Gate Flutter app behind Telegram

lib/auth/telegram_launcher.dart

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+export 'telegram_launcher_stub.dart'
+    if (dart.library.js_interop) 'telegram_launcher_web.dart';

lib/auth/telegram_launcher_stub.dart

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+void openTelegramUrl(String url) {}

lib/auth/telegram_launcher_web.dart

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+import 'dart:js_interop';
+
+@JS('window.open')
+external JSAny? _open(JSString url, JSString target, JSString features);
+
+void openTelegramUrl(String url) {
+  _open(url.toJS, '_blank'.toJS, 'noopener,noreferrer'.toJS);
+}