login method

@override Future<String?> login()

Implementation

@override
Future<String?> login() async {
  if (_clientId == null || _redirectUri == null) {
    throw Exception(
      'FlutterTelegramAuth not initialized. Call init() first.',
    );
  }

  final origin = web.window.location.origin;
  // URL for Telegram Web OAuth
  final authUrl =
      'https://oauth.telegram.org/auth?bot_id=$_clientId&origin=$origin&request_access=write&return_to=$_redirectUri';

  // Open popup
  final int width = 550;
  final int height = 470;
  final int left = (web.window.screen.width) ~/ 2 - (width ~/ 2);
  final int top = (web.window.screen.height) ~/ 2 - (height ~/ 2);

  final popup = web.window.open(
    authUrl,
    'TelegramLogin',
    'width=$width,height=$height,left=$left,top=$top,status=0,location=0',
  );

  if (popup == null) {
    // In package:web, window.open returns a WindowProxy which is usually not null
    // but we keep the logic for robustness if possible.
    throw Exception('Popup blocked. Please allow popups for this site.');
  }

  final completer = Completer<String?>();

  // Message handler function
  void onMessage(web.Event event) {
    if (event.isA<web.MessageEvent>()) {
      final messageEvent = event as web.MessageEvent;
      final data = messageEvent.data;
      if (data != null && data.isA<JSString>()) {
        final dataStr = (data as JSString).toDart;
        if (dataStr.startsWith('tgAuthResult=')) {
          final jsonStr = dataStr.substring('tgAuthResult='.length);
          if (!completer.isCompleted) {
            completer.complete(jsonStr);
          }
          web.window.removeEventListener('message', onMessage.toJS);
          popup.close();
        }
      }
    }
  }

  // Listen for the postMessage from the popup window
  web.window.addEventListener('message', onMessage.toJS);

  // Check periodically if the user closed the popup manually
  Timer? checkTimer;
  checkTimer = Timer.periodic(const Duration(milliseconds: 500), (timer) {
    if (popup.closed && !completer.isCompleted) {
      completer.complete(null); // User cancelled login
      web.window.removeEventListener('message', onMessage.toJS);
      checkTimer?.cancel();
    } else if (completer.isCompleted) {
      checkTimer?.cancel();
    }
  });

  return completer.future;
}