// 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/>.

//! Snapshot manifest type definition

use crate::bytes::Bytes;
use ethereum_types::H256;
use rlp::{DecoderError, Rlp, RlpStream};

/// Manifest data.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ManifestData {
    /// Snapshot format version.
    pub version: u64,
    /// List of state chunk hashes.
    pub state_hashes: Vec<H256>,
    /// List of block chunk hashes.
    pub block_hashes: Vec<H256>,
    /// The final, expected state root.
    pub state_root: H256,
    /// Block number this snapshot was taken at.
    pub block_number: u64,
    /// Block hash this snapshot was taken at.
    pub block_hash: H256,
}

impl ManifestData {
    /// Encode the manifest data to rlp.
    pub fn into_rlp(self) -> Bytes {
        let mut stream = RlpStream::new_list(6);
        stream.append(&self.version);
        stream.append_list(&self.state_hashes);
        stream.append_list(&self.block_hashes);
        stream.append(&self.state_root);
        stream.append(&self.block_number);
        stream.append(&self.block_hash);

        stream.out()
    }

    /// Try to restore manifest data from raw bytes, interpreted as RLP.
    pub fn from_rlp(raw: &[u8]) -> Result<Self, DecoderError> {
        let decoder = Rlp::new(raw);
        let (start, version) = if decoder.item_count()? == 5 {
            (0, 1)
        } else {
            (1, decoder.val_at(0)?)
        };

        let state_hashes: Vec<H256> = decoder.list_at(start + 0)?;
        let block_hashes: Vec<H256> = decoder.list_at(start + 1)?;
        let state_root: H256 = decoder.val_at(start + 2)?;
        let block_number: u64 = decoder.val_at(start + 3)?;
        let block_hash: H256 = decoder.val_at(start + 4)?;

        Ok(ManifestData {
            version: version,
            state_hashes: state_hashes,
            block_hashes: block_hashes,
            state_root: state_root,
            block_number: block_number,
            block_hash: block_hash,
        })
    }
}
