| (data.height as u32, data.header.block_hash()))
+    }
+
+    fn scan<K: Ord + Clone>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        stop_gap: usize,
+        batch_size: usize,
+    ) -> Result<ElectrumUpdate<K, TxHeight>, Error> {
+        let mut request_spks = keychain_spks
+            .into_iter()
+            .map(|(k, s)| {
+                let iter = s.into_iter();
+                (k, iter)
+            })
+            .collect::<BTreeMap<K, _>>();
+        let mut scanned_spks = BTreeMap::<(K, u32), (Script, bool)>::new();
+
+        let txids = txids.into_iter().collect::<Vec<_>>();
+        let outpoints = outpoints.into_iter().collect::<Vec<_>>();
+
+        let update = loop {
+            let mut update = prepare_update(self, local_chain)?;
+
+            if !request_spks.is_empty() {
+                if !scanned_spks.is_empty() {
+                    let mut scanned_spk_iter = scanned_spks
+                        .iter()
+                        .map(|(i, (spk, _))| (i.clone(), spk.clone()));
+                    match populate_with_spks::<K, _, _>(
+                        self,
+                        &mut update,
+                        &mut scanned_spk_iter,
+                        stop_gap,
+                        batch_size,
+                    ) {
+                        Err(InternalError::Reorg) => continue,
+                        Err(InternalError::ElectrumError(e)) => return Err(e),
+                        Ok(mut spks) => scanned_spks.append(&mut spks),
+                    };
+                }
+                for (keychain, keychain_spks) in &mut request_spks {
+                    match populate_with_spks::<K, u32, _>(
+                        self,
+                        &mut update,
+                        keychain_spks,
+                        stop_gap,
+                        batch_size,
+                    ) {
+                        Err(InternalError::Reorg) => continue,
+                        Err(InternalError::ElectrumError(e)) => return Err(e),
+                        Ok(spks) => scanned_spks.extend(
+                            spks.into_iter()
+                                .map(|(spk_i, spk)| ((keychain.clone(), spk_i), spk)),
+                        ),
+                    };
+                }
+            }
+
+            match populate_with_txids(self, &mut update, &mut txids.iter().cloned()) {
+                Err(InternalError::Reorg) => continue,
+                Err(InternalError::ElectrumError(e)) => return Err(e),
+                Ok(_) => {}
+            }
+
+            match populate_with_outpoints(self, &mut update, &mut outpoints.iter().cloned()) {
+                Err(InternalError::Reorg) => continue,
+                Err(InternalError::ElectrumError(e)) => return Err(e),
+                Ok(_txs) => { /* [TODO] cache full txs to reduce bandwidth */ }
+            }
+
+            // check for reorgs during scan process
+            let our_tip = update
+                .latest_checkpoint()
+                .expect("update must have atleast one checkpoint");
+            let server_blockhash = self.block_header(our_tip.height as usize)?.block_hash();
+            if our_tip.hash != server_blockhash {
+                continue; // reorg
+            } else {
+                break update;
+            }
+        };
+
+        let last_active_index = request_spks
+            .into_keys()
+            .filter_map(|k| {
+                scanned_spks
+                    .range((k.clone(), u32::MIN)..=(k.clone(), u32::MAX))
+                    .rev()
+                    .find(|(_, (_, active))| *active)
+                    .map(|((_, i), _)| (k, *i))
+            })
+            .collect::<BTreeMap<_, _>>();
+
+        Ok(ElectrumUpdate {
+            chain_update: update,
+            last_active_indices: last_active_index,
+        })
+    }
+}
+
+/// The result of [`ElectrumExt::scan`].
+pub struct ElectrumUpdate<K, P> {
+    /// The internal [`SparseChain`] update.
+    pub chain_update: SparseChain<P>,
+    /// The last keychain script pubkey indices, which had transaction histories.
+    pub last_active_indices: BTreeMap<K, u32>,
+}
+
+impl<K, P> Default for ElectrumUpdate<K, P> {
+    fn default() -> Self {
+        Self {
+            chain_update: Default::default(),
+            last_active_indices: Default::default(),
+        }
+    }
+}
+
+impl<K, P> AsRef<SparseChain<P>> for ElectrumUpdate<K, P> {
+    fn as_ref(&self) -> &SparseChain<P> {
+        &self.chain_update
+    }
+}
+
+impl<K: Ord + Clone + Debug, P: ChainPosition> ElectrumUpdate<K, P> {
+    /// Return a list of missing full transactions that are required to [`inflate_update`].
+    ///
+    /// [`inflate_update`]: bdk_chain::chain_graph::ChainGraph::inflate_update
+    pub fn missing_full_txs<G>(&self, graph: G) -> Vec<&Txid>
+    where
+        G: AsRef<TxGraph>,
+    {
+        self.chain_update
+            .txids()
+            .filter(|(_, txid)| graph.as_ref().get_tx(*txid).is_none())
+            .map(|(_, txid)| txid)
+            .collect()
+    }
+
+    /// Transform the [`ElectrumUpdate`] into a [`KeychainScan`], which can be applied to a
+    /// `tracker`.
+    ///
+    /// This will fail if there are missing full transactions not provided via `new_txs`.
+    pub fn into_keychain_scan<CG>(
+        self,
+        new_txs: Vec<Transaction>,
+        chain_graph: &CG,
+    ) -> Result<KeychainScan<K, P>, chain_graph::NewError<P>>
+    where
+        CG: AsRef<ChainGraph<P>>,
+    {
+        Ok(KeychainScan {
+            update: chain_graph
+                .as_ref()
+                .inflate_update(self.chain_update, new_txs)?,
+            last_active_indices: self.last_active_indices,
+        })
+    }
+}
+
+impl<K: Ord + Clone + Debug> ElectrumUpdate<K, TxHeight> {
+    /// Creates [`ElectrumUpdate<K, ConfirmationTime>`] from [`ElectrumUpdate<K, TxHeight>`].
+    pub fn into_confirmation_time_update(
+        self,
+        client: &electrum_client::Client,
+    ) -> Result<ElectrumUpdate<K, ConfirmationTime>, Error> {
+        let heights = self
+            .chain_update
+            .range_txids_by_height(..TxHeight::Unconfirmed)
+            .map(|(h, _)| match h {
+                TxHeight::Confirmed(h) => *h,
+                _ => unreachable!("already filtered out unconfirmed"),
+            })
+            .collect::<Vec<u32>>();
+
+        let height_to_time = heights
+            .clone()
+            .into_iter()
+            .zip(
+                client
+                    .batch_block_header(heights)?
+                    .into_iter()
+                    .map(|bh| bh.time as u64),
+            )
+            .collect::<HashMap<u32, u64>>();
+
+        let mut new_update = SparseChain::<ConfirmationTime>::from_checkpoints(
+            self.chain_update.range_checkpoints(..),
+        );
+
+        for &(tx_height, txid) in self.chain_update.txids() {
+            let conf_time = match tx_height {
+                TxHeight::Confirmed(height) => ConfirmationTime::Confirmed {
+                    height,
+                    time: height_to_time[&height],
+                },
+                TxHeight::Unconfirmed => ConfirmationTime::Unconfirmed,
+            };
+            let _ = new_update.insert_tx(txid, conf_time).expect("must insert");
+        }
+
+        Ok(ElectrumUpdate {
+            chain_update: new_update,
+            last_active_indices: self.last_active_indices,
+        })
+    }
+}
+
+#[derive(Debug)]
+enum InternalError {
+    ElectrumError(Error),
+    Reorg,
+}
+
+impl From<electrum_client::Error> for InternalError {
+    fn from(value: electrum_client::Error) -> Self {
+        Self::ElectrumError(value)
+    }
+}
+
+fn get_tip(client: &Client) -> Result<(u32, BlockHash), Error> {
+    // TODO: unsubscribe when added to the client, or is there a better call to use here?
+    client
+        .block_headers_subscribe()
+        .map(|data| (data.height as u32, data.header.block_hash()))
+}
+
+/// Prepare an update sparsechain "template" based on the checkpoints of the `local_chain`.
+fn prepare_update(
+    client: &Client,
+    local_chain: &BTreeMap<u32, BlockHash>,
+) -> Result<SparseChain, Error> {
+    let mut update = SparseChain::default();
+
+    // Find the local chain block that is still there so our update can connect to the local chain.
+    for (&existing_height, &existing_hash) in local_chain.iter().rev() {
+        // TODO: a batch request may be safer, as a reorg that happens when we are obtaining
+        //       `block_header`s will result in inconsistencies
+        let current_hash = client.block_header(existing_height as usize)?.block_hash();
+        let _ = update
+            .insert_checkpoint(BlockId {
+                height: existing_height,
+                hash: current_hash,
+            })
+            .expect("This never errors because we are working with a fresh chain");
+
+        if current_hash == existing_hash {
+            break;
+        }
+    }
+
+    // Insert the new tip so new transactions will be accepted into the sparsechain.
+    let tip = {
+        let (height, hash) = get_tip(client)?;
+        BlockId { height, hash }
+    };
+    if let Err(failure) = update.insert_checkpoint(tip) {
+        match failure {
+            sparse_chain::InsertCheckpointError::HashNotMatching { .. } => {
+                // There has been a re-org before we even begin scanning addresses.
+                // Just recursively call (this should never happen).
+                return prepare_update(client, local_chain);
+            }
+        }
+    }
+
+    Ok(update)
+}
+
+/// This atrocity is required because electrum thinks a height of 0 means "unconfirmed", but there is
+/// such thing as a genesis block.
+///
+/// We contain an expectation for the genesis coinbase txid to always have a chain position of
+/// [`TxHeight::Confirmed(0)`].
+fn determine_tx_height(raw_height: i32, tip_height: u32, txid: Txid) -> TxHeight {
+    if txid
+        == Txid::from_hex("4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b")
+            .expect("must deserialize genesis coinbase txid")
+    {
+        return TxHeight::Confirmed(0);
+    }
+    match raw_height {
+        h if h <= 0 => {
+            debug_assert!(
+                h == 0 || h == -1,
+                "unexpected height ({}) from electrum server",
+                h
+            );
+            TxHeight::Unconfirmed
+        }
+        h => {
+            let h = h as u32;
+            if h > tip_height {
+                TxHeight::Unconfirmed
+            } else {
+                TxHeight::Confirmed(h)
+            }
+        }
+    }
+}
+
+/// Populates the update [`SparseChain`] with related transactions and associated [`ChainPosition`]s
+/// of the provided `outpoints` (this is the tx which contains the outpoint and the one spending the
+/// outpoint).
+///
+/// Unfortunately, this is awkward to implement as electrum does not provide such an API. Instead, we
+/// will get the tx history of the outpoint's spk and try to find the containing tx and the
+/// spending tx.
+fn populate_with_outpoints(
+    client: &Client,
+    update: &mut SparseChain,
+    outpoints: &mut impl Iterator<Item = OutPoint>,
+) -> Result<HashMap<Txid, Transaction>, InternalError> {
+    let tip = update
+        .latest_checkpoint()
+        .expect("update must atleast have one checkpoint");
+
+    let mut full_txs = HashMap::new();
+    for outpoint in outpoints {
+        let txid = outpoint.txid;
+        let tx = client.transaction_get(&txid)?;
+        debug_assert_eq!(tx.txid(), txid);
+        let txout = match tx.output.get(outpoint.vout as usize) {
+            Some(txout) => txout,
+            None => continue,
+        };
+
+        // attempt to find the following transactions (alongside their chain positions), and
+        // add to our sparsechain `update`:
+        let mut has_residing = false; // tx in which the outpoint resides
+        let mut has_spending = false; // tx that spends the outpoint
+        for res in client.script_get_history(&txout.script_pubkey)? {
+            if has_residing && has_spending {
+                break;
+            }
+
+            if res.tx_hash == txid {
+                if has_residing {
+                    continue;
+                }
+                has_residing = true;
+                full_txs.insert(res.tx_hash, tx.clone());
+            } else {
+                if has_spending {
+                    continue;
+                }
+                let res_tx = match full_txs.get(&res.tx_hash) {
+                    Some(tx) => tx,
+                    None => {
+                        let res_tx = client.transaction_get(&res.tx_hash)?;
+                        full_txs.insert(res.tx_hash, res_tx);
+                        full_txs.get(&res.tx_hash).expect("just inserted")
+                    }
+                };
+                has_spending = res_tx
+                    .input
+                    .iter()
+                    .any(|txin| txin.previous_output == outpoint);
+                if !has_spending {
+                    continue;
+                }
+            };
+
+            let tx_height = determine_tx_height(res.height, tip.height, res.tx_hash);
+
+            if let Err(failure) = update.insert_tx(res.tx_hash, tx_height) {
+                match failure {
+                    sparse_chain::InsertTxError::TxTooHigh { .. } => {
+                        unreachable!("we should never encounter this as we ensured height <= tip");
+                    }
+                    sparse_chain::InsertTxError::TxMovedUnexpectedly { .. } => {
+                        return Err(InternalError::Reorg);
+                    }
+                }
+            }
+        }
+    }
+    Ok(full_txs)
+}
+
+/// Populate an update [`SparseChain`] with transactions (and associated block positions) from
+/// the given `txids`.
+fn populate_with_txids(
+    client: &Client,
+    update: &mut SparseChain,
+    txids: &mut impl Iterator<Item = Txid>,
+) -> Result<(), InternalError> {
+    let tip = update
+        .latest_checkpoint()
+        .expect("update must have atleast one checkpoint");
+    for txid in txids {
+        let tx = match client.transaction_get(&txid) {
+            Ok(tx) => tx,
+            Err(electrum_client::Error::Protocol(_)) => continue,
+            Err(other_err) => return Err(other_err.into()),
+        };
+
+        let spk = tx
+            .output
+            .get(0)
+            .map(|txo| &txo.script_pubkey)
+            .expect("tx must have an output");
+
+        let tx_height = match client
+            .script_get_history(spk)?
+            .into_iter()
+            .find(|r| r.tx_hash == txid)
+        {
+            Some(r) => determine_tx_height(r.height, tip.height, r.tx_hash),
+            None => continue,
+        };
+
+        if let Err(failure) = update.insert_tx(txid, tx_height) {
+            match failure {
+                sparse_chain::InsertTxError::TxTooHigh { .. } => {
+                    unreachable!("we should never encounter this as we ensured height <= tip");
+                }
+                sparse_chain::InsertTxError::TxMovedUnexpectedly { .. } => {
+                    return Err(InternalError::Reorg);
+                }
+            }
+        }
+    }
+    Ok(())
+}
+
+/// Populate an update [`SparseChain`] with transactions (and associated block positions) from
+/// the transaction history of the provided `spk`s.
+fn populate_with_spks<K, I, S>(
+    client: &Client,
+    update: &mut SparseChain,
+    spks: &mut S,
+    stop_gap: usize,
+    batch_size: usize,
+) -> Result<BTreeMap<I, (Script, bool)>, InternalError>
+where
+    K: Ord + Clone,
+    I: Ord + Clone,
+    S: Iterator<Item = (I, Script)>,
+{
+    let tip = update.latest_checkpoint().map_or(0, |cp| cp.height);
+    let mut unused_spk_count = 0_usize;
+    let mut scanned_spks = BTreeMap::new();
+
+    loop {
+        let spks = (0..batch_size)
+            .map_while(|_| spks.next())
+            .collect::<Vec<_>>();
+        if spks.is_empty() {
+            return Ok(scanned_spks);
+        }
+
+        let spk_histories = client.batch_script_get_history(spks.iter().map(|(_, s)| s))?;
+
+        for ((spk_index, spk), spk_history) in spks.into_iter().zip(spk_histories) {
+            if spk_history.is_empty() {
+                scanned_spks.insert(spk_index, (spk, false));
+                unused_spk_count += 1;
+                if unused_spk_count > stop_gap {
+                    return Ok(scanned_spks);
+                }
+                continue;
+            } else {
+                scanned_spks.insert(spk_index, (spk, true));
+                unused_spk_count = 0;
+            }
+
+            for tx in spk_history {
+                let tx_height = determine_tx_height(tx.height, tip, tx.tx_hash);
+
+                if let Err(failure) = update.insert_tx(tx.tx_hash, tx_height) {
+                    match failure {
+                        sparse_chain::InsertTxError::TxTooHigh { .. } => {
+                            unreachable!(
+                                "we should never encounter this as we ensured height <= tip"
+                            );
+                        }
+                        sparse_chain::InsertTxError::TxMovedUnexpectedly { .. } => {
+                            return Err(InternalError::Reorg);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

