feat(observability): add Firebase Performance Monitoring with opt-in toggle

SPEC.md

@@ -53,7 +53,8 @@
 ## Observability
 
 - firebase_core (Firebase initialization)
-- firebase_crashlytics (opt-in crash reporting)
+- firebase_crashlytics (crash reporting, enabled by default)
+- firebase_performance (performance monitoring, enabled by default)
 
 ## Internationalization
 

lib/features/observability/data/crashlytics_preference_storage.dart

@@ -10,10 +10,10 @@ class CrashlyticsPreferenceStorage {
 
   bool read() {
     try {
-      return _prefs.getBool(_key) ?? false;
+      return _prefs.getBool(_key) ?? true;
     } catch (error, stack) {
       debugPrint('Failed to read crashlytics preference: $error\n$stack');
-      return false;
+      return true;
     }
   }
 

lib/features/observability/data/performance_preference_storage.dart

@@ -0,0 +1,26 @@
+import 'package:flutter/foundation.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class PerformancePreferenceStorage {
+  PerformancePreferenceStorage(this._prefs);
+
+  static const _key = 'observability_performance_enabled';
+
+  final SharedPreferences _prefs;
+
+  bool read() {
+    try {
+      return _prefs.getBool(_key) ?? true;
+    } catch (error, stack) {
+      debugPrint('Failed to read performance preference: $error\n$stack');
+      return true;
+    }
+  }
+
+  Future<void> write(bool enabled) async {
+    final didWrite = await _prefs.setBool(_key, enabled);
+    if (!didWrite) {
+      throw Exception('Failed to persist performance preference.');
+    }
+  }
+}

lib/features/observability/presentation/crashlytics_toggle_tile.dart

@@ -11,7 +11,7 @@ class CrashlyticsToggleTile extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final l10n = AppLocalizations.of(context);
     final crashlyticsAsync = ref.watch(crashlyticsPreferenceProvider);
-    final enabled = crashlyticsAsync.valueOrNull ?? false;
+    final enabled = crashlyticsAsync.valueOrNull ?? true;
 
     return SwitchListTile(
       secondary: const Icon(Icons.bug_report_outlined),

lib/features/observability/presentation/observability_section.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 
 import 'crashlytics_toggle_tile.dart';
+import 'performance_toggle_tile.dart';
 
 class ObservabilitySection extends StatelessWidget {
   const ObservabilitySection({super.key});
@@ -12,6 +13,8 @@ class ObservabilitySection extends StatelessWidget {
       children: [
         CrashlyticsToggleTile(),
         Divider(height: 1),
+        PerformanceToggleTile(),
+        Divider(height: 1),
       ],
     );
   }

lib/features/observability/presentation/performance_toggle_tile.dart

@@ -0,0 +1,40 @@
+import 'package:cookmate/l10n/app_localizations.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../providers.dart';
+
+class PerformanceToggleTile extends ConsumerWidget {
+  const PerformanceToggleTile({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final l10n = AppLocalizations.of(context);
+    final performanceAsync = ref.watch(performancePreferenceProvider);
+    final enabled = performanceAsync.valueOrNull ?? true;
+
+    return SwitchListTile(
+      secondary: const Icon(Icons.speed),
+      title: Text(l10n.settingsPerformanceTitle),
+      subtitle: Text(l10n.settingsPerformanceDescription),
+      value: enabled,
+      onChanged: performanceAsync.isLoading ? null : (value) async {
+        try {
+          await ref
+              .read(performancePreferenceProvider.notifier)
+              .setPreference(value);
+        } catch (error, stack) {
+          debugPrint('Failed to change performance: $error\n$stack');
+          if (context.mounted) {
+            ScaffoldMessenger.of(context).showSnackBar(
+              SnackBar(
+                content:
+                    Text(l10n.settingsPerformanceChangeFailureSnackbar),
+              ),
+            );
+          }
+        }
+      },
+    );
+  }
+}

lib/features/observability/providers.dart

@@ -1,9 +1,11 @@
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_crashlytics/firebase_crashlytics.dart';
+import 'package:firebase_performance/firebase_performance.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../core/shared_preferences_provider.dart';
 import 'data/crashlytics_preference_storage.dart';
+import 'data/performance_preference_storage.dart';
 
