Patternflow

// In-memory sliding-window rate limiter. This app runs as a single long-lived
// process (the Pi), so process memory is a perfectly good store — no Redis.

const buckets = new Map<string, number[]>();

/** Returns true when the call is allowed, false when over the limit. */
export function rateLimit(key: string, limit: number, windowMs: number): boolean {
  const now = Date.now();
  const cutoff = now - windowMs;
  const hits = (buckets.get(key) ?? []).filter((t) => t > cutoff);
  if (hits.length >= limit) {
    buckets.set(key, hits);
    return false;
  }
  hits.push(now);
  buckets.set(key, hits);

  // Opportunistic cleanup so long-idle keys don't accumulate forever.
  if (buckets.size > 10_000) {
    for (const [k, v] of buckets) {
      if (v.every((t) => t <= cutoff)) buckets.delete(k);
    }
  }
  return true;
}