crates/esplora/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "bdk_esplora"
+version = "0.2.0"
+edition = "2021"
+homepage = "https://bitcoindevkit.org"
+repository = "https://github.com/bitcoindevkit/bdk"
+documentation = "https://docs.rs/bdk_esplora"
+description = "Fetch data from esplora in the form that accepts"
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk_chain = { path = "../chain", version = "0.4.0", features = ["serde", "miniscript"] }
+esplora-client = { version = "0.3", default-features = false }
+async-trait = { version = "0.1.66", optional = true }
+futures = { version = "0.3.26", optional = true }
+
+[features]
+default = ["async-https", "blocking"]
+async = ["async-trait", "futures", "esplora-client/async"]
+async-https = ["async", "esplora-client/async-https"]
+blocking = ["esplora-client/blocking"]

crates/esplora/README.md

@@ -0,0 +1,33 @@
+# BDK Esplora
+
+BDK Esplora extends [`esplora_client`](crate::esplora_client) to update [`bdk_chain`] structures
+from an Esplora server.
+
+## Usage
+
+There are two versions of the extension trait (blocking and async).
+
+For blocking-only:
+```toml
+bdk_esplora = { version = "0.1", features = ["blocking"] }
+```
+
+For async-only:
+```toml
+bdk_esplora = { version = "0.1", features = ["async"] }
+```
+
+For async-only (with https):
+```toml
+bdk_esplora = { version = "0.1", features = ["async-https"] }
+```
+
+To use the extension traits:
+```rust
+// for blocking
+use bdk_esplora::EsploraExt;
+// for async
+use bdk_esplora::EsploraAsyncExt;
+```
+
+For full examples, refer to [`example-crates/wallet_esplora`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora) (blocking) and [`example-crates/wallet_esplora_async`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora_async).

crates/esplora/src/async_ext.rs

@@ -0,0 +1,316 @@
+use std::collections::BTreeMap;
+
+use async_trait::async_trait;
+use bdk_chain::{
+    bitcoin::{BlockHash, OutPoint, Script, Txid},
+    chain_graph::ChainGraph,
+    keychain::KeychainScan,
+    sparse_chain, BlockId, ConfirmationTime,
+};
+use esplora_client::{Error, OutputStatus};
+use futures::stream::{FuturesOrdered, TryStreamExt};
+
+use crate::map_confirmation_time;
+
+/// Trait to extend [`esplora_client::AsyncClient`] functionality.
+///
+/// This is the async version of [`EsploraExt`]. Refer to
+/// [crate-level documentation] for more.
+///
+/// [`EsploraExt`]: crate::EsploraExt
+/// [crate-level documentation]: crate
+#[cfg(feature = "async")]
+#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
+#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
+pub trait EsploraAsyncExt {
+    /// Scan the blockchain (via esplora) for the data specified and returns a [`KeychainScan`].
+    ///
+    /// - `local_chain`: the most recent block hashes present locally
+    /// - `keychain_spks`: keychains that we want to scan transactions for
+    /// - `txids`: transactions for which we want updated [`ChainPosition`]s
+    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to included in the update
+    ///
+    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
+    /// transactions. `parallel_requests` specifies the max number of HTTP requests to make in
+    /// parallel.
+    ///
+    /// [`ChainPosition`]: bdk_chain::sparse_chain::ChainPosition
+    #[allow(clippy::result_large_err)] // FIXME
+    async fn scan<K: Ord + Clone + Send>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<
+            K,
+            impl IntoIterator<IntoIter = impl Iterator<Item = (u32, Script)> + Send> + Send,
+        >,
+        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
+        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
+        stop_gap: usize,
+        parallel_requests: usize,
+    ) -> Result<KeychainScan<K, ConfirmationTime>, Error>;
+
+    /// Convenience method to call [`scan`] without requiring a keychain.
+    ///
+    /// [`scan`]: EsploraAsyncExt::scan
+    #[allow(clippy::result_large_err)] // FIXME
+    async fn scan_without_keychain(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        misc_spks: impl IntoIterator<IntoIter = impl Iterator<Item = Script> + Send> + Send,
+        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
+        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
+        parallel_requests: usize,
+    ) -> Result<ChainGraph<ConfirmationTime>, Error> {
+        let wallet_scan = self
+            .scan(
+                local_chain,
+                [(
+                    (),
+                    misc_spks
+                        .into_iter()
+                        .enumerate()
+                        .map(|(i, spk)| (i as u32, spk)),
+                )]
+                .into(),
+                txids,
+                outpoints,
+                usize::MAX,
+                parallel_requests,
+            )
+            .await?;
+
+        Ok(wallet_scan.update)
+    }
+}
+
+#[cfg(feature = "async")]
+#[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
+#[cfg_attr(not(target_arch = "wasm32"), async_trait)]
+impl EsploraAsyncExt for esplora_client::AsyncClient {
+    #[allow(clippy::result_large_err)] // FIXME
+    async fn scan<K: Ord + Clone + Send>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<
+            K,
+            impl IntoIterator<IntoIter = impl Iterator<Item = (u32, Script)> + Send> + Send,
+        >,
+        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
+        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
+        stop_gap: usize,
+        parallel_requests: usize,
+    ) -> Result<KeychainScan<K, ConfirmationTime>, Error> {
+        let txids = txids.into_iter();
+        let outpoints = outpoints.into_iter();
+        let parallel_requests = parallel_requests.max(1);
+        let mut scan = KeychainScan::default();
+        let update = &mut scan.update;
+        let last_active_indices = &mut scan.last_active_indices;
+
+        for (&height, &original_hash) in local_chain.iter().rev() {
+            let update_block_id = BlockId {
+                height,
+                hash: self.get_block_hash(height).await?,
+            };
+            let _ = update
+                .insert_checkpoint(update_block_id)
+                .expect("cannot repeat height here");
+            if update_block_id.hash == original_hash {
+                break;
+            }
+        }
+        let tip_at_start = BlockId {
+            height: self.get_height().await?,
+            hash: self.get_tip_hash().await?,
+        };
+        if let Err(failure) = update.insert_checkpoint(tip_at_start) {
+            match failure {
+                sparse_chain::InsertCheckpointError::HashNotMatching { .. } => {
+                    // there was a re-org before we started scanning. We haven't consumed any iterators, so calling this function recursively is safe.
+                    return EsploraAsyncExt::scan(
+                        self,
+                        local_chain,
+                        keychain_spks,
+                        txids,
+                        outpoints,
+                        stop_gap,
+                        parallel_requests,
+                    )
+                    .await;
+                }
+            }
+        }
+
+        for (keychain, spks) in keychain_spks {
+            let mut spks = spks.into_iter();
+            let mut last_active_index = None;
+            let mut empty_scripts = 0;
+            type IndexWithTxs = (u32, Vec<esplora_client::Tx>);
+
+            loop {
+                let futures: FuturesOrdered<_> = (0..parallel_requests)
+                    .filter_map(|_| {
+                        let (index, script) = spks.next()?;
+                        let client = self.clone();
+                        Some(async move {
+                            let mut related_txs = client.scripthash_txs(&script, None).await?;
+
+                            let n_confirmed =
+                                related_txs.iter().filter(|tx| tx.status.confirmed).count();
+                            // esplora pages on 25 confirmed transactions. If there are 25 or more we
+                            // keep requesting to see if there's more.
+                            if n_confirmed >= 25 {
+                                loop {
+                                    let new_related_txs = client
+                                        .scripthash_txs(
+                                            &script,
+                                            Some(related_txs.last().unwrap().txid),
+                                        )
+                                        .await?;
+                                    let n = new_related_txs.len();
+                                    related_txs.extend(new_related_txs);
+                                    // we've reached the end
+                                    if n < 25 {
+                                        break;
+                                    }
+                                }
+                            }
+
+                            Result::<_, esplora_client::Error>::Ok((index, related_txs))
+                        })
+                    })
+                    .collect();
+
+                let n_futures = futures.len();
+
+                let idx_with_tx: Vec<IndexWithTxs> = futures.try_collect().await?;
+
+                for (index, related_txs) in idx_with_tx {
+                    if related_txs.is_empty() {
+                        empty_scripts += 1;
+                    } else {
+                        last_active_index = Some(index);
+                        empty_scripts = 0;
+                    }
+                    for tx in related_txs {
+                        let confirmation_time =
+                            map_confirmation_time(&tx.status, tip_at_start.height);
+
+                        if let Err(failure) = update.insert_tx(tx.to_tx(), confirmation_time) {
+                            use bdk_chain::{
+                                chain_graph::InsertTxError, sparse_chain::InsertTxError::*,
+                            };
+                            match failure {
+                                InsertTxError::Chain(TxTooHigh { .. }) => {
+                                    unreachable!("chain position already checked earlier")
+                                }
+                                InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                                | InsertTxError::UnresolvableConflict(_) => {
+                                    /* implies reorg during a scan. We deal with that below */
+                                }
+                            }
+                        }
+                    }
+                }
+
+                if n_futures == 0 || empty_scripts >= stop_gap {
+                    break;
+                }
+            }
+
+            if let Some(last_active_index) = last_active_index {
+                last_active_indices.insert(keychain, last_active_index);
+            }
+        }
+
+        for txid in txids {
+            let (tx, tx_status) =
+                match (self.get_tx(&txid).await?, self.get_tx_status(&txid).await?) {
+                    (Some(tx), Some(tx_status)) => (tx, tx_status),
+                    _ => continue,
+                };
+
+            let confirmation_time = map_confirmation_time(&tx_status, tip_at_start.height);
+
+            if let Err(failure) = update.insert_tx(tx, confirmation_time) {
+                use bdk_chain::{chain_graph::InsertTxError, sparse_chain::InsertTxError::*};
+                match failure {
+                    InsertTxError::Chain(TxTooHigh { .. }) => {
+                        unreachable!("chain position already checked earlier")
+                    }
+                    InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                    | InsertTxError::UnresolvableConflict(_) => {
+                        /* implies reorg during a scan. We deal with that below */
+                    }
+                }
+            }
+        }
+
+        for op in outpoints {
+            let mut op_txs = Vec::with_capacity(2);
+            if let (Some(tx), Some(tx_status)) = (
+                self.get_tx(&op.txid).await?,
+                self.get_tx_status(&op.txid).await?,
+            ) {
+                op_txs.push((tx, tx_status));
+                if let Some(OutputStatus {
+                    txid: Some(txid),
+                    status: Some(spend_status),
+                    ..
+                }) = self.get_output_status(&op.txid, op.vout as _).await?
+                {
+                    if let Some(spend_tx) = self.get_tx(&txid).await? {
+                        op_txs.push((spend_tx, spend_status));
+                    }
+                }
+            }
+
+            for (tx, status) in op_txs {
+                let confirmation_time = map_confirmation_time(&status, tip_at_start.height);
+
+                if let Err(failure) = update.insert_tx(tx, confirmation_time) {
+                    use bdk_chain::{chain_graph::InsertTxError, sparse_chain::InsertTxError::*};
+                    match failure {
+                        InsertTxError::Chain(TxTooHigh { .. }) => {
+                            unreachable!("chain position already checked earlier")
+                        }
+                        InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                        | InsertTxError::UnresolvableConflict(_) => {
+                            /* implies reorg during a scan. We deal with that below */
+                        }
+                    }
+                }
+            }
+        }
+
+        let reorg_occurred = {
+            if let Some(checkpoint) = update.chain().latest_checkpoint() {
+                self.get_block_hash(checkpoint.height).await? != checkpoint.hash
+            } else {
+                false
+            }
+        };
+
+        if reorg_occurred {
+            // A reorg occurred, so let's find out where all the txids we found are in the chain now.
+            // XXX: collect required because of weird type naming issues
+            let txids_found = update
+                .chain()
+                .txids()
+                .map(|(_, txid)| *txid)
+                .collect::<Vec<_>>();
+            scan.update = EsploraAsyncExt::scan_without_keychain(
+                self,
+                local_chain,
+                [],
+                txids_found,
+                [],
+                parallel_requests,
+            )
+            .await?;
+        }
+
+        Ok(scan)
+    }
+}

