use std::collections::HashSet;
use bitcoin::{Network, ScriptBuf};
use bitcoin::taproot::{LeafVersion, TapTree, ScriptLeaves, TapLeafHash, TaprootMerkleBranch, TapNodeHash};
use bitcoin::p2mr::{P2mrBuilder, P2mrControlBlock, P2mrSpendInfo};
use bitcoin::hashes::Hash;

use hex;
use log::debug;
use once_cell::sync::Lazy;

use p2mr_ref::data_structures::{TVScriptTree, TestVector, Direction, TestVectors, UtxoReturn};
use p2mr_ref::error::P2MRError;
use p2mr_ref::{create_p2mr_utxo, tagged_hash};

//  This file contains tests that execute against the BIP360 script-path-only test vectors.

static TEST_VECTORS: Lazy<TestVectors> = Lazy::new(|| {
    let bip360_test_vectors = include_str!("../../common/tests/data/p2mr_construction.json");
    let test_vectors: TestVectors = serde_json::from_str(bip360_test_vectors).unwrap();
    assert_eq!(test_vectors.version, 1);
    test_vectors
});

static P2TR_USING_V2_WITNESS_VERSION_ERROR: &str = "p2tr_using_v2_witness_version_error";
static P2MR_MISSING_LEAF_SCRIPT_TREE_ERROR_TEST: &str = "p2mr_missing_leaf_script_tree_error";
static P2MR_SINGLE_LEAF_SCRIPT_TREE_TEST: &str = "p2mr_single_leaf_script_tree";
static P2MR_DIFFERENT_VERSION_LEAVES_TEST: &str = "p2mr_different_version_leaves";
static P2MR_TWO_LEAF_SAME_VERSION_TEST: &str = "p2mr_two_leaf_same_version";
static P2MR_THREE_LEAF_COMPLEX_TEST: &str = "p2mr_three_leaf_complex";
static P2MR_THREE_LEAF_ALTERNATIVE_TEST: &str = "p2mr_three_leaf_alternative";
static P2MR_SIMPLE_LIGHTNING_CONTRACT_TEST: &str = "p2mr_simple_lightning_contract";

#[test]
fn test_p2tr_using_v2_witness_version_error() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2TR_USING_V2_WITNESS_VERSION_ERROR).unwrap();
    let test_result: anyhow::Result<()> = process_test_vector_p2tr(test_vector);
    assert!(matches!(test_result.unwrap_err().downcast_ref::<P2MRError>(),
        Some(P2MRError::P2trRequiresWitnessVersion1)));
}

// https://learnmeabitcoin.com/technical/upgrades/taproot/#example-2-script-path-spend-simple
#[test]
fn test_p2mr_missing_leaf_script_tree_error() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_MISSING_LEAF_SCRIPT_TREE_ERROR_TEST).unwrap();
    let test_result: anyhow::Result<()> = process_test_vector_p2mr(test_vector);
    assert!(matches!(test_result.unwrap_err().downcast_ref::<P2MRError>(),
        Some(P2MRError::MissingScriptTreeLeaf)));
}

// https://learnmeabitcoin.com/technical/upgrades/taproot/#example-2-script-path-spend-simple
#[test]
fn test_p2mr_single_leaf_script_tree() {
    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_SINGLE_LEAF_SCRIPT_TREE_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

#[test]
fn test_p2mr_different_version_leaves() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_DIFFERENT_VERSION_LEAVES_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

#[test]
fn test_p2mr_simple_lightning_contract() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_SIMPLE_LIGHTNING_CONTRACT_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

#[test]
fn test_p2mr_two_leaf_same_version() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_TWO_LEAF_SAME_VERSION_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

#[test]
fn test_p2mr_three_leaf_complex() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_THREE_LEAF_COMPLEX_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

