/**
 * DeepStudio Pro - Enhanced Production Server
 * Built with anycoder → https://huggingface.co/spaces/akhaliq/anycoder
 * 
 * Features:
 * - Graceful shutdown handling
 * - Request logging and metrics
 * - Health check endpoint
 * - Memory and performance monitoring
 * - Security headers
 */

const path = require('path');
const http = require('http');
const { parse } = require('url');

const dir = path.join(__dirname);

// Set production environment
process.env.NODE_ENV = 'production';
process.chdir(__dirname);

// Configuration with sensible defaults
const config = {
  port: parseInt(process.env.PORT, 10) || 7860,
  hostname: process.env.HOSTNAME || '0.0.0.0',
  keepAliveTimeout: parseInt(process.env.KEEP_ALIVE_TIMEOUT, 10) || 65000,
  requestTimeout: parseInt(process.env.REQUEST_TIMEOUT, 10) || 30000,
  maxRequestsPerSocket: parseInt(process.env.MAX_REQUESTS_PER_SOCKET, 10) || 0,
};

// Next.js configuration - optimized for production
const nextConfig = {
  env: {},
  webpack: null,
  eslint: { ignoreDuringBuilds: true },
  typescript: { 
    ignoreBuildErrors: false, 
    tsconfigPath: 'tsconfig.json' 
  },
  distDir: './.next',
  cleanDistDir: true,
  assetPrefix: '',
  cacheMaxMemorySize: 52428800,
  configOrigin: 'next.config.ts',
  useFileSystemPublicRoutes: true,
  generateEtags: true,
  pageExtensions: ['tsx', 'ts', 'jsx', 'js'],
  poweredByHeader: false, // Security: disable X-Powered-By
  compress: true,
  images: {
    deviceSizes: [640, 750, 828, 1080, 1200, 1920, 2048, 3840],
    imageSizes: [16, 32, 48, 64, 96, 128, 256, 384],
    path: '/_next/image',
    loader: 'default',
    loaderFile: '',
    domains: [],
    disableStaticImages: false,
    minimumCacheTTL: 60,
    formats: ['image/webp', 'image/avif'],
    dangerouslyAllowSVG: false,
    contentSecurityPolicy: "script-src 'none'; frame-src 'none'; sandbox;",
    contentDispositionType: 'attachment',
    remotePatterns: [],
    unoptimized: false,
  },
  devIndicators: { position: 'bottom-left' },
  onDemandEntries: { maxInactiveAge: 60000, pagesBufferLength: 5 },
  amp: { canonicalBase: '' },
  basePath: '',
  sassOptions: {},
  trailingSlash: false,
  i18n: null,
  productionBrowserSourceMaps: false,
  excludeDefaultMomentLocales: true,
  serverRuntimeConfig: {},
  publicRuntimeConfig: {},
  reactProductionProfiling: false,
  reactStrictMode: true,
  reactMaxHeadersLength: 6000,
  httpAgentOptions: { keepAlive: true },
  logging: {},
  expireTime: 31536000,
  staticPageGenerationTimeout: 60,
  output: 'standalone',
  modularizeImports: {
    '@mui/icons-material': { transform: '@mui/icons-material/{{member}}' },
    'lodash': { transform: 'lodash/{{member}}' },
  },
  outputFileTracingRoot: process.cwd(),
  experimental: {
    optimizeCss: true,
    optimizePackageImports: [
      'lucide-react',
      'date-fns',
      'lodash-es',
      'ramda',
      'antd',
      'react-bootstrap',
      'ahooks',
      '@ant-design/icons',
      '@headlessui/react',
      '@headlessui-float/react',
      '@heroicons/react/20/solid',
      '@heroicons/react/24/solid',
      '@heroicons/react/24/outline',
      '@visx/visx',
      '@tremor/react',
      'rxjs',
      '@mui/material',
      '@mui/icons-material',
      'recharts',
      'react-use',
      'framer-motion',
      '@radix-ui/react-icons',
    ],
  },
};

// Serialize config for Next.js
process.env.__NEXT_PRIVATE_STANDALONE_CONFIG = JSON.stringify(nextConfig);

// Metrics tracking
const metrics = {
  startTime: Date.now(),
  requests: { total: 0, success: 0, error: 0 },
  activeConnections: 0,
};

// Request logging middleware
function logRequest(req, res, startTime) {
  const duration = Date.now() - startTime;
  const logEntry = {
    timestamp: new Date().toISOString(),
    method: req.method,
    url: req.url,
    status: res.statusCode,
    duration: `${duration}ms`,
    userAgent: req.headers['user-agent'],
    ip: req.headers['x-forwarded-for'] || req.socket.remoteAddress,
  };
  
  // Log errors with more detail
  if (res.statusCode >= 400) {
    console.error('[REQUEST ERROR]', JSON.stringify(logEntry));
    metrics.requests.error++;
  } else {
    console.log('[REQUEST]', JSON.stringify(logEntry));
    metrics.requests.success++;
  }
  metrics.requests.total++;
}

