fix(download): route verification notifications to pending challenges

lib/services/notification_service.dart

@@ -6,6 +6,7 @@ import 'package:flutter_local_notifications/flutter_local_notifications.dart';
 import 'package:permission_handler/permission_handler.dart';
 import 'package:spotiflac_android/constants/app_info.dart';
 import 'package:spotiflac_android/l10n/app_localizations.dart';
+import 'package:spotiflac_android/services/verification_notification.dart';
 
 class NotificationService {
   static final NotificationService _instance = NotificationService._internal();
@@ -15,6 +16,8 @@ class NotificationService {
   final FlutterLocalNotificationsPlugin _notifications =
       FlutterLocalNotificationsPlugin();
   bool _isInitialized = false;
+  Future<void>? _initialization;
+  final verificationNotifications = VerificationNotificationRouter();
   bool _notificationPermissionRequested = false;
   AppLocalizations? _l10n;
 
@@ -43,9 +46,14 @@ class NotificationService {
   static const String libraryChannelDescription =
       'Shows local library scan progress';
 
-  Future<void> initialize() async {
-    if (_isInitialized) return;
+  Future<void> initialize() {
+    if (_isInitialized) return Future.value();
+    return _initialization ??= _initialize().whenComplete(() {
+      _initialization = null;
+    });
+  }
 
+  Future<void> _initialize() async {
     const androidSettings = AndroidInitializationSettings(
       '@mipmap/ic_launcher',
     );
@@ -60,7 +68,16 @@ class NotificationService {
       iOS: iosSettings,
     );
 
-    await _notifications.initialize(settings: initSettings);
+    await _notifications.initialize(
+      settings: initSettings,
+      onDidReceiveNotificationResponse: (response) {
+        verificationNotifications.receive(response.payload);
+      },
+    );
+    final launch = await _notifications.getNotificationAppLaunchDetails();
+    if (launch?.didNotificationLaunchApp == true) {
+      verificationNotifications.receive(launch?.notificationResponse?.payload);
+    }
 
     if (!kIsWeb && defaultTargetPlatform == TargetPlatform.android) {
       final androidImpl = _notifications
@@ -126,6 +143,7 @@ class NotificationService {
     required String title,
     required String body,
     required NotificationDetails details,
+    String? payload,
   }) async {
     if (!await _ensureNotificationPermission()) return;
 
@@ -135,6 +153,7 @@ class NotificationService {
         title: title,
         body: body,
         notificationDetails: details,
+        payload: payload,
       );
     } on PlatformException catch (e) {
       final isNotificationsNotAllowed =
@@ -305,7 +324,10 @@ class NotificationService {
     );
   }
 
-  Future<void> showVerificationRequired() async {
+  Future<void> showVerificationRequired({
+    required String extensionId,
+    required String itemId,
+  }) async {
     if (!_isInitialized) await initialize();
     unawaited(HapticFeedback.mediumImpact());
 
@@ -319,6 +341,11 @@ class NotificationService {
       id: verificationRequiredId,
       title: title,
       body: body,
+      payload: VerificationNotification(
+        extensionId: extensionId,
+        itemId: itemId,
+        tapId: 'dart:${DateTime.now().microsecondsSinceEpoch}',
+      ).encode(),
       details: _details(
         playSound: true,
         presentBadge: true,

lib/services/platform_bridge.dart

@@ -203,6 +203,8 @@ class PlatformBridge {
       StreamController<ExtensionSessionGrantEvent>.broadcast();
   static final StreamController<void> _libraryStorageEvents =
       StreamController<void>.broadcast();
+  static final StreamController<void> _verificationNotificationEvents =
+      StreamController<void>.broadcast();
   static final StreamController<List<String>>
   _iosBackgroundDownloadExpirationEvents =
       StreamController<List<String>>.broadcast();
@@ -223,6 +225,14 @@ class PlatformBridge {
     return _libraryStorageEvents.stream;
   }
 
+  static Stream<void> verificationNotificationEvents() {
+    _ensureBackendEventHandler();
+    return _verificationNotificationEvents.stream;
+  }
+
+  static Future<String?> consumeVerificationNotification() =>
+      _channel.invokeMethod<String>('consumeVerificationNotification');
+
   static Stream<List<String>> iosBackgroundDownloadExpirationEvents() {
     _ensureBackendEventHandler();
     return _iosBackgroundDownloadExpirationEvents.stream;
@@ -250,6 +260,9 @@ class PlatformBridge {
         case 'libraryStorageChanged':
           _libraryStorageEvents.add(null);
           return null;
+        case 'extensionVerificationNotificationTapped':
+          _verificationNotificationEvents.add(null);
+          return null;
         case 'iosBackgroundDownloadExpired':
           final raw = call.arguments;
           var itemIds = const <String>[];

lib/services/verification_notification.dart

@@ -0,0 +1,91 @@
+import 'dart:async';
+import 'dart:convert';
+
+class VerificationNotification {
+  const VerificationNotification({
+    required this.extensionId,
+    required this.itemId,
+    required this.tapId,
+  });
+
+  final String extensionId;
+  final String itemId;
+  final String tapId;
+
+  String encode() => jsonEncode({
+    'kind': 'extension_verification',
+    'extension_id': extensionId,
+    'item_id': itemId,
+    'tap_id': tapId,
+  });
+
+  static VerificationNotification? parse(Object? payload) {
+    try {
+      final value = payload is String ? jsonDecode(payload) : payload;
+      if (value is! Map || value['kind'] != 'extension_verification') {
+        return null;
+      }
+      final extensionId = value['extension_id'];
+      final itemId = value['item_id'];
+      final tapId = value['tap_id'];
+      if (extensionId is! String ||
+          extensionId.trim().isEmpty ||
+          itemId is! String ||
+          itemId.trim().isEmpty ||
+          tapId is! String ||
+          tapId.trim().isEmpty) {
+        return null;
+      }
+      return VerificationNotification(
+        extensionId: extensionId.trim(),
+        itemId: itemId.trim(),
+        tapId: tapId.trim(),
+      );
+    } on FormatException {
+      return null;
+    }
+  }
+}
+
+/// Holds cold-start taps until extensions and queue restoration are ready.
+/// A repeated native/plugin delivery must not launch a second challenge.
+class VerificationNotificationRouter {
+  final Map<String, VerificationNotification> _pending = {};
+  final Set<String> _handled = {};
+  final Set<String> _active = {};
+  Future<void> Function(VerificationNotification)? _handler;
+
+  void setHandler(Future<void> Function(VerificationNotification)? handler) {
+    _handler = handler;
+    _drain();
+  }
+
+  void receive(Object? payload) {
+    final target = VerificationNotification.parse(payload);
+    if (target == null ||
+        _handled.contains(target.tapId) ||
+        _active.contains(target.tapId)) {
+      return;
+    }
+    _pending.putIfAbsent(target.tapId, () => target);
+    _drain();
+  }
+
+  void _drain() {
+    final handler = _handler;
+    if (handler == null) return;
+    for (final target in _pending.values.toList()) {
+      _pending.remove(target.tapId);
+      _active.add(target.tapId);
+      // The queue deduplicates flows per extension. A different provider's
+      // notification must not wait behind an unrelated grant timeout.
+      unawaited(
+        Future<void>.sync(() => handler(target)).whenComplete(() {
+          _active.remove(target.tapId);
+          _handled.add(target.tapId);
+          if (_handled.length > 32) _handled.remove(_handled.first);
+        }),
+      );
+    }
+  }
+}