#[test]
fn test_p2mr_three_leaf_alternative() {

    let _ = env_logger::try_init(); // Use try_init to avoid reinitialization error

    let test_vectors = &*TEST_VECTORS;
    let test_vector = test_vectors.test_vector_map.get(P2MR_THREE_LEAF_ALTERNATIVE_TEST).unwrap();
    process_test_vector_p2mr(test_vector).unwrap();
}

fn process_test_vector_p2tr(test_vector: &TestVector) -> anyhow::Result<()> {
    let script_pubkey_hex = test_vector.expected.script_pubkey.as_ref().unwrap();
    let script_pubkey_bytes = hex::decode(script_pubkey_hex).unwrap();
    if script_pubkey_bytes[0] != 0x51 {
        return Err(P2MRError::P2trRequiresWitnessVersion1.into());
    }
    Ok(())
}

fn process_test_vector_p2mr(test_vector: &TestVector) -> anyhow::Result<()> {

    let tv_script_tree: Option<&TVScriptTree> = test_vector.given.script_tree.as_ref();

    let mut tv_leaf_count: u8 = 0;
    let mut current_branch_id: u8 = 0;

    // TaprootBuilder expects the addition of each leaf script with its associated depth
    // It then constructs the binary tree in DFS order, sorting siblings lexicographically & combining them via BIP341's tapbranch_hash
    // Use of TaprootBuilder avoids user error in constructing branches manually and ensures Merkle tree correctness and determinism
    let mut p2mr_builder: P2mrBuilder = P2mrBuilder::new();

    let mut control_block_data: Vec<(ScriptBuf, LeafVersion)> = Vec::new();

    // 1)  traverse test vector script tree and add leaves to P2MR builder
    if let Some(script_tree) = tv_script_tree {

        script_tree.traverse_with_right_subtree_first(0, Direction::Root,&mut |node, depth, direction| {

            if let TVScriptTree::Leaf(tv_leaf) = node {
                
                let tv_leaf_script_bytes = hex::decode(&tv_leaf.script).unwrap();
    
                // NOTE:  IOT to execute script_info.control_block(..), will add these to a vector
                let tv_leaf_script_buf = ScriptBuf::from_bytes(tv_leaf_script_bytes.clone());
                let tv_leaf_version = LeafVersion::from_consensus(tv_leaf.leaf_version).unwrap();
                control_block_data.push((tv_leaf_script_buf.clone(), tv_leaf_version));
                
                let mut modified_depth = depth + 1;
                if direction == Direction::Root {
                    modified_depth = depth;
                }
                debug!("traverse_with_depth: leaf_count: {}, depth: {}, modified_depth: {}, direction: {}, tv_leaf_script: {}", 
                    tv_leaf_count, depth, modified_depth, direction, tv_leaf.script);
                
                // NOTE: Some of the the test vectors in this project specify leaves with non-standard versions (ie: 250 / 0xfa)
                p2mr_builder = p2mr_builder.clone().add_leaf_with_ver(depth, tv_leaf_script_buf.clone(), tv_leaf_version)
                    .unwrap_or_else(|e| {
                        panic!("Failed to add leaf: {:?}", e);
                    });
    
                tv_leaf_count += 1;
            } else if let TVScriptTree::Branch { left, right } = node {
                // No need to calculate branch hash.
                // TaprootBuilder does this for us.
                debug!("branch_count: {}, depth: {}, direction: {}", current_branch_id, depth, direction);
                current_branch_id += 1;
            }
        });
    }else {
        return Err(P2MRError::MissingScriptTreeLeaf.into());
    }

    let spend_info: P2mrSpendInfo = p2mr_builder.clone()
        .finalize()
        .unwrap_or_else(|e| {
            panic!("finalize failed: {:?}", e);
        });

    let derived_merkle_root: TapNodeHash = spend_info.merkle_root.unwrap();

