const express = require('express');
const cors = require('cors');
const helmet = require('helmet');
const session = require('express-session');
const compression = require('compression');
const cookieParser = require('cookie-parser');
const path = require('path');
require('dotenv').config();

const logger = require('./utils/logger');
const metrics = require('./utils/metrics');
const healthCheck = require('./utils/health-check');
const { conditionalCsrfProtection, getCsrfToken } = require('./middleware/csrf');

const apiRoutes = require('./routes/api');
const authRoutes = require('./routes/auth');
const { requireAdmin, requireAuth } = require('./middleware/auth');

const app = express();
const PORT = process.env.PORT || 3333;

// Trust proxy for Docker/reverse proxy environments
// Only trust Docker internal networks for better security
app.set('trust proxy', ['127.0.0.1', '::1', '172.16.0.0/12', '192.168.0.0/16', '10.0.0.0/8']);

// Compression middleware for better performance
app.use(compression({
  filter: (req, res) => {
    if (req.headers['x-no-compression']) {
      return false;
    }
    return compression.filter(req, res);
  },
  level: 6 // Balance between speed and compression ratio
}));

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

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

// Metrics middleware - track all HTTP requests
app.use(metrics.middleware);

// Request logging middleware
app.use((req, res, next) => {
  const start = Date.now();
  
  res.on('finish', () => {
    const duration = Date.now() - start;
    logger.logRequest(req, res, duration);
  });
  
  next();
});

// Session configuration - PRODUCTION HARDENED
app.use(session({
  secret: process.env.SESSION_SECRET || 'influence-campaign-secret-key-change-in-production',
  resave: false,
  saveUninitialized: false,
  name: 'influence.sid', // Custom session name for security
  cookie: {
    secure: process.env.NODE_ENV === 'production' && process.env.HTTPS === 'true', // HTTPS only in production
    httpOnly: true, // Prevent JavaScript access
    maxAge: 3600000, // 1 hour (reduced from 24 hours)
    sameSite: 'strict' // CSRF protection
  }
}));

// CSRF Protection - Applied conditionally
app.use(conditionalCsrfProtection);

// Static files with proper caching
app.use(express.static(path.join(__dirname, 'public'), {
  maxAge: process.env.NODE_ENV === 'production' ? '1d' : 0,
  etag: true,
  lastModified: true,
  setHeaders: (res, filePath) => {
    // Cache images and assets longer
    if (filePath.match(/\.(jpg|jpeg|png|gif|ico|svg|woff|woff2|ttf|eot)$/)) {
      res.setHeader('Cache-Control', 'public, max-age=604800'); // 7 days
    }
    // Cache CSS and JS for 1 day
    else if (filePath.match(/\.(css|js)$/)) {
      res.setHeader('Cache-Control', 'public, max-age=86400'); // 1 day
    }
  }
}));

// Health check endpoint - COMPREHENSIVE
app.get('/api/health', async (req, res) => {
  try {
    const health = await healthCheck.checkAll();
    const statusCode = health.status === 'healthy' ? 200 : health.status === 'degraded' ? 200 : 503;
    res.status(statusCode).json(health);
  } catch (error) {
    logger.error('Health check failed', { error: error.message });
    res.status(503).json({
      status: 'unhealthy',
      error: error.message,
      timestamp: new Date().toISOString()
    });
  }
});

// Metrics endpoint for Prometheus
app.get('/api/metrics', async (req, res) => {
  try {
    res.set('Content-Type', metrics.getContentType());
    const metricsData = await metrics.getMetrics();
    res.end(metricsData);
  } catch (error) {
    logger.error('Metrics endpoint failed', { error: error.message });
    res.status(500).json({ error: 'Failed to generate metrics' });
  }
});

// CSRF token endpoint
app.get('/api/csrf-token', getCsrfToken);

// Routes
app.use('/api/auth', authRoutes);
app.use('/api', apiRoutes);

// Config endpoint - expose APP_URL to client
app.get('/api/config', (req, res) => {
  res.json({
    appUrl: process.env.APP_URL || `http://localhost:${PORT}`
  });
});

// Serve the main page
app.get('/', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'index.html'));
});

// Serve login page
app.get('/login.html', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'login.html'));
});

// Serve admin panel (protected)
app.get('/admin.html', requireAdmin, (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'admin.html'));
});

// Serve the admin page (protected)
app.get('/admin', requireAdmin, (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'admin.html'));
});

// Serve user dashboard (protected)
app.get('/dashboard.html', requireAuth, (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'dashboard.html'));
});

app.get('/dashboard', requireAuth, (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'dashboard.html'));
});

// Serve campaign landing pages
app.get('/campaign/:slug', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'campaign.html'));
});

// Serve campaign pages
app.get('/campaign/:slug', (req, res) => {
  res.sendFile(path.join(__dirname, 'public', 'campaign.html'));
});

// Error handling middleware
app.use((err, req, res, next) => {
  logger.error('Application error', {
    error: err.message,
    stack: err.stack,
    path: req.path,
    method: req.method,
    ip: req.ip
  });

  res.status(err.status || 500).json({
    error: 'Something went wrong!',
    message: process.env.NODE_ENV === 'development' ? err.message : 'Internal server error',
    ...(process.env.NODE_ENV === 'development' && { stack: err.stack })
  });
});

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

// Graceful shutdown
process.on('SIGTERM', () => {
  logger.info('SIGTERM received, shutting down gracefully');
  server.close(() => {
    logger.info('Server closed');
    process.exit(0);
  });
});

process.on('SIGINT', () => {
  logger.info('SIGINT received, shutting down gracefully');
  server.close(() => {
    logger.info('Server closed');
    process.exit(0);
  });
});

const server = app.listen(PORT, () => {
  logger.info('Server started', {
    port: PORT,
    environment: process.env.NODE_ENV,
    nodeVersion: process.version
  });
});

module.exports = app;