#![allow(unused)]
use crate::constants::{MAX_BLOCK_SIZE, NETWORK_VERSION};
use crate::crypto::sha3_256::{self, Sha3_256};
use crate::crypto::sign_ed25519::PublicKey;
use crate::primitives::asset::Asset;
use crate::primitives::transaction::{Transaction, TxIn, TxOut};
use bincode::{deserialize, serialize};
use bytes::Bytes;
use serde::{Deserialize, Serialize};
use std::convert::TryInto;

use rand::distributions::Alphanumeric;
use rand::{thread_rng, Rng};

use merkle_log::{MemoryStore, MerkleLog, Store};

/// Block header, which contains a smaller footprint view of the block.
/// Hash records are assumed to be 256 bit
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct BlockHeader {
    pub version: u32,
    pub bits: usize,
    pub nonce_and_mining_tx_hash: (Vec<u8>, String),
    pub b_num: u64,
    pub seed_value: Vec<u8>, // for commercial
    pub previous_hash: Option<String>,
    pub txs_merkle_root_and_hash: (String, String),
}

impl Default for BlockHeader {
    fn default() -> Self {
        Self::new()
    }
}

impl BlockHeader {
    /// Creates a new BlockHeader
    pub fn new() -> BlockHeader {
        BlockHeader {
            version: NETWORK_VERSION,
            bits: 0,
            nonce_and_mining_tx_hash: Default::default(),
            b_num: 0,
            seed_value: Vec::new(),
            previous_hash: None,
            txs_merkle_root_and_hash: Default::default(),
        }
    }

    /// Checks whether a BlockHeader is empty
    pub fn is_null(&self) -> bool {
        self.bits == 0
    }
}

/// A block, a collection of transactions for processing
#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct Block {
    pub header: BlockHeader,
    pub transactions: Vec<String>,
}

impl Default for Block {
    fn default() -> Self {
        Self::new()
    }
}

impl Block {
    /// Creates a new instance of a block
    pub fn new() -> Block {
        Block {
            header: BlockHeader::new(),
            transactions: Vec::new(),
        }
    }

    /// Sets the internal number of bits based on length
    pub fn set_bits(&mut self) {
        let bytes = Bytes::from(serialize(&self).unwrap());
        self.header.bits = bytes.len();
    }

    /// Checks whether a block has hit its maximum size
    pub fn is_full(&self) -> bool {
        let bytes = Bytes::from(serialize(&self).unwrap());
        bytes.len() >= MAX_BLOCK_SIZE
    }

    /// Get the merkle root for the current set of transactions
    pub async fn set_txs_merkle_root_and_hash(&mut self) {
        let merkle_root = build_hex_merkle_root(&self.transactions).await;
        let txs_hash = build_hex_txs_hash(&self.transactions);

        self.header.txs_merkle_root_and_hash = (merkle_root, txs_hash);
    }
}

/*---- FUNCTIONS ----*/

/// Converts a dynamic array into a static 32 bit
///
/// ### Arguments
///
/// * `bytes`   - Bytes to cast
pub fn from_slice(bytes: &[u8]) -> [u8; 32] {
    let mut array = [0; 32];
    let bytes = &bytes[..array.len()]; // panics if not enough data
    array.copy_from_slice(bytes);
    array
}

/// Generates a random transaction hash for testing
pub fn gen_random_hash() -> String {
    let rand_2: String = thread_rng()
        .sample_iter(&Alphanumeric)
        .take(32)
        .map(char::from)
        .collect();
    hex::encode(sha3_256::digest(rand_2.as_bytes()))
}

/// Builds hex encoded sha3 hash of the passed transactions
///
/// ### Arguments
///
/// * `transactions`    - Transactions to construct a merkle tree for
pub fn build_hex_txs_hash(transactions: &[String]) -> String {
    let txs = serialize(transactions).unwrap();
    hex::encode(sha3_256::digest(&txs))
}

/// Builds hex encoded merkle root of the passed transactions
///
/// ### Arguments
///
/// * `transactions`    - Transactions to construct a merkle tree for
pub async fn build_hex_merkle_root(transactions: &[String]) -> String {
    let merkle_result = build_merkle_tree(transactions).await;
    let merkle_root = merkle_result.map(|(t, _)| hex::encode(t.root()));
    merkle_root.unwrap_or_default()
}

