feat: implement idempotency key for critical API endpoints

lib/common/api/api_client.dart

@@ -16,6 +16,7 @@ import 'interceptors/bad_network_interceptor.dart';
 import 'interceptors/bad_request_interceptor.dart';
 import 'interceptors/connection_timeout_interceptor.dart';
 import 'interceptors/crashlytic_interceptor.dart';
+import 'interceptors/idempotency_interceptor.dart';
 import 'interceptors/internal_server_interceptor.dart';
 import 'interceptors/not_found_interceptor.dart';
 import 'interceptors/unauthorized_interceptor.dart';
@@ -30,6 +31,7 @@ class ApiClient {
     _dio.options.connectTimeout = const Duration(seconds: 20);
     _dio.options.validateStatus = (status) =>
         status != null && status >= 200 && status < 500;
+    _dio.interceptors.add(IdempotencyInterceptor(_dio));
     _dio.interceptors.add(BadNetworkErrorInterceptor());
     _dio.interceptors.add(BadRequestErrorInterceptor());
     _dio.interceptors.add(InternalServerErrorInterceptor());

lib/common/api/interceptors/idempotency_interceptor.dart

@@ -0,0 +1,104 @@
+import 'package:dio/dio.dart';
+import 'package:uuid/uuid.dart';
+
+/// Interceptor yang secara otomatis menambahkan header X-Idempotency-Key
+/// untuk endpoint-endpoint kritis yang memerlukan idempotency.
+///
+/// Key sebaiknya di-generate di level BLoC/Cubit saat user trigger action,
+/// lalu dikirim via headers. Interceptor ini hanya berfungsi sebagai fallback
+/// jika key belum di-set.
+///
+/// Jika response 409 dengan error code `request_in_progress`, interceptor
+/// akan retry setelah delay 1-2 detik.
+class IdempotencyInterceptor extends Interceptor {
+  static const _headerKey = 'X-Idempotency-Key';
+  static const _replayHeader = 'X-Idempotent-Replay';
+
+  // Endpoints that require idempotency keys (exact match)
+  static const _idempotentPaths = [
+    '/api/v1/payments',
+    '/api/v1/orders/void',
+  ];
+
+  // Endpoints that require idempotency keys (pattern match)
+  static final _idempotentPathPatterns = [
+    RegExp(r'/api/v1/orders/.+/add-items$'),
+    RegExp(r'/api/v1/orders/.+/refund$'),
+    RegExp(r'/api/v1/payments/.+/refund$'),
+  ];
+
+  static const _maxRetries = 3;
+  static const _retryDelay = Duration(seconds: 2);
+
+  final Dio _dio;
+
+  IdempotencyInterceptor(this._dio);
+
+  @override
+  void onRequest(RequestOptions options, RequestInterceptorHandler handler) {
+    if (options.method == 'POST' && _requiresIdempotencyKey(options.path)) {
+      // Gunakan key yang sudah di-set dari BLoC, atau generate baru sebagai fallback
+      options.headers[_headerKey] ??= const Uuid().v4();
+    }
+    handler.next(options);
+  }
+
+  @override
+  void onResponse(Response response, ResponseInterceptorHandler handler) {
+    // Log jika response adalah replay dari request sebelumnya
+    final isReplay = response.headers.value(_replayHeader);
+    if (isReplay == 'true') {
+      // Response ini adalah hasil dari request pertama yang sudah diproses.
+      // Treat as success — tidak perlu perlakuan khusus.
+    }
+    handler.next(response);
+  }
+
+  @override
+  void onError(DioException err, ErrorInterceptorHandler handler) async {
+    final response = err.response;
+    final options = err.requestOptions;
+
+    if (response == null) {
+      handler.next(err);
+      return;
+    }
+
+    // Handle 409 Conflict with request_in_progress
+    if (response.statusCode == 409 &&
+        _isRequestInProgress(response.data) &&
+        _requiresIdempotencyKey(options.path)) {
+      final retryCount = options.extra['_idempotency_retry_count'] ?? 0;
+
+      if (retryCount < _maxRetries) {
+        await Future.delayed(_retryDelay);
+
+        options.extra['_idempotency_retry_count'] = retryCount + 1;
+
+        try {
+          final retryResponse = await _dio.fetch(options);
+          handler.resolve(retryResponse);
+        } on DioException catch (e) {
+          handler.next(e);
+        }
+        return;
+      }
+    }
+
+    handler.next(err);
+  }
+
+  bool _requiresIdempotencyKey(String path) {
+    if (_idempotentPaths.any((p) => path.endsWith(p))) return true;
+    if (_idempotentPathPatterns.any((r) => r.hasMatch(path))) return true;
+    return false;
+  }
+
+  bool _isRequestInProgress(dynamic data) {
+    if (data is Map<String, dynamic>) {
+      final errorCode = data['error_code'] ?? data['code'] ?? '';
+      return errorCode == 'request_in_progress';
+    }
+    return false;
+  }
+}

lib/common/database/database_helper.dart

@@ -17,7 +17,7 @@ class DatabaseHelper {
 
     return await openDatabase(
       path,
-      version: 1, // Updated version for categories table
+      version: 2,
       onCreate: _onCreate,
       onUpgrade: _onUpgrade,
     );
@@ -38,6 +38,7 @@ class DatabaseHelper {
         business_type TEXT,
         image_url TEXT,
         printer_type TEXT,
+        print_to_checker INTEGER DEFAULT 0,
         metadata TEXT,
         is_active INTEGER,
         created_at TEXT,
@@ -107,7 +108,13 @@ class DatabaseHelper {
     await db.execute('CREATE INDEX idx_printers_type ON printers(type)');
   }
 
-  Future<void> _onUpgrade(Database db, int oldVersion, int newVersion) async {}
+  Future<void> _onUpgrade(Database db, int oldVersion, int newVersion) async {
+    if (oldVersion < 2) {
+      await db.execute(
+        'ALTER TABLE products ADD COLUMN print_to_checker INTEGER DEFAULT 0',
+      );
+    }
+  }
 
   Future<void> close() async {
     final db = await database;