// src/utils/versionGuard.js
const VERSION_URL = '/version.json';
const LS_KEY = '__app_version__';
const SESSION_REFRESH_FLAG = '__just_refreshed__';

async function fetchRemoteVersion() {
  const res = await fetch(VERSION_URL, { cache: 'no-store' }); // ★ 關鍵：不快取
  if (!res.ok) throw new Error('version.json fetch failed');
  return res.json();
}

async function unregisterAllSW() {
  if (!('serviceWorker' in navigator)) return;
  const regs = await navigator.serviceWorker.getRegistrations();
  await Promise.all(regs.map(r => r.unregister()));
}

async function clearCacheStorage() {
  if (!('caches' in window)) return;
  const keys = await caches.keys();
  await Promise.all(keys.map(k => caches.delete(k)));
}

export async function ensureFreshAssets() {
  try {
    const prev = localStorage.getItem(LS_KEY);
    const remote = await fetchRemoteVersion();
    const ver = remote.version || remote.buildId || remote.commit;
    if (!ver) return;

    if (prev && prev !== ver) {
      await unregisterAllSW();
      await clearCacheStorage();
      sessionStorage.setItem(SESSION_REFRESH_FLAG, '1');
      // 用 replace 避免回上一頁又載到舊 index.html
      location.replace(location.href.split('#')[0]);
      return;
    }

    if (!prev) localStorage.setItem(LS_KEY, ver);
  } catch (e) {
    console.warn('[versionGuard] check failed:', e);
  }
}

export async function syncLocalVersion() {
  try {
    const remote = await fetchRemoteVersion();
    const ver = remote.version || remote.buildId || remote.commit;
    if (ver) localStorage.setItem(LS_KEY, ver);
  } catch {}
}