Implement TaskViewModel with tests and mock data

This commit introduces the TaskViewModel, which manages the business logic for tasks. The ViewModel interacts with a mock data source, providing functionalities like fetching tasks, selecting a task, creating, and deleting tasks.

Additionally, comprehensive tests for TaskViewModel have been added to ensure its behavior aligns with expectations. The mock data source has also been updated to support the new functionalities.

Key Features:
- Task management in TaskViewModel.
- Tests for each major functionality in TaskViewModel.
- Mock data source to simulate data interactions.

lib/viewmodels/mock_data.dart

@@ -0,0 +1,20 @@
+import 'package:auto_gpt_flutter_client/models/task.dart';
+
+/// A list of mock tasks for the application.
+/// TODO: Remove this file when we implement TaskService
+List<Task> mockTasks = [
+  Task(id: 1, title: 'Task 1'),
+  Task(id: 2, title: 'Task 2'),
+  Task(id: 3, title: 'Task 3'),
+  // ... add more mock tasks as needed
+];
+
+/// Adds a task to the mock data.
+void addTask(Task task) {
+  mockTasks.add(task);
+}
+
+/// Removes a task from the mock data based on its ID.
+void removeTask(int id) {
+  mockTasks.removeWhere((task) => task.id == id);
+}

lib/viewmodels/task_viewmodel.dart

@@ -0,0 +1,68 @@
+import 'package:auto_gpt_flutter_client/models/task.dart';
+import 'package:auto_gpt_flutter_client/viewmodels/mock_data.dart';
+import 'package:flutter/foundation.dart';
+import 'package:collection/collection.dart';
+
+// TODO: Update whole class once we have created TaskService
+class TaskViewModel with ChangeNotifier {
+  List<Task> _tasks = [];
+  Task? _selectedTask; // This will store the currently selected task
+
+  /// Returns the list of tasks.
+  List<Task> get tasks => _tasks;
+
+  /// Returns the currently selected task.
+  Task? get selectedTask => _selectedTask;
+
+  /// Adds a task.
+  void createTask(String title) {
+    // Generate an ID (This is a simplistic approach for mock data)
+    final id = _tasks.length + 1;
+    final newTask = Task(id: id, title: title);
+
+    // Add to data source
+    addTask(newTask);
+
+    // Update local tasks list and notify listeners
+    _tasks.add(newTask);
+    notifyListeners();
+  }
+
+  /// Deletes a task.
+  void deleteTask(int id) {
+    // Remove from data source
+    removeTask(id);
+
+    // Update local tasks list and notify listeners
+    _tasks.removeWhere((task) => task.id == id);
+    notifyListeners();
+  }
+
+  /// Fetches tasks from the data source.
+  void fetchTasks() {
+    try {
+      _tasks = mockTasks;
+      notifyListeners(); // Notify listeners to rebuild UI
+      print("Tasks fetched successfully!");
+    } catch (error) {
+      print("Error fetching tasks: $error");
+      // TODO: Handle additional error scenarios or log them as required
+    }
+  }
+
+  /// Handles the selection of a task by its ID.
+  void selectTask(int id) {
+    final task = _tasks.firstWhereOrNull((t) => t.id == id);
+
+    if (task != null) {
+      _selectedTask = task;
+      print("Selected task with ID: ${task.id} and Title: ${task.title}");
+      notifyListeners(); // Notify listeners to rebuild UI
+    } else {
+      final errorMessage =
+          "Error: Attempted to select a task with ID: $id that does not exist in the data source.";
+      print(errorMessage);
+      throw ArgumentError(errorMessage);
+    }
+  }
+}

