Source

// Lingo's service worker. It keeps the app and every course on the device, so lessons work with no
// connection once Lingo has loaded. Progress syncs to the account when the connection is back.
// The build (vite.config.ts) fills in the version and the list of files.
const CACHE = "lingo-shell-__VERSION__";
const SHELL = __SHELL__;

self.addEventListener("install", (e) => {
  e.waitUntil(caches.open(CACHE).then((c) => c.addAll(SHELL)).then(() => self.skipWaiting()));
});

self.addEventListener("activate", (e) => {
  e.waitUntil(
    caches.keys()
      .then((keys) => Promise.all(keys.filter((k) => k.startsWith("lingo-shell-") && k !== CACHE).map((k) => caches.delete(k))))
      .then(() => self.clients.claim()),
  );
});

self.addEventListener("fetch", (e) => {
  const req = e.request;
  const url = new URL(req.url);
  if (req.method !== "GET" || url.origin !== location.origin || url.pathname.startsWith("/__bounded/")) return;
  if (req.mode === "navigate") {
    // Every page is the same app: fresh when online, the saved copy when not.
    e.respondWith(
      fetch(req)
        .then((res) => {
          if (res.ok && (res.headers.get("content-type") || "").includes("text/html")) {
            const copy = res.clone();
            void caches.open(CACHE).then((c) => c.put("/", copy));
          }
          return res;
        })
        .catch(() => caches.match("/", { cacheName: CACHE })),
    );
    return;
  }
  e.respondWith(caches.match(req, { cacheName: CACHE, ignoreSearch: url.pathname === "/" }).then((hit) => hit || fetch(req)));
});