crates/esplora/src/blocking_ext.rs

@@ -0,0 +1,290 @@
+use std::collections::BTreeMap;
+
+use bdk_chain::{
+    bitcoin::{BlockHash, OutPoint, Script, Txid},
+    chain_graph::ChainGraph,
+    keychain::KeychainScan,
+    sparse_chain, BlockId, ConfirmationTime,
+};
+use esplora_client::{Error, OutputStatus};
+
+use crate::map_confirmation_time;
+
+/// Trait to extend [`esplora_client::BlockingClient`] functionality.
+///
+/// Refer to [crate-level documentation] for more.
+///
+/// [crate-level documentation]: crate
+pub trait EsploraExt {
+    /// Scan the blockchain (via esplora) for the data specified and returns a [`KeychainScan`].
+    ///
+    /// - `local_chain`: the most recent block hashes present locally
+    /// - `keychain_spks`: keychains that we want to scan transactions for
+    /// - `txids`: transactions for which we want updated [`ChainPosition`]s
+    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to included in the update
+    ///
+    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
+    /// transactions. `parallel_requests` specifies the max number of HTTP requests to make in
+    /// parallel.
+    ///
+    /// [`ChainPosition`]: bdk_chain::sparse_chain::ChainPosition
+    #[allow(clippy::result_large_err)] // FIXME
+    fn scan<K: Ord + Clone>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        stop_gap: usize,
+        parallel_requests: usize,
+    ) -> Result<KeychainScan<K, ConfirmationTime>, Error>;
+
+    /// Convenience method to call [`scan`] without requiring a keychain.
+    ///
+    /// [`scan`]: EsploraExt::scan
+    #[allow(clippy::result_large_err)] // FIXME
+    fn scan_without_keychain(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        misc_spks: impl IntoIterator<Item = Script>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        parallel_requests: usize,
+    ) -> Result<ChainGraph<ConfirmationTime>, Error> {
+        let wallet_scan = self.scan(
+            local_chain,
+            [(
+                (),
+                misc_spks
+                    .into_iter()
+                    .enumerate()
+                    .map(|(i, spk)| (i as u32, spk)),
+            )]
+            .into(),
+            txids,
+            outpoints,
+            usize::MAX,
+            parallel_requests,
+        )?;
+
+        Ok(wallet_scan.update)
+    }
+}
+
+impl EsploraExt for esplora_client::BlockingClient {
+    fn scan<K: Ord + Clone>(
+        &self,
+        local_chain: &BTreeMap<u32, BlockHash>,
+        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        stop_gap: usize,
+        parallel_requests: usize,
+    ) -> Result<KeychainScan<K, ConfirmationTime>, Error> {
+        let parallel_requests = parallel_requests.max(1);
+        let mut scan = KeychainScan::default();
+        let update = &mut scan.update;
+        let last_active_indices = &mut scan.last_active_indices;
+
+        for (&height, &original_hash) in local_chain.iter().rev() {
+            let update_block_id = BlockId {
+                height,
+                hash: self.get_block_hash(height)?,
+            };
+            let _ = update
+                .insert_checkpoint(update_block_id)
+                .expect("cannot repeat height here");
+            if update_block_id.hash == original_hash {
+                break;
+            }
+        }
+        let tip_at_start = BlockId {
+            height: self.get_height()?,
+            hash: self.get_tip_hash()?,
+        };
+        if let Err(failure) = update.insert_checkpoint(tip_at_start) {
+            match failure {
+                sparse_chain::InsertCheckpointError::HashNotMatching { .. } => {
+                    // there was a re-org before we started scanning. We haven't consumed any iterators, so calling this function recursively is safe.
+                    return EsploraExt::scan(
+                        self,
+                        local_chain,
+                        keychain_spks,
+                        txids,
+                        outpoints,
+                        stop_gap,
+                        parallel_requests,
+                    );
+                }
+            }
+        }
+
+        for (keychain, spks) in keychain_spks {
+            let mut spks = spks.into_iter();
+            let mut last_active_index = None;
+            let mut empty_scripts = 0;
+            type IndexWithTxs = (u32, Vec<esplora_client::Tx>);
+
+            loop {
+                let handles = (0..parallel_requests)
+                    .filter_map(
+                        |_| -> Option<std::thread::JoinHandle<Result<IndexWithTxs, _>>> {
+                            let (index, script) = spks.next()?;
+                            let client = self.clone();
+                            Some(std::thread::spawn(move || {
+                                let mut related_txs = client.scripthash_txs(&script, None)?;
+
+                                let n_confirmed =
+                                    related_txs.iter().filter(|tx| tx.status.confirmed).count();
+                                // esplora pages on 25 confirmed transactions. If there are 25 or more we
+                                // keep requesting to see if there's more.
+                                if n_confirmed >= 25 {
+                                    loop {
+                                        let new_related_txs = client.scripthash_txs(
+                                            &script,
+                                            Some(related_txs.last().unwrap().txid),
+                                        )?;
+                                        let n = new_related_txs.len();
+                                        related_txs.extend(new_related_txs);
+                                        // we've reached the end
+                                        if n < 25 {
+                                            break;
+                                        }
+                                    }
+                                }
+
+                                Result::<_, esplora_client::Error>::Ok((index, related_txs))
+                            }))
+                        },
+                    )
+                    .collect::<Vec<_>>();
+
+                let n_handles = handles.len();
+
+                for handle in handles {
+                    let (index, related_txs) = handle.join().unwrap()?; // TODO: don't unwrap
+                    if related_txs.is_empty() {
+                        empty_scripts += 1;
+                    } else {
+                        last_active_index = Some(index);
+                        empty_scripts = 0;
+                    }
+                    for tx in related_txs {
+                        let confirmation_time =
+                            map_confirmation_time(&tx.status, tip_at_start.height);
+
+                        if let Err(failure) = update.insert_tx(tx.to_tx(), confirmation_time) {
+                            use bdk_chain::{
+                                chain_graph::InsertTxError, sparse_chain::InsertTxError::*,
+                            };
+                            match failure {
+                                InsertTxError::Chain(TxTooHigh { .. }) => {
+                                    unreachable!("chain position already checked earlier")
+                                }
+                                InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                                | InsertTxError::UnresolvableConflict(_) => {
+                                    /* implies reorg during a scan. We deal with that below */
+                                }
+                            }
+                        }
+                    }
+                }
+
+                if n_handles == 0 || empty_scripts >= stop_gap {
+                    break;
+                }
+            }
+
+            if let Some(last_active_index) = last_active_index {
+                last_active_indices.insert(keychain, last_active_index);
+            }
+        }
+
+        for txid in txids.into_iter() {
+            let (tx, tx_status) = match (self.get_tx(&txid)?, self.get_tx_status(&txid)?) {
+                (Some(tx), Some(tx_status)) => (tx, tx_status),
+                _ => continue,
+            };
+
+            let confirmation_time = map_confirmation_time(&tx_status, tip_at_start.height);
+
+            if let Err(failure) = update.insert_tx(tx, confirmation_time) {
+                use bdk_chain::{chain_graph::InsertTxError, sparse_chain::InsertTxError::*};
+                match failure {
+                    InsertTxError::Chain(TxTooHigh { .. }) => {
+                        unreachable!("chain position already checked earlier")
+                    }
+                    InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                    | InsertTxError::UnresolvableConflict(_) => {
+                        /* implies reorg during a scan. We deal with that below */
+                    }
+                }
+            }
+        }
+
+        for op in outpoints.into_iter() {
+            let mut op_txs = Vec::with_capacity(2);
+            if let (Some(tx), Some(tx_status)) =
+                (self.get_tx(&op.txid)?, self.get_tx_status(&op.txid)?)
+            {
+                op_txs.push((tx, tx_status));
+                if let Some(OutputStatus {
+                    txid: Some(txid),
+                    status: Some(spend_status),
+                    ..
+                }) = self.get_output_status(&op.txid, op.vout as _)?
+                {
+                    if let Some(spend_tx) = self.get_tx(&txid)? {
+                        op_txs.push((spend_tx, spend_status));
+                    }
+                }
+            }
+
+            for (tx, status) in op_txs {
+                let confirmation_time = map_confirmation_time(&status, tip_at_start.height);
+
+                if let Err(failure) = update.insert_tx(tx, confirmation_time) {
+                    use bdk_chain::{chain_graph::InsertTxError, sparse_chain::InsertTxError::*};
+                    match failure {
+                        InsertTxError::Chain(TxTooHigh { .. }) => {
+                            unreachable!("chain position already checked earlier")
+                        }
+                        InsertTxError::Chain(TxMovedUnexpectedly { .. })
+                        | InsertTxError::UnresolvableConflict(_) => {
+                            /* implies reorg during a scan. We deal with that below */
+                        }
+                    }
+                }
+            }
+        }
+
+        let reorg_occurred = {
+            if let Some(checkpoint) = update.chain().latest_checkpoint() {
+                self.get_block_hash(checkpoint.height)? != checkpoint.hash
+            } else {
+                false
+            }
+        };
+
+        if reorg_occurred {
+            // A reorg occurred, so let's find out where all the txids we found are now in the chain.
+            // XXX: collect required because of weird type naming issues
+            let txids_found = update
+                .chain()
+                .txids()
+                .map(|(_, txid)| *txid)
+                .collect::<Vec<_>>();
+            scan.update = EsploraExt::scan_without_keychain(
+                self,
+                local_chain,
+                [],
+                txids_found,
+                [],
+                parallel_requests,
+            )?;
+        }
+
+        Ok(scan)
+    }
+}

crates/esplora/src/lib.rs

@@ -0,0 +1,27 @@
+#![doc = include_str!("../README.md")]
+use bdk_chain::ConfirmationTime;
+use esplora_client::TxStatus;
+
+pub use esplora_client;
+
+#[cfg(feature = "blocking")]
+mod blocking_ext;
+#[cfg(feature = "blocking")]
+pub use blocking_ext::*;
+
+#[cfg(feature = "async")]
+mod async_ext;
+#[cfg(feature = "async")]
+pub use async_ext::*;
+
+pub(crate) fn map_confirmation_time(
+    tx_status: &TxStatus,
+    height_at_start: u32,
+) -> ConfirmationTime {
+    match (tx_status.block_time, tx_status.block_height) {
+        (Some(time), Some(height)) if height <= height_at_start => {
+            ConfirmationTime::Confirmed { height, time }
+        }
+        _ => ConfirmationTime::Unconfirmed,
+    }
+}

crates/file_store/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "bdk_file_store"
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/bitcoindevkit/bdk"
+documentation = "https://docs.rs/bdk_file_store"
+description = "A simple append-only flat file implementation of Persist for Bitcoin Dev Kit."
+keywords = ["bitcoin", "persist", "persistence", "bdk", "file"]
+authors = ["Bitcoin Dev Kit Developers"]
+readme = "README.md"
+
+[dependencies]
+bdk_chain = { path = "../chain", version = "0.4.0", features = [ "serde", "miniscript" ] }
+bincode = { version = "1" }
+serde = { version = "1", features = ["derive"] }
+
+[dev-dependencies]
+tempfile = "3"

crates/file_store/README.md

@@ -0,0 +1,10 @@
+# BDK File Store
+
+This is a simple append-only flat file implementation of
+[`Persist`](`bdk_chain::keychain::persist::Persist`).
+
+The main structure is [`KeychainStore`](`crate::KeychainStore`), which can be used with [`bdk`]'s
+`Wallet` to persist wallet data into a flat file.
+
+[`bdk`]: https://docs.rs/bdk/latest
+[`bdk_chain`]: https://docs.rs/bdk_chain/latest

