app.js

const express = require('express');
const { fetchStreamedChatContent } = require('streamed-chatgpt-api');
const cors = require('cors');
const app = express();
const port = process.env.PORT || 3000;

const corsOpts = {
    origin: '*',

    methods: [
        'GET',
        'POST',
    ],

    allowedHeaders: [
        'Content-Type',
    ],
};

app.use(cors(corsOpts));
// express middleware 
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
app.use(express.static('public'));

// Create an object to store chat history
const chatHistory = {};
const historyLength = 5; // Change this value to set the desired chat history length

// Define a route to serve the index.html file
app.get('/', (_, res) => {
    res.sendFile('index.html', { root: __dirname + '/public' });
});

app.post('/chat', (req, res) => {
    const apiKey = process.env.OPENAI_API_KEY;
    console.log(apiKey);
    const { message, username } = req.body;

    // Check if username is provided
    if (!username) {
        return res.status(400).send('A username is required.');
    }

    // Initialize chat history for the user if it doesn't exist
    if (!chatHistory[username]) {
        chatHistory[username] = [];
    }

    // Update chat history with the user's message
    chatHistory[username].push({ role: 'user', content: message });

    // Prepare the message input with the user's chat history
    // just giving an empty string as system role to keep chat ouput short
    const messageInput = [
        {
            role: 'system',
            content: '',
        },
    ];

    const recentHistory = chatHistory[username].slice(-historyLength);
    recentHistory.forEach(msg => {
        messageInput.push(msg);
    });

    res.setHeader('Content-Type', 'text/html; charset=UTF-8');
    res.setHeader('Transfer-Encoding', 'chunked');

    let completeResponse = '';

    console.log(messageInput)
    fetchStreamedChatContent({
        apiKey,
        messageInput,
        maxTokens: 1000,
        temperature: 0.1,
    }, (content) => {
        res.write(content);
        completeResponse += content;
    }, () => {
        res.end();
        chatHistory[username].push({ role: 'assistant', content: completeResponse });
    },
        () => {
            res.write("I'm sorry, there was an error processing your request.");
            res.end();
        });
});

app.listen(port, () => {
    console.log(`Server is running on port ${port}`);
});