let singleton: UserChannel = null;

export default class UserChannel {
  private subscription;
  private constructor(private ws) {
    this.subscription = null;
  }

  async connect(): Promise<boolean> {
    this.subscription = this.ws.subscribe(`user_channel`);
    const subscription = this.subscription;
    const self = this;
    return new Promise((resolve, reject) => {
      subscription.on('error', () => { resolve(false) });
      subscription.on('ready', () => {
        resolve(true)
      });
      subscription.on('close', self.close);
    });
  }

  on(event: string, callback: (...args) => void) {
    if (this.subscription) this.subscription.on(event, callback);
  }

  static async getInstance(ws) {
    if (singleton) return singleton;
    else return new UserChannel(ws);
  }
  close() {
    this.subscription.close();
    singleton = null;
  }
}