// 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/>.

//! Blockchain DB extras.

use std::io::Write;

use common_types::{
    engines::epoch::Transition as EpochTransition, receipt::TypedReceipt, BlockNumber,
};
use ethereum_types::{H256, H264, U256};
use kvdb::PREFIX_LEN as DB_PREFIX_LEN;
use parity_util_mem::MallocSizeOf;
use rlp;
use rlp_derive::{RlpDecodable, RlpEncodable};

use crate::db::Key;

/// Represents index of extra data in database
#[derive(Copy, Debug, Hash, Eq, PartialEq, Clone)]
pub enum ExtrasIndex {
    /// Block details index
    BlockDetails = 0,
    /// Block hash index
    BlockHash = 1,
    /// Transaction address index
    TransactionAddress = 2,
    /// Block receipts index
    BlockReceipts = 4,
    /// Epoch transition data index.
    EpochTransitions = 5,
    /// Pending epoch transition data index.
    PendingEpochTransition = 6,
}

fn with_index(hash: &H256, i: ExtrasIndex) -> H264 {
    let mut result = H264::default();
    result.as_bytes_mut()[0] = i as u8;
    result.as_bytes_mut()[1..].clone_from_slice(hash.as_bytes());
    result
}

/// Wrapper for block number used as a DB key.
pub struct BlockNumberKey([u8; 5]);

impl AsRef<[u8]> for BlockNumberKey {
    fn as_ref(&self) -> &[u8] {
        &self.0[..]
    }
}

impl Key<H256> for BlockNumber {
    type Target = BlockNumberKey;

    fn key(&self) -> Self::Target {
        let mut result = [0u8; 5];
        result[0] = ExtrasIndex::BlockHash as u8;
        result[1] = (self >> 24) as u8;
        result[2] = (self >> 16) as u8;
        result[3] = (self >> 8) as u8;
        result[4] = *self as u8;
        BlockNumberKey(result)
    }
}

impl Key<BlockDetails> for H256 {
    type Target = H264;

    fn key(&self) -> H264 {
        with_index(self, ExtrasIndex::BlockDetails)
    }
}

impl Key<TransactionAddress> for H256 {
    type Target = H264;

    fn key(&self) -> H264 {
        with_index(self, ExtrasIndex::TransactionAddress)
    }
}

impl Key<BlockReceipts> for H256 {
    type Target = H264;

    fn key(&self) -> H264 {
        with_index(self, ExtrasIndex::BlockReceipts)
    }
}

impl Key<common_types::engines::epoch::PendingTransition> for H256 {
    type Target = H264;

    fn key(&self) -> H264 {
        with_index(self, ExtrasIndex::PendingEpochTransition)
    }
}

/// length of epoch keys.
pub const EPOCH_KEY_LEN: usize = DB_PREFIX_LEN + 16;

/// epoch key prefix.
/// used to iterate over all epoch transitions in order from genesis.
pub const EPOCH_KEY_PREFIX: &'static [u8; DB_PREFIX_LEN] = &[
    ExtrasIndex::EpochTransitions as u8,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
    0,
];

/// Epoch transitions key
pub struct EpochTransitionsKey([u8; EPOCH_KEY_LEN]);

impl AsRef<[u8]> for EpochTransitionsKey {
    fn as_ref(&self) -> &[u8] {
        &self.0[..]
    }
}

impl Key<EpochTransitions> for u64 {
    type Target = EpochTransitionsKey;

    fn key(&self) -> Self::Target {
        let mut arr = [0u8; EPOCH_KEY_LEN];
        arr[..DB_PREFIX_LEN].copy_from_slice(&EPOCH_KEY_PREFIX[..]);

        write!(&mut arr[DB_PREFIX_LEN..], "{:016x}", self)
            .expect("format arg is valid; no more than 16 chars will be written; qed");

        EpochTransitionsKey(arr)
    }
}

/// Familial details concerning a block
#[derive(Debug, Clone, MallocSizeOf)]
pub struct BlockDetails {
    /// Block number
    pub number: BlockNumber,
    /// Total difficulty of the block and all its parents
    pub total_difficulty: U256,
    /// Parent block hash
    pub parent: H256,
    /// List of children block hashes
    pub children: Vec<H256>,
    /// Whether the block is considered finalized
    pub is_finalized: bool,
}

impl rlp::Encodable for BlockDetails {
    fn rlp_append(&self, stream: &mut rlp::RlpStream) {
        let use_short_version = !self.is_finalized;

        match use_short_version {
            true => {
                stream.begin_list(4);
            }
            false => {
                stream.begin_list(5);
            }
        }

        stream.append(&self.number);
        stream.append(&self.total_difficulty);
        stream.append(&self.parent);
        stream.append_list(&self.children);
        if !use_short_version {
            stream.append(&self.is_finalized);
        }
    }
}

impl rlp::Decodable for BlockDetails {
    fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
        let use_short_version = match rlp.item_count()? {
            4 => true,
            5 => false,
            _ => return Err(rlp::DecoderError::RlpIncorrectListLen),
        };

        Ok(BlockDetails {
            number: rlp.val_at(0)?,
            total_difficulty: rlp.val_at(1)?,
            parent: rlp.val_at(2)?,
            children: rlp.list_at(3)?,
            is_finalized: if use_short_version {
                false
            } else {
                rlp.val_at(4)?
            },
        })
    }
}

/// Represents address of certain transaction within block
#[derive(Debug, PartialEq, Clone, RlpEncodable, RlpDecodable, MallocSizeOf)]
pub struct TransactionAddress {
    /// Block hash
    pub block_hash: H256,
    /// Transaction index within the block
    pub index: usize,
}

/// Contains all block receipts.
#[derive(Clone, MallocSizeOf)]
pub struct BlockReceipts {
    /// Block receipts
    pub receipts: Vec<TypedReceipt>,
}

impl rlp::Encodable for BlockReceipts {
    fn rlp_append(&self, s: &mut rlp::RlpStream) {
        TypedReceipt::rlp_append_list(s, &self.receipts);
    }
}

impl rlp::Decodable for BlockReceipts {
    fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
        Ok(BlockReceipts::new(TypedReceipt::decode_rlp_list(rlp)?))
    }
}

impl BlockReceipts {
    /// Create new block receipts wrapper.
    pub fn new(receipts: Vec<TypedReceipt>) -> Self {
        BlockReceipts { receipts: receipts }
    }
}

/// Candidate transitions to an epoch with specific number.
#[derive(Clone, RlpEncodable, RlpDecodable)]
pub struct EpochTransitions {
    /// Epoch number
    pub number: u64,
    /// List of candidate transitions
    pub candidates: Vec<EpochTransition>,
}

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

    use super::BlockReceipts;

    #[test]
    fn encode_block_receipts() {
        let br = BlockReceipts::new(Vec::new());

        let mut s = RlpStream::new_list(2);
        s.append(&br);
        assert!(!s.is_finished(), "List shouldn't finished yet");
        s.append(&br);
        assert!(s.is_finished(), "List should be finished now");
        s.out();
    }
}