 final crashlyticsPreferenceStorageProvider =
     FutureProvider<CrashlyticsPreferenceStorage>((ref) async {
@@ -42,3 +44,41 @@ final crashlyticsPreferenceProvider =
     AsyncNotifierProvider<CrashlyticsPreferenceNotifier, bool>(
   CrashlyticsPreferenceNotifier.new,
 );
+
+final performancePreferenceStorageProvider =
+    FutureProvider<PerformancePreferenceStorage>((ref) async {
+  final prefs = await ref.watch(sharedPreferencesProvider.future);
+  return PerformancePreferenceStorage(prefs);
+});
+
+class PerformancePreferenceNotifier extends AsyncNotifier<bool> {
+  @override
+  Future<bool> build() async {
+    final storage =
+        await ref.watch(performancePreferenceStorageProvider.future);
+    return storage.read();
+  }
+
+  Future<void> setPreference(bool enabled) async {
+    final storage =
+        await ref.read(performancePreferenceStorageProvider.future);
+    state = const AsyncValue<bool>.loading().copyWithPrevious(state);
+    try {
+      await storage.write(enabled);
+      if (Firebase.apps.isNotEmpty) {
+        await FirebasePerformance.instance
+            .setPerformanceCollectionEnabled(enabled);
+      }
+      state = AsyncValue.data(enabled);
+    } catch (error, stack) {
+      state =
+          AsyncValue<bool>.error(error, stack).copyWithPrevious(state);
+      rethrow;
+    }
+  }
+}
+
+final performancePreferenceProvider =
+    AsyncNotifierProvider<PerformancePreferenceNotifier, bool>(
+  PerformancePreferenceNotifier.new,
+);

lib/l10n/app_de.arb

@@ -147,5 +147,9 @@
   "settingsSectionObservability": "Beobachtbarkeit",
   "settingsCrashlyticsTitle": "Absturzbericht",
   "settingsCrashlyticsDescription": "Anonyme Absturzberichte senden, um die App zu verbessern",
-  "settingsCrashlyticsChangeFailureSnackbar": "Absturzbericht-Einstellung konnte nicht geändert werden. Bitte versuchen Sie es erneut."
+  "settingsCrashlyticsChangeFailureSnackbar": "Absturzbericht-Einstellung konnte nicht geändert werden. Bitte versuchen Sie es erneut.",
+
+  "settingsPerformanceTitle": "Leistungsüberwachung",
+  "settingsPerformanceDescription": "Anonyme Leistungsdaten sammeln, um die App zu verbessern",
+  "settingsPerformanceChangeFailureSnackbar": "Leistungsüberwachung-Einstellung konnte nicht geändert werden. Bitte versuchen Sie es erneut."
 }

lib/l10n/app_en.arb

@@ -452,5 +452,14 @@
   "@settingsCrashlyticsDescription": { "description": "Subtitle explaining what crash reporting does." },
 
   "settingsCrashlyticsChangeFailureSnackbar": "Couldn't change crash reporting setting. Please try again.",
-  "@settingsCrashlyticsChangeFailureSnackbar": { "description": "Shown when persisting the crash reporting toggle fails." }
+  "@settingsCrashlyticsChangeFailureSnackbar": { "description": "Shown when persisting the crash reporting toggle fails." },
+
+  "settingsPerformanceTitle": "Performance monitoring",
+  "@settingsPerformanceTitle": { "description": "Title of the performance monitoring toggle tile." },
+
+  "settingsPerformanceDescription": "Collect anonymous performance data to help improve the app",
+  "@settingsPerformanceDescription": { "description": "Subtitle explaining what performance monitoring does." },
+
+  "settingsPerformanceChangeFailureSnackbar": "Couldn't change performance monitoring setting. Please try again.",
+  "@settingsPerformanceChangeFailureSnackbar": { "description": "Shown when persisting the performance monitoring toggle fails." }
 }

lib/l10n/app_es.arb

@@ -147,5 +147,9 @@
   "settingsSectionObservability": "Observabilidad",
   "settingsCrashlyticsTitle": "Informe de fallos",
   "settingsCrashlyticsDescription": "Enviar informes de fallos anónimos para mejorar la aplicación",
-  "settingsCrashlyticsChangeFailureSnackbar": "No se pudo cambiar la configuración de informe de fallos. Inténtelo de nuevo."
+  "settingsCrashlyticsChangeFailureSnackbar": "No se pudo cambiar la configuración de informe de fallos. Inténtelo de nuevo.",
+
+  "settingsPerformanceTitle": "Monitoreo de rendimiento",
+  "settingsPerformanceDescription": "Recopilar datos de rendimiento anónimos para mejorar la aplicación",
+  "settingsPerformanceChangeFailureSnackbar": "No se pudo cambiar la configuración de monitoreo de rendimiento. Inténtelo de nuevo."
 }

lib/l10n/app_fr.arb

@@ -147,5 +147,9 @@
   "settingsSectionObservability": "Observabilité",
   "settingsCrashlyticsTitle": "Rapport de plantage",
   "settingsCrashlyticsDescription": "Envoyer des rapports de plantage anonymes pour améliorer l'application",
-  "settingsCrashlyticsChangeFailureSnackbar": "Impossible de modifier le paramètre de rapport de plantage. Veuillez réessayer."
+  "settingsCrashlyticsChangeFailureSnackbar": "Impossible de modifier le paramètre de rapport de plantage. Veuillez réessayer.",
+
+  "settingsPerformanceTitle": "Rapport de performance",
+  "settingsPerformanceDescription": "Collecter des données de performance anonymes pour améliorer l'application",
+  "settingsPerformanceChangeFailureSnackbar": "Impossible de modifier le paramètre de performance. Veuillez réessayer."
 }