crates/file_store/src/file_store.rs

@@ -0,0 +1,404 @@
+//! Module for persisting data on disk.
+//!
+//! The star of the show is [`KeychainStore`], which maintains an append-only file of
+//! [`KeychainChangeSet`]s which can be used to restore a [`KeychainTracker`].
+use bdk_chain::{
+    keychain::{KeychainChangeSet, KeychainTracker},
+    sparse_chain,
+};
+use bincode::{DefaultOptions, Options};
+use core::marker::PhantomData;
+use std::{
+    fs::{File, OpenOptions},
+    io::{self, Read, Seek, Write},
+    path::Path,
+};
+
+/// BDK File Store magic bytes length.
+const MAGIC_BYTES_LEN: usize = 12;
+
+/// BDK File Store magic bytes.
+const MAGIC_BYTES: [u8; MAGIC_BYTES_LEN] = [98, 100, 107, 102, 115, 48, 48, 48, 48, 48, 48, 48];
+
+/// Persists an append only list of `KeychainChangeSet<K,P>` to a single file.
+/// [`KeychainChangeSet<K,P>`] record the changes made to a [`KeychainTracker<K,P>`].
+#[derive(Debug)]
+pub struct KeychainStore<K, P> {
+    db_file: File,
+    changeset_type_params: core::marker::PhantomData<(K, P)>,
+}
+
+fn bincode() -> impl bincode::Options {
+    DefaultOptions::new().with_varint_encoding()
+}
+
+impl<K, P> KeychainStore<K, P>
+where
+    K: Ord + Clone + core::fmt::Debug,
+    P: sparse_chain::ChainPosition,
+    KeychainChangeSet<K, P>: serde::Serialize + serde::de::DeserializeOwned,
+{
+    /// Creates a new store from a [`File`].
+    ///
+    /// The file must have been opened with read and write permissions.
+    ///
+    /// [`File`]: std::fs::File
+    pub fn new(mut file: File) -> Result<Self, FileError> {
+        file.rewind()?;
+
+        let mut magic_bytes = [0_u8; MAGIC_BYTES_LEN];
+        file.read_exact(&mut magic_bytes)?;
+
+        if magic_bytes != MAGIC_BYTES {
+            return Err(FileError::InvalidMagicBytes(magic_bytes));
+        }
+
+        Ok(Self {
+            db_file: file,
+            changeset_type_params: Default::default(),
+        })
+    }
+
+    /// Creates or loads a store from `db_path`. If no file exists there, it will be created.
+    pub fn new_from_path<D: AsRef<Path>>(db_path: D) -> Result<Self, FileError> {
+        let already_exists = db_path.as_ref().exists();
+
+        let mut db_file = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create(true)
+            .open(db_path)?;
+
+        if !already_exists {
+            db_file.write_all(&MAGIC_BYTES)?;
+        }
+
+        Self::new(db_file)
+    }
+
+    /// Iterates over the stored changeset from first to last, changing the seek position at each
+    /// iteration.
+    ///
+    /// The iterator may fail to read an entry and therefore return an error. However, the first time
+    /// it returns an error will be the last. After doing so, the iterator will always yield `None`.
+    ///
+    /// **WARNING**: This method changes the write position in the underlying file. You should
+    /// always iterate over all entries until `None` is returned if you want your next write to go
+    /// at the end; otherwise, you will write over existing entries.
+    pub fn iter_changesets(&mut self) -> Result<EntryIter<'_, KeychainChangeSet<K, P>>, io::Error> {
+        self.db_file
+            .seek(io::SeekFrom::Start(MAGIC_BYTES_LEN as _))?;
+
+        Ok(EntryIter::new(&mut self.db_file))
+    }
+
+    /// Loads all the changesets that have been stored as one giant changeset.
+    ///
+    /// This function returns a tuple of the aggregate changeset and a result that indicates
+    /// whether an error occurred while reading or deserializing one of the entries. If so the
+    /// changeset will consist of all of those it was able to read.
+    ///
+    /// You should usually check the error. In many applications, it may make sense to do a full
+    /// wallet scan with a stop-gap after getting an error, since it is likely that one of the
+    /// changesets it was unable to read changed the derivation indices of the tracker.
+    ///
+    /// **WARNING**: This method changes the write position of the underlying file. The next
+    /// changeset will be written over the erroring entry (or the end of the file if none existed).
+    pub fn aggregate_changeset(&mut self) -> (KeychainChangeSet<K, P>, Result<(), IterError>) {
+        let mut changeset = KeychainChangeSet::default();
+        let result = (|| {
+            let iter_changeset = self.iter_changesets()?;
+            for next_changeset in iter_changeset {
+                changeset.append(next_changeset?);
+            }
+            Ok(())
+        })();
+
+        (changeset, result)
+    }
+
+    /// Reads and applies all the changesets stored sequentially to the tracker, stopping when it fails
+    /// to read the next one.
+    ///
+    /// **WARNING**: This method changes the write position of the underlying file. The next
+    /// changeset will be written over the erroring entry (or the end of the file if none existed).
+    pub fn load_into_keychain_tracker(
+        &mut self,
+        tracker: &mut KeychainTracker<K, P>,
+    ) -> Result<(), IterError> {
+        for changeset in self.iter_changesets()? {
+            tracker.apply_changeset(changeset?)
+        }
+        Ok(())
+    }
+
+    /// Append a new changeset to the file and truncate the file to the end of the appended changeset.
+    ///
+    /// The truncation is to avoid the possibility of having a valid but inconsistent changeset
+    /// directly after the appended changeset.
+    pub fn append_changeset(
+        &mut self,
+        changeset: &KeychainChangeSet<K, P>,
+    ) -> Result<(), io::Error> {
+        if changeset.is_empty() {
+            return Ok(());
+        }
+
+        bincode()
+            .serialize_into(&mut self.db_file, changeset)
+            .map_err(|e| match *e {
+                bincode::ErrorKind::Io(inner) => inner,
+                unexpected_err => panic!("unexpected bincode error: {}", unexpected_err),
+            })?;
+
+        // truncate file after this changeset addition
+        // if this is not done, data after this changeset may represent valid changesets, however
+        // applying those changesets on top of this one may result in an inconsistent state
+        let pos = self.db_file.stream_position()?;
+        self.db_file.set_len(pos)?;
+
+        // We want to make sure that derivation indices changes are written to disk as soon as
+        // possible, so you know about the write failure before you give out the address in the application.
+        if !changeset.derivation_indices.is_empty() {
+            self.db_file.sync_data()?;
+        }
+
+        Ok(())
+    }
+}
+
+/// Error that occurs due to problems encountered with the file.
+#[derive(Debug)]
+pub enum FileError {
+    /// IO error, this may mean that the file is too short.
+    Io(io::Error),
+    /// Magic bytes do not match what is expected.
+    InvalidMagicBytes([u8; MAGIC_BYTES_LEN]),
+}
+
+impl core::fmt::Display for FileError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Io(e) => write!(f, "io error trying to read file: {}", e),
+            Self::InvalidMagicBytes(b) => write!(
+                f,
+                "file has invalid magic bytes: expected={:?} got={:?}",
+                MAGIC_BYTES, b
+            ),
+        }
+    }
+}
+
+impl From<io::Error> for FileError {
+    fn from(value: io::Error) -> Self {
+        Self::Io(value)
+    }
+}
+
+impl std::error::Error for FileError {}
+
+/// Error type for [`EntryIter`].
+#[derive(Debug)]
+pub enum IterError {
+    /// Failure to read from the file.
+    Io(io::Error),
+    /// Failure to decode data from the file.
+    Bincode(bincode::ErrorKind),
+}
+
+impl core::fmt::Display for IterError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            IterError::Io(e) => write!(f, "io error trying to read entry {}", e),
+            IterError::Bincode(e) => write!(f, "bincode error while reading entry {}", e),
+        }
+    }
+}
+
+impl std::error::Error for IterError {}
+
+/// Iterator over entries in a file store.
+///
+/// Reads and returns an entry each time [`next`] is called. If an error occurs while reading the
+/// iterator will yield a `Result::Err(_)` instead and then `None` for the next call to `next`.
+///
+/// [`next`]: Self::next
+pub struct EntryIter<'a, V> {
+    db_file: &'a mut File,
+    types: PhantomData<V>,
+    error_exit: bool,
+}
+
+impl<'a, V> EntryIter<'a, V> {
+    pub fn new(db_file: &'a mut File) -> Self {
+        Self {
+            db_file,
+            types: PhantomData,
+            error_exit: false,
+        }
+    }
+}
+
+impl<'a, V> Iterator for EntryIter<'a, V>
+where
+    V: serde::de::DeserializeOwned,
+{
+    type Item = Result<V, IterError>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let result = (|| {
+            let pos = self.db_file.stream_position()?;
+
+            match bincode().deserialize_from(&mut self.db_file) {
+                Ok(changeset) => Ok(Some(changeset)),
+                Err(e) => {
+                    if let bincode::ErrorKind::Io(inner) = &*e {
+                        if inner.kind() == io::ErrorKind::UnexpectedEof {
+                            let eof = self.db_file.seek(io::SeekFrom::End(0))?;
+                            if pos == eof {
+                                return Ok(None);
+                            }
+                        }
+                    }
+
+                    self.db_file.seek(io::SeekFrom::Start(pos))?;
+                    Err(IterError::Bincode(*e))
+                }
+            }
+        })();
+
+        let result = result.transpose();
+
+        if let Some(Err(_)) = &result {
+            self.error_exit = true;
+        }
+
+        result
+    }
+}
+
+impl From<io::Error> for IterError {
+    fn from(value: io::Error) -> Self {
+        IterError::Io(value)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use bdk_chain::{
+        keychain::{DerivationAdditions, KeychainChangeSet},
+        TxHeight,
+    };
+    use std::{
+        io::{Read, Write},
+        vec::Vec,
+    };
+    use tempfile::NamedTempFile;
+    #[derive(
+        Debug,
+        Clone,
+        Copy,
+        PartialOrd,
+        Ord,
+        PartialEq,
+        Eq,
+        Hash,
+        serde::Serialize,
+        serde::Deserialize,
+    )]
+    enum TestKeychain {
+        External,
+        Internal,
+    }
+
+    impl core::fmt::Display for TestKeychain {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            match self {
+                Self::External => write!(f, "external"),
+                Self::Internal => write!(f, "internal"),
+            }
+        }
+    }
+
+    #[test]
+    fn magic_bytes() {
+        assert_eq!(&MAGIC_BYTES, "bdkfs0000000".as_bytes());
+    }
+
+    #[test]
+    fn new_fails_if_file_is_too_short() {
+        let mut file = NamedTempFile::new().unwrap();
+        file.write_all(&MAGIC_BYTES[..MAGIC_BYTES_LEN - 1])
+            .expect("should write");
+
+        match KeychainStore::<TestKeychain, TxHeight>::new(file.reopen().unwrap()) {
+            Err(FileError::Io(e)) => assert_eq!(e.kind(), std::io::ErrorKind::UnexpectedEof),
+            unexpected => panic!("unexpected result: {:?}", unexpected),
+        };
+    }
+
+    #[test]
+    fn new_fails_if_magic_bytes_are_invalid() {
+        let invalid_magic_bytes = "ldkfs0000000";
+
+        let mut file = NamedTempFile::new().unwrap();
+        file.write_all(invalid_magic_bytes.as_bytes())
+            .expect("should write");
+
+        match KeychainStore::<TestKeychain, TxHeight>::new(file.reopen().unwrap()) {
+            Err(FileError::InvalidMagicBytes(b)) => {
+                assert_eq!(b, invalid_magic_bytes.as_bytes())
+            }
+            unexpected => panic!("unexpected result: {:?}", unexpected),
+        };
+    }
+
+    #[test]
+    fn append_changeset_truncates_invalid_bytes() {
+        // initial data to write to file (magic bytes + invalid data)
+        let mut data = [255_u8; 2000];
+        data[..MAGIC_BYTES_LEN].copy_from_slice(&MAGIC_BYTES);
+
+        let changeset = KeychainChangeSet {
+            derivation_indices: DerivationAdditions(
+                vec![(TestKeychain::External, 42)].into_iter().collect(),
+            ),
+            chain_graph: Default::default(),
+        };
+
+        let mut file = NamedTempFile::new().unwrap();
+        file.write_all(&data).expect("should write");
+
+        let mut store = KeychainStore::<TestKeychain, TxHeight>::new(file.reopen().unwrap())
+            .expect("should open");
+        match store.iter_changesets().expect("seek should succeed").next() {
+            Some(Err(IterError::Bincode(_))) => {}
+            unexpected_res => panic!("unexpected result: {:?}", unexpected_res),
+        }
+
+        store.append_changeset(&changeset).expect("should append");
+
+        drop(store);
+
+        let got_bytes = {
+            let mut buf = Vec::new();
+            file.reopen()
+                .unwrap()
+                .read_to_end(&mut buf)
+                .expect("should read");
+            buf
+        };
+
+        let expected_bytes = {
+            let mut buf = MAGIC_BYTES.to_vec();
+            DefaultOptions::new()
+                .with_varint_encoding()
+                .serialize_into(&mut buf, &changeset)
+                .expect("should encode");
+            buf
+        };
+
+        assert_eq!(got_bytes, expected_bytes);
+    }
+}

crates/file_store/src/lib.rs

@@ -0,0 +1,32 @@
+#![doc = include_str!("../README.md")]
+mod file_store;
+use bdk_chain::{
+    keychain::{KeychainChangeSet, KeychainTracker, PersistBackend},
+    sparse_chain::ChainPosition,
+};
+pub use file_store::*;
+
+impl<K, P> PersistBackend<K, P> for KeychainStore<K, P>
+where
+    K: Ord + Clone + core::fmt::Debug,
+    P: ChainPosition,
+    KeychainChangeSet<K, P>: serde::Serialize + serde::de::DeserializeOwned,
+{
+    type WriteError = std::io::Error;
+
+    type LoadError = IterError;
+
+    fn append_changeset(
+        &mut self,
+        changeset: &KeychainChangeSet<K, P>,
+    ) -> Result<(), Self::WriteError> {
+        KeychainStore::append_changeset(self, changeset)
+    }
+
+    fn load_into_keychain_tracker(
+        &mut self,
+        tracker: &mut KeychainTracker<K, P>,
+    ) -> Result<(), Self::LoadError> {
+        KeychainStore::load_into_keychain_tracker(self, tracker)
+    }
+}

crates/file_store/tests/test_file_store.rs

@@ -0,0 +1 @@
+

example-crates/keychain_tracker_electrum/.gitignore

@@ -0,0 +1 @@
+/target

example-crates/keychain_tracker_electrum/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "keychain_tracker_electrum_example"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bdk_chain = { path = "../../crates/chain", features = ["serde"] }
+bdk_electrum = { path = "../../crates/electrum" }
+keychain_tracker_example_cli = { path = "../keychain_tracker_example_cli"}

example-crates/keychain_tracker_electrum/README.md

@@ -0,0 +1,6 @@
+# Keychain Tracker with electrum
+
+This example shows how you use the `KeychainTracker` from `bdk_chain` to create a simple command
+line wallet.
+
+

