use serde_derive::Serialize;
use std::sync::Arc;
use types::{
    beacon_state::CloneConfig, BeaconState, EthSpec, ExecPayload, FullPayload, Hash256,
    SignedBeaconBlock,
};

/// Represents some block and its associated state. Generally, this will be used for tracking the
/// head, justified head and finalized head.
#[derive(Clone, Serialize, PartialEq, Debug)]
pub struct BeaconSnapshot<E: EthSpec, Payload: ExecPayload<E> = FullPayload<E>> {
    pub beacon_block: Arc<SignedBeaconBlock<E, Payload>>,
    pub beacon_block_root: Hash256,
    pub beacon_state: BeaconState<E>,
}

impl<E: EthSpec, Payload: ExecPayload<E>> BeaconSnapshot<E, Payload> {
    /// Create a new checkpoint.
    pub fn new(
        beacon_block: Arc<SignedBeaconBlock<E, Payload>>,
        beacon_block_root: Hash256,
        beacon_state: BeaconState<E>,
    ) -> Self {
        Self {
            beacon_block,
            beacon_block_root,
            beacon_state,
        }
    }

    /// Returns the state root from `self.beacon_block`.
    ///
    /// ## Caution
    ///
    /// It is not strictly enforced that `root(self.beacon_state) == self.beacon_state_root()`.
    pub fn beacon_state_root(&self) -> Hash256 {
        self.beacon_block.message().state_root()
    }

    /// Update all fields of the checkpoint.
    pub fn update(
        &mut self,
        beacon_block: Arc<SignedBeaconBlock<E, Payload>>,
        beacon_block_root: Hash256,
        beacon_state: BeaconState<E>,
    ) {
        self.beacon_block = beacon_block;
        self.beacon_block_root = beacon_block_root;
        self.beacon_state = beacon_state;
    }

    pub fn clone_with(&self, clone_config: CloneConfig) -> Self {
        Self {
            beacon_block: self.beacon_block.clone(),
            beacon_block_root: self.beacon_block_root,
            beacon_state: self.beacon_state.clone_with(clone_config),
        }
    }
}