In the previous lesson, we explored the ChatManager struct, which plays a crucial role in managing chat data within our application. Now, we will take the next step in our journey by building the chat service layer. This layer is essential for integrating the language model with chat sessions, allowing us to process user messages and generate AI responses. By the end of this lesson, you will understand how to set up the ChatService struct, create chat sessions, and process messages using OpenAI's API.

The service layer acts as a bridge between the ChatManager, where data is managed, and the AI model, which generates responses. It is responsible for orchestrating the flow of data and ensuring that user interactions are handled smoothly. Let's dive into the details of setting up this important component.

The ChatService struct is the heart of our service layer. It is responsible for managing chat sessions and interacting with the OpenAI client to generate AI responses. To begin, we need to set up the struct and its components.

First, we import the necessary packages, including the ChatManager from our previous lesson and the go-openai client. We also use the github.com/google/uuid package to generate unique chat IDs. Here's how the struct is initialized:

In this setup, we instantiate ChatManager to manage chat data, initialize the openai.Client, and load the systemPrompt using the loadSystemPrompt function, which we'll discuss next.

The system prompt is a crucial component that guides the AI's responses. It provides context and instructions for the AI, ensuring that it behaves in a manner consistent with our application's goals. In this section, we'll implement the loadSystemPrompt function to load the prompt from a file.

This function attempts to read the system prompt from a specified file path. If successful, it returns the prompt as a string. In case of an error, it logs an error message and returns a default prompt. This ensures that the application can continue functioning even if the file is missing or corrupted.

Creating a new chat session is a fundamental task of the ChatService. The CreateChat method is responsible for generating a unique chat ID and initializing a chat session using the ChatManager.

In this method, we generate a unique chatID using the uuid package. We then call the CreateChat method of ChatManager, passing the userID, chatID, and systemPrompt. This initializes a new chat session, which is ready to receive messages.

The ProcessMessage method is where the magic happens. It processes user messages, interacts with the OpenAI client to generate AI responses, and updates the chat history. Below, we outline the steps involved in this process, followed by the corresponding code implementation:

1. Retrieve the chat using GetChat, and return an error if the chat is not found.
2. Add the user's message to the chat history.
3. Send the conversation, including the system prompt and all messages, to the OpenAI client to generate a response.
4. Add the AI's response to the chat history and return it to the user.
5. Handle any errors with the AI client gracefully.

In the context of a customer service agent, we configure our model with specific parameters to optimize its performance. The Temperature is set to 0.7, which balances creativity and coherence in the AI's responses, ensuring they are both engaging and relevant. The MaxCompletionTokens is set to 500, allowing the model to provide detailed and informative answers without overwhelming the user, thus maintaining a smooth and effective customer service experience.

Let's see the ChatService in action by simulating a chat session. We'll use the main function to create a chat session and process a user message.

In this example, we initialize the ChatService, simulate a user ID, and create a new chat session, printing the chat ID. We then simulate sending a message and print the AI's response, demonstrating the flow from user input to AI response and showcasing the functionality of the ChatService.

This output illustrates a successful interaction where a new chat session is created, and the AI responds to the user's greeting with a helpful message. The AI's response is tailored to assist with IT services, showcasing the system's ability to provide relevant and context-aware assistance.

In this lesson, we explored the ChatService struct and its role in integrating the language model with chat sessions. We learned how to set up the struct, load the system prompt, create chat sessions, and process user messages. The service layer is a vital component of our chatbot application, ensuring that user interactions are handled smoothly and efficiently.

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