// Rust Bitcoin Library
// Written in 2014 by
//     Andrew Poelstra <apoelstra@wpsoftware.net>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software.
// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
//

//! Bitcoin Block
//!
//! A block is a bundle of transactions with a proof-of-work attached,
//! which commits to an earlier block to form the blockchain. This
//! module describes structures and functions needed to describe
//! these blocks and the blockchain.
//!

use hashes::{sha256d, Hash};

use util;
use util::Error::{BlockBadTarget, BlockBadProofOfWork};
use util::hash::{BitcoinHash, MerkleRoot, bitcoin_merkle_root};
use util::uint::Uint256;
use consensus::encode::Encodable;
use network::constants::Network;
use blockdata::transaction::Transaction;
use blockdata::constants::max_target;
use hashes::HashEngine;

/// A block header, which contains all the block's information except
/// the actual transactions
#[derive(Copy, PartialEq, Eq, Clone, Debug)]
pub struct BlockHeader {
    /// The protocol version. Should always be 1.
    pub version: u32,
    /// Reference to the previous block in the chain
    pub prev_blockhash: sha256d::Hash,
    /// The root hash of the merkle tree of transactions in the block
    pub merkle_root: sha256d::Hash,
    /// The timestamp of the block, as claimed by the miner
    pub time: u32,
    /// The target value below which the blockhash must lie, encoded as a
    /// a float (with well-defined rounding, of course)
    pub bits: u32,
    /// The nonce, selected to obtain a low enough blockhash
    pub nonce: u32,
}

/// A Bitcoin block, which is a collection of transactions with an attached
/// proof of work.
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct Block {
    /// The block header
    pub header: BlockHeader,
    /// List of transactions contained in the block
    pub txdata: Vec<Transaction>
}

impl Block {
    /// check if merkle root of header matches merkle root of the transaction list
    pub fn check_merkle_root (&self) -> bool {
        self.header.merkle_root == self.merkle_root()
    }

    /// check if witness commitment in coinbase is matching the transaction list
    pub fn check_witness_commitment(&self) -> bool {

        // witness commitment is optional if there are no transactions using SegWit in the block
        if self.txdata.iter().all(|t| t.input.iter().all(|i| i.witness.is_empty())) {
            return true;
        }
        if self.txdata.len() > 0 {
            let coinbase = &self.txdata[0];
            if coinbase.is_coin_base() {
                // commitment is in the last output that starts with below magic
                if let Some(pos) = coinbase.output.iter()
                    .rposition(|o| {
                        o.script_pubkey.len () >= 38 &&
                        o.script_pubkey[0..6] == [0x6a, 0x24, 0xaa, 0x21, 0xa9, 0xed] }) {
                    let commitment = sha256d::Hash::from_slice(&coinbase.output[pos].script_pubkey.as_bytes()[6..38]).unwrap();
                    // witness reserved value is in coinbase input witness
                    if coinbase.input[0].witness.len() == 1 && coinbase.input[0].witness[0].len() == 32 {
                        let witness_root = self.witness_root();
                        return commitment == Self::compute_witness_commitment(&witness_root, coinbase.input[0].witness[0].as_slice())
                    }
                }
            }
        }
        false
    }

    /// compute witness commitment for the transaction list
    pub fn compute_witness_commitment (witness_root: &sha256d::Hash, witness_reserved_value: &[u8]) -> sha256d::Hash {
        let mut encoder = sha256d::Hash::engine();
        witness_root.consensus_encode(&mut encoder).unwrap();
        encoder.input(witness_reserved_value);
        sha256d::Hash::from_engine(encoder)
    }

    /// Merkle root of transactions hashed for witness
    pub fn witness_root(&self) -> sha256d::Hash {
        let mut txhashes = vec!(sha256d::Hash::default());
        txhashes.extend(self.txdata.iter().skip(1).map(|t|t.bitcoin_hash()));
        bitcoin_merkle_root(txhashes)
    }
}

impl MerkleRoot for Block {
    fn merkle_root(&self) -> sha256d::Hash {
        bitcoin_merkle_root(self.txdata.iter().map(|obj| obj.txid()).collect())
    }
}

impl BlockHeader {
    /// Computes the target [0, T] that a blockhash must land in to be valid
    pub fn target(&self) -> Uint256 {
        // This is a floating-point "compact" encoding originally used by
        // OpenSSL, which satoshi put into consensus code, so we're stuck
        // with it. The exponent needs to have 3 subtracted from it, hence
        // this goofy decoding code:
        let (mant, expt) = {
            let unshifted_expt = self.bits >> 24;
            if unshifted_expt <= 3 {
                ((self.bits & 0xFFFFFF) >> (8 * (3 - unshifted_expt as usize)), 0)
            } else {
                (self.bits & 0xFFFFFF, 8 * ((self.bits >> 24) - 3))
            }
        };

        // The mantissa is signed but may not be negative
        if mant > 0x7FFFFF {
            Default::default()
        } else {
            Uint256::from_u64(mant as u64).unwrap() << (expt as usize)
        }
    }

