Pause polling and show a banner when the backend is unreachable

Adds a centralized BackendReachability singleton fed by a Dio interceptor (connection-level failures only) and connectivity_plus. PolledValue subscribes to it and pauses on offline / reloads immediately on reconnect, replacing the previous per-card error cascade. MainShell renders a global OfflineBanner with Retry and Settings actions; cards downgrade error→stale when offline so the banner is the only red element. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-07-08 19:21:54 +02:00 · 2026-05-31 18:21:55 -04:00
parent 8be65f3ffa
commit b5da90be59
15 changed files with 388 additions and 47 deletions
@@ -0,0 +1,96 @@
+import 'dart:async';
+
+import 'package:connectivity_plus/connectivity_plus.dart';
+import 'package:dio/dio.dart';
+import 'package:flutter/foundation.dart';
+
+import 'oott_api.dart';
+
+class BackendReachability extends ChangeNotifier {
+  BackendReachability._internal() {
+    _subscription = Connectivity().onConnectivityChanged.listen(
+      _handleConnectivityChange,
+    );
+    Connectivity().checkConnectivity().then(_handleConnectivityChange);
+  }
+
+  static final BackendReachability instance = BackendReachability._internal();
+
+  StreamSubscription<List<ConnectivityResult>>? _subscription;
+  Future<void> Function()? _prober;
+
+  bool _deviceHasNetwork = true;
+  bool _isBackendReachable = true;
+  DateTime? _lastSuccessAt;
+  DateTime? _lastFailureAt;
+  String? _lastErrorMessage;
+  bool _probing = false;
+
+  bool get deviceHasNetwork => _deviceHasNetwork;
+  bool get isBackendReachable => _isBackendReachable;
+  bool get isOnline => _deviceHasNetwork && _isBackendReachable;
+  bool get isProbing => _probing;
+  DateTime? get lastSuccessAt => _lastSuccessAt;
+  DateTime? get lastFailureAt => _lastFailureAt;
+  String? get lastErrorMessage => _lastErrorMessage;
+
+  void setProber(Future<void> Function() prober) {
+    _prober = prober;
+  }
+
+  void recordSuccess() {
+    _lastSuccessAt = DateTime.now();
+    _lastErrorMessage = null;
+    final wasReachable = _isBackendReachable;
+    _isBackendReachable = true;
+    if (!wasReachable) notifyListeners();
+  }
+
+  void recordFailure(DioException error) {
+    if (!_isConnectionLevel(error)) return;
+    _lastFailureAt = DateTime.now();
+    _lastErrorMessage = dioErrorToUserMessage(error);
+    final wasReachable = _isBackendReachable;
+    _isBackendReachable = false;
+    if (wasReachable) notifyListeners();
+  }
+
+  Future<void> probe() async {
+    final prober = _prober;
+    if (prober == null || _probing) return;
+    _probing = true;
+    notifyListeners();
+    try {
+      await prober();
+    } catch (_) {
+      // Interceptor records the outcome; nothing else to do here.
+    } finally {
+      _probing = false;
+      notifyListeners();
+    }
+  }
+
+  void _handleConnectivityChange(List<ConnectivityResult> results) {
+    final hasNetwork = results.any((r) => r != ConnectivityResult.none);
+    if (hasNetwork == _deviceHasNetwork) return;
+    _deviceHasNetwork = hasNetwork;
+    notifyListeners();
+    if (hasNetwork) {
+      unawaited(probe());
+    }
+  }
+
+  bool _isConnectionLevel(DioException error) {
+    if (error.type == DioExceptionType.cancel) return false;
+    // Anything without a response from the server is a connection-level
+    // failure (timeouts, connection refused, DNS, TLS, web fetch errors
+    // surfaced as DioExceptionType.unknown, etc.).
+    return error.response == null;
+  }
+
+  @override
+  void dispose() {
+    _subscription?.cancel();
+    super.dispose();
+  }
+}