chore: use custom behavioursubject instead

lib/features/todo/todo_page_view_model.dart

@@ -22,16 +22,15 @@ class TodoPageViewModel {
   final ValueNotifier<List<Todo>> todosNotifier = ValueNotifier([]);
   final ValueNotifier<bool> showCompletedTodosNotifier = ValueNotifier(false);
 
+  StreamSubscription<List<Todo>>? _subscription;
+
   bool get hasNonCompletedTodos =>
       todosNotifier.value.where((element) => element.completed).isNotEmpty;
 
   void init() {
-    _todoRepository.addListener(_onUpdateTodos);
-  }
-
-  void _onUpdateTodos() {
-    todosNotifier.value =
-        _todoRepository.todos.map((entity) => entity.toTodo()).toList();
+    _subscription = _todoRepository.watch().listen((todos) {
+      todosNotifier.value = todos;
+    });
   }
 
   Future<void> add({required String title}) async {
@@ -55,6 +54,7 @@ class TodoPageViewModel {
   }
 
   void dispose() {
-    _todoRepository.removeListener(_onUpdateTodos);
+    _subscription?.cancel();
+    _subscription = null;
   }
 }

lib/features/todo/todo_repository.dart

@@ -1,48 +1,48 @@
-import 'package:flutter/foundation.dart';
+import 'dart:async';
+
 import 'package:todo/features/todo/todo.dart';
 import 'package:todo/features/todo/todo_entity.dart';
 import 'package:uuid/uuid.dart';
 
-// provide a uniform way for services and view models to interact with your data
+// Provide a uniform way for services and view models to interact with your data
 class TodoRepository {
   TodoRepository({required FakeLocalDataSource fakeLocalDataSource})
       : _fakeLocalDataSource = fakeLocalDataSource;
 
   final FakeLocalDataSource _fakeLocalDataSource;
-  final ValueNotifier<List<TodoEntity>> _todosNotifier = ValueNotifier([]);
-  List<TodoEntity> get todos => _todosNotifier.value;
+  final BehaviorSubject<List<Todo>> _todosController = BehaviorSubject([]);
 
-  void addListener(void Function() listener) =>
-      _todosNotifier.addListener(listener);
-  void removeListener(void Function() listener) =>
-      _todosNotifier.removeListener(listener);
+  Stream<List<Todo>> watch() {
+    return _todosController.stream;
+  }
 
   Future<void> addTodo({required String title}) async {
     const uuid = Uuid();
     final id = uuid.v4();
     final todo = TodoEntity(id: id, title: title, completed: false);
 
     _fakeLocalDataSource.add();
-    _todosNotifier.value = [..._todosNotifier.value, todo];
+    _todosController.add([..._todosController.value, todo.toTodo()]);
   }
 
   Future<void> removeTodo(Todo todo) async {
     _fakeLocalDataSource.remove();
 
-    _todosNotifier.value =
-        _todosNotifier.value.where((t) => t.id != todo.id).toList();
+    _todosController
+        .add(_todosController.value.where((t) => t.id != todo.id).toList());
   }
 
   Future<void> toggleDone(Todo todo) async {
     _fakeLocalDataSource.update();
 
-    final updatedTodos = _todosNotifier.value.map((t) {
+    final updatedTodos = _todosController.value.map((t) {
       if (t.id == todo.id) {
-        return TodoEntity(id: t.id, title: t.title, completed: !t.completed);
+        return Todo(id: t.id, title: t.title, completed: !t.completed);
       }
       return t;
     }).toList();
-    _todosNotifier.value = updatedTodos;
+
+    _todosController.add(updatedTodos);
   }
 }
 
@@ -53,3 +53,39 @@ class FakeLocalDataSource {
 
   Future<void> update() async {}
 }
+
+class BehaviorSubject<T> {
+  // StreamController with broadcast mode
+  final StreamController<T> _controller;
+  T _currentValue;
+
+  // Constructor to initialize with an initial value
+  BehaviorSubject(T initialValue)
+      : _currentValue = initialValue,
+        _controller = StreamController<T>.broadcast();
+
+  // Getter for the current value
+  T get value => _currentValue;
+
+  // Adds a new value and broadcasts it to all listeners
+  void add(T newValue) {
+    _currentValue = newValue;
+    _controller.add(newValue);
+  }
+
+  // Exposes the stream to listen to changes
+  Stream<T> get stream => _controller.stream;
+
+  // Subscribes a listener and immediately emits the current value
+  StreamSubscription<T> listen(void Function(T) onData) {
+    final subscription = _controller.stream.listen(onData);
+    // Emit the current value immediately
+    onData(_currentValue);
+    return subscription;
+  }
+
+  // Closes the StreamController when done
+  Future<void> close() async {
+    await _controller.close();
+  }
+}

lib/shared/locator.dart

@@ -8,6 +8,8 @@ void setupLocators() {
   locator.registerLazySingleton<DateService>(() => DateService());
 
   locator.registerLazySingleton<TodoRepository>(
-    () => TodoRepository(),
+    () => TodoRepository(
+      fakeLocalDataSource: FakeLocalDataSource(),
+    ),
   );
 }