Enhance data route

lib/src/middlewares/data_fetch_middleware.dart

@@ -1,8 +1,7 @@
 import 'package:core/core.dart';
 import 'package:dart_frog/dart_frog.dart';
-import 'package:data_repository/data_repository.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/middlewares/ownership_check_middleware.dart';
-import 'package:flutter_news_app_api_server_full_source_code/src/services/dashboard_summary_service.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/registry/data_operation_registry.dart';
 import 'package:logging/logging.dart';
 
 final _log = Logger('DataFetchMiddleware');
@@ -31,9 +30,7 @@ Middleware dataFetchMiddleware() {
       final item = await _fetchItem(context, modelName, id);
 
       if (item == null) {
-        _log.warning(
-          'Item not found for model "$modelName", id "$id".',
-        );
+        _log.warning('Item not found for model "$modelName", id "$id".');
         throw NotFoundException(
           'The requested item of type "$modelName" with id "$id" was not found.',
         );
@@ -50,79 +47,30 @@ Middleware dataFetchMiddleware() {
 }
 
 /// Helper function to fetch an item from the correct repository based on the
-/// model name.
+/// model name by using the [DataOperationRegistry].
 ///
-/// This function contains the switch statement that maps a `modelName` string
-/// to a specific `DataRepository` call.
+/// This function looks up the appropriate fetcher function from the registry
+/// and invokes it. This avoids a large `switch` statement and makes the
+/// system easily extensible.
 ///
 /// Throws [OperationFailedException] for unsupported model types.
 Future<dynamic> _fetchItem(
   RequestContext context,
   String modelName,
   String id,
 ) async {
-  // The `userId` is not needed here because this middleware's purpose is to
-  // fetch the item regardless of ownership. Ownership is checked in a
-  // subsequent middleware. We pass `null` for `userId` to ensure we are
-  // performing a global lookup for the item.
-  const String? userId = null;
-
   try {
-    switch (modelName) {
-      case 'headline':
-        return await context.read<DataRepository<Headline>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'topic':
-        return await context
-            .read<DataRepository<Topic>>()
-            .read(id: id, userId: userId);
-      case 'source':
-        return await context.read<DataRepository<Source>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'country':
-        return await context.read<DataRepository<Country>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'language':
-        return await context.read<DataRepository<Language>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'user':
-        return await context
-            .read<DataRepository<User>>()
-            .read(id: id, userId: userId);
-      case 'user_app_settings':
-        return await context.read<DataRepository<UserAppSettings>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'user_content_preferences':
-        return await context
-            .read<DataRepository<UserContentPreferences>>()
-            .read(
-              id: id,
-              userId: userId,
-            );
-      case 'remote_config':
-        return await context.read<DataRepository<RemoteConfig>>().read(
-              id: id,
-              userId: userId,
-            );
-      case 'dashboard_summary':
-        // This is a special case that doesn't use a standard repository.
-        return await context.read<DashboardSummaryService>().getSummary();
-      default:
-        _log.warning('Unsupported model type "$modelName" for fetch operation.');
-        throw OperationFailedException(
-          'Unsupported model type "$modelName" for fetch operation.',
-        );
+    final registry = context.read<DataOperationRegistry>();
+    final fetcher = registry.itemFetchers[modelName];
+
+    if (fetcher == null) {
+      _log.warning('Unsupported model type "$modelName" for fetch operation.');
+      throw OperationFailedException(
+        'Unsupported model type "$modelName" for fetch operation.',
+      );
     }
+
+    return await fetcher(context, id);
   } on NotFoundException {
     // The repository will throw this if the item doesn't exist.
     // We return null to let the main middleware handler throw a more

