server.js

const express = require('express');
const mongoose = require('mongoose');
const cors = require('cors');
const helmet = require('helmet');
const rateLimit = require('express-rate-limit');
const http = require('http');
const socketIo = require('socket.io');
require('dotenv').config();

const app = express();
const server = http.createServer(app);

// Socket.io setup
const io = socketIo(server, {
  cors: {
    origin: process.env.CLIENT_URL || "http://localhost:3000",
    methods: ["GET", "POST"]
  }
});

// Security middleware
app.use(helmet({
  crossOriginEmbedderPolicy: false,
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      styleSrc: ["'self'", "'unsafe-inline'"],
      scriptSrc: ["'self'"],
      imgSrc: ["'self'", "data:", "https:"],
    },
  },
}));

// Rate limiting
const limiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 100 // limit each IP to 100 requests per windowMs
});
app.use(limiter);

// CORS configuration for cross-region access
app.use(cors({
  origin: [
    process.env.CLIENT_URL || "http://localhost:3000",
    "https://your-domain.com",
    "https://your-china-domain.com"
  ],
  credentials: true
}));

app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ extended: true, limit: '10mb' }));

// MongoDB connection
const connectDB = async () => {
  try {
    const conn = await mongoose.connect(process.env.MONGODB_URI || 'mongodb://localhost:27017/client-portal', {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    });
    console.log(`MongoDB Connected: ${conn.connection.host}`);
  } catch (error) {
    console.error('Database connection error:', error);
    process.exit(1);
  }
};

// Routes
app.use('/api/auth', require('./routes/auth'));
app.use('/api/forms', require('./routes/forms'));
app.use('/api/submissions', require('./routes/submissions'));
app.use('/api/users', require('./routes/users'));

// Health check endpoint
app.get('/api/health', (req, res) => {
  res.json({ 
    status: 'OK', 
    timestamp: new Date().toISOString(),
    region: process.env.REGION || 'unknown'
  });
});

// Socket.io connection handling
io.on('connection', (socket) => {
  console.log('User connected:', socket.id);

  socket.on('join-room', (room) => {
    socket.join(room);
    console.log(`User ${socket.id} joined room: ${room}`);
  });

  socket.on('disconnect', () => {
    console.log('User disconnected:', socket.id);
  });
});

// Make io accessible to routes
app.set('io', io);

// Error handling middleware
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ message: 'Something went wrong!' });
});

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

const PORT = process.env.PORT || 5000;

// Start server
const startServer = async () => {
  await connectDB();
  server.listen(PORT, () => {
    console.log(`Server running on port ${PORT}`);
    console.log(`Environment: ${process.env.NODE_ENV || 'development'}`);
  });
};

startServer();