example-crates/keychain_tracker_electrum/src/main.rs

@@ -0,0 +1,245 @@
+use bdk_chain::bitcoin::{Address, OutPoint, Txid};
+use bdk_electrum::bdk_chain::{self, bitcoin::Network, TxHeight};
+use bdk_electrum::{
+    electrum_client::{self, ElectrumApi},
+    ElectrumExt, ElectrumUpdate,
+};
+use keychain_tracker_example_cli::{
+    self as cli,
+    anyhow::{self, Context},
+    clap::{self, Parser, Subcommand},
+};
+use std::{collections::BTreeMap, fmt::Debug, io, io::Write};
+
+#[derive(Subcommand, Debug, Clone)]
+enum ElectrumCommands {
+    /// Scans the addresses in the wallet using the esplora API.
+    Scan {
+        /// When a gap this large has been found for a keychain, it will stop.
+        #[clap(long, default_value = "5")]
+        stop_gap: usize,
+        #[clap(flatten)]
+        scan_options: ScanOptions,
+    },
+    /// Scans particular addresses using the esplora API.
+    Sync {
+        /// Scan all the unused addresses.
+        #[clap(long)]
+        unused_spks: bool,
+        /// Scan every address that you have derived.
+        #[clap(long)]
+        all_spks: bool,
+        /// Scan unspent outpoints for spends or changes to confirmation status of residing tx.
+        #[clap(long)]
+        utxos: bool,
+        /// Scan unconfirmed transactions for updates.
+        #[clap(long)]
+        unconfirmed: bool,
+        #[clap(flatten)]
+        scan_options: ScanOptions,
+    },
+}
+
+#[derive(Parser, Debug, Clone, PartialEq)]
+pub struct ScanOptions {
+    /// Set batch size for each script_history call to electrum client.
+    #[clap(long, default_value = "25")]
+    pub batch_size: usize,
+}
+
+fn main() -> anyhow::Result<()> {
+    let (args, keymap, tracker, db) = cli::init::<ElectrumCommands, _>()?;
+
+    let electrum_url = match args.network {
+        Network::Bitcoin => "ssl://electrum.blockstream.info:50002",
+        Network::Testnet => "ssl://electrum.blockstream.info:60002",
+        Network::Regtest => "tcp://localhost:60401",
+        Network::Signet => "tcp://signet-electrumx.wakiyamap.dev:50001",
+    };
+    let config = electrum_client::Config::builder()
+        .validate_domain(matches!(args.network, Network::Bitcoin))
+        .build();
+
+    let client = electrum_client::Client::from_config(electrum_url, config)?;
+
+    let electrum_cmd = match args.command.clone() {
+        cli::Commands::ChainSpecific(electrum_cmd) => electrum_cmd,
+        general_command => {
+            return cli::handle_commands(
+                general_command,
+                |transaction| {
+                    let _txid = client.transaction_broadcast(transaction)?;
+                    Ok(())
+                },
+                &tracker,
+                &db,
+                args.network,
+                &keymap,
+            )
+        }
+    };
+
+    let response = match electrum_cmd {
+        ElectrumCommands::Scan {
+            stop_gap,
+            scan_options: scan_option,
+        } => {
+            let (spk_iterators, local_chain) = {
+                // Get a short lock on the tracker to get the spks iterators
+                // and local chain state
+                let tracker = &*tracker.lock().unwrap();
+                let spk_iterators = tracker
+                    .txout_index
+                    .spks_of_all_keychains()
+                    .into_iter()
+                    .map(|(keychain, iter)| {
+                        let mut first = true;
+                        let spk_iter = iter.inspect(move |(i, _)| {
+                            if first {
+                                eprint!("\nscanning {}: ", keychain);
+                                first = false;
+                            }
+
+                            eprint!("{} ", i);
+                            let _ = io::stdout().flush();
+                        });
+                        (keychain, spk_iter)
+                    })
+                    .collect::<BTreeMap<_, _>>();
+                let local_chain = tracker.chain().checkpoints().clone();
+                (spk_iterators, local_chain)
+            };
+
+            // we scan the spks **without** a lock on the tracker
+            client.scan(
+                &local_chain,
+                spk_iterators,
+                core::iter::empty(),
+                core::iter::empty(),
+                stop_gap,
+                scan_option.batch_size,
+            )?
+        }
+        ElectrumCommands::Sync {
+            mut unused_spks,
+            mut utxos,
+            mut unconfirmed,
+            all_spks,
+            scan_options,
+        } => {
+            // Get a short lock on the tracker to get the spks we're interested in
+            let tracker = tracker.lock().unwrap();
+
+            if !(all_spks || unused_spks || utxos || unconfirmed) {
+                unused_spks = true;
+                unconfirmed = true;
+                utxos = true;
+            } else if all_spks {
+                unused_spks = false;
+            }
+
+            let mut spks: Box<dyn Iterator<Item = bdk_chain::bitcoin::Script>> =
+                Box::new(core::iter::empty());
+            if all_spks {
+                let all_spks = tracker
+                    .txout_index
+                    .all_spks()
+                    .iter()
+                    .map(|(k, v)| (*k, v.clone()))
+                    .collect::<Vec<_>>();
+                spks = Box::new(spks.chain(all_spks.into_iter().map(|(index, script)| {
+                    eprintln!("scanning {:?}", index);
+                    script
+                })));
+            }
+            if unused_spks {
+                let unused_spks = tracker
+                    .txout_index
+                    .unused_spks(..)
+                    .map(|(k, v)| (*k, v.clone()))
+                    .collect::<Vec<_>>();
+                spks = Box::new(spks.chain(unused_spks.into_iter().map(|(index, script)| {
+                    eprintln!(
+                        "Checking if address {} {:?} has been used",
+                        Address::from_script(&script, args.network).unwrap(),
+                        index
+                    );
+
+                    script
+                })));
+            }
+
+            let mut outpoints: Box<dyn Iterator<Item = OutPoint>> = Box::new(core::iter::empty());
+
+            if utxos {
+                let utxos = tracker
+                    .full_utxos()
+                    .map(|(_, utxo)| utxo)
+                    .collect::<Vec<_>>();
+                outpoints = Box::new(
+                    utxos
+                        .into_iter()
+                        .inspect(|utxo| {
+                            eprintln!(
+                                "Checking if outpoint {} (value: {}) has been spent",
+                                utxo.outpoint, utxo.txout.value
+                            );
+                        })
+                        .map(|utxo| utxo.outpoint),
+                );
+            };
+
+            let mut txids: Box<dyn Iterator<Item = Txid>> = Box::new(core::iter::empty());
+
+            if unconfirmed {
+                let unconfirmed_txids = tracker
+                    .chain()
+                    .range_txids_by_height(TxHeight::Unconfirmed..)
+                    .map(|(_, txid)| *txid)
+                    .collect::<Vec<_>>();
+
+                txids = Box::new(unconfirmed_txids.into_iter().inspect(|txid| {
+                    eprintln!("Checking if {} is confirmed yet", txid);
+                }));
+            }
+
+            let local_chain = tracker.chain().checkpoints().clone();
+            // drop lock on tracker
+            drop(tracker);
+
+            // we scan the spks **without** a lock on the tracker
+            ElectrumUpdate {
+                chain_update: client
+                    .scan_without_keychain(
+                        &local_chain,
+                        spks,
+                        txids,
+                        outpoints,
+                        scan_options.batch_size,
+                    )
+                    .context("scanning the blockchain")?,
+                ..Default::default()
+            }
+        }
+    };
+
+    let missing_txids = response.missing_full_txs(&*tracker.lock().unwrap());
+
+    // fetch the missing full transactions **without** a lock on the tracker
+    let new_txs = client
+        .batch_transaction_get(missing_txids)
+        .context("fetching full transactions")?;
+
+    {
+        // Get a final short lock to apply the changes
+        let mut tracker = tracker.lock().unwrap();
+        let changeset = {
+            let scan = response.into_keychain_scan(new_txs, &*tracker)?;
+            tracker.determine_changeset(&scan)?
+        };
+        db.lock().unwrap().append_changeset(&changeset)?;
+        tracker.apply_changeset(changeset);
+    };
+
+    Ok(())
+}

example-crates/keychain_tracker_esplora/.gitignore

@@ -0,0 +1,3 @@
+/target
+Cargo.lock
+.bdk_example_db

example-crates/keychain_tracker_esplora/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "keychain_tracker_esplora_example"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk_chain = { path = "../../crates/chain", features = ["serde", "miniscript"] }
+bdk_esplora = { path = "../../crates/esplora" }
+keychain_tracker_example_cli = { path = "../keychain_tracker_example_cli" }

example-crates/keychain_tracker_esplora/src/main.rs

@@ -0,0 +1,241 @@
+use bdk_chain::bitcoin::{Address, OutPoint, Txid};
+use bdk_chain::{bitcoin::Network, TxHeight};
+use bdk_esplora::esplora_client;
+use bdk_esplora::EsploraExt;
+
+use std::io::{self, Write};
+
+use keychain_tracker_example_cli::{
+    self as cli,
+    anyhow::{self, Context},
+    clap::{self, Parser, Subcommand},
+};
+
+#[derive(Subcommand, Debug, Clone)]
+enum EsploraCommands {
+    /// Scans the addresses in the wallet using the esplora API.
+    Scan {
+        /// When a gap this large has been found for a keychain, it will stop.
+        #[clap(long, default_value = "5")]
+        stop_gap: usize,
+
+        #[clap(flatten)]
+        scan_options: ScanOptions,
+    },
+    /// Scans particular addresses using esplora API.
+    Sync {
+        /// Scan all the unused addresses.
+        #[clap(long)]
+        unused_spks: bool,
+        /// Scan every address that you have derived.
+        #[clap(long)]
+        all_spks: bool,
+        /// Scan unspent outpoints for spends or changes to confirmation status of residing tx.
+        #[clap(long)]
+        utxos: bool,
+        /// Scan unconfirmed transactions for updates.
+        #[clap(long)]
+        unconfirmed: bool,
+
+        #[clap(flatten)]
+        scan_options: ScanOptions,
+    },
+}
+
+#[derive(Parser, Debug, Clone, PartialEq)]
+pub struct ScanOptions {
+    #[clap(long, default_value = "5")]
+    pub parallel_requests: usize,
+}
+
+fn main() -> anyhow::Result<()> {
+    let (args, keymap, keychain_tracker, db) = cli::init::<EsploraCommands, _>()?;
+    let esplora_url = match args.network {
+        Network::Bitcoin => "https://mempool.space/api",
+        Network::Testnet => "https://mempool.space/testnet/api",
+        Network::Regtest => "http://localhost:3002",
+        Network::Signet => "https://mempool.space/signet/api",
+    };
+
+    let client = esplora_client::Builder::new(esplora_url).build_blocking()?;
+
+    let esplora_cmd = match args.command {
+        cli::Commands::ChainSpecific(esplora_cmd) => esplora_cmd,
+        general_command => {
+            return cli::handle_commands(
+                general_command,
+                |transaction| Ok(client.broadcast(transaction)?),
+                &keychain_tracker,
+                &db,
+                args.network,
+                &keymap,
+            )
+        }
+    };
+
+    match esplora_cmd {
+        EsploraCommands::Scan {
+            stop_gap,
+            scan_options,
+        } => {
+            let (spk_iterators, local_chain) = {
+                // Get a short lock on the tracker to get the spks iterators
+                // and local chain state
+                let tracker = &*keychain_tracker.lock().unwrap();
+                let spk_iterators = tracker
+                    .txout_index
+                    .spks_of_all_keychains()
+                    .into_iter()
+                    .map(|(keychain, iter)| {
+                        let mut first = true;
+                        (
+                            keychain,
+                            iter.inspect(move |(i, _)| {
+                                if first {
+                                    eprint!("\nscanning {}: ", keychain);
+                                    first = false;
+                                }
+
+                                eprint!("{} ", i);
+                                let _ = io::stdout().flush();
+                            }),
+                        )
+                    })
+                    .collect();
+
+                let local_chain = tracker.chain().checkpoints().clone();
+                (spk_iterators, local_chain)
+            };
+
+            // we scan the iterators **without** a lock on the tracker
+            let wallet_scan = client
+                .scan(
+                    &local_chain,
+                    spk_iterators,
+                    core::iter::empty(),
+                    core::iter::empty(),
+                    stop_gap,
+                    scan_options.parallel_requests,
+                )
+                .context("scanning the blockchain")?;
+            eprintln!();
+
+            {
+                // we take a short lock to apply results to tracker and db
+                let tracker = &mut *keychain_tracker.lock().unwrap();
+                let db = &mut *db.lock().unwrap();
+                let changeset = tracker.apply_update(wallet_scan)?;
+                db.append_changeset(&changeset)?;
+            }
+        }
+        EsploraCommands::Sync {
+            mut unused_spks,
+            mut utxos,
+            mut unconfirmed,
+            all_spks,
+            scan_options,
+        } => {
+            // Get a short lock on the tracker to get the spks we're interested in
+            let tracker = keychain_tracker.lock().unwrap();
+
+            if !(all_spks || unused_spks || utxos || unconfirmed) {
+                unused_spks = true;
+                unconfirmed = true;
+                utxos = true;
+            } else if all_spks {
+                unused_spks = false;
+            }
+
+            let mut spks: Box<dyn Iterator<Item = bdk_chain::bitcoin::Script>> =
+                Box::new(core::iter::empty());
+            if all_spks {
+                let all_spks = tracker
+                    .txout_index
+                    .all_spks()
+                    .iter()
+                    .map(|(k, v)| (*k, v.clone()))
+                    .collect::<Vec<_>>();
+                spks = Box::new(spks.chain(all_spks.into_iter().map(|(index, script)| {
+                    eprintln!("scanning {:?}", index);
+                    script
+                })));
+            }
+            if unused_spks {
+                let unused_spks = tracker
+                    .txout_index
+                    .unused_spks(..)
+                    .map(|(k, v)| (*k, v.clone()))
+                    .collect::<Vec<_>>();
+                spks = Box::new(spks.chain(unused_spks.into_iter().map(|(index, script)| {
+                    eprintln!(
+                        "Checking if address {} {:?} has been used",
+                        Address::from_script(&script, args.network).unwrap(),
+                        index
+                    );
+
+                    script
+                })));
+            }
+
+            let mut outpoints: Box<dyn Iterator<Item = OutPoint>> = Box::new(core::iter::empty());
+
+            if utxos {
+                let utxos = tracker
+                    .full_utxos()
+                    .map(|(_, utxo)| utxo)
+                    .collect::<Vec<_>>();
+                outpoints = Box::new(
+                    utxos
+                        .into_iter()
+                        .inspect(|utxo| {
+                            eprintln!(
+                                "Checking if outpoint {} (value: {}) has been spent",
+                                utxo.outpoint, utxo.txout.value
+                            );
+                        })
+                        .map(|utxo| utxo.outpoint),
+                );
+            };
+
+            let mut txids: Box<dyn Iterator<Item = Txid>> = Box::new(core::iter::empty());
+
+            if unconfirmed {
+                let unconfirmed_txids = tracker
+                    .chain()
+                    .range_txids_by_height(TxHeight::Unconfirmed..)
+                    .map(|(_, txid)| *txid)
+                    .collect::<Vec<_>>();
+
+                txids = Box::new(unconfirmed_txids.into_iter().inspect(|txid| {
+                    eprintln!("Checking if {} is confirmed yet", txid);
+                }));
+            }
+
+            let local_chain = tracker.chain().checkpoints().clone();
+
+            // drop lock on tracker
+            drop(tracker);
+
+            // we scan the desired spks **without** a lock on the tracker
+            let scan = client
+                .scan_without_keychain(
+                    &local_chain,
+                    spks,
+                    txids,
+                    outpoints,
+                    scan_options.parallel_requests,
+                )
+                .context("scanning the blockchain")?;
+
+            {
+                // we take a short lock to apply the results to the tracker and db
+                let tracker = &mut *keychain_tracker.lock().unwrap();
+                let changeset = tracker.apply_update(scan.into())?;
+                let db = &mut *db.lock().unwrap();
+                db.append_changeset(&changeset)?;
+            }
+        }
+    }
+
+    Ok(())
+}

