Node.js Rate Limiter

interface RateLimiterOptions {
  windowMs: number;
  max: number;
}

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

export class RateLimiter {
  private store = new Map<string, Entry>();
  private windowMs: number;
  private max: number;

  constructor({ windowMs = 60_000, max = 60 }: RateLimiterOptions) {
    this.windowMs = windowMs;
    this.max = max;
  }

  check(key: string): { allowed: boolean; remaining: number; resetAt: number } {
    const now = Date.now();
    const entry = this.store.get(key);

    if (!entry || now >= entry.resetAt) {
      const resetAt = now + this.windowMs;
      this.store.set(key, { count: 1, resetAt });
      return { allowed: true, remaining: this.max - 1, resetAt };
    }

    if (entry.count >= this.max) {
      return { allowed: false, remaining: 0, resetAt: entry.resetAt };
    }

    entry.count++;
    return { allowed: true, remaining: this.max - entry.count, resetAt: entry.resetAt };
  }

  reset(key: string): void {
    this.store.delete(key);
  }
}