let bannerVisible = false;

function showUpdateBanner() {
  if (bannerVisible) return;
  const banner = document.getElementById("updateBanner");
  if (!banner) return;
  banner.hidden = false;
  bannerVisible = true;
}

async function applyUpdate() {
  const reg = await navigator.serviceWorker?.getRegistration();
  if (reg?.waiting) {
    reg.waiting.postMessage({ type: "SKIP_WAITING" });
  } else {
    await reg?.update();
    location.reload();
  }
}

export function wireAppUpdates() {
  if (!("serviceWorker" in navigator)) return;

  let refreshing = false;
  navigator.serviceWorker.addEventListener("controllerchange", () => {
    if (refreshing) return;
    refreshing = true;
    location.reload();
  });

  navigator.serviceWorker.addEventListener("message", (event) => {
    if (event.data?.type === "UPDATE_AVAILABLE") showUpdateBanner();
  });

  const button = document.getElementById("updateBannerBtn");
  button?.addEventListener("click", () => applyUpdate());

  const checkVersion = async () => {
    try {
      const reg = await navigator.serviceWorker.getRegistration();
      await reg?.update();

      const built = document.querySelector('meta[name="app-build"]')?.content;
      if (!built) return;

      const res = await fetch("/version.json", { cache: "no-store" });
      if (!res.ok) return;
      const data = await res.json();
      if (data.buildHash && data.buildHash !== built) {
        showUpdateBanner();
      }
    } catch {
      /* ignore — offline or transient */
    }
  };

  window.addEventListener("focus", checkVersion);
  document.addEventListener("visibilitychange", () => {
    if (document.visibilityState === "visible") checkVersion();
  });
  checkVersion();
}