example-crates/keychain_tracker_example_cli/.gitignore

@@ -0,0 +1 @@
+/target

example-crates/keychain_tracker_example_cli/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "keychain_tracker_example_cli"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[dependencies]
+bdk_chain = { path = "../../crates/chain", features = ["serde", "miniscript"]}
+bdk_file_store = { path = "../../crates/file_store" }
+bdk_tmp_plan = { path = "../../nursery/tmp_plan" }
+bdk_coin_select = { path = "../../nursery/coin_select" }
+
+clap = { version = "3.2.23", features = ["derive", "env"] }
+anyhow = "1"
+serde = { version = "1", features = ["derive"] }
+serde_json = { version = "^1.0" }

example-crates/keychain_tracker_example_cli/README.md

@@ -0,0 +1 @@
+Provides common command line processing logic between examples using the `KeychainTracker`

example-crates/keychain_tracker_example_cli/src/lib.rs

@@ -0,0 +1,692 @@
+pub extern crate anyhow;
+use anyhow::{anyhow, Context, Result};
+use bdk_chain::{
+    bitcoin::{
+        secp256k1::Secp256k1,
+        util::sighash::{Prevouts, SighashCache},
+        Address, LockTime, Network, Sequence, Transaction, TxIn, TxOut,
+    },
+    chain_graph::InsertTxError,
+    keychain::{DerivationAdditions, KeychainChangeSet, KeychainTracker},
+    miniscript::{
+        descriptor::{DescriptorSecretKey, KeyMap},
+        Descriptor, DescriptorPublicKey,
+    },
+    sparse_chain::{self, ChainPosition},
+    DescriptorExt, FullTxOut,
+};
+use bdk_coin_select::{coin_select_bnb, CoinSelector, CoinSelectorOpt, WeightedValue};
+use bdk_file_store::KeychainStore;
+use clap::{Parser, Subcommand};
+use std::{
+    cmp::Reverse, collections::HashMap, fmt::Debug, path::PathBuf, sync::Mutex, time::Duration,
+};
+
+pub use bdk_file_store;
+pub use clap;
+
+#[derive(Parser)]
+#[clap(author, version, about, long_about = None)]
+#[clap(propagate_version = true)]
+pub struct Args<C: clap::Subcommand> {
+    #[clap(env = "DESCRIPTOR")]
+    pub descriptor: String,
+    #[clap(env = "CHANGE_DESCRIPTOR")]
+    pub change_descriptor: Option<String>,
+
+    #[clap(env = "BITCOIN_NETWORK", long, default_value = "signet")]
+    pub network: Network,
+
+    #[clap(env = "BDK_DB_PATH", long, default_value = ".bdk_example_db")]
+    pub db_path: PathBuf,
+
+    #[clap(env = "BDK_CP_LIMIT", long, default_value = "20")]
+    pub cp_limit: usize,
+
+    #[clap(subcommand)]
+    pub command: Commands<C>,
+}
+
+#[derive(Subcommand, Debug, Clone)]
+pub enum Commands<C: clap::Subcommand> {
+    #[clap(flatten)]
+    ChainSpecific(C),
+    /// Address generation and inspection.
+    Address {
+        #[clap(subcommand)]
+        addr_cmd: AddressCmd,
+    },
+    /// Get the wallet balance.
+    Balance,
+    /// TxOut related commands.
+    #[clap(name = "txout")]
+    TxOut {
+        #[clap(subcommand)]
+        txout_cmd: TxOutCmd,
+    },
+    /// Send coins to an address.
+    Send {
+        value: u64,
+        address: Address,
+        #[clap(short, default_value = "largest-first")]
+        coin_select: CoinSelectionAlgo,
+    },
+}
+
+#[derive(Clone, Debug)]
+pub enum CoinSelectionAlgo {
+    LargestFirst,
+    SmallestFirst,
+    OldestFirst,
+    NewestFirst,
+    BranchAndBound,
+}
+
+impl Default for CoinSelectionAlgo {
+    fn default() -> Self {
+        Self::LargestFirst
+    }
+}
+
+impl core::str::FromStr for CoinSelectionAlgo {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        use CoinSelectionAlgo::*;
+        Ok(match s {
+            "largest-first" => LargestFirst,
+            "smallest-first" => SmallestFirst,
+            "oldest-first" => OldestFirst,
+            "newest-first" => NewestFirst,
+            "bnb" => BranchAndBound,
+            unknown => return Err(anyhow!("unknown coin selection algorithm '{}'", unknown)),
+        })
+    }
+}
+
+impl core::fmt::Display for CoinSelectionAlgo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        use CoinSelectionAlgo::*;
+        write!(
+            f,
+            "{}",
+            match self {
+                LargestFirst => "largest-first",
+                SmallestFirst => "smallest-first",
+                OldestFirst => "oldest-first",
+                NewestFirst => "newest-first",
+                BranchAndBound => "bnb",
+            }
+        )
+    }
+}
+
+#[derive(Subcommand, Debug, Clone)]
+pub enum AddressCmd {
+    /// Get the next unused address.
+    Next,
+    /// Get a new address regardless of the existing unused addresses.
+    New,
+    /// List all addresses
+    List {
+        #[clap(long)]
+        change: bool,
+    },
+    Index,
+}
+
+#[derive(Subcommand, Debug, Clone)]
+pub enum TxOutCmd {
+    List {
+        /// Return only spent outputs.
+        #[clap(short, long)]
+        spent: bool,
+        /// Return only unspent outputs.
+        #[clap(short, long)]
+        unspent: bool,
+        /// Return only confirmed outputs.
+        #[clap(long)]
+        confirmed: bool,
+        /// Return only unconfirmed outputs.
+        #[clap(long)]
+        unconfirmed: bool,
+    },
+}
+
+#[derive(
+    Debug, Clone, Copy, PartialOrd, Ord, PartialEq, Eq, serde::Deserialize, serde::Serialize,
+)]
+pub enum Keychain {
+    External,
+    Internal,
+}
+
+impl core::fmt::Display for Keychain {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Keychain::External => write!(f, "external"),
+            Keychain::Internal => write!(f, "internal"),
+        }
+    }
+}
+
+/// A structure defining the output of an [`AddressCmd`]` execution.
+#[derive(serde::Serialize, serde::Deserialize)]
+pub struct AddrsOutput {
+    keychain: String,
+    index: u32,
+    addrs: Address,
+    used: bool,
+}
+
+pub fn run_address_cmd<P>(
+    tracker: &Mutex<KeychainTracker<Keychain, P>>,
+    db: &Mutex<KeychainStore<Keychain, P>>,
+    addr_cmd: AddressCmd,
+    network: Network,
+) -> Result<()>
+where
+    P: bdk_chain::sparse_chain::ChainPosition,
+    KeychainChangeSet<Keychain, P>: serde::Serialize + serde::de::DeserializeOwned,
+{
+    let mut tracker = tracker.lock().unwrap();
+    let txout_index = &mut tracker.txout_index;
+
+    let addr_cmmd_output = match addr_cmd {
+        AddressCmd::Next => Some(txout_index.next_unused_spk(&Keychain::External)),
+        AddressCmd::New => Some(txout_index.reveal_next_spk(&Keychain::External)),
+        _ => None,
+    };
+
+    if let Some(((index, spk), additions)) = addr_cmmd_output {
+        let mut db = db.lock().unwrap();
+        // update database since we're about to give out a new address
+        db.append_changeset(&additions.into())?;
+
+        let spk = spk.clone();
+        let address =
+            Address::from_script(&spk, network).expect("should always be able to derive address");
+        eprintln!("This is the address at index {}", index);
+        println!("{}", address);
+    }
+
+    match addr_cmd {
+        AddressCmd::Next | AddressCmd::New => {
+            /* covered */
+            Ok(())
+        }
+        AddressCmd::Index => {
+            for (keychain, derivation_index) in txout_index.last_revealed_indices() {
+                println!("{:?}: {}", keychain, derivation_index);
+            }
+            Ok(())
+        }
+        AddressCmd::List { change } => {
+            let target_keychain = match change {
+                true => Keychain::Internal,
+                false => Keychain::External,
+            };
+            for (index, spk) in txout_index.revealed_spks_of_keychain(&target_keychain) {
+                let address = Address::from_script(spk, network)
+                    .expect("should always be able to derive address");
+                println!(
+                    "{:?} {} used:{}",
+                    index,
+                    address,
+                    txout_index.is_used(&(target_keychain, index))
+                );
+            }
+            Ok(())
+        }
+    }
+}
+
+pub fn run_balance_cmd<P: ChainPosition>(tracker: &Mutex<KeychainTracker<Keychain, P>>) {
+    let tracker = tracker.lock().unwrap();
+    let (confirmed, unconfirmed) =
+        tracker
+            .full_utxos()
+            .fold((0, 0), |(confirmed, unconfirmed), (_, utxo)| {
+                if utxo.chain_position.height().is_confirmed() {
+                    (confirmed + utxo.txout.value, unconfirmed)
+                } else {
+                    (confirmed, unconfirmed + utxo.txout.value)
+                }
+            });
+
+    println!("confirmed: {}", confirmed);
+    println!("unconfirmed: {}", unconfirmed);
+}
+
+pub fn run_txo_cmd<K: Debug + Clone + Ord, P: ChainPosition>(
+    txout_cmd: TxOutCmd,
+    tracker: &Mutex<KeychainTracker<K, P>>,
+    network: Network,
+) {
+    match txout_cmd {
+        TxOutCmd::List {
+            unspent,
+            spent,
+            confirmed,
+            unconfirmed,
+        } => {
+            let tracker = tracker.lock().unwrap();
+            #[allow(clippy::type_complexity)] // FIXME
+            let txouts: Box<dyn Iterator<Item = (&(K, u32), FullTxOut<P>)>> = match (unspent, spent)
+            {
+                (true, false) => Box::new(tracker.full_utxos()),
+                (false, true) => Box::new(
+                    tracker
+                        .full_txouts()
+                        .filter(|(_, txout)| txout.spent_by.is_some()),
+                ),
+                _ => Box::new(tracker.full_txouts()),
+            };
+
+            #[allow(clippy::type_complexity)] // FIXME
+            let txouts: Box<dyn Iterator<Item = (&(K, u32), FullTxOut<P>)>> =
+                match (confirmed, unconfirmed) {
+                    (true, false) => Box::new(
+                        txouts.filter(|(_, txout)| txout.chain_position.height().is_confirmed()),
+                    ),
+                    (false, true) => Box::new(
+                        txouts.filter(|(_, txout)| !txout.chain_position.height().is_confirmed()),
+                    ),
+                    _ => txouts,
+                };
+
+            for (spk_index, full_txout) in txouts {
+                let address =
+                    Address::from_script(&full_txout.txout.script_pubkey, network).unwrap();
+
+                println!(
+                    "{:?} {} {} {} spent:{:?}",
+                    spk_index,
+                    full_txout.txout.value,
+                    full_txout.outpoint,
+                    address,
+                    full_txout.spent_by
+                )
+            }
+        }
+    }
+}
+
+#[allow(clippy::type_complexity)] // FIXME
+pub fn create_tx<P: ChainPosition>(
+    value: u64,
+    address: Address,
+    coin_select: CoinSelectionAlgo,
+    keychain_tracker: &mut KeychainTracker<Keychain, P>,
+    keymap: &HashMap<DescriptorPublicKey, DescriptorSecretKey>,
+) -> Result<(
+    Transaction,
+    Option<(DerivationAdditions<Keychain>, (Keychain, u32))>,
+)> {
+    let mut additions = DerivationAdditions::default();
+
+    let assets = bdk_tmp_plan::Assets {
+        keys: keymap.iter().map(|(pk, _)| pk.clone()).collect(),
+        ..Default::default()
+    };
+
+    // TODO use planning module
+    let mut candidates = planned_utxos(keychain_tracker, &assets).collect::<Vec<_>>();
+
+    // apply coin selection algorithm
+    match coin_select {
+        CoinSelectionAlgo::LargestFirst => {
+            candidates.sort_by_key(|(_, utxo)| Reverse(utxo.txout.value))
+        }
+        CoinSelectionAlgo::SmallestFirst => candidates.sort_by_key(|(_, utxo)| utxo.txout.value),
+        CoinSelectionAlgo::OldestFirst => {
+            candidates.sort_by_key(|(_, utxo)| utxo.chain_position.clone())
+        }
+        CoinSelectionAlgo::NewestFirst => {
+            candidates.sort_by_key(|(_, utxo)| Reverse(utxo.chain_position.clone()))
+        }
+        CoinSelectionAlgo::BranchAndBound => {}
+    }
+
+    // turn the txos we chose into weight and value
+    let wv_candidates = candidates
+        .iter()
+        .map(|(plan, utxo)| {
+            WeightedValue::new(
+                utxo.txout.value,
+                plan.expected_weight() as _,
+                plan.witness_version().is_some(),
+            )
+        })
+        .collect();
+
+    let mut outputs = vec![TxOut {
+        value,
+        script_pubkey: address.script_pubkey(),
+    }];
+
+    let internal_keychain = if keychain_tracker
+        .txout_index
+        .keychains()
+        .get(&Keychain::Internal)
+        .is_some()
+    {
+        Keychain::Internal
+    } else {
+        Keychain::External
+    };
+
+    let ((change_index, change_script), change_additions) = keychain_tracker
+        .txout_index
+        .next_unused_spk(&internal_keychain);
+    additions.append(change_additions);
+
+    // Clone to drop the immutable reference.
