Add backup and restore functionality for rental data in settings

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

lib/screens/settings_screen.dart

@@ -1,3 +1,4 @@
+import 'package:file_picker/file_picker.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import 'package:rental_income_tracker/state/rent_controller.dart';
@@ -12,6 +13,32 @@ class SettingsScreen extends StatefulWidget {
 class _SettingsScreenState extends State<SettingsScreen> {
   final TextEditingController _rentController = TextEditingController();
 
+  Future<bool> _confirmImport() async {
+    final result = await showDialog<bool>(
+      context: context,
+      builder: (context) {
+        return AlertDialog(
+          title: const Text('Import backup file?'),
+          content: const Text(
+            'This will overwrite current local settings and logged entries with the contents of the selected backup file.',
+          ),
+          actions: <Widget>[
+            TextButton(
+              onPressed: () => Navigator.of(context).pop(false),
+              child: const Text('Cancel'),
+            ),
+            FilledButton(
+              onPressed: () => Navigator.of(context).pop(true),
+              child: const Text('Import'),
+            ),
+          ],
+        );
+      },
+    );
+
+    return result ?? false;
+  }
+
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
@@ -103,16 +130,71 @@ class _SettingsScreenState extends State<SettingsScreen> {
               const SizedBox(height: 12),
               FilledButton.icon(
                 onPressed: () async {
-                  final path = await controller.exportJson();
+                  final directoryPath = await FilePicker.platform
+                      .getDirectoryPath(dialogTitle: 'Choose backup folder');
+                  if (directoryPath == null || !context.mounted) {
+                    return;
+                  }
+
+                  final path = await controller.exportBackupToDirectory(
+                    directoryPath,
+                  );
                   if (!context.mounted) {
                     return;
                   }
-                  ScaffoldMessenger.of(
-                    context,
-                  ).showSnackBar(SnackBar(content: Text('Exported to $path')));
+                  ScaffoldMessenger.of(context).showSnackBar(
+                    SnackBar(content: Text('Backup saved to $path')),
+                  );
                 },
                 icon: const Icon(Icons.download),
-                label: const Text('Export JSON'),
+                label: const Text('Create backup'),
+              ),
+              const SizedBox(height: 12),
+              FilledButton.icon(
+                onPressed: () async {
+                  final shouldImport = await _confirmImport();
+                  if (!shouldImport || !context.mounted) {
+                    return;
+                  }
+
+                  final result = await FilePicker.platform.pickFiles(
+                    dialogTitle: 'Choose backup file',
+                    type: FileType.custom,
+                    allowedExtensions: <String>['json'],
+                    withData: false,
+                  );
+                  final filePath = result?.files.single.path;
+                  if (filePath == null || !context.mounted) {
+                    return;
+                  }
+
+                  try {
+                    final path = await controller.importBackupFromFile(
+                      filePath,
+                    );
+                    if (!context.mounted) {
+                      return;
+                    }
+                    _rentController.text = controller.settings.rentUsd
+                        .toStringAsFixed(2);
+                    ScaffoldMessenger.of(context).showSnackBar(
+                      SnackBar(content: Text('Imported backup from $path')),
+                    );
+                  } catch (_) {
+                    if (!context.mounted) {
+                      return;
+                    }
+                    ScaffoldMessenger.of(context).showSnackBar(
+                      SnackBar(
+                        content: Text(
+                          controller.errorMessage ?? 'Restore failed.',
+                        ),
+                      ),
+                    );
+                  }
+                },
+                icon: const Icon(Icons.restore),
+                label: const Text('Import backup file'),
               ),
               const SizedBox(height: 16),
               const Text(

lib/state/rent_controller.dart

@@ -5,7 +5,6 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter_dotenv/flutter_dotenv.dart';
 import 'package:http/http.dart' as http;
 import 'package:intl/intl.dart';
-import 'package:path_provider/path_provider.dart';
 import 'package:rental_income_tracker/models/app_settings.dart';
 import 'package:rental_income_tracker/models/monthly_rent_record.dart';
 import 'package:rental_income_tracker/services/notification_service.dart';
@@ -417,7 +416,7 @@ class RentController extends ChangeNotifier {
     }
   }
 
-  Future<String> exportJson() async {
+  String _buildBackupJson() {
     final records = _records.values.toList()
       ..sort((a, b) {
         final byYear = a.year.compareTo(b.year);
@@ -433,14 +432,72 @@ class RentController extends ChangeNotifier {
       'records': records.map((e) => e.toJson()).toList(),
     };
 
-    final jsonString = const JsonEncoder.withIndent('  ').convert(payload);
-    final dir = await getApplicationDocumentsDirectory();
+    return const JsonEncoder.withIndent('  ').convert(payload);
+  }
+
+  Future<String> exportBackupToDirectory(String directoryPath) async {
+    final jsonString = _buildBackupJson();
     final timestamp = DateFormat('yyyyMMdd_HHmmss').format(DateTime.now());
-    final file = File('${dir.path}/rent_tracker_export_$timestamp.json');
+    final normalizedDirectory = directoryPath.endsWith(Platform.pathSeparator)
+        ? directoryPath.substring(0, directoryPath.length - 1)
+        : directoryPath;
+    final file = File(
+      '$normalizedDirectory${Platform.pathSeparator}rent_tracker_backup_$timestamp.json',
+    );
     await file.writeAsString(jsonString);
     return file.path;
   }
 
+  Future<void> _restoreFromPayload(Map<String, dynamic> payload) async {
+    final settingsJson = payload['settings'] as Map<String, dynamic>?;
+    final recordsJson = payload['records'] as List<dynamic>?;
+    if (settingsJson == null || recordsJson == null) {
+      throw StateError('Backup file is missing settings or records.');
+    }
+
+    _settings = AppSettings.fromJson(settingsJson);
+    final restoredRecords = <String, MonthlyRentRecord>{};
+    for (final item in recordsJson) {
+      final record = MonthlyRentRecord.fromJson(item as Map<String, dynamic>);
+      restoredRecords[record.key] = record;
+    }
+    _records = restoredRecords;
+
+    await _storageService.saveSettings(_settings);
+    await _storageService.saveRecords(_records);
+    await _notificationService.cancelAll();
+    await _syncNotificationScheduleForCurrentMonth();
+    notifyListeners();
+  }
+
+  Future<String> importBackupFromFile(String filePath) async {
+    _errorMessage = null;
+    _setLoading(true);
+
+    try {
+      final file = File(filePath);
+      if (!await file.exists()) {
+        throw StateError('Selected backup file could not be found.');
+      }
+
+      final raw = await file.readAsString();
+      final payload = jsonDecode(raw) as Map<String, dynamic>;
+
+      await _restoreFromPayload(payload);
+
+      return file.path;
+    } catch (err, stackTrace) {
+      if (kDebugMode) {
+        debugPrint('[RentController] importBackupFromFile failed: $err');
+        debugPrint(stackTrace.toString());
+      }
+      _errorMessage = err.toString();
+      rethrow;
+    } finally {
+      _setLoading(false);
+    }
+  }
+
   List<RentTableRow> buildRowsForSelectedYear() {
     final now = DateTime.now();
     final maxMonth = _selectedYear < now.year