use super::{Error, Store};
use crate::forwards_iter::SimpleForwardsBlockRootsIterator;
use crate::impls::beacon_state::{get_full_state, store_full_state};
use parking_lot::RwLock;
use std::collections::HashMap;
use std::marker::PhantomData;
use std::sync::Arc;
use types::*;

type DBHashMap = HashMap<Vec<u8>, Vec<u8>>;

/// A thread-safe `HashMap` wrapper.
pub struct MemoryStore<E: EthSpec> {
    db: RwLock<DBHashMap>,
    _phantom: PhantomData<E>,
}

impl<E: EthSpec> Clone for MemoryStore<E> {
    fn clone(&self) -> Self {
        Self {
            db: RwLock::new(self.db.read().clone()),
            _phantom: PhantomData,
        }
    }
}

impl<E: EthSpec> MemoryStore<E> {
    /// Create a new, empty database.
    pub fn open() -> Self {
        Self {
            db: RwLock::new(HashMap::new()),
            _phantom: PhantomData,
        }
    }

    fn get_key_for_col(col: &str, key: &[u8]) -> Vec<u8> {
        let mut col = col.as_bytes().to_vec();
        col.append(&mut key.to_vec());
        col
    }
}

impl<E: EthSpec> Store<E> for MemoryStore<E> {
    type ForwardsBlockRootsIterator = SimpleForwardsBlockRootsIterator;

    /// Get the value of some key from the database. Returns `None` if the key does not exist.
    fn get_bytes(&self, col: &str, key: &[u8]) -> Result<Option<Vec<u8>>, Error> {
        let column_key = Self::get_key_for_col(col, key);

        Ok(self.db.read().get(&column_key).cloned())
    }

    /// Puts a key in the database.
    fn put_bytes(&self, col: &str, key: &[u8], val: &[u8]) -> Result<(), Error> {
        let column_key = Self::get_key_for_col(col, key);

        self.db.write().insert(column_key, val.to_vec());

        Ok(())
    }

    /// Return true if some key exists in some column.
    fn key_exists(&self, col: &str, key: &[u8]) -> Result<bool, Error> {
        let column_key = Self::get_key_for_col(col, key);

        Ok(self.db.read().contains_key(&column_key))
    }

    /// Delete some key from the database.
    fn key_delete(&self, col: &str, key: &[u8]) -> Result<(), Error> {
        let column_key = Self::get_key_for_col(col, key);

        self.db.write().remove(&column_key);

        Ok(())
    }

    /// Store a state in the store.
    fn put_state(&self, state_root: &Hash256, state: &BeaconState<E>) -> Result<(), Error> {
        store_full_state(self, state_root, state)
    }

    /// Fetch a state from the store.
    fn get_state(
        &self,
        state_root: &Hash256,
        _: Option<Slot>,
    ) -> Result<Option<BeaconState<E>>, Error> {
        get_full_state(self, state_root)
    }

    fn forwards_block_roots_iterator(
        store: Arc<Self>,
        start_slot: Slot,
        end_state: BeaconState<E>,
        end_block_root: Hash256,
        _: &ChainSpec,
    ) -> Self::ForwardsBlockRootsIterator {
        SimpleForwardsBlockRootsIterator::new(store, start_slot, end_state, end_block_root)
    }
}
