import Subscription from './Contracts/Subscription';

class SubscriptionManager {
  /**
   *
   *
   * @type {Map<string, Function>}
   */
  private subscribers: Map<string, Function> = new Map();

  /**
   *
   *
   * @type {number}
   */
  private idCounter: number = 0;

  /**
   *
   *
   * @type {IterableIterator<string>}
   */
  private idGenerator: IterableIterator<string>;

  /**
   *
   *
   * @return {SubscriptionManager}
   */
  public constructor() {
    this.idGenerator = this.subscriptionIDGenerator();
  }

  /**
   *
   *
   * @param  {Subscription} subscription
   * @return {string}
   */
  public add(subscription: Subscription) {
    const subscriberID = this.idGenerator.next().value;

    this.subscribers.set(subscriberID, subscription);

    return subscriberID;
  }

  /**
   *
   *
   * @param  {string} subscriberId
   * @return {boolean}
   */
  public remove(subscriberId: string) {
    return this.subscribers.delete(subscriberId);
  }

  /**
   *
   *
   * @param {object | null}
   */
  public notify(payload: object | null) {
    this.subscribers.forEach(subscriber => subscriber(payload));
  }

  /**
   *
   *
   * @return {IterableIterator<string>}
   */
  private *subscriptionIDGenerator() {
    while (true) {
      yield ('trending-subscriber' + this.idCounter++);
    }
  }
}

export default SubscriptionManager;