lib/src/registry/data_operation_registry.dart

@@ -0,0 +1,240 @@
+import 'package:core/core.dart';
+import 'package:dart_frog/dart_frog.dart';
+import 'package:data_repository/data_repository.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/middlewares/ownership_check_middleware.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/services/dashboard_summary_service.dart';
+
+// --- Typedefs for Data Operations ---
+
+/// A function that fetches a single item by its ID.
+typedef ItemFetcher =
+    Future<dynamic> Function(RequestContext context, String id);
+
+/// A function that fetches a paginated list of items.
+typedef AllItemsReader =
+    Future<PaginatedResponse<dynamic>> Function(
+      RequestContext context,
+      String? userId,
+      Map<String, dynamic>? filter,
+      List<SortOption>? sort,
+      PaginationOptions? pagination,
+    );
+
+/// A function that creates a new item.
+typedef ItemCreator =
+    Future<dynamic> Function(
+      RequestContext context,
+      dynamic item,
+      String? userId,
+    );
+
+/// A function that updates an existing item.
+typedef ItemUpdater =
+    Future<dynamic> Function(
+      RequestContext context,
+      String id,
+      dynamic item,
+      String? userId,
+    );
+
+/// A function that deletes an item by its ID.
+typedef ItemDeleter =
+    Future<void> Function(RequestContext context, String id, String? userId);
+
+/// {@template data_operation_registry}
+/// A centralized registry for all data handling functions (CRUD operations).
+///
+/// This class uses a map-based strategy to associate model names (strings)
+/// with their corresponding data operation functions. This approach avoids
+/// large, repetitive `switch` statements in the route handlers, making the
+/// code more maintainable, scalable, and easier to read.
+///
+/// By centralizing these mappings, we create a single source of truth for how
+/// data operations are performed for each model, improving consistency across
+/// the API.
+/// {@endtemplate}
+class DataOperationRegistry {
+  /// {@macro data_operation_registry}
+  DataOperationRegistry() {
+    _registerOperations();
+  }
+
+  // --- Private Maps to Hold Operation Functions ---
+
+  final Map<String, ItemFetcher> _itemFetchers = {};
+  final Map<String, AllItemsReader> _allItemsReaders = {};
+  final Map<String, ItemCreator> _itemCreators = {};
+  final Map<String, ItemUpdater> _itemUpdaters = {};
+  final Map<String, ItemDeleter> _itemDeleters = {};
+
+  // --- Public Getters to Access Operation Maps ---
+
+  /// Provides access to the map of item fetcher functions.
+  Map<String, ItemFetcher> get itemFetchers => _itemFetchers;
+
+  /// Provides access to the map of collection reader functions.
+  Map<String, AllItemsReader> get allItemsReaders => _allItemsReaders;
+
+  /// Provides access to the map of item creator functions.
+  Map<String, ItemCreator> get itemCreators => _itemCreators;
+
+  /// Provides access to the map of item updater functions.
+  Map<String, ItemUpdater> get itemUpdaters => _itemUpdaters;
+
+  /// Provides access to the map of item deleter functions.
+  Map<String, ItemDeleter> get itemDeleters => _itemDeleters;
+
+  /// Populates the operation maps with their respective functions.
+  void _registerOperations() {
+    // --- Register Item Fetchers ---
+    _itemFetchers.addAll({
+      'headline': (c, id) =>
+          c.read<DataRepository<Headline>>().read(id: id, userId: null),
+      'topic': (c, id) =>
+          c.read<DataRepository<Topic>>().read(id: id, userId: null),
+      'source': (c, id) =>
+          c.read<DataRepository<Source>>().read(id: id, userId: null),
+      'country': (c, id) =>
+          c.read<DataRepository<Country>>().read(id: id, userId: null),
+      'language': (c, id) =>
+          c.read<DataRepository<Language>>().read(id: id, userId: null),
+      'user': (c, id) =>
+          c.read<DataRepository<User>>().read(id: id, userId: null),
+      'user_app_settings': (c, id) =>
+          c.read<DataRepository<UserAppSettings>>().read(id: id, userId: null),
+      'user_content_preferences': (c, id) => c
+          .read<DataRepository<UserContentPreferences>>()
+          .read(id: id, userId: null),
+      'remote_config': (c, id) =>
+          c.read<DataRepository<RemoteConfig>>().read(id: id, userId: null),
+      'dashboard_summary': (c, id) =>
+          c.read<DashboardSummaryService>().getSummary(),
+    });
+
+    // --- Register "Read All" Readers ---
+    _allItemsReaders.addAll({
+      'headline': (c, uid, f, s, p) => c
+          .read<DataRepository<Headline>>()
+          .readAll(userId: uid, filter: f, sort: s, pagination: p),
+      'topic': (c, uid, f, s, p) => c.read<DataRepository<Topic>>().readAll(
+        userId: uid,
+        filter: f,
+        sort: s,
+        pagination: p,
+      ),
+      'source': (c, uid, f, s, p) => c.read<DataRepository<Source>>().readAll(
+        userId: uid,
+        filter: f,
+        sort: s,
+        pagination: p,
+      ),
+      'country': (c, uid, f, s, p) => c.read<DataRepository<Country>>().readAll(
+        userId: uid,
+        filter: f,
+        sort: s,
+        pagination: p,
+      ),
+      'language': (c, uid, f, s, p) => c
+          .read<DataRepository<Language>>()
