import { ReadAllStorage, ReadGetAllStorage, ReadStorage } from '@neo-one/node-core-esnext-esm';
import LRU from 'lru-cache';

type SerializeKeyString<Key> = ((key: Key) => string);

export function createReadStorage<Key, Value>({
  cache,
  storage,
  serializeKeyString,
}: {
  readonly cache: LRU.Cache<string, Value>;
  readonly storage: ReadStorage<Key, Value>;
  readonly serializeKeyString: SerializeKeyString<Key>;
}): ReadStorage<Key, Value> {
  const get = async (key: Key): Promise<Value> => {
    const keyString = serializeKeyString(key);
    const value = cache.get(keyString);
    if (value !== undefined) {
      return value;
    }

    return storage.get(key).then((val) => {
      cache.set(keyString, val);

      return val;
    });
  };

  const tryGet = async (key: Key): Promise<Value | undefined> => {
    const keyString = serializeKeyString(key);
    const value = cache.get(keyString);
    if (value !== undefined) {
      return value;
    }

    return storage.tryGet(key).then((val) => {
      if (val !== undefined) {
        cache.set(keyString, val);
      }

      return val;
    });
  };

  return { get, tryGet };
}

export function createReadAllStorage<Key, Value>({
  cache,
  storage,
  serializeKeyString,
}: {
  readonly cache: LRU.Cache<string, Value>;
  readonly storage: ReadAllStorage<Key, Value>;
  readonly serializeKeyString: SerializeKeyString<Key>;
}): ReadAllStorage<Key, Value> {
  const readStorage = createReadStorage({
    cache,
    storage,
    serializeKeyString,
  });

  return {
    get: readStorage.get,
    tryGet: readStorage.tryGet,
    all$: storage.all$,
  };
}

export function createReadGetAllStorage<Key, Keys, Value>({
  cache,
  storage,
  serializeKeyString,
}: {
  readonly cache: LRU.Cache<string, Value>;
  readonly storage: ReadGetAllStorage<Key, Keys, Value>;
  readonly serializeKeyString: SerializeKeyString<Key>;
}): ReadGetAllStorage<Key, Keys, Value> {
  const readStorage = createReadStorage({
    cache,
    storage,
    serializeKeyString,
  });

  return {
    get: readStorage.get,
    tryGet: readStorage.tryGet,
    getAll$: storage.getAll$,
  };
}