export interface Clock { now(): number; setTimer(callback: () => void, delayMs: number): unknown; clearTimer(timer: unknown): void; }
export const systemClock: Clock = {
  now: () => Date.now(),
  setTimer: (callback, delayMs) => setTimeout(callback, Math.min(delayMs, 2_147_483_647)),
  clearTimer: (timer) => clearTimeout(timer as NodeJS.Timeout),
};

export class LoopScheduler {
  private wakeTimer?: unknown;
  private deadlineTimer?: unknown;
  private generation = 0;
  constructor(private readonly clock: Clock) {}
  arm(wakeAt: number | undefined, deadlineAt: number | undefined, onWake: () => void, onDeadline: () => void): void {
    this.cancel();
    const generation = this.generation;
    if (wakeAt !== undefined) this.wakeTimer = this.clock.setTimer(() => { if (generation === this.generation) onWake(); }, Math.max(0, wakeAt - this.clock.now()));
    if (deadlineAt !== undefined) this.deadlineTimer = this.clock.setTimer(() => { if (generation === this.generation) onDeadline(); }, Math.max(0, deadlineAt - this.clock.now()));
  }
  cancel(): void {
    this.generation++;
    if (this.wakeTimer !== undefined) this.clock.clearTimer(this.wakeTimer);
    if (this.deadlineTimer !== undefined) this.clock.clearTimer(this.deadlineTimer);
    this.wakeTimer = undefined; this.deadlineTimer = undefined;
  }
}