/**
 * Request utility functions
 * Helpers for extracting information from Express requests
 */

/**
 * Extract client IP address from request
 * Considers proxy headers (X-Forwarded-For, X-Real-IP)
 *
 * @param {Object} req - Express request object
 * @returns {string|null} - Client IP address or null
 */
function getClientIP(req) {
  try {
    // Check X-Forwarded-For header (used by proxies/load balancers)
    const forwardedFor = req.headers['x-forwarded-for'];
    if (forwardedFor) {
      // X-Forwarded-For can contain multiple IPs, take the first one (client IP)
      const ips = forwardedFor.split(',').map(ip => ip.trim());
      if (ips.length > 0 && ips[0]) {
        return ips[0];
      }
    }

    // Check X-Real-IP header (used by some proxies)
    const realIP = req.headers['x-real-ip'];
    if (realIP) {
      return realIP;
    }

    // Fallback to req.ip (Express built-in)
    if (req.ip) {
      // Express sometimes returns IPv6-mapped IPv4 (::ffff:192.168.1.1)
      // Convert to standard IPv4 format
      return req.ip.replace(/^::ffff:/, '');
    }

    // Fallback to socket remote address
    if (req.connection && req.connection.remoteAddress) {
      return req.connection.remoteAddress.replace(/^::ffff:/, '');
    }

    return null;
  } catch (error) {
    console.error('Error extracting client IP:', error);
    return null;
  }
}

module.exports = {
  getClientIP,
};