+          .readAll(userId: uid, filter: f, sort: s, pagination: p),
+      'user': (c, uid, f, s, p) => c.read<DataRepository<User>>().readAll(
+        userId: uid,
+        filter: f,
+        sort: s,
+        pagination: p,
+      ),
+    });
+
+    // --- Register Item Creators ---
+    _itemCreators.addAll({
+      'headline': (c, item, uid) => c.read<DataRepository<Headline>>().create(
+        item: item as Headline,
+        userId: uid,
+      ),
+      'topic': (c, item, uid) => c.read<DataRepository<Topic>>().create(
+        item: item as Topic,
+        userId: uid,
+      ),
+      'source': (c, item, uid) => c.read<DataRepository<Source>>().create(
+        item: item as Source,
+        userId: uid,
+      ),
+      'country': (c, item, uid) => c.read<DataRepository<Country>>().create(
+        item: item as Country,
+        userId: uid,
+      ),
+      'language': (c, item, uid) => c.read<DataRepository<Language>>().create(
+        item: item as Language,
+        userId: uid,
+      ),
+      'remote_config': (c, item, uid) => c
+          .read<DataRepository<RemoteConfig>>()
+          .create(item: item as RemoteConfig, userId: uid),
+    });
+
+    // --- Register Item Updaters ---
+    _itemUpdaters.addAll({
+      'headline': (c, id, item, uid) => c
+          .read<DataRepository<Headline>>()
+          .update(id: id, item: item as Headline, userId: uid),
+      'topic': (c, id, item, uid) => c.read<DataRepository<Topic>>().update(
+        id: id,
+        item: item as Topic,
+        userId: uid,
+      ),
+      'source': (c, id, item, uid) => c.read<DataRepository<Source>>().update(
+        id: id,
+        item: item as Source,
+        userId: uid,
+      ),
+      'country': (c, id, item, uid) => c.read<DataRepository<Country>>().update(
+        id: id,
+        item: item as Country,
+        userId: uid,
+      ),
+      'language': (c, id, item, uid) => c
+          .read<DataRepository<Language>>()
+          .update(id: id, item: item as Language, userId: uid),
+      'user': (c, id, item, uid) {
+        final repo = c.read<DataRepository<User>>();
+        final existingUser = c.read<FetchedItem<dynamic>>().data as User;
+        final updatedUser = existingUser.copyWith(
+          feedActionStatus: (item as User).feedActionStatus,
+        );
+        return repo.update(id: id, item: updatedUser, userId: uid);
+      },
+      'user_app_settings': (c, id, item, uid) => c
+          .read<DataRepository<UserAppSettings>>()
+          .update(id: id, item: item as UserAppSettings, userId: uid),
+      'user_content_preferences': (c, id, item, uid) => c
+          .read<DataRepository<UserContentPreferences>>()
+          .update(id: id, item: item as UserContentPreferences, userId: uid),
+      'remote_config': (c, id, item, uid) => c
+          .read<DataRepository<RemoteConfig>>()
+          .update(id: id, item: item as RemoteConfig, userId: uid),
+    });
+
+    // --- Register Item Deleters ---
+    _itemDeleters.addAll({
+      'headline': (c, id, uid) =>
+          c.read<DataRepository<Headline>>().delete(id: id, userId: uid),
+      'topic': (c, id, uid) =>
+          c.read<DataRepository<Topic>>().delete(id: id, userId: uid),
+      'source': (c, id, uid) =>
+          c.read<DataRepository<Source>>().delete(id: id, userId: uid),
+      'country': (c, id, uid) =>
+          c.read<DataRepository<Country>>().delete(id: id, userId: uid),
+      'language': (c, id, uid) =>
+          c.read<DataRepository<Language>>().delete(id: id, userId: uid),
+      'user': (c, id, uid) =>
+          c.read<DataRepository<User>>().delete(id: id, userId: uid),
+      'user_app_settings': (c, id, uid) =>
+          c.read<DataRepository<UserAppSettings>>().delete(id: id, userId: uid),
+      'user_content_preferences': (c, id, uid) => c
+          .read<DataRepository<UserContentPreferences>>()
+          .delete(id: id, userId: uid),
+      'remote_config': (c, id, uid) =>
+          c.read<DataRepository<RemoteConfig>>().delete(id: id, userId: uid),
+    });
+  }
+}

routes/_middleware.dart

@@ -6,6 +6,7 @@ import 'package:flutter_news_app_api_server_full_source_code/src/config/app_depe
 import 'package:flutter_news_app_api_server_full_source_code/src/middlewares/error_handler.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/models/request_id.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/rbac/permission_service.dart';
+import 'package:flutter_news_app_api_server_full_source_code/src/registry/data_operation_registry.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/registry/model_registry.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/auth_service.dart';
 import 'package:flutter_news_app_api_server_full_source_code/src/services/auth_token_service.dart';
@@ -84,6 +85,9 @@ Handler middleware(Handler handler) {
           // 2. Provide all dependencies to the inner handler.
           final deps = AppDependencies.instance;
           return handler
+              .use(
+                provider<DataOperationRegistry>((_) => DataOperationRegistry()),
+              )
               .use(provider<ModelRegistryMap>((_) => modelRegistry))
               .use(
                 provider<DataRepository<Headline>>(