Welcome to the next step in our journey of building a personal tutor service with DeepSeek models. In the previous lesson, we explored the TutorService class, which acts as a bridge between managing tutoring session data and generating AI responses. Now, we will focus on the TutorController, a crucial component that manages tutoring sessions and handles student queries by interacting with both the model and service layers. The controller is responsible for orchestrating the flow of data between the student interface and the backend services, ensuring that student interactions are processed efficiently and effectively.

The TutorController class is the heart of our controller layer. It is responsible for managing tutoring sessions and processing student queries. Let's begin by examining the structure of the TutorController class in JavaScript.

In this snippet, we:

• Import the Node.js built-in crypto library for generating unique identifiers.
• Import the TutorService class for managing tutoring data and processing student queries.
• Initialize the TutorController with an instance of TutorService.
• Create a testSession object to simulate session management for testing purposes.

The testSession object is a simple in-memory store used to simulate session management for testing. It allows us to mimic the behavior of student sessions typically managed by a web application or browser. In a real-world scenario, student sessions help track individual students as they interact with a web application, maintaining their state and data across multiple requests. By using testSession, we can focus on testing the core functionality of the TutorController without needing a full session management system. Once we are confident that the controller works correctly, we will later integrate a more robust session management solution when developing our RESTful API.

Before creating a tutoring session, we need to ensure that a student session exists. The ensureStudentSession method checks if a student ID is present in the testSession. If not, it generates a new student ID.

This method ensures that a student session is available by checking the testSession object for a studentId. If it doesn't exist, a new student ID is generated using crypto.randomUUID() and stored in the session. The method then returns the student ID, either the newly created one or the existing one.

One of the primary responsibilities of the TutorController is to create new tutoring sessions. The createSession method handles session creation requests.

In this method, we:

1. Retrieve the studentId: We first check the testSession for a studentId.

2. Handle Session Expiry: If the session has expired (i.e., no studentId is found), we return an error response using our helper method _errorResponse with a 401 status code, which we will discuss later. This approach ensures that the client can handle the error gracefully, providing a better user experience.

3. Create a Tutoring Session: If the session is valid, we call the createSession method of the TutorService with the student ID to create a new tutoring session. We then return a success response containing a unique session ID and a success message using our helper method _successResponse, which we will discuss later.

The sendQuery method is responsible for processing student queries and returning the tutor's response or an error message.

In this method:

1. We first check if the student session is valid by retrieving the studentId from the testSession. If no studentId is found, we return an error response with a 401 status code.

2. We then validate that both sessionId and studentQuery are provided. If either is missing, we return an error response with a 400 status code.

3. If all validations pass, we attempt to process the query using the processQuery method of the TutorService. This method takes the studentId, sessionId, and studentQuery as parameters. Since this is an asynchronous operation, we use await.

4. If the query is processed successfully, we return the tutor's response in a success response format.

5. If a ValueError occurs (e.g., if the session ID doesn't exist), we return an error response with a 404 status code.

6. If a RuntimeError occurs (e.g., if there's an issue with the AI model), we return an error response with a 500 status code.

7. For any other unexpected errors, we return a generic error response with a 500 status code.

The TutorController includes two helper methods for formatting responses: _successResponse and _errorResponse. These methods ensure consistent response formats throughout the controller.

These methods create standardized response formats:

• _successResponse returns an object with a status field set to "success" and a data field containing the provided data.
• _errorResponse returns an object with a status field set to "error" and an error field with message and code details.

Unlike the Python version, we do not return tuples. Instead, the error response object includes the status code as part of the error details, which is a common convention in JavaScript applications.

To see the TutorController in action, let's integrate it into the main application. This example demonstrates how to create a tutoring session and handle a student query, showcasing the controller's functionality.

In this example, we first initialize the TutorController. We ensure a student session is available for testing. We then create a new tutoring session and handle the response. If successful, we simulate a student query about the differences between mitosis and meiosis and use the sendQuery method to process it. The response is checked for errors, and either the error message or the tutor's response is printed. This example demonstrates the flow from ensuring a student session to creating a tutoring session and handling a student query, highlighting the controller's role in managing interactions.

In this lesson, we explored the TutorController class and its role in managing tutoring sessions and handling student queries. We learned how to implement the controller, create tutoring sessions, and process student questions using the TutorService. The controller is a vital component of our personal tutor application, ensuring that student interactions are managed efficiently and effectively.

As you move on to the practice exercises, take the opportunity to experiment with the TutorController'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!