export const cache = <T>(ttl: number) => {
  type Cache = { promise: Promise<T>, timestamp: number };
  const store = new Map<string, Cache>();

  const get = async (key: string, fetcher: () => Promise<T>) => {
    if (store.has(key)) {
      const cached = store.get(key)!;

      if (Date.now() - cached.timestamp < ttl) {
        return cached.promise;
      } else {
        store.delete(key);
      }
    }

    try {
      const promise = fetcher();

      store.set(key, {
        promise,
        timestamp: Date.now()
      });

      return promise;
    } catch (error) {
      store.delete(key);

      throw error;
    }
  }

  return {
    get
  };
};