    /// Computes the target value in float format from Uint256 format.
    pub fn compact_target_from_u256(value: &Uint256) -> u32 {
        let mut size = (value.bits() + 7) / 8;
        let mut compact = if size <= 3 {
            (value.low_u64() << (8 * (3 - size))) as u32
        } else {
            let bn = *value >> (8 * (size - 3));
            bn.low_u32()
        };

        if (compact & 0x00800000) != 0 {
            compact >>= 8;
            size += 1;
        }

        compact | (size << 24) as u32
    }

    /// Compute the popular "difficulty" measure for mining
    pub fn difficulty(&self, network: Network) -> u64 {
        (max_target(network) / self.target()).low_u64()
    }

    /// Checks that the proof-of-work for the block is valid.
    pub fn validate_pow(&self, required_target: &Uint256) -> Result<(), util::Error> {
        use byteorder::{ByteOrder, LittleEndian};

        let target = &self.target();
        if target != required_target {
            return Err(BlockBadTarget);
        }
        let data: [u8; 32] = self.bitcoin_hash().into_inner();
        let mut ret = [0u64; 4];
        LittleEndian::read_u64_into(&data, &mut ret);
        let hash = &Uint256(ret);
        if hash <= target { Ok(()) } else { Err(BlockBadProofOfWork) }
    }

    /// Returns the total work of the block
    pub fn work(&self) -> Uint256 {
        // 2**256 / (target + 1) == ~target / (target+1) + 1    (eqn shamelessly stolen from bitcoind)
        let mut ret = !self.target();
        let mut ret1 = self.target();
        ret1.increment();
        ret = ret / ret1;
        ret.increment();
        ret
    }
}

impl BitcoinHash for BlockHeader {
    fn bitcoin_hash(&self) -> sha256d::Hash {
        use consensus::encode::serialize;
        sha256d::Hash::hash(&serialize(self))
    }
}

impl BitcoinHash for Block {
    fn bitcoin_hash(&self) -> sha256d::Hash {
        self.header.bitcoin_hash()
    }
}

impl_consensus_encoding!(BlockHeader, version, prev_blockhash, merkle_root, time, bits, nonce);
impl_consensus_encoding!(Block, header, txdata);
serde_struct_impl!(BlockHeader, version, prev_blockhash, merkle_root, time, bits, nonce);
serde_struct_impl!(Block, header, txdata);

#[cfg(test)]
mod tests {
    use hex::decode as hex_decode;

    use blockdata::block::{Block, BlockHeader};
    use consensus::encode::{deserialize, serialize};
    use util::hash::MerkleRoot;

    #[test]
    fn block_test() {
        let some_block = hex_decode("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").unwrap();
        let cutoff_block = hex_decode("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").unwrap();

        let prevhash = hex_decode("4ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000").unwrap();
        let merkle = hex_decode("bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914c").unwrap();

        let decode: Result<Block, _> = deserialize(&some_block);
        let bad_decode: Result<Block, _> = deserialize(&cutoff_block);

        assert!(decode.is_ok());
        assert!(bad_decode.is_err());
        let real_decode = decode.unwrap();
        assert_eq!(real_decode.header.version, 1);
        assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
        assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root());
        assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
        assert_eq!(real_decode.header.time, 1231965655);
        assert_eq!(real_decode.header.bits, 486604799);
        assert_eq!(real_decode.header.nonce, 2067413810);
        // [test] TODO: check the transaction data

        // should be also ok for a non-witness block as commitment is optional in that case
        assert!(real_decode.check_witness_commitment());

        assert_eq!(serialize(&real_decode), some_block);
    }

    // Check testnet block 000000000000045e0b1660b6445b5e5c5ab63c9a4f956be7e1e69be04fa4497b
    #[test]
    fn segwit_block_test() {
        let segwit_block = hex_decode("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        let decode: Result<Block, _> = deserialize(&segwit_block);

        let prevhash = hex_decode("2aa2f2ca794ccbd40c16e2f3333f6b8b683f9e7179b2c4d74906000000000000").unwrap();
        let merkle = hex_decode("10bc26e70a2f672ad420a6153dd0c28b40a6002c55531bfc99bf8994a8e8f67e").unwrap();

        assert!(decode.is_ok());
        let real_decode = decode.unwrap();
        assert_eq!(real_decode.header.version, 0x20000000);  // VERSIONBITS but no bits set
        assert_eq!(serialize(&real_decode.header.prev_blockhash), prevhash);
        assert_eq!(serialize(&real_decode.header.merkle_root), merkle);
        assert_eq!(real_decode.header.merkle_root, real_decode.merkle_root());
        assert_eq!(real_decode.header.time, 1472004949);
        assert_eq!(real_decode.header.bits, 0x1a06d450);
        assert_eq!(real_decode.header.nonce, 1879759182);
        // [test] TODO: check the transaction data

        assert!(real_decode.check_witness_commitment());

        assert_eq!(serialize(&real_decode), segwit_block);
    }

    #[test]
    fn compact_roundrtip_test() {
        let some_header = hex_decode("010000004ddccd549d28f385ab457e98d1b11ce80bfea2c5ab93015ade4973e400000000bf4473e53794beae34e64fccc471dace6ae544180816f89591894e0f417a914cd74d6e49ffff001d323b3a7b").unwrap();

        let header: BlockHeader = deserialize(&some_header).expect("Can't deserialize correct block header");

        assert_eq!(header.bits, BlockHeader::compact_target_from_u256(&header.target()));
    }
}