function preciseCountdown(duration) { // duration 為總倒計(jì)時(shí)時(shí)長(zhǎng)（毫秒）
  let startTime = Date.now();
  let expected = duration;

  function step() {
    const now = Date.now();
    const elapsed = now - startTime; // 實(shí)際已過(guò)去的時(shí)間
    const remaining = duration - elapsed; // 剩余時(shí)間

    if (remaining <= 0) {
      console.log("倒計(jì)時(shí)結(jié)束");
      return;
    }

    // 計(jì)算本次執(zhí)行的偏差（實(shí)際流逝 - 理論流逝）
    const drift = elapsed - expected;
    // 調(diào)整下一次觸發(fā)的時(shí)間，目標(biāo)是每1000ms執(zhí)行一次
    expected += 1000;
    const nextInterval = 1000 - drift; // 動(dòng)態(tài)調(diào)整間隔

    console.log(`剩余時(shí)間: ${Math.round(remaining/1000)}秒，偏差: ${drift}ms`);

    setTimeout(step, Math.max(0, nextInterval)); // 確保間隔不為負(fù)
  }

  setTimeout(step, 1000);
}

// 開(kāi)始一個(gè)10秒的倒計(jì)時(shí)
preciseCountdown(10000);

function highPrecisionCountdown(duration) {
  const startTime = performance.now(); // 使用高精度時(shí)間起點(diǎn)

  function update() {
    const currentTime = performance.now();
    const elapsed = currentTime - startTime;
    const remaining = Math.max(duration - elapsed, 0);

    if (remaining <= 0) {
      console.log("高精度倒計(jì)時(shí)結(jié)束");
      return;
    }

    console.log(`高精度剩余時(shí)間: ${(remaining / 1000).toFixed(3)}秒`);
    requestAnimationFrame(update); // 與屏幕刷新率同步，更平滑
  }

  requestAnimationFrame(update);
}

highPrecisionCountdown(10000);

let serverTimeDelta = 0; // 服務(wù)器時(shí)間 - 客戶端時(shí)間 的差值

// 初始化時(shí)校準(zhǔn)時(shí)間
async function calibrateTime() {
  const beforeRequest = Date.now();
  const response = await fetch('/api/server-time'); // 假設(shè)該接口返回服務(wù)器時(shí)間戳（毫秒）
  const serverTime = await response.json();
  const afterRequest = Date.now();

  // 估算網(wǎng)絡(luò)傳輸耗時(shí)，假設(shè)請(qǐng)求和響應(yīng)時(shí)間對(duì)稱
  const roundTripTime = afterRequest - beforeRequest;
  const oneWayTime = roundTripTime / 2;
  const estimatedServerTimeWhenReceived = serverTime + oneWayTime;

  serverTimeDelta = estimatedServerTimeWhenReceived - afterRequest;
}

// 在倒計(jì)時(shí)計(jì)算中，使用校準(zhǔn)后的時(shí)間
function getCalibratedTime() {
  return Date.now() + serverTimeDelta;
}

// 創(chuàng)建 Worker
const countdownWorker = new Worker('countdown-worker.js');

// 監(jiān)聽(tīng) Worker 發(fā)來(lái)的消息
countdownWorker.onmessage = function(e) {
  if (e.data.status === 'update') {
    console.log(`剩余時(shí)間: ${e.data.remaining}ms`);
  } else if (e.data.status === 'finished') {
    console.log("倒計(jì)時(shí)結(jié)束");
    countdownWorker.terminate();
  }
};

// 向 Worker 發(fā)送指令，開(kāi)始倒計(jì)時(shí)
countdownWorker.postMessage({
  command: 'start',
  duration: 10000 // 10秒
});

let timer;
self.onmessage = function(e) {
  if (e.data.command === 'start') {
    const duration = e.data.duration;
    const startTime = Date.now();

    function step() {
      const elapsed = Date.now() - startTime;
      const remaining = duration - elapsed;

      if (remaining <= 0) {
        self.postMessage({ status: 'finished' });
        return;
      }

      self.postMessage({
        status: 'update',
        remaining: remaining
      });

      // 使用動(dòng)態(tài)調(diào)整的 setTimeout
      const drift = elapsed % 1000;
      timer = setTimeout(step, 1000 - drift);
    }

    step();
  } else if (e.data.command === 'stop') {
    clearTimeout(timer);
  }
};

let startTime = Date.now();
let totalPausedTime = 0;
let timerId;

function startCountdown(duration) {
  startTime = Date.now();
  timerId = setInterval(() => updateCountdown(duration), 1000);
}

function updateCountdown(duration) {
  const currentTime = Date.now();
  // 已過(guò)去的時(shí)間需要減去暫停的總時(shí)間
  const elapsed = currentTime - startTime - totalPausedTime;
  const remaining = Math.max(duration - elapsed, 0);

  if (remaining <= 0) {
    clearInterval(timerId);
    console.log("倒計(jì)時(shí)結(jié)束");
  } else {
    console.log(`剩余: ${Math.round(remaining/1000)}秒`);
  }
}

document.addEventListener('visibilitychange', () => {
  if (document.hidden) {
    // 頁(yè)面隱藏，暫停計(jì)時(shí)并記錄暫停開(kāi)始時(shí)刻
    clearInterval(timerId);
    this.pauseStartTime = Date.now();
  } else {
    // 頁(yè)面再次可見(jiàn)，計(jì)算暫停了多久并累加，然后重啟計(jì)時(shí)器
    totalPausedTime += Date.now() - this.pauseStartTime;
    startCountdown(10000); // 需要知道總時(shí)長(zhǎng)，這里假設(shè)10秒
  }
});