/**
 * In-memory rate limiter for admin login and user authentication.
 * Admin: max 5 attempts per IP per 15 minutes.
 * User auth: max 10 attempts per (IP + username) per 15 minutes.
 */

const MAX_ADMIN_ATTEMPTS = 5;
const MAX_USER_ATTEMPTS = 10;
const WINDOW_MS = 15 * 60 * 1000; // 15 minutes

interface RateLimitEntry {
  count: number;
  resetAt: number;
}

const attempts = new Map<string, RateLimitEntry>();

// Clean up expired entries periodically
setInterval(() => {
  const now = Date.now();
  for (const [key, entry] of attempts) {
    if (entry.resetAt <= now) {
      attempts.delete(key);
    }
  }
}, 60_000).unref();

/**
 * Check if the IP is rate limited. Returns remaining attempts, or 0 if blocked.
 */
export function checkRateLimit(ip: string): { allowed: boolean; remaining: number; retryAfterMs: number } {
  const now = Date.now();
  const entry = attempts.get(`admin:${ip}`);

  if (!entry || entry.resetAt <= now) {
    attempts.set(`admin:${ip}`, { count: 1, resetAt: now + WINDOW_MS });
    return { allowed: true, remaining: MAX_ADMIN_ATTEMPTS - 1, retryAfterMs: 0 };
  }

  if (entry.count >= MAX_ADMIN_ATTEMPTS) {
    return { allowed: false, remaining: 0, retryAfterMs: entry.resetAt - now };
  }

  entry.count++;
  return { allowed: true, remaining: MAX_ADMIN_ATTEMPTS - entry.count, retryAfterMs: 0 };
}

/**
 * Check rate limit for user authentication, keyed by IP + username.
 */
export function checkUserAuthRateLimit(ip: string, username: string): { allowed: boolean; remaining: number; retryAfterMs: number } {
  const now = Date.now();
  const key = `user:${ip}:${username}`;
  const entry = attempts.get(key);

  if (!entry || entry.resetAt <= now) {
    attempts.set(key, { count: 1, resetAt: now + WINDOW_MS });
    return { allowed: true, remaining: MAX_USER_ATTEMPTS - 1, retryAfterMs: 0 };
  }

  if (entry.count >= MAX_USER_ATTEMPTS) {
    return { allowed: false, remaining: 0, retryAfterMs: entry.resetAt - now };
  }

  entry.count++;
  return { allowed: true, remaining: MAX_USER_ATTEMPTS - entry.count, retryAfterMs: 0 };
}