Added Google Drive storage location

lib/services/app_state.dart

@@ -1,24 +1,46 @@
+import 'dart:async';
 import 'dart:io';
 
+import 'package:connectivity_plus/connectivity_plus.dart';
 import 'package:flutter/foundation.dart';
+import 'package:shared_preferences/shared_preferences.dart';
 import 'package:uuid/uuid.dart';
 
 import '../models/fuel_entry.dart';
 import '../models/vehicle.dart';
+import 'drive_auth_service.dart';
+import 'drive_sync_service.dart';
 import 'storage_service.dart';
 
+const _prefsKeyDriveFolderId = 'drive_app_folder_id';
+const _prefsKeyDriveFolderPath = 'drive_app_folder_path';
+
 /// Single source of truth for the app's in-memory data (vehicles + fuel
-/// entries), backed by [StorageService] for persistence. Screens read from
-/// this via Provider and call its mutating methods, which take care of
-/// writing through to disk and notifying listeners.
+/// entries), backed by [StorageService] for local persistence and
+/// [DriveSyncService] for pushing/pulling the shared Drive copy. Screens
+/// read from this via Provider and call its mutating methods, which write
+/// through to local disk immediately and kick off a best-effort background
+/// sync to Drive.
 class AppState extends ChangeNotifier {
   final StorageService storage = StorageService();
+  final DriveAuthService driveAuth = DriveAuthService();
+  late final DriveSyncService driveSync =
+      DriveSyncService(authService: driveAuth, storageService: storage);
   final _uuid = const Uuid();
 
   List<Vehicle> vehicles = [];
   List<FuelEntry> fuelEntries = [];
   bool isLoading = true;
 
+  bool isDriveConnected = false;
+  String? driveAccountEmail;
+  String? driveFolderPath;
+  bool isSyncing = false;
+  DateTime? lastSyncedAt;
+  Object? lastSyncError;
+
+  StreamSubscription<List<ConnectivityResult>>? _connectivitySubscription;
+
   Future<void> init() async {
     await storage.init();
     final data = await storage.loadData();
@@ -26,6 +48,100 @@ class AppState extends ChangeNotifier {
     fuelEntries = data.entries;
     isLoading = false;
     notifyListeners();
+
+    _connectivitySubscription = Connectivity().onConnectivityChanged.listen((results) {
+      if (results.any((r) => r != ConnectivityResult.none)) {
+        unawaited(syncNow());
+      }
+    });
+
+    unawaited(_restoreDriveConnection());
+  }
+
+  @override
+  void dispose() {
+    _connectivitySubscription?.cancel();
+    super.dispose();
+  }
+
+  Future<void> _restoreDriveConnection() async {
+    final signedIn = await driveAuth.attemptSilentSignIn();
+    if (!signedIn) return;
+
+    isDriveConnected = true;
+    driveAccountEmail = driveAuth.currentAccountEmail;
+
+    final prefs = await SharedPreferences.getInstance();
+    final folderId = prefs.getString(_prefsKeyDriveFolderId);
+    driveFolderPath = prefs.getString(_prefsKeyDriveFolderPath);
+    if (folderId != null) {
+      driveSync.configure(folderId);
+    }
+    notifyListeners();
+
+    if (folderId != null) {
+      unawaited(syncNow());
+    }
+  }
+
+  Future<void> connectDrive() async {
+    final email = await driveAuth.signIn();
+    isDriveConnected = true;
+    driveAccountEmail = email;
+    notifyListeners();
+  }
+
+  Future<void> disconnectDrive() async {
+    await driveAuth.signOut();
+    driveSync.clearConfiguration();
+    isDriveConnected = false;
+    driveAccountEmail = null;
+    driveFolderPath = null;
+
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.remove(_prefsKeyDriveFolderId);
+    await prefs.remove(_prefsKeyDriveFolderPath);
+    notifyListeners();
+  }
+
+  Future<void> chooseDriveFolder({
+    required String parentId,
+    required String breadcrumbPath,
+  }) async {
+    final folderId = await driveSync.selectAppFolder(parentId);
+    driveFolderPath = breadcrumbPath;
+
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_prefsKeyDriveFolderId, folderId);
+    await prefs.setString(_prefsKeyDriveFolderPath, breadcrumbPath);
+    notifyListeners();
+
+    unawaited(syncNow());
+  }
+
+  Future<void> syncNow() async {
+    if (isSyncing || !driveSync.isConfigured) return;
+
+    isSyncing = true;
+    notifyListeners();
+
+    final result = await driveSync.syncNow(
+      localVehicles: vehicles,
+      localFuelEntries: fuelEntries,
+    );
+
+    if (result.ranSync) {
+      vehicles = result.vehicles!;
+      fuelEntries = result.fuelEntries!;
+      await storage.saveData(vehicles: vehicles, entries: fuelEntries);
+      lastSyncedAt = DateTime.now();
+      lastSyncError = null;
+    } else if (result.error != null) {
+      lastSyncError = result.error;
+    }
+
+    isSyncing = false;
+    notifyListeners();
   }
 
   Future<void> addVehicle({
@@ -40,6 +156,7 @@ class AppState extends ChangeNotifier {
       model: model,
       color: color,
       licensePlate: licensePlate,
+      updatedAt: DateTime.now().toUtc(),
     ));
     await _persist();
   }
@@ -47,7 +164,7 @@ class AppState extends ChangeNotifier {
   Future<void> updateVehicle(Vehicle updated) async {
     final index = vehicles.indexWhere((v) => v.id == updated.id);
     if (index != -1) {
-      vehicles[index] = updated;
+      vehicles[index] = updated.copyWith(updatedAt: DateTime.now().toUtc());
       await _persist();
     }
   }
@@ -83,6 +200,7 @@ class AppState extends ChangeNotifier {
       pricePerGallon: pricePerGallon,
       totalCost: totalCost,
       receiptImagePath: storedImagePath,
+      updatedAt: DateTime.now().toUtc(),
     );
     fuelEntries.add(entry);
     await _persist();
@@ -117,13 +235,9 @@ class AppState extends ChangeNotifier {
     }
   }
 
-  Future<void> changeSaveDirectory(String newPath) async {
-    await storage.setSaveDirectory(newPath);
-    notifyListeners();
-  }
-
   Future<void> _persist() async {
     await storage.saveData(vehicles: vehicles, entries: fuelEntries);
     notifyListeners();
+    unawaited(syncNow());
   }
 }