const DefaultInterval = 2000;

const Log = console;

export class CheckSessionIFrame {
  private readonly _client_id: any;
  private readonly _callback: any;
  private _url: any;
  private readonly _interval: number;
  private readonly _stopOnError: boolean;
  private readonly _frame_origin: string;
  private readonly _frame: HTMLIFrameElement;
  private _boundMessageEvent: any;
  private _timer: number;
  constructor(callback, client_id, url, interval = DefaultInterval, stopOnError = true) {
    this._callback = callback;
    this._client_id = client_id;
    this._url = url;
    this._interval = interval || DefaultInterval;
    this._stopOnError = stopOnError;
    const idx = url.indexOf('/', url.indexOf('//') + 2);
    this._frame_origin = url.substring(0, idx);
    this._frame = window.document.createElement('iframe');
    this._frame.style.visibility = 'hidden';
    this._frame.style.position = 'absolute';
    this._frame.style.display = 'none';
    // @ts-ignore
    this._frame.width = 0;
    // @ts-ignore
    this._frame.height = 0;

    this._frame.src = url;
  }

  load() {
    return new Promise<void>(resolve => {
      this._frame.onload = () => {
        resolve();
      };
      window.document.body.appendChild(this._frame);
      this._boundMessageEvent = this._message.bind(this);
      window.addEventListener('message', this._boundMessageEvent, false);
    });
  }

  _message(e) {
    if (e.origin === this._frame_origin && e.source === this._frame.contentWindow) {
      if (e.data === 'error') {
        Log.error('CheckSessionIFrame: error message from check session op iframe');
        if (this._stopOnError) {
          this.stop();
        }
      } else if (e.data === 'changed') {
        Log.debug(e);
        Log.debug('CheckSessionIFrame: changed message from check session op iframe');
        this.stop();
        this._callback();
      } else {
        Log.debug('CheckSessionIFrame: ' + e.data + ' message from check session op iframe');
      }
    }
  }

  start(session_state) {
    Log.debug('CheckSessionIFrame.start :' + session_state);
    this.stop();
    const send = () => {
      this._frame.contentWindow.postMessage(
        this._client_id + ' ' + session_state,
        this._frame_origin,
      );
    };
    send();
    this._timer = window.setInterval(send, this._interval);
  }

  stop() {
    if (this._timer) {
      Log.debug('CheckSessionIFrame.stop');
      window.clearInterval(this._timer);
      this._timer = null;
    }
  }
}