Welcome to the next step in our journey of building a personal tutor service! In the previous lesson, we focused on the TutorController, which manages tutoring sessions and handles student queries by interacting with both the model and service layers. Now, we will take a significant step forward by creating a RESTful API for our personal tutor service using Express.js, a popular web framework for Node.js. We'll start by setting up the main Express application, then adapt the TutorController to integrate with session management and HTTP request handling in JavaScript.

RESTful APIs are a way for different software systems to communicate over the internet. They provide a set of rules that allow programs to exchange data using standard HTTP methods like GET, POST, PUT, and DELETE. In the JavaScript ecosystem, Express.js is a widely used, minimal, and flexible web framework for building APIs and web applications with Node.js.

To get started with Express.js, you can install it using npm by running the following command in your terminal:

For session management, static file serving, and template rendering, we'll also need a few additional packages:

• express-session provides session management for Express.
• ejs is a simple and popular template engine for rendering HTML pages.

Now, let's see how to set up our Express application and connect the components we've already built, allowing students to interact with our personal tutor service through a web interface.

First, we need to initialize the Express application:

Here, we import the Express module and create an application instance with express(). We also set up middleware to parse JSON and URL-encoded request bodies, which is necessary for handling incoming data from clients.

Express does not have built-in session management, but the express-session package provides this functionality. Sessions allow us to store data for individual users between HTTP requests, such as a unique student ID.

The secret is used to sign the session ID cookie, ensuring session data cannot be tampered with. The cookie options can be adjusted for security as needed.

Next, we create an instance of our TutorController to handle the core operations of our personal tutor service:

This controller will manage tutoring sessions and process student queries, serving as the bridge between our API endpoints and the underlying service layer.

Unlike some frameworks, Express does not provide built-in request validation. For this lesson, we'll use simple custom validation logic to ensure incoming requests have the required fields. (You can use libraries like express-validator or joi for more advanced validation in the future.)

For example, to validate a query request:

This middleware checks that both session_id and query are present in the request body before proceeding.

To ensure each student has a unique identifier, we can use session middleware to check for a student ID in the session and create one if it doesn't exist:

This middleware ensures that every user interacting with the API has a unique student_id stored in their session.

Now that we've initialized our Express application and created our controller instance, let's create the API endpoints that will allow students to interact with our personal tutor service. In Express, routes are defined using methods like app.get() and app.post().

This route handles GET requests to the root path (/). It ensures the student has a unique ID and renders the tutor.ejs template, passing the student_id to the template.

Next, let's define a route for creating new tutoring sessions:

This route handles POST requests to /api/create_session. It uses the getStudentId middleware to identify the student, then calls the controller's createSession method. If an error occurs, it passes the error to the error handler; otherwise, it returns the session data.

Now, let's create a route for sending queries to the tutor:

This route handles POST requests to /api/send_query. It validates the request body, ensures the student has a unique ID, and processes the query using the controller.

To ensure consistent error responses across our API, we can add a custom error-handling middleware in Express:

This middleware catches errors passed to next() and returns a JSON response with a consistent structure.

Now that we've defined our routes and prepared our controller for integration with Express, the final step is to start the server:

This code starts the Express server on the specified port and logs a message to the console when the server is ready.

The TutorController has been designed to work seamlessly with Express.js, handling student IDs and session management effectively. Let's examine its key methods and how they integrate with our API.

The controller uses JavaScript class syntax and returns response objects that are easy to handle in Express route handlers. Error handling is performed using standard JavaScript conventions.

To interact with our personal tutor service, a student can follow these steps:

1. Access the Index Route (/): The student begins by accessing the index route of the API. This step ensures that a student session is established. A student session is a way to keep track of the student's interactions with the service. It is stored using Express's session management, which utilizes cookies to maintain session data on the client side. The server responds with the tutor interface, ready for interaction.

2. Create a Tutoring Session (/api/create_session): Before sending a query, the student needs to create a new tutoring session. This is done by sending a request to the /api/create_session route. The server will respond with a unique session ID, which is essential for identifying the tutoring session in subsequent interactions. The student session ensures that the tutoring session is associated with the correct student, allowing for personalized academic support.

3. Send a Query (/api/send_query): With the tutoring session established, the student can now send academic questions to the personal tutor. This involves sending a request to the /api/send_query route, including the session ID and the query content. The server processes the query using the DeepSeek model and responds with the tutor's explanation, allowing the student to continue the learning conversation. The student session helps maintain continuity in the conversation by linking the queries to the correct student and tutoring session.

By following these steps, a student can effectively receive personalized academic support from our personal tutor service, leveraging the RESTful API to manage tutoring sessions and exchange queries while utilizing student sessions for a seamless learning experience.

In this lesson, we successfully built a RESTful API for our personal tutor service using Express.js. We set up an Express application, defined routes for tutoring operations, and explored how the TutorController integrates with session management and request handling in JavaScript. This lesson marks a significant milestone in our course, as it brings together all the components we've developed so far into a functional web application that can deliver personalized academic support at scale.

As you move on to the practice exercises, take the opportunity to experiment with the Express.js API and reinforce the concepts covered in this lesson. This hands-on practice will prepare you for further development and exploration of additional Express.js features and RESTful API concepts. Keep up the great work, and I look forward to seeing your progress!