collapsed_queue.ts

class CollapsedQueue<K, V> {
  private jobs: Map<K, V> = new Map();
  
  constructor(
    private timeout: number,
    private collapse: (oldValue: V, newValue: V) => V,
    private doJob: (key: K, value: V) => void,
  ) {}

  enqueue(key: K, value: V) {
    if (this.jobs.has(key)) {
      const old = this.jobs.get(key)!;
      const merged = this.collapse(old, value);
      this.jobs.set(key, merged);
    } else {
      this.jobs.set(key, value);
      setTimeout(() => {
        const value = this.jobs.get(key);
        this.jobs.delete(key);
        this.doJob(key, value);
      }, this.timeout);
    }
  }
}