/**
 * LuckyChit Web Server
 * Express server to serve Flutter web build with proper caching
 * 
 * Usage:
 *   node web-server.js
 *   Or with PM2:
 *   pm2 start web-server.js --name "luckychit-web"
 */

const express = require('express');
const path = require('path');
const fs = require('fs');

const app = express();
const PORT = process.env.PORT || 8080;
const BUILD_DIR = path.join(__dirname, 'build/web');

// Check if build directory exists
if (!fs.existsSync(BUILD_DIR)) {
  console.error('❌ Error: build/web directory not found!');
  console.error('   Please run: flutter build web --release');
  process.exit(1);
}

// Security headers
app.use((req, res, next) => {
  res.setHeader('X-Content-Type-Options', 'nosniff');
  res.setHeader('X-Frame-Options', 'SAMEORIGIN');
  res.setHeader('X-XSS-Protection', '1; mode=block');
  next();
});

// Serve static files with caching strategy
app.use(express.static(BUILD_DIR, {
  maxAge: '1y', // Cache static assets for 1 year
  immutable: true,
  setHeaders: (res, filePath) => {
    // Don't cache HTML files (always serve fresh)
    if (filePath.endsWith('.html')) {
      res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate');
      res.setHeader('Pragma', 'no-cache');
      res.setHeader('Expires', '0');
    }
  }
}));

// Handle Flutter routes (SPA - Single Page Application)
// Any route not found as a static file should serve index.html
app.get('*', (req, res) => {
  res.sendFile(path.join(BUILD_DIR, 'index.html'));
});

// Error handling
app.use((err, req, res, next) => {
  console.error('Error:', err);
  res.status(500).send('Internal Server Error');
});

// Start server
app.listen(PORT, '0.0.0.0', () => {
  console.log('');
  console.log('✅ LuckyChit Flutter Web App');
  console.log('============================');
  console.log(`🌐 Running on: http://localhost:${PORT}`);
  console.log(`📁 Serving: ${BUILD_DIR}`);
  console.log('');
  console.log('📝 Logs:');
  console.log('   Access: http://localhost:' + PORT);
  console.log('');
});

// 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);
});