/// Builds a merkle tree of the passed transactions
///
/// ### Arguments
///
/// * `transactions`    - Transactions to construct a merkle tree for
pub async fn build_merkle_tree(
    transactions: &[String],
) -> Option<(MerkleLog<Sha3_256>, MemoryStore)> {
    let mut store = MemoryStore::default();

    if let Some((first_entry, other_entries)) = transactions.split_first() {
        let mut log = MerkleLog::<Sha3_256>::new(&first_entry, &mut store)
            .await
            .unwrap();

        for entry in other_entries {
            log.append(entry, &mut store).await.unwrap();
        }

        return Some((log, store));
    }

    None
}

/*---- TESTS ----*/

#[cfg(test)]
mod tests {
    use super::*;

    #[actix_rt::test]
    /// Ensures that the merkle root is set to a valid empty string when no tx's are present
    async fn should_construct_merkle_root_with_no_tx() {
        let mut block = Block::new();
        block.set_txs_merkle_root_and_hash().await;

        assert_eq!(
            block.header.txs_merkle_root_and_hash,
            (
                String::new(),
                "48dda5bbe9171a6656206ec56c595c5834b6cf38c5fe71bcb44fe43833aee9df".to_owned()
            )
        );
    }

    #[actix_rt::test]
    /// Ensures that a static set of tx produces a valid merkle root hash
    async fn should_construct_a_valid_merkle_root() {
        let mut block = Block::new();
        block.transactions = vec![
            "f479fc771c19c64b14b1b9e446ccccf36b6d705c891eb9a7662c82134e362732".to_string(),
            "ac24e4c5dc8d0a29cac34ddcf7902bc2f2e8a98ec376def02c06db267d0f5477".to_string(),
            "4d04366cb153bdcc11b97a9d1176fc889eafc63edbd2c010a6a62a4f9232d156".to_string(),
            "6486b86af39db28e4f61c7b484e0869ad478e8cb2475b91e92d1b721b70d1746".to_string(),
            "03b45b843d60b1e43241553c9aeb95fed82cc1bbb599c6c066ddaa75709b3186".to_string(),
            "8d0250ea0864ac426fe4f4142dae721c74da732476de83d424e1ba0b638238a7".to_string(),
            "f57e38fb8499b7c2b3d4cf75a24a5dd8a8f7b46f28b9671eb8168ffb93a85424".to_string(),
            "e0acad209b680e61c3ef4624d9a61b32a5e7e3f0691a8f8d41fd50b1c946e338".to_string(),
        ];

        block.set_txs_merkle_root_and_hash().await;
        assert_eq!(
            block.header.txs_merkle_root_and_hash,
            (
                "49adba4740eb78c38318bbe2951a3c49e8a5bda6b892870bdcbe0713cf1e0af2".to_owned(),
                "2bf86b48530112f14cbc516f2f7085cdc886a88b475d52e9eaa8cef526479e0f".to_owned()
            )
        );
    }

    #[actix_rt::test]
    /// Ensures that a tx's entry in the merkle tree can be successfully proven
    async fn should_produce_valid_merkle_proof() {
        let mut transactions = vec![
            "f479fc771c19c64b14b1b9e446ccccf36b6d705c891eb9a7662c82134e362732".to_string(),
            "ac24e4c5dc8d0a29cac34ddcf7902bc2f2e8a98ec376def02c06db267d0f5477".to_string(),
            "4d04366cb153bdcc11b97a9d1176fc889eafc63edbd2c010a6a62a4f9232d156".to_string(),
            "6486b86af39db28e4f61c7b484e0869ad478e8cb2475b91e92d1b721b70d1746".to_string(),
            "03b45b843d60b1e43241553c9aeb95fed82cc1bbb599c6c066ddaa75709b3186".to_string(),
            "8d0250ea0864ac426fe4f4142dae721c74da732476de83d424e1bab638238a7".to_string(),
            "f57e38fb8499b7c2b3d4cf75a24a5dd8a8f7b46f28b9671eb8168ffb93a85424".to_string(),
            "e0acad209b680e61c3ef4624d9a61b32a5e7e3f0691a8f8d41fd50b1c946e338".to_string(),
        ];

        let (mtree, store) = build_merkle_tree(&transactions).await.unwrap();
        let check_entry = sha3_256::digest(transactions[0].as_bytes());
        let proof = mtree
            .prove(0, &from_slice(&check_entry), &store)
            .await
            .unwrap();

        assert!(mtree.verify(0, &from_slice(&check_entry), &proof));
    }
}