// A sliding-window count per key, for the doors a stranger can knock on.

export class RateLimit {
	private hits = new Map<string, number[]>();

	constructor(
		private limit: number,
		private windowMs: number
	) {}

	/** True if the key may act now; the act is recorded when it is allowed. */
	allow(key: string, now = Date.now()): boolean {
		const since = now - this.windowMs;
		const recent = (this.hits.get(key) ?? []).filter((t) => t > since);
		if (recent.length >= this.limit) {
			this.hits.set(key, recent);
			return false;
		}
		recent.push(now);
		this.hits.set(key, recent);
		if (this.hits.size > 10000) this.prune(now);
		return true;
	}

	prune(now = Date.now()): void {
		const since = now - this.windowMs;
		for (const [key, times] of this.hits) {
			if (!times.some((t) => t > since)) this.hits.delete(key);
		}
	}
}