/**
 * A dependency-free fixed-window rate limiter keyed by an opaque string (client IP,
 * account email, staff id, …). Returns true while the key is under `limit` in the
 * current `windowMs` window, false once it is exhausted. Expired buckets are swept
 * lazily so the map cannot grow without bound under key rotation. In its own module
 * so both the api router and the public-share route can share it without a cycle.
 */
export function makeRateLimiter(limit: number, windowMs: number): (key: string, now?: number) => boolean {
  const buckets = new Map<string, { count: number; resetAt: number }>()
  return (key: string, now = Date.now()): boolean => {
    if (buckets.size > 5000) for (const [k, b] of buckets) if (now >= b.resetAt) buckets.delete(k)
    const bucket = buckets.get(key)
    if (bucket === undefined || now >= bucket.resetAt) {
      buckets.set(key, { count: 1, resetAt: now + windowMs })
      return true
    }
    if (bucket.count >= limit) return false
    bucket.count += 1
    return true
  }
}