server.js

const express = require('express');
const path = require('path');
const helmet = require('helmet');
const cors = require('cors');
const rateLimit = require('express-rate-limit');
const compression = require('compression');
const morgan = require('morgan');

const app = express();
const PORT = process.env.PORT || 3000;

// Security middleware
app.use(helmet({
  contentSecurityPolicy: {
    directives: {
      defaultSrc: ["'self'"],
      styleSrc: ["'self'", "'unsafe-inline'", "https://fonts.googleapis.com", "https://cdnjs.cloudflare.com"],
      fontSrc: ["'self'", "https://fonts.gstatic.com", "https://cdnjs.cloudflare.com"],
      scriptSrc: ["'self'", "https://unpkg.com", "https://cdnjs.cloudflare.com"],
      connectSrc: ["'self'", "https://unpkg.com", "https://cdnjs.cloudflare.com"],
      imgSrc: ["'self'", "data:"],
      objectSrc: ["'none'"],
      baseUri: ["'self'"],
      formAction: ["'self'"],
    },
  },
  crossOriginEmbedderPolicy: false
}));

// CORS configuration
app.use(cors({
  origin: process.env.NODE_ENV === 'production'
    ? process.env.FRONTEND_URL || false
    : true,
  credentials: true
}));

// Rate limiting
const limiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 100, // limit each IP to 100 requests per windowMs
  message: {
    error: 'Too many requests from this IP, please try again later.',
    retryAfter: '15 minutes'
  },
  standardHeaders: true,
  legacyHeaders: false,
});

// Compression middleware
app.use(compression());

// Request logging
if (process.env.NODE_ENV !== 'test') {
  app.use(morgan('combined'));
}

// Apply rate limiting to all routes
app.use(limiter);

// Body parsing middleware for JSON (useful for future API endpoints)
app.use(express.json({ limit: '10mb' }));
app.use(express.urlencoded({ extended: true, limit: '10mb' }));

// Serve static files from the current directory with caching headers
app.use(express.static(__dirname, {
  maxAge: process.env.NODE_ENV === 'production' ? '1d' : 0,
  etag: true
}));

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

// Handle all routes by serving index.html (for SPA behavior)
app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'index.html'));
});

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

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

app.listen(PORT, () => {
  console.log(`🚀 PDF Compressor server is running on port ${PORT}`);
  console.log(`📊 Environment: ${process.env.NODE_ENV || 'development'}`);
  console.log(`🔗 Visit: http://localhost:${PORT}`);
  console.log(`❤️  Health check: http://localhost:${PORT}/health`);
});

// Graceful shutdown
process.on('SIGTERM', () => {
  console.log('SIGTERM received, shutting down gracefully');
  process.exit(0);
});

process.on('SIGINT', () => {
  console.log('SIGINT received, shutting down gracefully');
  process.exit(0);
});