use super::BeaconChain;
use db::stores::BeaconBlockAtSlotError;
use db::ClientDB;
use ssz_helpers::ssz_beacon_block::SszBeaconBlock;
use std::sync::Arc;
use types::Hash256;
use validation::block_validation::BeaconBlockValidationContext;

pub enum BlockValidationContextError {
    UnknownCrystallizedState,
    UnknownActiveState,
    UnknownAttesterProposerMaps,
    NoParentHash,
    UnknownJustifiedBlock,
    BlockAlreadyKnown,
    BlockSlotLookupError(BeaconBlockAtSlotError),
}

impl From<BeaconBlockAtSlotError> for BlockValidationContextError {
    fn from(e: BeaconBlockAtSlotError) -> BlockValidationContextError {
        BlockValidationContextError::BlockSlotLookupError(e)
    }
}

impl<T> BeaconChain<T>
where
    T: ClientDB + Sized,
{
    pub(crate) fn block_validation_context(
        &self,
        block: &SszBeaconBlock,
        parent_block: &SszBeaconBlock,
        present_slot: u64,
    ) -> Result<BeaconBlockValidationContext<T>, BlockValidationContextError> {
        /*
         * Load the crystallized state for this block from our caches.
         *
         * Fail if the crystallized state is unknown.
         */
        let cry_state_root = Hash256::from(parent_block.cry_state_root());
        let cry_state = self
            .crystallized_states
            .get(&cry_state_root)
            .ok_or(BlockValidationContextError::UnknownCrystallizedState)?;

        /*
         * Load the active state for this block from our caches.
         *
         * Fail if the active state is unknown.
         */
        let act_state_root = Hash256::from(parent_block.act_state_root());
        let act_state = self
            .active_states
            .get(&act_state_root)
            .ok_or(BlockValidationContextError::UnknownActiveState)?;

        /*
         * Learn the last justified slot from the crystallized state and load
         * the hash of this block from the database
         */
        let last_justified_slot = cry_state.last_justified_slot;
        let parent_block_hash = block
            .parent_hash()
            .ok_or(BlockValidationContextError::NoParentHash)?;
        let (last_justified_block_hash, _) = self
            .store
            .block
            .block_at_slot(&parent_block_hash, last_justified_slot)?
            .ok_or(BlockValidationContextError::UnknownJustifiedBlock)?;

        /*
         * Load the attester and proposer maps for the crystallized state.
         */
        let (attester_map, proposer_map) = self
            .attester_proposer_maps
            .get(&cry_state_root)
            .ok_or(BlockValidationContextError::UnknownAttesterProposerMaps)?;

        Ok(BeaconBlockValidationContext {
            present_slot,
            cycle_length: self.config.cycle_length,
            last_justified_slot: cry_state.last_justified_slot,
            last_justified_block_hash: Hash256::from(&last_justified_block_hash[..]),
            last_finalized_slot: self.last_finalized_slot,
            recent_block_hashes: Arc::new(act_state.recent_block_hashes.clone()),
            proposer_map: proposer_map.clone(),
            attester_map: attester_map.clone(),
            block_store: self.store.block.clone(),
            validator_store: self.store.validator.clone(),
            pow_store: self.store.pow_chain.clone(),
        })
    }
}