// Security headers middleware
function setSecurityHeaders(res) {
  res.setHeader('X-DNS-Prefetch-Control', 'on');
  res.setHeader('Strict-Transport-Security', 'max-age=63072000; includeSubDomains; preload');
  res.setHeader('X-Frame-Options', 'SAMEORIGIN');
  res.setHeader('X-Content-Type-Options', 'nosniff');
  res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
  res.setHeader('Permissions-Policy', 'camera=(), microphone=(), geolocation=()');
}

// Health check handler
function healthCheck(req, res) {
  const uptime = Date.now() - metrics.startTime;
  const health = {
    status: 'healthy',
    timestamp: new Date().toISOString(),
    uptime: `${Math.floor(uptime / 1000)}s`,
    version: process.env.npm_package_version || '2.0.0',
    nodejs: process.version,
    memory: process.memoryUsage(),
    metrics: {
      requests: metrics.requests,
      activeConnections: metrics.activeConnections,
    },
  };
  
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify(health, null, 2));
}

// Metrics endpoint for monitoring
function metricsEndpoint(req, res) {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    ...metrics,
    memory: process.memoryUsage(),
    cpu: process.cpuUsage(),
    uptime: process.uptime(),
  }, null, 2));
}

// Main server startup
async function startServer() {
  const { startServer: startNextServer } = require('next/dist/server/lib/start-server');
  
  // Validate keep-alive timeout
  let keepAliveTimeout = config.keepAliveTimeout;
  if (
    Number.isNaN(keepAliveTimeout) ||
    !Number.isFinite(keepAliveTimeout) ||
    keepAliveTimeout < 0
  ) {
    keepAliveTimeout = undefined;
  }

  console.log(`
╔══════════════════════════════════════════════════════════════╗
║           DeepStudio Pro - Starting Production Server        ║
║     Built with anycoder → https://huggingface.co/spaces/akhaliq/anycoder    ║
╠══════════════════════════════════════════════════════════════╣
  Port:        ${config.port}
  Hostname:    ${config.hostname}
  Node Env:    ${process.env.NODE_ENV}
  Node Ver:    ${process.version}
  Start Time:  ${new Date().toISOString()}
╚══════════════════════════════════════════════════════════════╝
  `);

  try {
    // Start the Next.js server
    const server = await startNextServer({
      dir,
      isDev: false,
      config: nextConfig,
      hostname: config.hostname,
      port: config.port,
      allowRetry: false,
      keepAliveTimeout,
    });

    // Get the underlying HTTP server to add custom middleware
    const httpServer = server.server;

    // Track connections for graceful shutdown
    httpServer.on('connection', (socket) => {
      metrics.activeConnections++;
      socket.on('close', () => {
        metrics.activeConnections--;
      });
    });

    // Custom request handling for health checks and metrics
    const originalHandler = httpServer.listeners('request')[0];
    httpServer.removeAllListeners('request');
    
    httpServer.on('request', (req, res) => {
      const startTime = Date.now();
      
      // Set security headers on all responses
      setSecurityHeaders(res);
      
      // Intercept health check requests
      const parsedUrl = parse(req.url, true);
      if (parsedUrl.pathname === '/api/health') {
        healthCheck(req, res);
        return;
      }
      
      // Metrics endpoint (basic auth in production recommended)
      if (parsedUrl.pathname === '/api/metrics') {
        metricsEndpoint(req, res);
        return;
      }
      
      // Log response when finished
      res.on('finish', () => logRequest(req, res, startTime));
      
      // Pass to Next.js handler
      originalHandler(req, res);
    });

    // Graceful shutdown handling
    const shutdown = (signal) => {
      console.log(`\n[SHUTDOWN] Received ${signal}. Starting graceful shutdown...`);
      console.log(`[SHUTDOWN] Active connections: ${metrics.activeConnections}`);
      
      // Stop accepting new connections
      httpServer.close(() => {
        console.log('[SHUTDOWN] HTTP server closed');
        process.exit(0);
      });

      // Force shutdown after timeout
      setTimeout(() => {
        console.error('[SHUTDOWN] Forced shutdown after timeout');
        process.exit(1);
      }, 30000);
    };

    process.on('SIGTERM', () => shutdown('SIGTERM'));
    process.on('SIGINT', () => shutdown('SIGINT'));

    // Handle uncaught errors
    process.on('uncaughtException', (err) => {
      console.error('[FATAL] Uncaught exception:', err);
      process.exit(1);
    });

    process.on('unhandledRejection', (reason, promise) => {
      console.error('[FATAL] Unhandled rejection at:', promise, 'reason:', reason);
      process.exit(1);
    });

    console.log(`[READY] Server running at http://${config.hostname}:${config.port}`);
    return server;

  } catch (err) {
    console.error('[FATAL] Failed to start server:', err);
    process.exit(1);
  }
}

// Start the server
startServer();