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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

use diem_crypto_derive::{BCSCryptoHash, CryptoHasher};
use diem_types::block_info::BlockInfo;
use serde::{Deserialize, Serialize};
use std::fmt::{Display, Formatter};

/// VoteData keeps the information about the block, and its parent.
#[derive(Deserialize, Serialize, Clone, Debug, PartialEq, Eq, CryptoHasher, BCSCryptoHash)]
pub struct VoteData {
    /// Contains all the block information needed for voting for the proposed round.
    proposed: BlockInfo,
    /// Contains all the block information for the block the proposal is extending.
    parent: BlockInfo,
}

impl Display for VoteData {
    fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
        write!(
            f,
            "VoteData: [block id: {}, epoch: {}, round: {:02}, parent_block_id: {}, parent_block_round: {:02}]",
            self.proposed().id(), self.proposed().epoch(), self.proposed().round(), self.parent().id(), self.parent().round(),
        )
    }
}

impl VoteData {
    /// Constructs a new VoteData from the block information of a proposed block and the block it extends.
    pub fn new(proposed: BlockInfo, parent: BlockInfo) -> Self {
        Self { proposed, parent }
    }

    /// Returns block information associated to the block being extended by the proposal.
    pub fn parent(&self) -> &BlockInfo {
        &self.parent
    }

    /// Returns block information associated to the block being voted on.
    pub fn proposed(&self) -> &BlockInfo {
        &self.proposed
    }

    /// Well-formedness checks that are independent of the current state.
    pub fn verify(&self) -> anyhow::Result<()> {
        anyhow::ensure!(
            self.parent.epoch() == self.proposed.epoch(),
            "Parent and proposed epochs do not match",
        );
        anyhow::ensure!(
            self.parent.round() < self.proposed.round(),
            "Proposed round is less than parent round",
        );
        anyhow::ensure!(
            self.parent.timestamp_usecs() <= self.proposed.timestamp_usecs(),
            "Proposed happened before parent",
        );
        anyhow::ensure!(
            // if decoupled execution is turned on, the versions are dummy values (0),
            // but the genesis block per epoch uses the ground truth version number,
            // so we bypass the version check here.
            self.proposed.version() == 0 || self.parent.version() <= self.proposed.version(),
            "Proposed version is less than parent version",
        );
        Ok(())
    }
}