feat: add RetryInterceptor for AppResourcesGetCommand server error handling (#36)

- Add RetryInterceptor Dio interceptor with exponential backoff (3 retries at 2000ms, 4000ms, 8000ms)
- Retry on HTTP >= 500 (server errors) and connection/timeout errors
- Fail fast on HTTP 401 with 'Authentication token has expired.' exception
- Add interceptors barrel file
- Refactor command_runner.dart to use _buildDefaultDatasource() static method

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: SERDUN <26858237+SERDUN@users.noreply.github.com>

Author: SERDUN

lib/src/command_runner.dart

@@ -8,6 +8,7 @@ import 'package:pub_updater/pub_updater.dart';
 import 'package:webtrit_phone_tools/src/commands/commands.dart';
 import 'package:webtrit_phone_tools/src/version.dart';
 
+import 'commands/app_resources/interceptors/interceptors.dart';
 import 'commands/constants.dart';
 import 'utils/utils.dart';
 
@@ -32,18 +33,7 @@ class WebtritPhoneToolsCommandRunner extends CompletionCommandRunner<int> {
     PubUpdater? pubUpdater,
   })  : _logger = logger ?? Logger(),
         _httpClient = httpClient ?? HttpClient(configuratorApiUrl, Logger()),
-        _datasource = datasource ??
-            ConfiguratorBackandDatasource(
-              Dio(BaseOptions(baseUrl: 'https://us-central1-webtrit-configurator.cloudfunctions.net/api/v1'))
-                ..interceptors.add(
-                  LogInterceptor(
-                    requestBody: true,
-                    responseBody: true,
-                    logPrint: print,
-                  ),
-                ),
-              UnauthorizedInterceptor(),
-            ),
+        _datasource = datasource ?? _buildDefaultDatasource(),
         _keystoreReadmeUpdater = keystoreReadmeUpdater ?? KeystoreReadmeUpdater(Logger()),
         _pubUpdater = pubUpdater ?? PubUpdater(),
         super(executableName, description) {
@@ -79,6 +69,17 @@ class WebtritPhoneToolsCommandRunner extends CompletionCommandRunner<int> {
     addCommand(UpdateCommand(logger: _logger, pubUpdater: _pubUpdater));
   }
 
+  static ConfiguratorBackandDatasource _buildDefaultDatasource() {
+    final dio = Dio(BaseOptions(baseUrl: 'https://us-central1-webtrit-configurator.cloudfunctions.net/api/v1'))
+      ..interceptors.add(LogInterceptor(
+        requestBody: true,
+        responseBody: true,
+        logPrint: print,
+      ));
+    dio.interceptors.add(RetryInterceptor(dio: dio));
+    return ConfiguratorBackandDatasource(dio, UnauthorizedInterceptor());
+  }
+
   @override
   void printUsage() => _logger.info(usage);
 

lib/src/commands/app_resources/interceptors/interceptors.dart

@@ -0,0 +1 @@
+export 'retry_interceptor.dart';

lib/src/commands/app_resources/interceptors/retry_interceptor.dart

@@ -0,0 +1,64 @@
+import 'package:data/datasource/datasource.dart';
+
+class RetryInterceptor extends Interceptor {
+  RetryInterceptor({
+    required Dio dio,
+    int maxRetries = 3,
+    List<int> retryDelaysMs = const [2000, 4000, 8000],
+  })  : assert(retryDelaysMs.length >= maxRetries, 'retryDelaysMs must contain at least maxRetries entries'),
+        _dio = dio,
+        _maxRetries = maxRetries,
+        _retryDelaysMs = retryDelaysMs;
+
+  static const _retryCountKey = 'retryCount';
+
+  final Dio _dio;
+  final int _maxRetries;
+  final List<int> _retryDelaysMs;
+
+  @override
+  void onError(DioException err, ErrorInterceptorHandler handler) => _handleError(err, handler);
+
+  Future<void> _handleError(DioException err, ErrorInterceptorHandler handler) async {
+    try {
+      if (_isUnauthorized(err)) {
+        handler.reject(_buildUnauthorizedException(err));
+        return;
+      }
+
+      final retryCount = (err.requestOptions.extra[_retryCountKey] as int?) ?? 0;
+
+      if (!_shouldRetry(err) || retryCount >= _maxRetries) {
+        handler.next(err);
+        return;
+      }
+
+      await Future<void>.delayed(Duration(milliseconds: _retryDelaysMs[retryCount]));
+      err.requestOptions.extra[_retryCountKey] = retryCount + 1;
+      handler.resolve(await _dio.fetch(err.requestOptions));
+    } on DioException catch (e) {
+      handler.next(e);
+    } catch (_) {
+      handler.next(err);
+    }
+  }
+
+  bool _isUnauthorized(DioException err) => err.response?.statusCode == 401;
+
+  bool _shouldRetry(DioException err) => _isServerError(err) || _isConnectionError(err);
+
+  bool _isServerError(DioException err) => (err.response?.statusCode ?? 0) >= 500;
+
+  bool _isConnectionError(DioException err) =>
+      err.type == DioExceptionType.connectionTimeout ||
+      err.type == DioExceptionType.sendTimeout ||
+      err.type == DioExceptionType.receiveTimeout ||
+      err.type == DioExceptionType.connectionError;
+
+  DioException _buildUnauthorizedException(DioException err) => DioException(
+        requestOptions: err.requestOptions,
+        response: err.response,
+        type: err.type,
+        error: Exception('Authentication token has expired.'),
+      );
+}