import { NextRequest } from 'next/server';

/**
 * Extract client IP address from Next.js request headers
 *
 * This function handles various proxy and forwarding scenarios:
 * - Vercel's x-forwarded-for header (may contain multiple IPs)
 * - x-real-ip header (direct client IP)
 * - Fallback for development environments
 *
 * @param request - Next.js request object
 * @returns Client IP address as a string, or 'unknown-ip' as fallback
 */
export function getClientIp(request: NextRequest): string {
  // Check Vercel's forwarded IP header first
  // In production, this is the most reliable source
  const forwardedFor = request.headers.get('x-forwarded-for');
  if (forwardedFor) {
    // x-forwarded-for may contain multiple IPs in format: "client, proxy1, proxy2"
    // The first IP is the original client IP
    return forwardedFor.split(',')[0].trim();
  }

  // Check for real IP header (used by some proxies and load balancers)
  const realIp = request.headers.get('x-real-ip');
  if (realIp) {
    return realIp;
  }

  // Fallback to a default identifier for development environments
  // or when headers are not available
  return 'unknown-ip';
}