added categories, import export, settings

lib/services/backup_service.dart

@@ -0,0 +1,161 @@
+/// Build, share, and restore a Receipity JSON backup.
+library;
+
+import 'dart:convert';
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:file_picker/file_picker.dart';
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+import 'package:share_plus/share_plus.dart';
+
+import 'backup_format.dart';
+import 'product_repository.dart';
+
+class BackupService {
+  BackupService(this.repository);
+
+  final ProductRepository repository;
+
+  Future<BackupDocument> buildBackup() async {
+    final products = await repository.dumpTable('products');
+    final shops = await repository.dumpTable('shops');
+    final images = <String, String>{};
+
+    Future<void> addImage(String? path) async {
+      final key = backupImageKey(path);
+      if (key == null || images.containsKey(key)) return;
+      final file = File(path!);
+      if (!file.existsSync()) return;
+      images[key] = base64Encode(await file.readAsBytes());
+    }
+
+    final rewrittenProducts = <Map<String, Object?>>[];
+    for (final row in products) {
+      final copy = Map<String, Object?>.from(row);
+      final path = copy['image_path'] as String?;
+      await addImage(path);
+      copy['image_path'] = backupImageKey(path);
+      rewrittenProducts.add(copy);
+    }
+
+    final rewrittenShops = <Map<String, Object?>>[];
+    for (final row in shops) {
+      final copy = Map<String, Object?>.from(row);
+      final path = copy['receipt_image_path'] as String?;
+      await addImage(path);
+      copy['receipt_image_path'] = backupImageKey(path);
+      rewrittenShops.add(copy);
+    }
+
+    return BackupDocument(
+      version: kBackupVersion,
+      exportedAt: DateTime.now().toIso8601String(),
+      darkMode: await repository.getDarkMode(),
+      supermarkets: await repository.dumpTable('supermarkets'),
+      products: rewrittenProducts,
+      shops: rewrittenShops,
+      shopItems: await repository.dumpTable('shop_items'),
+      images: images,
+    );
+  }
+
+  Future<bool> exportBackup() async {
+    final document = await buildBackup();
+    final bytes = Uint8List.fromList(utf8.encode(document.encode()));
+    final stamp = DateTime.now().toIso8601String().split('T').first;
+    final fileName = 'receipity-backup-$stamp.json';
+
+    try {
+      final saved = await FilePicker.saveFile(
+        dialogTitle: 'Save Receipity backup',
+        fileName: fileName,
+        bytes: bytes,
+        mimeType: 'application/json',
+        type: FileType.custom,
+        allowedExtensions: const ['json'],
+      );
+      return saved != null;
+    } catch (_) {
+      // Fall through to the share sheet if save-as is unavailable.
+    }
+
+    final dir = await getTemporaryDirectory();
+    final file = File(p.join(dir.path, fileName));
+    await file.writeAsBytes(bytes, flush: true);
+    final result = await SharePlus.instance.share(
+      ShareParams(
+        files: [XFile(file.path, mimeType: 'application/json')],
+        subject: 'Receipity backup',
+        text: 'Receipity backup $stamp',
+      ),
+    );
+    return result.status != ShareResultStatus.dismissed;
+  }
+
+  Future<bool> importBackup() async {
+    final picked = await FilePicker.pickFile(
+      dialogTitle: 'Import Receipity backup',
+      type: FileType.custom,
+      allowedExtensions: const ['json'],
+    );
+    if (picked == null) return false;
+    final bytes = await picked.readAsBytes();
+    await restoreBackup(utf8.decode(bytes));
+    return true;
+  }
+
+  Future<void> restoreBackup(String json) async {
+    final document = BackupDocument.parse(json);
+    await repository.clearImageFolders();
+
+    final products = <Map<String, Object?>>[];
+    final now = DateTime.now().toIso8601String();
+    for (final row in document.products) {
+      final copy = Map<String, Object?>.from(row);
+      copy['image_path'] = await _restoreImage(copy['image_path'], document.images);
+      copy['created_at'] ??= now;
+      copy['updated_at'] ??= copy['created_at'];
+      if (copy['normalized_name'] == null && copy['name'] is String) {
+        copy['normalized_name'] = ProductRepository.normalizeName(
+          copy['name']! as String,
+        );
+      }
+      products.add(copy);
+    }
+
+    final shops = <Map<String, Object?>>[];
+    for (final row in document.shops) {
+      final copy = Map<String, Object?>.from(row);
+      copy['receipt_image_path'] = await _restoreImage(
+        copy['receipt_image_path'],
+        document.images,
+      );
+      copy['created_at'] ??= now;
+      shops.add(copy);
+    }
+
+    await repository.replaceAllData(
+      supermarkets: document.supermarkets,
+      products: products,
+      shops: shops,
+      shopItems: document.shopItems,
+      darkMode: document.darkMode,
+    );
+  }
+
+  Future<String?> _restoreImage(
+    Object? key,
+    Map<String, String> images,
+  ) async {
+    if (key is! String || key.isEmpty) return null;
+    final encoded = images[key];
+    if (encoded == null) return null;
+    try {
+      return await repository.writeImageBytes(key, base64Decode(encoded));
+    } catch (_) {
+      return null;
+    }
+  }
+}