const WINDOW_MS = 15 * 60 * 1000; // 15 minutes
const MAX_ATTEMPTS = 5;

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

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

function cleanup() {
  const now = Date.now();
  for (const [key, entry] of store) {
    if (now >= entry.resetAt) {
      store.delete(key);
    }
  }
}

let cleanupInterval: ReturnType<typeof setInterval> | null = null;

function ensureCleanupRunning() {
  if (cleanupInterval) return;
  cleanupInterval = setInterval(cleanup, 5 * 60 * 1000);
  if (typeof cleanupInterval === "object" && "unref" in cleanupInterval) {
    cleanupInterval.unref();
  }
}

export function checkRateLimit(key: string): {
  allowed: boolean;
  remaining: number;
  retryAfterMs: number;
} {
  ensureCleanupRunning();
  const now = Date.now();
  const entry = store.get(key);

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

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

  entry.count += 1;
  return {
    allowed: true,
    remaining: MAX_ATTEMPTS - entry.count,
    retryAfterMs: 0,
  };
}

export function getClientIp(request: Request): string {
  const forwarded = request.headers.get("x-forwarded-for");
  if (forwarded) {
    return forwarded.split(",")[0].trim();
  }
  return "unknown";
}