/**
 * Tractatus Express Server
 * Main application entry point
 */

require('dotenv').config();

const express = require('express');
const helmet = require('helmet');
const cors = require('cors');
const rateLimit = require('express-rate-limit');
const cookieParser = require('cookie-parser');
// const csrf = require('csurf');  // Disabled - deprecated package, will implement modern solution in Phase 3

const config = require('./config/app.config');
const logger = require('./utils/logger.util');
const { connect: connectDb, close: closeDb } = require('./utils/db.util');
const { connect: connectMongoose, close: closeMongoose } = require('./utils/mongoose.util');
const { notFound, errorHandler } = require('./middleware/error.middleware');

// Security middleware (Quick Wins)
const { securityHeadersMiddleware } = require('./middleware/security-headers.middleware');
const { publicRateLimiter, formRateLimiter, authRateLimiter } = require('./middleware/rate-limit.middleware');
const { sanitizeErrorResponse, sanitizeResponseData } = require('./middleware/response-sanitization.middleware');
const { setCsrfToken, csrfProtection, getCsrfToken } = require('./middleware/csrf-protection.middleware');

// Create Express app
const app = express();

// Trust proxy (for rate limiting behind reverse proxy)
app.set('trust proxy', 1);

// ============================================================
// SECURITY MIDDLEWARE (Quick Wins - inst_041-046)
// ============================================================

// Enhanced security headers (replaces helmet CSP with more specific policy)
app.use(securityHeadersMiddleware);

// Keep helmet for other security features (but CSP already set above)
app.use(helmet({
  contentSecurityPolicy: false  // Disabled - using our custom CSP in securityHeadersMiddleware
}));

// CORS
app.use(cors(config.cors));

// Cookie parser (required for CSRF)
app.use(cookieParser());

// Set CSRF token cookie on all requests
app.use(setCsrfToken);

// Response data sanitization (removes sensitive fields)
app.use(sanitizeResponseData);

// Raw body capture for Stripe webhooks (must be before JSON parser)
app.use('/api/koha/webhook', express.raw({ type: 'application/json' }), (req, res, next) => {
  req.rawBody = req.body;
  next();
});

// Body parsers (reduced limit from 10mb to 1mb for security)
app.use(express.json({ limit: '1mb' }));
app.use(express.urlencoded({ extended: true, limit: '1mb' }));

// Request logging
app.use(logger.request);

// Analytics tracking (privacy-respecting, self-hosted)
const { trackPageView } = require('./middleware/analytics.middleware');
app.use(trackPageView);

// CSRF Protection (Modern Implementation - Phase 0 Complete)
// Uses SameSite cookies + double-submit cookie pattern
// Protection is applied selectively to state-changing routes (POST, PUT, DELETE, PATCH)
// Webhooks and public endpoints are excluded

// Enhanced rate limiting (Quick Wins)
// Public endpoints: 100 requests per 15 minutes per IP
app.use(publicRateLimiter);

// Cache control middleware for static assets
app.use((req, res, next) => {
  const path = req.path;

  // Version manifest and service worker: No cache (always fetch fresh)
  if (path === '/version.json' || path === '/service-worker.js') {
    res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, proxy-revalidate');
    res.setHeader('Pragma', 'no-cache');
    res.setHeader('Expires', '0');
  }
  // HTML files: No cache (always fetch fresh - users must see updates immediately)
  else if (path.endsWith('.html') || path === '/') {
    res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, proxy-revalidate, max-age=0');
    res.setHeader('Pragma', 'no-cache');
  }
  // Admin JS/HTML files: NEVER cache (always fetch fresh)
  else if (path.startsWith('/js/admin/') || path.startsWith('/admin/')) {
    res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate, proxy-revalidate');
    res.setHeader('Pragma', 'no-cache');
    res.setHeader('Expires', '0');
  }
  // CSS and JS files: Short cache for active development
  // With versioned URLs (?v=timestamp), browsers will fetch new versions when HTML updates
  else if (path.endsWith('.css') || path.endsWith('.js')) {
    res.setHeader('Cache-Control', 'public, max-age=3600'); // 1 hour - reasonable for active development
  }
  // Images and fonts: Long cache
  else if (path.match(/\.(jpg|jpeg|png|gif|svg|ico|woff|woff2|ttf|eot)$/)) {
    res.setHeader('Cache-Control', 'public, max-age=31536000, immutable'); // 1 year
  }
  // PWA manifest: Medium cache
  else if (path === '/manifest.json') {
    res.setHeader('Cache-Control', 'public, max-age=86400'); // 1 day
  }
  // Everything else: Short cache
  else {
    res.setHeader('Cache-Control', 'public, max-age=3600'); // 1 hour
  }

  next();
});

// Blog post URL rewriting: /blog/:slug → /blog-post.html?slug=:slug
// This provides cleaner URLs for blog posts (SEO-friendly)
app.get('/blog/:slug', (req, res) => {
  res.redirect(301, `/blog-post.html?slug=${req.params.slug}`);
});

// Static files
app.use(express.static('public'));

// Health check endpoint (minimal, no sensitive data)
app.get('/health', (req, res) => {
  res.json({
    status: 'ok',
    timestamp: new Date().toISOString()
  });
});

// CSRF token endpoint (modern implementation)
// Returns the CSRF token from cookie for client-side usage
app.get('/api/csrf-token', getCsrfToken);