    // 2)  verify derived merkle root against test vector
    let test_vector_merkle_root = test_vector.intermediary.merkle_root.as_ref().unwrap();
    assert_eq!( 
        derived_merkle_root.to_string(),
        *test_vector_merkle_root, 
        "Merkle root mismatch"
    );
    debug!("just passed merkle root validation: {}", test_vector_merkle_root);

    let test_vector_leaf_hashes_vec: Vec<String> = test_vector.intermediary.leaf_hashes.clone();
    let test_vector_leaf_hash_set: HashSet<String> = test_vector_leaf_hashes_vec.iter().cloned().collect();
    let test_vector_control_blocks_vec = &test_vector.expected.script_path_control_blocks;
    let test_vector_control_blocks_set: HashSet<String> = test_vector_control_blocks_vec.as_ref().unwrap().iter().cloned().collect();
    let tap_tree: TapTree = p2mr_builder.clone().into_inner().try_into_taptree().unwrap();
    let script_leaves: ScriptLeaves = tap_tree.script_leaves();

    // TO-DO:  Investigate why the ordering of script leaves seems to be reverse of test vectors.
    // 3) Iterate through leaves of derived script tree and verify both script leaf hashes and control blocks
    for derived_leaf in script_leaves {

        let version = derived_leaf.version();
        let script = derived_leaf.script();
        let merkle_branch: &TaprootMerkleBranch = derived_leaf.merkle_branch();

        let derived_leaf_hash: TapLeafHash = TapLeafHash::from_script(script, version);
        let leaf_hash = hex::encode(derived_leaf_hash.as_raw_hash().to_byte_array());
        assert!(
            test_vector_leaf_hash_set.contains(&leaf_hash),
            "Leaf hash not found in expected set for {}", leaf_hash
        );
        debug!("just passed leaf_hash validation: {}", leaf_hash);
    
        // Each leaf in the script tree has a corresponding control block.
        // Specific to P2TR, the 3 sections of the control block (control byte, public key & merkle path) are highlighted here:
        //    https://learnmeabitcoin.com/technical/upgrades/taproot/#script-path-spend-control-block
        // The control block, which includes the Merkle path, must be 33 + 32 * n bytes, where n is the number of Merkle path hashes (n ≥ 0).
        // There is no consensus limit on n, but large Merkle trees increase the witness size, impacting block weight.
        // NOTE:  Control blocks could have also been obtained from spend_info.control_block(..) using the data in control_block_data
        debug!("merkle_branch nodes: {:?}", merkle_branch);
        let derived_control_block: P2mrControlBlock = P2mrControlBlock{
            merkle_branch: merkle_branch.clone(),
        };
        let serialized_control_block = derived_control_block.serialize();
        debug!("derived_control_block: {:?}, merkle_branch size: {}, control_block size: {}, serialized size: {}", 
            derived_control_block,
            merkle_branch.len(),
            derived_control_block.size(),
            serialized_control_block.len());
        let derived_serialized_control_block = hex::encode(serialized_control_block);
        assert!(
            test_vector_control_blocks_set.contains(&derived_serialized_control_block),
            "Control block mismatch: {}, expected: {:?}", derived_serialized_control_block, test_vector_control_blocks_set
        );
        debug!("leaf_hash: {}, derived_serialized_control_block: {}", leaf_hash, derived_serialized_control_block);

    }

    let p2mr_utxo_return: UtxoReturn = create_p2mr_utxo(derived_merkle_root.to_string());

    assert_eq!( 
        p2mr_utxo_return.script_pubkey_hex,
        *test_vector.expected.script_pubkey.as_ref().unwrap(),
        "Script pubkey mismatch"
    );
    debug!("just passed script_pubkey validation. script_pubkey = {}", p2mr_utxo_return.script_pubkey_hex);

    let bech32m_address: String = p2mr_utxo_return.bech32m_address;
    debug!("derived bech32m address for bitcoin_network: {} : {}", p2mr_utxo_return.bitcoin_network, bech32m_address);

    if p2mr_utxo_return.bitcoin_network == Network::Bitcoin {
        assert_eq!(bech32m_address, *test_vector.expected.bip350_address.as_ref().unwrap(), "Bech32m address mismatch.");
    }

    Ok(())
}