+    let change_script = change_script.clone();
+
+    let change_plan = bdk_tmp_plan::plan_satisfaction(
+        &keychain_tracker
+            .txout_index
+            .keychains()
+            .get(&internal_keychain)
+            .expect("must exist")
+            .at_derivation_index(change_index),
+        &assets,
+    )
+    .expect("failed to obtain change plan");
+
+    let mut change_output = TxOut {
+        value: 0,
+        script_pubkey: change_script,
+    };
+
+    let cs_opts = CoinSelectorOpt {
+        target_feerate: 0.5,
+        min_drain_value: keychain_tracker
+            .txout_index
+            .keychains()
+            .get(&internal_keychain)
+            .expect("must exist")
+            .dust_value(),
+        ..CoinSelectorOpt::fund_outputs(
+            &outputs,
+            &change_output,
+            change_plan.expected_weight() as u32,
+        )
+    };
+
+    // TODO: How can we make it easy to shuffle in order of inputs and outputs here?
+    // apply coin selection by saying we need to fund these outputs
+    let mut coin_selector = CoinSelector::new(&wv_candidates, &cs_opts);
+
+    // just select coins in the order provided until we have enough
+    // only use the first result (least waste)
+    let selection = match coin_select {
+        CoinSelectionAlgo::BranchAndBound => {
+            coin_select_bnb(Duration::from_secs(10), coin_selector.clone())
+                .map_or_else(|| coin_selector.select_until_finished(), |cs| cs.finish())?
+        }
+        _ => coin_selector.select_until_finished()?,
+    };
+    let (_, selection_meta) = selection.best_strategy();
+
+    // get the selected utxos
+    let selected_txos = selection.apply_selection(&candidates).collect::<Vec<_>>();
+
+    if let Some(drain_value) = selection_meta.drain_value {
+        change_output.value = drain_value;
+        // if the selection tells us to use change and the change value is sufficient, we add it as an output
+        outputs.push(change_output)
+    }
+
+    let mut transaction = Transaction {
+        version: 0x02,
+        lock_time: keychain_tracker
+            .chain()
+            .latest_checkpoint()
+            .and_then(|block_id| LockTime::from_height(block_id.height).ok())
+            .unwrap_or(LockTime::ZERO)
+            .into(),
+        input: selected_txos
+            .iter()
+            .map(|(_, utxo)| TxIn {
+                previous_output: utxo.outpoint,
+                sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
+                ..Default::default()
+            })
+            .collect(),
+        output: outputs,
+    };
+
+    let prevouts = selected_txos
+        .iter()
+        .map(|(_, utxo)| utxo.txout.clone())
+        .collect::<Vec<_>>();
+    let sighash_prevouts = Prevouts::All(&prevouts);
+
+    // first, set tx values for the plan so that we don't change them while signing
+    for (i, (plan, _)) in selected_txos.iter().enumerate() {
+        if let Some(sequence) = plan.required_sequence() {
+            transaction.input[i].sequence = sequence
+        }
+    }
+
+    // create a short lived transaction
+    let _sighash_tx = transaction.clone();
+    let mut sighash_cache = SighashCache::new(&_sighash_tx);
+
+    for (i, (plan, _)) in selected_txos.iter().enumerate() {
+        let requirements = plan.requirements();
+        let mut auth_data = bdk_tmp_plan::SatisfactionMaterial::default();
+        assert!(
+            !requirements.requires_hash_preimages(),
+            "can't have hash pre-images since we didn't provide any."
+        );
+        assert!(
+            requirements.signatures.sign_with_keymap(
+                i,
+                keymap,
+                &sighash_prevouts,
+                None,
+                None,
+                &mut sighash_cache,
+                &mut auth_data,
+                &Secp256k1::default(),
+            )?,
+            "we should have signed with this input."
+        );
+
+        match plan.try_complete(&auth_data) {
+            bdk_tmp_plan::PlanState::Complete {
+                final_script_sig,
+                final_script_witness,
+            } => {
+                if let Some(witness) = final_script_witness {
+                    transaction.input[i].witness = witness;
+                }
+
+                if let Some(script_sig) = final_script_sig {
+                    transaction.input[i].script_sig = script_sig;
+                }
+            }
+            bdk_tmp_plan::PlanState::Incomplete(_) => {
+                return Err(anyhow!(
+                    "we weren't able to complete the plan with our keys."
+                ));
+            }
+        }
+    }
+
+    let change_info = if selection_meta.drain_value.is_some() {
+        Some((additions, (internal_keychain, change_index)))
+    } else {
+        None
+    };
+
+    Ok((transaction, change_info))
+}
+
+pub fn handle_commands<C: clap::Subcommand, P>(
+    command: Commands<C>,
+    broadcast: impl FnOnce(&Transaction) -> Result<()>,
+    // we Mutex around these not because we need them for a simple CLI app but to demonstrate how
+    // all the stuff we're doing can be made thread-safe and not keep locks up over an IO bound.
+    tracker: &Mutex<KeychainTracker<Keychain, P>>,
+    store: &Mutex<KeychainStore<Keychain, P>>,
+    network: Network,
+    keymap: &HashMap<DescriptorPublicKey, DescriptorSecretKey>,
+) -> Result<()>
+where
+    P: ChainPosition,
+    KeychainChangeSet<Keychain, P>: serde::Serialize + serde::de::DeserializeOwned,
+{
+    match command {
+        // TODO: Make these functions return stuffs
+        Commands::Address { addr_cmd } => run_address_cmd(tracker, store, addr_cmd, network),
+        Commands::Balance => {
+            run_balance_cmd(tracker);
+            Ok(())
+        }
+        Commands::TxOut { txout_cmd } => {
+            run_txo_cmd(txout_cmd, tracker, network);
+            Ok(())
+        }
+        Commands::Send {
+            value,
+            address,
+            coin_select,
+        } => {
+            let (transaction, change_index) = {
+                // take mutable ref to construct tx -- it is only open for a short time while building it.
+                let tracker = &mut *tracker.lock().unwrap();
+                let (transaction, change_info) =
+                    create_tx(value, address, coin_select, tracker, keymap)?;
+
+                if let Some((change_derivation_changes, (change_keychain, index))) = change_info {
+                    // We must first persist to disk the fact that we've got a new address from the
+                    // change keychain so future scans will find the tx we're about to broadcast.
+                    // If we're unable to persist this, then we don't want to broadcast.
+                    let store = &mut *store.lock().unwrap();
+                    store.append_changeset(&change_derivation_changes.into())?;
+
+                    // We don't want other callers/threads to use this address while we're using it
+                    // but we also don't want to scan the tx we just created because it's not
+                    // technically in the blockchain yet.
+                    tracker.txout_index.mark_used(&change_keychain, index);
+                    (transaction, Some((change_keychain, index)))
+                } else {
+                    (transaction, None)
+                }
+            };
+
+            match (broadcast)(&transaction) {
+                Ok(_) => {
+                    println!("Broadcasted Tx : {}", transaction.txid());
+                    let mut tracker = tracker.lock().unwrap();
+                    match tracker.insert_tx(transaction.clone(), P::unconfirmed()) {
+                        Ok(changeset) => {
+                            let store = &mut *store.lock().unwrap();
+                            // We know the tx is at least unconfirmed now. Note if persisting here fails,
+                            // it's not a big deal since we can always find it again form
+                            // blockchain.
+                            store.append_changeset(&changeset)?;
+                            Ok(())
+                        }
+                        Err(e) => match e {
+                            InsertTxError::Chain(e) => match e {
+                                // TODO: add insert_unconfirmed_tx to the chaingraph and sparsechain
+                                sparse_chain::InsertTxError::TxTooHigh { .. } => unreachable!("we are inserting at unconfirmed position"),
+                                sparse_chain::InsertTxError::TxMovedUnexpectedly { txid, original_pos, ..} => Err(anyhow!("the tx we created {} has already been confirmed at block {:?}", txid, original_pos)),
+                            },
+                            InsertTxError::UnresolvableConflict(e) => Err(e).context("another tx that conflicts with the one we tried to create has been confirmed"),
+                        }
+                    }
+                }
+                Err(e) => {
+                    let tracker = &mut *tracker.lock().unwrap();
+                    if let Some((keychain, index)) = change_index {
+                        // We failed to broadcast, so allow our change address to be used in the future
+                        tracker.txout_index.unmark_used(&keychain, index);
+                    }
+                    Err(e)
+                }
+            }
+        }
+        Commands::ChainSpecific(_) => {
+            todo!("example code is meant to handle this!")
+        }
+    }
+}
+
+#[allow(clippy::type_complexity)] // FIXME
+pub fn init<C: clap::Subcommand, P>() -> anyhow::Result<(
+    Args<C>,
+    KeyMap,
+    // These don't need to have mutexes around them, but we want the cli example code to make it obvious how they
+    // are thread-safe, forcing the example developers to show where they would lock and unlock things.
+    Mutex<KeychainTracker<Keychain, P>>,
+    Mutex<KeychainStore<Keychain, P>>,
+)>
+where
+    P: sparse_chain::ChainPosition,
+    KeychainChangeSet<Keychain, P>: serde::Serialize + serde::de::DeserializeOwned,
+{
+    let args = Args::<C>::parse();
+    let secp = Secp256k1::default();
+    let (descriptor, mut keymap) =
+        Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, &args.descriptor)?;
+
+    let mut tracker = KeychainTracker::default();
+    tracker.set_checkpoint_limit(Some(args.cp_limit));
+
+    tracker
+        .txout_index
+        .add_keychain(Keychain::External, descriptor);
+
+    let internal = args
+        .change_descriptor
+        .clone()
+        .map(|descriptor| Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, &descriptor))
+        .transpose()?;
+    if let Some((internal_descriptor, internal_keymap)) = internal {
+        keymap.extend(internal_keymap);
+        tracker
+            .txout_index
+            .add_keychain(Keychain::Internal, internal_descriptor);
+    };
+
+    let mut db = KeychainStore::<Keychain, P>::new_from_path(args.db_path.as_path())?;
+
+    if let Err(e) = db.load_into_keychain_tracker(&mut tracker) {
+        match tracker.chain().latest_checkpoint()  {
+            Some(checkpoint) => eprintln!("Failed to load all changesets from {}. Last checkpoint was at height {}. Error: {}", args.db_path.display(), checkpoint.height, e),
+            None => eprintln!("Failed to load any checkpoints from {}: {}", args.db_path.display(), e),
+
+        }
+        eprintln!("⚠ Consider running a rescan of chain data.");
+    }
+
+    Ok((args, keymap, Mutex::new(tracker), Mutex::new(db)))
+}
+
+pub fn planned_utxos<'a, AK: bdk_tmp_plan::CanDerive + Clone, P: ChainPosition>(
+    tracker: &'a KeychainTracker<Keychain, P>,
+    assets: &'a bdk_tmp_plan::Assets<AK>,
+) -> impl Iterator<Item = (bdk_tmp_plan::Plan<AK>, FullTxOut<P>)> + 'a {
+    tracker
+        .full_utxos()
+        .filter_map(move |((keychain, derivation_index), full_txout)| {
+            Some((
+                bdk_tmp_plan::plan_satisfaction(
+                    &tracker
+                        .txout_index
+                        .keychains()
+                        .get(keychain)
+                        .expect("must exist since we have a utxo for it")
+                        .at_derivation_index(*derivation_index),
+                    assets,
+                )?,
+                full_txout,
+            ))
+        })
+}

example-crates/wallet_electrum/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "wallet_electrum_example"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+bdk = { path = "../../crates/bdk" }
+bdk_electrum = { path = "../../crates/electrum" }
+bdk_file_store = { path = "../../crates/file_store" }

