import { kv } from '@vercel/kv';

/**
 * Rate limit configuration
 */
const RATE_LIMIT_WINDOW = 60 * 60 * 1000; // 1 hour in milliseconds
const MAX_REQUESTS_PER_WINDOW = 5;

/**
 * Rate limit key prefix
 */
const RATE_LIMIT_PREFIX = 'ratelimit:signup:';

/**
 * Check if an IP address has exceeded rate limits
 * @param identifier - IP address or unique identifier
 * @returns Object with allowed status and retry information
 */
export async function checkRateLimit(identifier: string): Promise<{
  allowed: boolean;
  remaining: number;
  resetAt: number;
}> {
  const key = `${RATE_LIMIT_PREFIX}${identifier}`;
  const now = Date.now();
  
  try {
    // Get current count
    const count = await kv.get<number>(key) || 0;
    
    if (count >= MAX_REQUESTS_PER_WINDOW) {
      // Get TTL to determine reset time
      const ttl = await kv.ttl(key);
      const resetAt = now + (ttl * 1000);
      
      return {
        allowed: false,
        remaining: 0,
        resetAt,
      };
    }
    
    // Increment counter
    const newCount = count + 1;
    
    if (count === 0) {
      // First request - set with expiry
      await kv.set(key, newCount, {
        px: RATE_LIMIT_WINDOW,
      });
    } else {
      // Subsequent request - increment without changing TTL
      await kv.incr(key);
    }
    
    // Calculate reset time
    const ttl = await kv.ttl(key);
    const resetAt = now + (ttl * 1000);
    
    return {
      allowed: true,
      remaining: MAX_REQUESTS_PER_WINDOW - newCount,
      resetAt,
    };
  } catch (error) {
    // If rate limiting fails, allow the request
    console.error('Rate limit check failed:', error);
    return {
      allowed: true,
      remaining: MAX_REQUESTS_PER_WINDOW,
      resetAt: now + RATE_LIMIT_WINDOW,
    };
  }
}

/**
 * Get client IP from request headers
 */
export function getClientIp(request: Request): string {
  // Try various headers that might contain the IP
  const headers = request.headers;
  
  return (
    headers.get('x-forwarded-for')?.split(',')[0]?.trim() ||
    headers.get('x-real-ip') ||
    headers.get('cf-connecting-ip') || // Cloudflare
    'unknown'
  );
}