// API routes
const apiRoutes = require('./routes/index');
app.use('/api', apiRoutes);

// Homepage (temporary)
app.get('/', (req, res) => {
  res.send(`
    <!DOCTYPE html>
    <html>
    <head>
      <title>Tractatus AI Safety Framework</title>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1">
      <style>
        body {
          font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
          max-width: 800px;
          margin: 50px auto;
          padding: 20px;
          line-height: 1.6;
        }
        h1 { color: #2563eb; }
        .status { color: #059669; font-weight: bold; }
        code { background: #f3f4f6; padding: 2px 6px; border-radius: 3px; }
      </style>
    </head>
    <body>
      <h1>Tractatus AI Safety Framework</h1>
      <p class="status">✓ Server Running</p>
      <p>Development environment for the Tractatus-Based LLM Safety Framework website.</p>

      <h2>Status</h2>
      <ul>
        <li>✓ MongoDB connected (port 27017)</li>
        <li>✓ Express server running (port ${config.port})</li>
        <li>✓ Database initialized (10 collections)</li>
        <li>✓ Core models implemented</li>
        <li>✓ API routes complete (auth, documents, blog, admin)</li>
        <li>✓ Governance services active (6 core services)</li>
        <li>⏳ Frontend (pending)</li>
      </ul>

      <h2>Available Endpoints</h2>
      <ul>
        <li><code>GET /health</code> - Health check</li>
        <li><code>GET /api</code> - API documentation</li>
        <li><code>POST /api/auth/login</code> - Admin login</li>
        <li><code>GET /api/documents</code> - List framework documents</li>
        <li><code>GET /api/blog</code> - List published blog posts</li>
        <li><code>GET /api/admin/stats</code> - System statistics (auth required)</li>
      </ul>

      <p><em>Phase 1 Development - Not for public use</em></p>
    </body>
    </html>
  `);
});

// ============================================================
// ERROR HANDLING (Quick Wins)
// ============================================================

// 404 handler
app.use(notFound);

// Enhanced error handler (sanitizes responses, hides stack traces)
app.use(sanitizeErrorResponse);

// Fallback to original error handler if needed
app.use(errorHandler);

// Server startup
async function start() {
  try {
    // Connect to MongoDB (native driver)
    await connectDb();

    // Connect Mongoose (for ODM models)
    await connectMongoose();

    // Sync instructions from file to database
    try {
      const { syncInstructions } = require('../scripts/sync-instructions-to-db.js');
      const syncResult = await syncInstructions({ silent: true });
      if (syncResult && syncResult.success) {
        logger.info(`✅ Instructions synced to database: ${syncResult.finalCount} active rules`);
        if (syncResult.added > 0 || syncResult.deactivated > 0) {
          logger.info(`   Added: ${syncResult.added}, Updated: ${syncResult.updated}, Deactivated: ${syncResult.deactivated}`);
        }
      }
    } catch (err) {
      logger.warn(`⚠️  Instruction sync failed: ${err.message}`);
      logger.warn('   Admin UI may show outdated rule counts');
    }

    // Initialize governance services
    const BoundaryEnforcer = require('./services/BoundaryEnforcer.service');
    await BoundaryEnforcer.initialize();

    const PluralisticDeliberationOrchestrator = require('./services/PluralisticDeliberationOrchestrator.service');
    await PluralisticDeliberationOrchestrator.initialize();

    const InstructionPersistenceClassifier = require('./services/InstructionPersistenceClassifier.service');
    await InstructionPersistenceClassifier.initialize();

    const MetacognitiveVerifier = require('./services/MetacognitiveVerifier.service');
    await MetacognitiveVerifier.initialize();

    const CrossReferenceValidator = require('./services/CrossReferenceValidator.service');
    await CrossReferenceValidator.initialize();

    const ContextPressureMonitor = require('./services/ContextPressureMonitor.service');
    await ContextPressureMonitor.initialize();

    logger.info('✅ Governance services initialized (6 core services)');

    // Start server
    const server = app.listen(config.port, () => {
      logger.info(`🚀 Tractatus server started`);
      logger.info(`✅ Environment: ${config.env}`);
      logger.info(`✅ Port: ${config.port}`);
      logger.info(`✅ MongoDB: ${config.mongodb.db}`);
      logger.info(`🔒 Security: Quick Wins active (headers, rate limiting, input validation)`);
      logger.info(`📊 Security logs: ${process.env.HOME}/var/log/tractatus/security-audit.log`);
      logger.info(`✨ Ready for development`);
      console.log(`\n🌐 http://localhost:${config.port}\n`);
    });

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

  } catch (error) {
    logger.error('Failed to start server:', error);
    process.exit(1);
  }
}

// Graceful shutdown
async function shutdown(server) {
  logger.info('Shutting down gracefully...');

  server.close(async () => {
    logger.info('HTTP server closed');

    await closeDb();
    logger.info('Native MongoDB connection closed');

    await closeMongoose();
    logger.info('Mongoose connection closed');

    process.exit(0);
  });

  // Force shutdown after 10 seconds
  setTimeout(() => {
    logger.error('Forced shutdown after timeout');
    process.exit(1);
  }, 10000);
}

// Start server if run directly
if (require.main === module) {
  start();
}

module.exports = app;