/* AquaFlow service worker: lets the cashier terminal open and run with no network.
 *
 * - Page loads (navigations): network first, falling back to the cached copy,
 *   and to the cached /terminal page for anything else, so a cashier who opens
 *   the app offline still lands on the till.
 * - Next.js build assets (/_next/static/*): cache first. They are content-hashed
 *   and immutable, so a cached copy is always correct.
 * - API calls (/api/*) and every non-GET request: never cached. Sales go through
 *   the IndexedDB queue in the page, not through this worker.
 *
 * Bump CACHE_VERSION to drop every cached page and asset on the next visit.
 */
const CACHE_VERSION = "aquaflow-v1";
const APP_SHELL = ["/terminal", "/login"];

async function cacheShell() {
  const cache = await caches.open(CACHE_VERSION);
  for (const path of APP_SHELL) {
    try {
      const res = await fetch(path, { credentials: "same-origin" });
      if (!res.ok) continue;
      await cache.put(path, res.clone());
      // Also cache the scripts and styles the page needs to boot.
      const html = await res.text();
      const assets = Array.from(html.matchAll(/(?:src|href)="(\/_next\/static\/[^"]+)"/g), (m) => m[1]);
      await Promise.all(
        Array.from(new Set(assets)).map((url) =>
          cache.match(url).then((hit) => hit || fetch(url).then((r) => r.ok && cache.put(url, r)))
        )
      );
    } catch (e) {
      // Offline during install: the runtime handlers below fill the cache later.
    }
  }
}

self.addEventListener("install", (event) => {
  event.waitUntil(cacheShell().then(() => self.skipWaiting()));
});

self.addEventListener("activate", (event) => {
  event.waitUntil(
    caches
      .keys()
      .then((keys) => Promise.all(keys.filter((k) => k !== CACHE_VERSION).map((k) => caches.delete(k))))
      .then(() => self.clients.claim())
  );
});

self.addEventListener("fetch", (event) => {
  const req = event.request;
  if (req.method !== "GET") return;
  const url = new URL(req.url);
  if (url.origin !== self.location.origin) return;
  if (url.pathname.startsWith("/api/")) return;

  if (req.mode === "navigate") {
    event.respondWith(
      fetch(req)
        .then((res) => {
          if (res.ok) {
            const copy = res.clone();
            caches.open(CACHE_VERSION).then((c) => c.put(url.pathname, copy));
          }
          return res;
        })
        .catch(async () => {
          const cache = await caches.open(CACHE_VERSION);
          return (await cache.match(url.pathname)) || (await cache.match("/terminal")) || Response.error();
        })
    );
    return;
  }

  if (url.pathname.startsWith("/_next/static/")) {
    event.respondWith(
      caches.open(CACHE_VERSION).then(async (cache) => {
        const hit = await cache.match(req);
        if (hit) return hit;
        const res = await fetch(req);
        if (res.ok) cache.put(req, res.clone());
        return res;
      })
    );
  }
});