/**
 * A cache that stores values for a specifed period of time.
 * TTL = time to live, FYI
 * FYI = for your information, LOL
 * LOL = laughing out loud
 * ME = ridiculous
 */
class TtlCache {
  constructor() {
    this.hash = {};
  }

  /**
   * @param key {string|number|function|object|null|undefined} the key to hash on
   * @param value the value to store for the given key
   * @param ttl the time to live. how long to keep in the cache. if nothing is passed in, then it will never expire
   * */
  set(key, value, ttl=Number.POSITIVE_INFINITY) {
    this.hash[key] = {
      end : Date.now() + ttl,
      value : value
    };
  }

  /**
   * @return the value for the given key. undefined if its not in the Ttlcache
   * */
  get(key) {
    let hashItem = this.hash[key];

    if (hashItem) {
      if (Date.now() <= hashItem.end) {
        return hashItem.value;
      } else {
        delete this.hash[key]; // cleanup
      }
    }

    return undefined;
  }
}

module.exports = TtlCache;