Update ChatViewModel to Use ChatService and Step Model

This commit refactors the ChatViewModel to use the newly created ChatService and Step model for chat-related functionalities. The changes include:

- Replaced mock data source with real API calls via ChatService.
- Introduced _currentTaskId to keep track of the current task ID.
- Added fetchChatsForTask method to fetch steps related to the current task and populate the chat list.
- Implemented sendChatMessage to execute a step and add both user and agent messages to the chat list.

By making these changes, the ChatViewModel is now fully integrated with the backend services and models, thus enabling a more realistic and dynamic chat experience.

lib/viewmodels/chat_viewmodel.dart

@@ -1,46 +1,138 @@
+import 'package:auto_gpt_flutter_client/models/step.dart';
+import 'package:auto_gpt_flutter_client/models/step_request_body.dart';
+import 'package:flutter/foundation.dart';
+import 'package:auto_gpt_flutter_client/services/chat_service.dart';
 import 'package:auto_gpt_flutter_client/models/chat.dart';
 import 'package:auto_gpt_flutter_client/models/message_type.dart';
-import 'package:flutter/foundation.dart';
-import 'mock_data.dart'; // Import the mock data
 
-// TODO: Update whole class once we have created TaskService
 class ChatViewModel with ChangeNotifier {
+  final ChatService _chatService;
   List<Chat> _chats = [];
+  String? _currentTaskId;
+
+  ChatViewModel(this._chatService);
 
   /// Returns the current list of chats.
   List<Chat> get chats => _chats;
 
-  /// Fetches chats from the mock data source for a specific task.
-  void fetchChatsForTask(int taskId) {
+  String? get currentTaskId => _currentTaskId;
+
+  void setCurrentTaskId(String taskId) {
+    if (_currentTaskId != taskId) {
+      _currentTaskId = taskId;
+      fetchChatsForTask();
+    }
+  }
+
+  void clearCurrentTaskAndChats() {
+    _currentTaskId = null;
+    _chats.clear();
+    notifyListeners(); // Notify listeners to rebuild UI
+  }
+
+  /// Fetches chats from the data source for a specific task.
+  void fetchChatsForTask() async {
+    if (_currentTaskId == null) {
+      print("Error: Task ID is not set.");
+      return;
+    }
     try {
-      _chats = mockChats.where((chat) => chat.taskId == taskId).toList();
-      notifyListeners(); // Notify listeners to rebuild UI
-      print("Chats fetched successfully for task ID: $taskId");
+      // Fetch task steps from the data source
+      final List<dynamic> stepsJsonList =
+          await _chatService.listTaskSteps(_currentTaskId!);
+
+      // Convert each map into a Step object
+      List<Step> steps =
+          stepsJsonList.map((stepMap) => Step.fromMap(stepMap)).toList();
+
+      // Initialize an empty list to store Chat objects
+      List<Chat> chats = [];
+
+      // Generate current timestamp
+      DateTime currentTimestamp = DateTime.now();
+
+      for (Step step in steps) {
+        // Create a Chat object for 'input' if it exists and is not empty
+        if (step.input.isNotEmpty) {
+          chats.add(Chat(
+            id: step.stepId,
+            taskId: step.taskId,
+            message: step.input,
+            timestamp: currentTimestamp,
+            messageType: MessageType.user,
+          ));
+        }
+
+        // Create a Chat object for 'output'
+        chats.add(Chat(
+          id: step.stepId,
+          taskId: step.taskId,
+          message: step.output,
+          timestamp: currentTimestamp,
+          messageType: MessageType.agent,
+        ));
+      }
+
+      // Assign the chats list
+      _chats = chats;
+
+      // Notify listeners to rebuild UI
+      notifyListeners();
+
+      print(
+          "Chats (and steps) fetched successfully for task ID: $_currentTaskId");
     } catch (error) {
       print("Error fetching chats: $error");
       // TODO: Handle additional error scenarios or log them as required
     }
   }
 
-  /// Simulates sending a chat message for a specific task.
-  void sendChatMessage(int taskId, String message) {
-    final userChat = Chat(
-        id: _chats.length + 1,
-        taskId: taskId,
-        message: message,
+  /// Sends a chat message for a specific task.
+  void sendChatMessage(String message) async {
+    if (_currentTaskId == null) {
+      print("Error: Task ID is not set.");
+      return;
+    }
+    try {
+      // Create the request body for executing the step
+      StepRequestBody requestBody = StepRequestBody(input: message);
+
+      // Execute the step and get the response
+      Map<String, dynamic> executedStepResponse =
+          await _chatService.executeStep(_currentTaskId!, requestBody);
+
+      // Create a Chat object from the returned step
+      Step executedStep = Step.fromMap(executedStepResponse);
+
+      // Create a Chat object for the user message
+      final userChat = Chat(
+        id: executedStep.stepId,
+        taskId: executedStep.taskId,
+        message: executedStep.input,
         timestamp: DateTime.now(),
-        messageType: MessageType.user);
+        messageType: MessageType.user,
+      );
 
-    // For now, we'll simulate an agent's reply after the user's message
-    final agentChat = Chat(
-        id: _chats.length + 2,
-        taskId: taskId,
-        message: 'Automated reply to: $message',
-        timestamp: DateTime.now().add(const Duration(seconds: 2)),
-        messageType: MessageType.agent);
+      // Create a Chat object for the agent message
+      final agentChat = Chat(
+        id: executedStep.stepId,
+        taskId: executedStep.taskId,
+        message: executedStep.output,
+        timestamp: DateTime.now(),
+        messageType: MessageType.agent,
+      );
 
-    _chats.addAll([userChat, agentChat]);
-    notifyListeners(); // Notify UI of the new chats
-    print("User chat and automated agent reply added for task ID: $taskId");
+      // Add the user and agent chats to the list
+      _chats.add(userChat);
+      _chats.add(agentChat);
+
+      // Notify UI of the new chats
+      notifyListeners();
+
+      print("Chats added for task ID: $_currentTaskId");
+    } catch (error) {
+      print("Error sending chat: $error");
+      // TODO: Handle additional error scenarios or log them as required
+    }
   }
 }