/* Sudoku Tools offline worker. This file intentionally has no dependencies. */
const CACHE_PREFIX = "sudoku-tools-shell-";
const CACHE_VERSION = "v1";
const CACHE_NAME = `${CACHE_PREFIX}${CACHE_VERSION}`;
const CORE_ASSETS = ["./", "./manifest.webmanifest", "./favicon.svg"];
const BUILD_ASSET_PATTERN =
  /(?:(?:\.\/)?assets\/)?[A-Za-z0-9][A-Za-z0-9._-]*-[A-Za-z0-9_-]{6,}\.(?:css|js|json|png|svg|wasm)/gu;

async function cacheAssetTree(cache, assetUrl, discovered, depth = 0) {
  const url = new URL(assetUrl, self.registration.scope).href;
  if (discovered.has(url)) return;
  discovered.add(url);
  const response = await fetch(url, { cache: "no-cache" });
  if (!response.ok) return;
  await cache.put(url, response.clone());
  const contentType = response.headers.get("content-type") ?? "";
  if (depth >= 3 || !/(?:javascript|text\/css)/iu.test(contentType)) return;
  const source = await response.text();
  await Promise.all(
    [...source.matchAll(BUILD_ASSET_PATTERN)].map((match) => {
      const reference = match[0];
      const base = reference.includes("assets/")
        ? self.registration.scope
        : url;
      return cacheAssetTree(
        cache,
        new URL(reference, base).href,
        discovered,
        depth + 1,
      );
    }),
  );
}

async function cacheDocumentAssets(cache) {
  const response = await fetch("./", { cache: "no-cache" });
  if (!response.ok) throw new Error("Could not cache the application shell.");
  await cache.put("./", response.clone());
  const html = await response.text();
  const urls = new Set(CORE_ASSETS.slice(1));
  for (const match of html.matchAll(/(?:src|href)=["']([^"'#]+)["']/giu)) {
    const raw = match[1];
    if (raw === undefined) continue;
    const resolved = new URL(raw, self.registration.scope);
    if (resolved.origin === self.location.origin) urls.add(resolved.href);
  }
  const canonicalUrls = new Set([new URL("./", self.registration.scope).href]);
  await Promise.all(
    [...urls].map((url) => cacheAssetTree(cache, url, canonicalUrls)),
  );
  await Promise.all(
    (await cache.keys())
      .filter((request) => !canonicalUrls.has(request.url))
      .map((request) => cache.delete(request)),
  );
}

self.addEventListener("install", (event) => {
  event.waitUntil(
    caches
      .open(CACHE_NAME)
      .then(cacheDocumentAssets)
      .then(() => self.skipWaiting()),
  );
});

self.addEventListener("activate", (event) => {
  event.waitUntil(
    caches
      .keys()
      .then((keys) =>
        Promise.all(
          keys
            .filter((key) => key.startsWith(CACHE_PREFIX) && key !== CACHE_NAME)
            .map((key) => caches.delete(key)),
        ),
      )
      .then(() => self.clients.claim()),
  );
});

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

  if (request.mode === "navigate") {
    event.respondWith(
      fetch(request)
        .then(async (response) => {
          if (response.ok) {
            const cache = await caches.open(CACHE_NAME);
            await cache.put("./", response.clone());
          }
          return response;
        })
        .catch(async () => {
          const cached = await caches.match("./");
          return cached ?? Response.error();
        }),
    );
    return;
  }

  event.respondWith(
    caches.match(request).then(
      (cached) =>
        cached ??
        fetch(request).then(async (response) => {
          if (response.ok && response.type === "basic") {
            const cache = await caches.open(CACHE_NAME);
            await cache.put(request, response.clone());
          }
          return response;
        }),
    ),
  );
});