index.js

require('dotenv').config();
const express = require('express');
const mongoose = require('mongoose');
const helmet = require('helmet');
const cors = require('cors');
const morgan = require('morgan');
const rateLimit = require('express-rate-limit');

const app = express();

// Security middleware
app.use(helmet());
app.use(cors());

// Rate limiting - General
const limiter = rateLimit({
    windowMs: parseInt(process.env.RATE_LIMIT_WINDOW_MS) || 15 * 60 * 1000,
    max: parseInt(process.env.RATE_LIMIT_MAX_REQUESTS) || 100,
    message: { error: 'Too many requests, please try again later.' },
    standardHeaders: true,
    legacyHeaders: false,
});
app.use(limiter);

// Logging middleware
if (process.env.NODE_ENV === 'development') {
    app.use(morgan('dev'));
} else {
    app.use(morgan('combined'));
}

// Body parsing middleware
app.use(express.json({ limit: '10kb' }));
app.use(express.urlencoded({ extended: true, limit: '10kb' }));

// MongoDB connection
const connectDB = async () => {
    try {
        await mongoose.connect(process.env.MONGODB_URI || 'mongodb://localhost:27017/jobListings');
        console.log('✅ Connected to MongoDB');
    } catch (error) {
        console.error('❌ MongoDB connection error:', error.message);
        process.exit(1);
    }
};

mongoose.connection.on('disconnected', () => {
    console.log('⚠️ MongoDB disconnected');
});

mongoose.connection.on('error', (err) => {
    console.error('❌ MongoDB error:', err.message);
});

// Routes
const jobRoutes = require('./routes/jobs');
app.use('/api/jobs', jobRoutes);

// Health check endpoint
app.get('/health', (req, res) => {
    res.status(200).json({
        status: 'OK',
        timestamp: new Date().toISOString(),
        uptime: process.uptime(),
    });
});

// 404 handler
app.use((req, res) => {
    res.status(404).json({ error: 'Route not found' });
});

// Global error handler
app.use((err, req, res, next) => {
    console.error('Error:', err.stack);
    res.status(err.status || 500).json({
        error: process.env.NODE_ENV === 'production' 
            ? 'Internal server error' 
            : err.message,
    });
});

// Graceful shutdown
const gracefulShutdown = async () => {
    console.log('\n🔄 Graceful shutdown initiated...');
    await mongoose.connection.close();
    console.log('✅ MongoDB connection closed');
    process.exit(0);
};

process.on('SIGTERM', gracefulShutdown);
process.on('SIGINT', gracefulShutdown);

// Start server
const PORT = process.env.PORT || 3000;

connectDB().then(() => {
    app.listen(PORT, () => {
        console.log(`🚀 Server is running on port ${PORT}`);
        console.log(`📝 Environment: ${process.env.NODE_ENV || 'development'}`);
    });
});

module.exports = app;