// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

use std::collections::BTreeSet;

use engines::{
    clique::{ADDRESS_LENGTH, NULL_MIXHASH, NULL_NONCE, SIGNATURE_LENGTH, VANITY_LENGTH},
    EngineError,
};
use error::Error;
use ethereum_types::{Address, H256};
use ethkey::{public_to_address, recover as ec_recover, Signature};
use lru_cache::LruCache;
use parking_lot::RwLock;
use rlp::encode;
use types::header::Header;

/// How many recovered signature to cache in the memory.
pub const CREATOR_CACHE_NUM: usize = 4096;
lazy_static! {
    /// key: header hash
    /// value: creator address
    static ref CREATOR_BY_HASH: RwLock<LruCache<H256, Address>> = RwLock::new(LruCache::new(CREATOR_CACHE_NUM));
}

/// Recover block creator from signature
pub fn recover_creator(header: &Header) -> Result<Address, Error> {
    // Initialization
    let mut cache = CREATOR_BY_HASH.write();

    if let Some(creator) = cache.get_mut(&header.hash()) {
        return Ok(*creator);
    }

    let data = header.extra_data();
    if data.len() < VANITY_LENGTH {
        Err(EngineError::CliqueMissingVanity)?
    }

    if data.len() < VANITY_LENGTH + SIGNATURE_LENGTH {
        Err(EngineError::CliqueMissingSignature)?
    }

    // Split `signed_extra data` and `signature`
    let (signed_data_slice, signature_slice) = data.split_at(data.len() - SIGNATURE_LENGTH);

    // convert `&[u8]` to `[u8; 65]`
    let signature = {
        let mut s = [0; SIGNATURE_LENGTH];
        s.copy_from_slice(signature_slice);
        s
    };

    // modify header and hash it
    let unsigned_header = &mut header.clone();
    unsigned_header.set_extra_data(signed_data_slice.to_vec());
    let msg = unsigned_header.hash();

    let pubkey = ec_recover(&Signature::from(signature), &msg)?;
    let creator = public_to_address(&pubkey);

    cache.insert(header.hash(), creator.clone());
    Ok(creator)
}

/// Extract signer list from extra_data.
///
/// Layout of extra_data:
/// ----
/// VANITY: 32 bytes
/// Signers: N * 32 bytes as hex encoded (20 characters)
/// Signature: 65 bytes
/// --
pub fn extract_signers(header: &Header) -> Result<BTreeSet<Address>, Error> {
    let data = header.extra_data();

    if data.len() <= VANITY_LENGTH + SIGNATURE_LENGTH {
        Err(EngineError::CliqueCheckpointNoSigner)?
    }

    // extract only the portion of extra_data which includes the signer list
    let signers_raw = &data[(VANITY_LENGTH)..data.len() - (SIGNATURE_LENGTH)];

    if signers_raw.len() % ADDRESS_LENGTH != 0 {
        Err(EngineError::CliqueCheckpointInvalidSigners(
            signers_raw.len(),
        ))?
    }

    let num_signers = signers_raw.len() / 20;

    let signers: BTreeSet<Address> = (0..num_signers)
        .map(|i| {
            let start = i * ADDRESS_LENGTH;
            let end = start + ADDRESS_LENGTH;
            signers_raw[start..end].into()
        })
        .collect();

    Ok(signers)
}

/// Retrieve `null_seal`
pub fn null_seal() -> Vec<Vec<u8>> {
    vec![encode(&NULL_MIXHASH.to_vec()), encode(&NULL_NONCE.to_vec())]
}