Welcome to the next step in our journey of building a chatbot service. In the previous lesson, we explored the ChatService struct, which acts as a bridge between managing chat data and generating AI responses. Now, we will focus on the ChatController, a crucial component that manages chat sessions and handles messages by interacting with both the model and service layers. The controller is responsible for orchestrating the flow of data between the user interface and the backend services, ensuring that user interactions are processed efficiently and effectively.

The ChatController struct is the heart of our controller layer. It is responsible for managing chat sessions and processing user messages. Let's begin by examining the structure of the ChatController struct.

In this snippet, we:

• Define the ChatController struct with fields for ChatService and session store.
• Create a constructor NewChatController to initialize the ChatController with an instance of ChatService and a session store.

Before creating a chat, we need to ensure that a user session exists. The EnsureUserSession method checks if a user ID is present in the session. If not, it generates a new user ID.

This method ensures that a user session is available by checking the session for a user_id. If it doesn't exist, a new user ID is generated and stored in the session.

One of the primary responsibilities of the ChatController is to create new chat sessions. The CreateChat method simulates a chat creation request.

In this method, we:

1. Retrieve the user_id: We first ensure the user session and retrieve the user_id.

2. Create a Chat Session: If the session is valid, we call the CreateChat method of the ChatService with the user ID to create a new chat session. We then return a response containing a unique chat ID and a success message.

The SendMessage method is responsible for processing user messages and returning the AI's response or an error message.

In this method, we first ensure the user session is valid. If any required fields are missing, an error is returned. The method attempts to process the message using the ProcessMessage method of the ChatService. If successful, the AI's response is returned. If an error occurs, an appropriate error message is returned.

To see the ChatController in action, let's integrate it into the main application. This example demonstrates how to create a chat session and handle a user message, showcasing the controller's functionality.

In this example, the main function initializes a ChatController to manage chat sessions and ensures a user session is active. It then creates a new chat session, handling any errors by printing them. If successful, it extracts and prints the chat_id. A sample user message is defined and sent to the chat session, with the AI's response being printed if successful, or an error message if not.

In this lesson, we explored the ChatController struct and its role in managing chat sessions and handling user messages. We learned how to implement the controller, create chat sessions, and process messages using the ChatService. The controller is a vital component of our chatbot application, ensuring that user interactions are managed efficiently and effectively.

As you move on to the practice exercises, take the opportunity to experiment with the ChatController's functionality. This hands-on practice will reinforce the concepts covered in this lesson and prepare you for the next steps in our course. Keep up the great work, and I look forward to seeing your progress!