server.js

const express = require('express');
const bodyParser = require('body-parser');
const bcrypt = require('bcryptjs');
const initializeDB = require('./database'); // Import MySQL connection logic

const app = express();
const PORT = 3000;

// Middleware setup
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

// Serve the static frontend file (index.html)
app.use(express.static(__dirname)); 

let dbPool; // Use a connection pool for MySQL

/**
 * Function to initialize the database and start the Express server.
 */
async function startServer() {
    try {
        // STEP 1: Initialize the database connection (using MySQL)
        dbPool = await initializeDB(); 
        
        // --- API ROUTES ---

        // 1. Registration Route: Handles new user creation
        app.post('/api/register', async (req, res) => {
            const { name: full_name, email, password } = req.body; 

            if (!full_name || !email || !password) {
                return res.status(400).json({ success: false, message: 'All fields are required.' });
            }

            try {
                // Check for existing user: Using dbPool.execute()
                const [rows] = await dbPool.execute('SELECT id FROM users WHERE email = ?', [email]);
                if (rows.length > 0) {
                    return res.status(409).json({ success: false, message: 'Email already registered.' });
                }

                // Securely hash the password
                const hashedPassword = await bcrypt.hash(password, 10);
                
                // Insert new user into the MySQL database: Using dbPool.execute()
                const [result] = await dbPool.execute(
                    'INSERT INTO users (full_name, email, password) VALUES (?, ?, ?)', 
                    [full_name, email, hashedPassword]
                );

                console.log(`New user registered with ID: ${result.insertId}`);
                res.status(201).json({ success: true, message: 'Registration successful! You can now log in.' });

            } catch (error) {
                console.error('Registration error:', error);
                res.status(500).json({ success: false, message: 'Server error during registration.' });
            }
        });

        // 2. Login Route: Handles user sign-in
        app.post('/api/login', async (req, res) => {
            const { email, password } = req.body;

            try {
                // Find user by email: Using dbPool.execute()
                const [rows] = await dbPool.execute('SELECT * FROM users WHERE email = ?', [email]);
                const user = rows[0];

                if (!user) {
                    return res.status(401).json({ success: false, message: 'Invalid credentials.' });
                }

                // Compare submitted password with stored hash
                const isMatch = await bcrypt.compare(password, user.password);

                if (!isMatch) {
                    return res.status(401).json({ success: false, message: 'Invalid credentials.' });
                }

                // Login successful!
                res.status(200).json({ 
                    success: true, 
                    message: `Welcome back, ${user.full_name}! Login successful.`
                });

            } catch (error) {
                console.error('Login error:', error);
                res.status(500).json({ success: false, message: 'Server error during login.' });
            }
        });

        // STEP 2: Start the server
        app.listen(PORT, () => {
            console.log(`Server running on http://localhost:${PORT}`);
        });

    } catch (error) {
        console.error('Failed to start server due to database error. Please resolve the connection error above.');
        process.exit(1);
    }
}

startServer();