example-crates/wallet_electrum/src/main.rs

@@ -0,0 +1,104 @@
+use std::{io::Write, str::FromStr};
+
+use bdk::{
+    bitcoin::{Address, Network},
+    SignOptions, Wallet,
+};
+use bdk_electrum::{
+    electrum_client::{self, ElectrumApi},
+    ElectrumExt,
+};
+use bdk_file_store::KeychainStore;
+
+const SEND_AMOUNT: u64 = 5000;
+const STOP_GAP: usize = 50;
+const BATCH_SIZE: usize = 5;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("Hello, world!");
+
+    let db_path = std::env::temp_dir().join("bdk-electrum-example");
+    let db = KeychainStore::new_from_path(db_path)?;
+    let external_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/0/*)";
+    let internal_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/1/*)";
+
+    let mut wallet = Wallet::new(
+        external_descriptor,
+        Some(internal_descriptor),
+        db,
+        Network::Testnet,
+    )?;
+
+    let address = wallet.get_address(bdk::wallet::AddressIndex::New);
+    println!("Generated Address: {}", address);
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance before syncing: {} sats", balance.total());
+
+    print!("Syncing...");
+    // Scanning the chain...
+    let electrum_url = "ssl://electrum.blockstream.info:60002";
+    let client = electrum_client::Client::new(electrum_url)?;
+    let local_chain = wallet.checkpoints();
+    let spks = wallet
+        .spks_of_all_keychains()
+        .into_iter()
+        .map(|(k, spks)| {
+            let mut first = true;
+            (
+                k,
+                spks.inspect(move |(spk_i, _)| {
+                    if first {
+                        first = false;
+                        print!("\nScanning keychain [{:?}]:", k);
+                    }
+                    print!(" {}", spk_i);
+                    let _ = std::io::stdout().flush();
+                }),
+            )
+        })
+        .collect();
+    let electrum_update = client
+        .scan(
+            local_chain,
+            spks,
+            core::iter::empty(),
+            core::iter::empty(),
+            STOP_GAP,
+            BATCH_SIZE,
+        )?
+        .into_confirmation_time_update(&client)?;
+    println!();
+    let new_txs = client.batch_transaction_get(electrum_update.missing_full_txs(&wallet))?;
+    let update = electrum_update.into_keychain_scan(new_txs, &wallet)?;
+    wallet.apply_update(update)?;
+    wallet.commit()?;
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance after syncing: {} sats", balance.total());
+
+    if balance.total() < SEND_AMOUNT {
+        println!(
+            "Please send at least {} sats to the receiving address",
+            SEND_AMOUNT
+        );
+        std::process::exit(0);
+    }
+
+    let faucet_address = Address::from_str("mkHS9ne12qx9pS9VojpwU5xtRd4T7X7ZUt")?;
+
+    let mut tx_builder = wallet.build_tx();
+    tx_builder
+        .add_recipient(faucet_address.script_pubkey(), SEND_AMOUNT)
+        .enable_rbf();
+
+    let (mut psbt, _) = tx_builder.finish()?;
+    let finalized = wallet.sign(&mut psbt, SignOptions::default())?;
+    assert!(finalized);
+
+    let tx = psbt.extract_tx();
+    client.transaction_broadcast(&tx)?;
+    println!("Tx broadcasted! Txid: {}", tx.txid());
+
+    Ok(())
+}

example-crates/wallet_esplora/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "bdk-esplora-wallet-example"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk = { path = "../../crates/bdk" }
+bdk_esplora = { path = "../../crates/esplora", features = ["blocking"] }
+bdk_file_store = { path = "../../crates/file_store" }

example-crates/wallet_esplora/src/main.rs

@@ -0,0 +1,96 @@
+use bdk::{
+    bitcoin::{Address, Network},
+    wallet::AddressIndex,
+    SignOptions, Wallet,
+};
+use bdk_esplora::esplora_client;
+use bdk_esplora::EsploraExt;
+use bdk_file_store::KeychainStore;
+use std::{io::Write, str::FromStr};
+
+const SEND_AMOUNT: u64 = 5000;
+const STOP_GAP: usize = 50;
+const PARALLEL_REQUESTS: usize = 5;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let db_path = std::env::temp_dir().join("bdk-esplora-example");
+    let db = KeychainStore::new_from_path(db_path)?;
+    let external_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/0/*)";
+    let internal_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/1/*)";
+
+    let mut wallet = Wallet::new(
+        external_descriptor,
+        Some(internal_descriptor),
+        db,
+        Network::Testnet,
+    )?;
+
+    let address = wallet.get_address(AddressIndex::New);
+    println!("Generated Address: {}", address);
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance before syncing: {} sats", balance.total());
+
+    print!("Syncing...");
+    // Scanning the chain...
+    let esplora_url = "https://mempool.space/testnet/api";
+    let client = esplora_client::Builder::new(esplora_url).build_blocking()?;
+    let checkpoints = wallet.checkpoints();
+    let spks = wallet
+        .spks_of_all_keychains()
+        .into_iter()
+        .map(|(k, spks)| {
+            let mut first = true;
+            (
+                k,
+                spks.inspect(move |(spk_i, _)| {
+                    if first {
+                        first = false;
+                        print!("\nScanning keychain [{:?}]:", k);
+                    }
+                    print!(" {}", spk_i);
+                    let _ = std::io::stdout().flush();
+                }),
+            )
+        })
+        .collect();
+    let update = client.scan(
+        checkpoints,
+        spks,
+        core::iter::empty(),
+        core::iter::empty(),
+        STOP_GAP,
+        PARALLEL_REQUESTS,
+    )?;
+    println!();
+    wallet.apply_update(update)?;
+    wallet.commit()?;
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance after syncing: {} sats", balance.total());
+
+    if balance.total() < SEND_AMOUNT {
+        println!(
+            "Please send at least {} sats to the receiving address",
+            SEND_AMOUNT
+        );
+        std::process::exit(0);
+    }
+
+    let faucet_address = Address::from_str("mkHS9ne12qx9pS9VojpwU5xtRd4T7X7ZUt")?;
+
+    let mut tx_builder = wallet.build_tx();
+    tx_builder
+        .add_recipient(faucet_address.script_pubkey(), SEND_AMOUNT)
+        .enable_rbf();
+
+    let (mut psbt, _) = tx_builder.finish()?;
+    let finalized = wallet.sign(&mut psbt, SignOptions::default())?;
+    assert!(finalized);
+
+    let tx = psbt.extract_tx();
+    client.broadcast(&tx)?;
+    println!("Tx broadcasted! Txid: {}", tx.txid());
+
+    Ok(())
+}

example-crates/wallet_esplora_async/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "wallet_esplora_async"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk = { path = "../../crates/bdk" }
+bdk_esplora = { path = "../../crates/esplora", features = ["async-https"] }
+bdk_file_store = { path = "../../crates/file_store" }
+tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros"] }

example-crates/wallet_esplora_async/src/main.rs

@@ -0,0 +1,99 @@
+use std::{io::Write, str::FromStr};
+
+use bdk::{
+    bitcoin::{Address, Network},
+    wallet::AddressIndex,
+    SignOptions, Wallet,
+};
+use bdk_esplora::{esplora_client, EsploraAsyncExt};
+use bdk_file_store::KeychainStore;
+
+const SEND_AMOUNT: u64 = 5000;
+const STOP_GAP: usize = 50;
+const PARALLEL_REQUESTS: usize = 5;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let db_path = std::env::temp_dir().join("bdk-esplora-example");
+    let db = KeychainStore::new_from_path(db_path)?;
+    let external_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/0/*)";
+    let internal_descriptor = "wpkh(tprv8ZgxMBicQKsPdy6LMhUtFHAgpocR8GC6QmwMSFpZs7h6Eziw3SpThFfczTDh5rW2krkqffa11UpX3XkeTTB2FvzZKWXqPY54Y6Rq4AQ5R8L/84'/0'/0'/1/*)";
+
+    let mut wallet = Wallet::new(
+        external_descriptor,
+        Some(internal_descriptor),
+        db,
+        Network::Testnet,
+    )?;
+
+    let address = wallet.get_address(AddressIndex::New);
+    println!("Generated Address: {}", address);
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance before syncing: {} sats", balance.total());
+
+    print!("Syncing...");
+    // Scanning the blockchain
+    let esplora_url = "https://mempool.space/testnet/api";
+    let client = esplora_client::Builder::new(esplora_url).build_async()?;
+    let checkpoints = wallet.checkpoints();
+    let spks = wallet
+        .spks_of_all_keychains()
+        .into_iter()
+        .map(|(k, spks)| {
+            let mut first = true;
+            (
+                k,
+                spks.inspect(move |(spk_i, _)| {
+                    if first {
+                        first = false;
+                        print!("\nScanning keychain [{:?}]:", k);
+                    }
+                    print!(" {}", spk_i);
+                    let _ = std::io::stdout().flush();
+                }),
+            )
+        })
+        .collect();
+    let update = client
+        .scan(
+            checkpoints,
+            spks,
+            std::iter::empty(),
+            std::iter::empty(),
+            STOP_GAP,
+            PARALLEL_REQUESTS,
+        )
+        .await?;
+    println!();
+    wallet.apply_update(update)?;
+    wallet.commit()?;
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance after syncing: {} sats", balance.total());
+
+    if balance.total() < SEND_AMOUNT {
+        println!(
+            "Please send at least {} sats to the receiving address",
+            SEND_AMOUNT
+        );
+        std::process::exit(0);
+    }
+
+    let faucet_address = Address::from_str("mkHS9ne12qx9pS9VojpwU5xtRd4T7X7ZUt")?;
+
+    let mut tx_builder = wallet.build_tx();
+    tx_builder
+        .add_recipient(faucet_address.script_pubkey(), SEND_AMOUNT)
+        .enable_rbf();
+
+    let (mut psbt, _) = tx_builder.finish()?;
+    let finalized = wallet.sign(&mut psbt, SignOptions::default())?;
+    assert!(finalized);
+
+    let tx = psbt.extract_tx();
+    client.broadcast(&tx).await?;
+    println!("Tx broadcasted! Txid: {}", tx.txid());
+
+    Ok(())
+}

examples/address_validator.rs

@@ -1,63 +0,0 @@
-// Bitcoin Dev Kit
-// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
-//
-// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
-//
-// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
-// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
-// You may not use this file except in accordance with one or both of these
-// licenses.
-
-use std::sync::Arc;
-
-use bdk::bitcoin;
-use bdk::database::MemoryDatabase;
-use bdk::descriptor::HdKeyPaths;
-#[allow(deprecated)]
-use bdk::wallet::address_validator::{AddressValidator, AddressValidatorError};
-use bdk::KeychainKind;
-use bdk::Wallet;
-
-use bdk::wallet::AddressIndex::New;
-use bitcoin::hashes::hex::FromHex;
-use bitcoin::util::bip32::Fingerprint;
-use bitcoin::{Network, Script};
-
-#[derive(Debug)]
-struct DummyValidator;
-#[allow(deprecated)]
-impl AddressValidator for DummyValidator {
-    fn validate(
-        &self,
-        keychain: KeychainKind,
-        hd_keypaths: &HdKeyPaths,
-        script: &Script,
-    ) -> Result<(), AddressValidatorError> {
-        let (_, path) = hd_keypaths
-            .values()
-            .find(|(fing, _)| fing == &Fingerprint::from_hex("bc123c3e").unwrap())
-            .ok_or(AddressValidatorError::InvalidScript)?;
-
-        println!(
-            "Validating `{:?}` {} address, script: {}",
-            keychain, path, script
-        );
-
-        Ok(())
-    }
-}
-
-fn main() -> Result<(), bdk::Error> {
-    let descriptor = "sh(and_v(v:pk(tpubDDpWvmUrPZrhSPmUzCMBHffvC3HyMAPnWDSAQNBTnj1iZeJa7BZQEttFiP4DS4GCcXQHezdXhn86Hj6LHX5EDstXPWrMaSneRWM8yUf6NFd/*),after(630000)))";
-    let mut wallet = Wallet::new(descriptor, None, Network::Regtest, MemoryDatabase::new())?;
-
-    #[allow(deprecated)]
-    wallet.add_address_validator(Arc::new(DummyValidator));
-
-    wallet.get_address(New)?;
-    wallet.get_address(New)?;
-    wallet.get_address(New)?;
-
-    Ok(())
-}

examples/compact_filters_balance.rs

@@ -1,41 +0,0 @@
-// Bitcoin Dev Kit
-// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
-//
-// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
-//
-// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
-// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
-// You may not use this file except in accordance with one or both of these
-// licenses.
-
-use bdk::blockchain::compact_filters::*;
-use bdk::database::MemoryDatabase;
-use bdk::*;
-use bitcoin::*;
-use blockchain::compact_filters::CompactFiltersBlockchain;
-use blockchain::compact_filters::CompactFiltersError;
-use log::info;
-use std::sync::Arc;
-
-/// This will return wallet balance using compact filters
-/// Requires a synced local bitcoin node 0.21 running on testnet with blockfilterindex=1 and peerblockfilters=1
-fn main() -> Result<(), CompactFiltersError> {
-    env_logger::init();
-    info!("start");
-
-    let num_threads = 4;
-    let mempool = Arc::new(Mempool::default());
-    let peers = (0..num_threads)
-        .map(|_| Peer::connect("localhost:18333", Arc::clone(&mempool), Network::Testnet))
-        .collect::<Result<_, _>>()?;
-    let blockchain = CompactFiltersBlockchain::new(peers, "./wallet-filters", Some(500_000))?;
-    info!("done {:?}", blockchain);
-    let descriptor = "wpkh(tpubD6NzVbkrYhZ4X2yy78HWrr1M9NT8dKeWfzNiQqDdMqqa9UmmGztGGz6TaLFGsLfdft5iu32gxq1T4eMNxExNNWzVCpf9Y6JZi5TnqoC9wJq/*)";
-
-    let database = MemoryDatabase::default();
-    let wallet = Arc::new(Wallet::new(descriptor, None, Network::Testnet, database).unwrap());
-    wallet.sync(&blockchain, SyncOptions::default()).unwrap();
-    info!("balance: {}", wallet.get_balance()?);
-    Ok(())
-}