pubspec.lock

@@ -34,13 +34,13 @@ packages:
     source: hosted
     version: "1.1.1"
   collection:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: collection
-      sha256: "4a07be6cb69c84d677a6c3096fcf960cc3285a8330b4603e0d463d15d9bd934c"
+      sha256: f092b211a4319e98e5ff58223576de6c2803db36221657b46c82574721240687
       url: "https://pub.dev"
     source: hosted
-    version: "1.17.1"
+    version: "1.17.2"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -75,14 +75,6 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
-  js:
-    dependency: transitive
-    description:
-      name: js
-      sha256: f2c445dce49627136094980615a031419f7f3eb393237e4ecd97ac15dea343f3
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.6.7"
   lints:
     dependency: transitive
     description:
@@ -95,18 +87,18 @@ packages:
     dependency: transitive
     description:
       name: matcher
-      sha256: "6501fbd55da300384b768785b83e5ce66991266cec21af89ab9ae7f5ce1c4cbb"
+      sha256: "1803e76e6653768d64ed8ff2e1e67bea3ad4b923eb5c56a295c3e634bad5960e"
       url: "https://pub.dev"
     source: hosted
-    version: "0.12.15"
+    version: "0.12.16"
   material_color_utilities:
     dependency: transitive
     description:
       name: material_color_utilities
-      sha256: d92141dc6fe1dad30722f9aa826c7fbc896d021d792f80678280601aff8cf724
+      sha256: "9528f2f296073ff54cb9fee677df673ace1218163c3bc7628093e7eed5203d41"
       url: "https://pub.dev"
     source: hosted
-    version: "0.2.0"
+    version: "0.5.0"
   meta:
     dependency: transitive
     description:
@@ -132,10 +124,10 @@ packages:
     dependency: transitive
     description:
       name: source_span
-      sha256: dd904f795d4b4f3b870833847c461801f6750a9fa8e61ea5ac53f9422b31f250
+      sha256: "53e943d4206a5e30df338fd4c6e7a077e02254531b138a15aec3bd143c1a8b3c"
       url: "https://pub.dev"
     source: hosted
-    version: "1.9.1"
+    version: "1.10.0"
   stack_trace:
     dependency: transitive
     description:
@@ -172,10 +164,10 @@ packages:
     dependency: transitive
     description:
       name: test_api
-      sha256: eb6ac1540b26de412b3403a163d919ba86f6a973fe6cc50ae3541b80092fdcfb
+      sha256: "75760ffd7786fffdfb9597c35c5b27eaeec82be8edfb6d71d32651128ed7aab8"
       url: "https://pub.dev"
     source: hosted
-    version: "0.5.1"
+    version: "0.6.0"
   vector_math:
     dependency: transitive
     description:
@@ -184,5 +176,13 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.1.4"
+  web:
+    dependency: transitive
+    description:
+      name: web
+      sha256: dc8ccd225a2005c1be616fe02951e2e342092edf968cf0844220383757ef8f10
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.1.4-beta"
 sdks:
-  dart: ">=3.0.0-417.2.beta <4.0.0"
+  dart: ">=3.1.0-185.0.dev <4.0.0"

pubspec.yaml

@@ -30,6 +30,7 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
+  collection: ^1.15.0
 
 
   # The following adds the Cupertino Icons font to your application.

test/task_viewmodel_test.dart

@@ -0,0 +1,79 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:auto_gpt_flutter_client/viewmodels/task_viewmodel.dart';
+import 'package:auto_gpt_flutter_client/viewmodels/mock_data.dart';
+
+void main() {
+  group('TaskViewModel', () {
+    late TaskViewModel viewModel;
+
+    setUp(() {
+      viewModel = TaskViewModel();
+    });
+
+    test('Fetches tasks successfully', () {
+      viewModel.fetchTasks();
+      expect(viewModel.tasks, isNotEmpty);
+    });
+
+    test('Selects a task successfully', () {
+      viewModel.fetchTasks();
+      viewModel.selectTask(1);
+      expect(viewModel.selectedTask, isNotNull);
+    });
+
+    test(
+        'Notifiers are properly telling UI to update after fetching a task or selecting a task',
+        () {
+      bool hasNotified = false;
+      viewModel.addListener(() {
+        hasNotified = true;
+      });
+
+      viewModel.fetchTasks();
+      expect(hasNotified, true);
+
+      hasNotified = false; // Reset for next test
+      viewModel.selectTask(1);
+      expect(hasNotified, true);
+    });
+
+    test('Simulate error happening while fetching a task', () {
+      // TODO: Implement once you have error handling in place in fetchTasks.
+    });
+
+    test('No tasks are fetched', () {
+      // Clear mock data for this test
+      mockTasks.clear();
+
+      viewModel.fetchTasks();
+      expect(viewModel.tasks, isEmpty);
+    });
+
+    test('No task is selected', () {
+      expect(viewModel.selectedTask, isNull);
+    });
+
+    test('Creates a task successfully', () {
+      final initialCount = viewModel.tasks.length;
+      viewModel.createTask('New Task');
+      expect(viewModel.tasks.length, initialCount + 1);
+    });
+
+    test('Deletes a task successfully', () {
+      viewModel.fetchTasks();
+      final initialCount = viewModel.tasks.length;
+      viewModel.deleteTask(1);
+      expect(viewModel.tasks.length, initialCount - 1);
+    });
+
+    test('Deletes a task with invalid id', () {
+      final initialCount = viewModel.tasks.length;
+      viewModel.deleteTask(9999); // Assuming no task with this id exists
+      expect(viewModel.tasks.length, initialCount); // Count remains same
+    });
+
+    test('Select a task that doesn\'t exist', () {
+      expect(() => viewModel.selectTask(9999), throwsA(isA<ArgumentError>()));
+    });
+  });
+}