Source

// Drop's service worker. It keeps the app's own files so an installed Drop opens quickly, and
// receives files shared to Drop from another app (the share sheet on Android), handing them to
// the page that opens. The build (vite.config.ts) fills in the version and the list of app files.
const CACHE = "drop-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("drop-shell-") && k !== CACHE).map((k) => caches.delete(k))))
      .then(() => self.clients.claim()),
  );
});

// Files shared to Drop wait here (in memory, never uploaded) until the sending screen asks for them.
let shared = null;
let sharedTaken = null;

self.addEventListener("fetch", (e) => {
  const req = e.request;
  const url = new URL(req.url);
  if (req.method === "POST" && url.pathname === "/share-target") {
    e.respondWith((async () => {
      const data = await req.formData().catch(() => null);
      shared = data ? data.getAll("files").filter((f) => typeof f !== "string") : [];
      return Response.redirect("/send?shared=1", 303);
    })());
    // Stay awake until the page has taken the files, or for a minute.
    e.waitUntil(new Promise((resolve) => { sharedTaken = resolve; setTimeout(resolve, 60000); }));
    return;
  }
  if (req.method !== "GET" || url.origin !== location.origin || url.pathname.startsWith("/__bounded/")) return;
  if (req.mode === "navigate") {
    // Every page is the same app shell: fresh when online, the saved copy when not.
    e.respondWith(fetch(req).catch(() => caches.match("/", { cacheName: CACHE })));
    return;
  }
  e.respondWith(caches.match(req, { cacheName: CACHE }).then((hit) => hit || fetch(req)));
});

self.addEventListener("message", (e) => {
  if (e.data !== "drop:shared?" || !e.source) return;
  e.source.postMessage({ t: "drop:shared", files: shared || [] });
  shared = null;
  sharedTaken?.();
});