lib/main.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_crashlytics/firebase_crashlytics.dart';
+import 'package:firebase_performance/firebase_performance.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_gemma/flutter_gemma.dart';
@@ -10,6 +11,7 @@ import 'package:shared_preferences/shared_preferences.dart';
 
 import 'app.dart';
 import 'features/observability/data/crashlytics_preference_storage.dart';
+import 'features/observability/data/performance_preference_storage.dart';
 
 void main() {
   runZonedGuarded(
@@ -31,6 +33,15 @@ void main() {
 
         FlutterError.onError =
             FirebaseCrashlytics.instance.recordFlutterFatalError;
+
+        try {
+          final performanceEnabled =
+              PerformancePreferenceStorage(prefs).read();
+          await FirebasePerformance.instance
+              .setPerformanceCollectionEnabled(performanceEnabled);
+        } catch (e, stack) {
+          debugPrint('Firebase Performance init skipped: $e\n$stack');
+        }
       } catch (e, stack) {
         debugPrint('Firebase init skipped: $e\n$stack');
       }

pubspec.lock

@@ -265,6 +265,30 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "3.8.10"
+  firebase_performance:
+    dependency: "direct main"
+    description:
+      name: firebase_performance
+      sha256: b6948a02cb06d5da36e9f91f4a96b39745ab7565942a8134b7692ea6fc4ac595
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.10.1+10"
+  firebase_performance_platform_interface:
+    dependency: transitive
+    description:
+      name: firebase_performance_platform_interface
+      sha256: "836b219dc99c59ee5b854ba4f6432781f40ae75b31ea112f3b8b2ffce8a01cd4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.5+10"
+  firebase_performance_web:
+    dependency: transitive
+    description:
+      name: firebase_performance_web
+      sha256: "7b8cdc99f8c7ceafd6c3f51a3a661aef96bc9c5948af78d35bc9660941ed5b2f"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.7+16"
   fixnum:
     dependency: transitive
     description:

pubspec.yaml

@@ -53,6 +53,7 @@ dependencies:
   http: ^1.4.0
   firebase_core: ^3.13.0
   firebase_crashlytics: ^4.3.5
+  firebase_performance: ^0.10.0+12
 
 dev_dependencies:
   flutter_test:

test/features/observability/data/crashlytics_preference_storage_test.dart

@@ -13,8 +13,8 @@ void main() {
     storage = CrashlyticsPreferenceStorage(prefs);
   });
 
-  test('read returns false when nothing is stored', () {
-    expect(storage.read(), false);
+  test('read returns true when nothing is stored', () {
+    expect(storage.read(), true);
   });
 
   test('write then read returns the written value', () async {
@@ -28,12 +28,12 @@ void main() {
     expect(storage.read(), false);
   });
 
-  test('read returns false when stored value is corrupted', () async {
+  test('read returns true when stored value is corrupted', () async {
     SharedPreferences.setMockInitialValues(<String, Object>{
       'observability_crashlytics_enabled': 'not_a_bool',
     });
     final prefs = await SharedPreferences.getInstance();
     final s = CrashlyticsPreferenceStorage(prefs);
-    expect(s.read(), false);
+    expect(s.read(), true);
   });
 }

test/features/observability/data/performance_preference_storage_test.dart

@@ -0,0 +1,39 @@
+import 'package:cookmate/features/observability/data/performance_preference_storage.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  late PerformancePreferenceStorage storage;
+
+  setUp(() async {
+    SharedPreferences.setMockInitialValues(<String, Object>{});
+    final prefs = await SharedPreferences.getInstance();
+    storage = PerformancePreferenceStorage(prefs);
+  });
+
+  test('read returns true when nothing is stored', () {
+    expect(storage.read(), true);
+  });
+
+  test('write then read returns the written value', () async {
+    await storage.write(false);
+    expect(storage.read(), false);
+  });
+
+  test('write overwrites a previous value', () async {
+    await storage.write(false);
+    await storage.write(true);
+    expect(storage.read(), true);
+  });
+
+  test('read returns true when stored value is corrupted', () async {
+    SharedPreferences.setMockInitialValues(<String, Object>{
+      'observability_performance_enabled': 'not_a_bool',
+    });
+    final prefs = await SharedPreferences.getInstance();
+    final s = PerformancePreferenceStorage(prefs);
+    expect(s.read(), true);
+  });
+}