interface FileCoalescer {
  readonly schedule: (file: string, delayMs?: number) => boolean;
  readonly clear: () => void;
}

export function createFileCoalescer(
  handler: (file: string) => void,
  defaultDelayMs: number,
): FileCoalescer {
  const pending = new Map<string, ReturnType<typeof setTimeout>>();

  return {
    schedule(file: string, delayMs = defaultDelayMs): boolean {
      if (pending.has(file)) {
        return false;
      }
      const timer = setTimeout(() => {
        pending.delete(file);
        handler(file);
      }, delayMs);
      pending.set(file, timer);
      return true;
    },
    clear(): void {
      for (const timer of pending.values()) {
        clearTimeout(timer);
      }
      pending.clear();
    },
  };
}