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// 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/>.

//! Epoch verifiers and transitions.

use ethereum_types::H256;

use rlp::{Decodable, DecoderError, Encodable, Rlp, RlpStream};

/// A full epoch transition.
#[derive(Debug, Clone)]
pub struct Transition {
    /// Block hash at which the transition occurred.
    pub block_hash: H256,
    /// Block number at which the transition occurred.
    pub block_number: u64,
    /// "transition/epoch" proof from the engine combined with a finality proof.
    pub proof: Vec<u8>,
}

impl Encodable for Transition {
    fn rlp_append(&self, s: &mut RlpStream) {
        s.begin_list(3)
            .append(&self.block_hash)
            .append(&self.block_number)
            .append(&self.proof);
    }
}

impl Decodable for Transition {
    fn decode(rlp: &Rlp) -> Result<Self, DecoderError> {
        Ok(Transition {
            block_hash: rlp.val_at(0)?,
            block_number: rlp.val_at(1)?,
            proof: rlp.val_at(2)?,
        })
    }
}

/// An epoch transition pending a finality proof.
/// Not all transitions need one.
pub struct PendingTransition {
    /// "transition/epoch" proof from the engine.
    pub proof: Vec<u8>,
}

impl Encodable for PendingTransition {
    fn rlp_append(&self, s: &mut RlpStream) {
        s.append(&self.proof);
    }
}

impl Decodable for PendingTransition {
    fn decode(rlp: &Rlp) -> Result<Self, DecoderError> {
        Ok(PendingTransition {
            proof: rlp.as_val()?,
        })
    }
}