WIP

books/sw.js

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+// Generated by render_books.py -- do not edit by hand.
+//
+// STRATEGY decides what a same-origin GET does:
+//
+//   network-first  ask the network, fall back to the cache when it fails.
+//                  Offline, fetch rejects immediately, so the fallback is
+//                  effectively instant -- the only cost is one round trip
+//                  while online, and you never see a stale page.
+//   cache-first    answer from the cache the moment there is a hit. Fastest
+//                  possible load, but a rebuild needs two reloads to appear.
+//
+// Either way every response that arrives is written back to the cache, so the
+// offline copy stays current, and a new build changes VERSION, dropping the
+// caches belonging to older builds.
+const STRATEGY = 'network-first';
+const NETWORK_TIMEOUT_MS = 3000;
+const VERSION = 'c5d29c3cdf15';
+const CACHE = 'bible-' + VERSION;
+const ASSETS = [
+  "./",
+  "./1CH.html",
+  "./1CO.html",
+  "./1ES.html",
+  "./1JN.html",
+  "./1KI.html",
+  "./1MA.html",
+  "./1PE.html",
+  "./1SA.html",
+  "./1TH.html",
+  "./1TI.html",
+  "./2CH.html",
+  "./2CO.html",
+  "./2ES.html",
+  "./2JN.html",
+  "./2KI.html",
+  "./2MA.html",
+  "./2PE.html",
+  "./2SA.html",
+  "./2TH.html",
+  "./2TI.html",
+  "./3JN.html",
+  "./3MA.html",
+  "./4MA.html",
+  "./ACT.html",
+  "./AMO.html",
+  "./BAR.html",
+  "./COL.html",
+  "./DAG.html",
+  "./DAN.html",
+  "./DEU.html",
+  "./ECC.html",
+  "./EPH.html",
+  "./ESG.html",
+  "./EST.html",
+  "./EXO.html",
+  "./EZK.html",
+  "./EZR.html",
+  "./FRT.html",
+  "./GAL.html",
+  "./GEN.html",
+  "./GLO.html",
+  "./HAB.html",
+  "./HAG.html",
+  "./HEB.html",
+  "./HOS.html",
+  "./ISA.html",
+  "./JAS.html",
+  "./JDG.html",
+  "./JDT.html",
+  "./JER.html",
+  "./JHN.html",
+  "./JOB.html",
+  "./JOL.html",
+  "./JON.html",
+  "./JOS.html",
+  "./JUD.html",
+  "./LAM.html",
+  "./LEV.html",
+  "./LUK.html",
+  "./MAL.html",
+  "./MAN.html",
+  "./MAT.html",
+  "./MIC.html",
+  "./MRK.html",
+  "./NAM.html",
+  "./NEH.html",
+  "./NUM.html",
+  "./OBA.html",
+  "./PHM.html",
+  "./PHP.html",
+  "./PRO.html",
+  "./PS2.html",
+  "./PSA.html",
+  "./REV.html",
+  "./ROM.html",
+  "./RUT.html",
+  "./SIR.html",
+  "./SNG.html",
+  "./TIT.html",
+  "./TOB.html",
+  "./WIS.html",
+  "./ZEC.html",
+  "./ZEP.html",
+  "./app.js",
+  "./bible.css",
+  "./icons/apple-touch-icon.png",
+  "./icons/icon-192.png",
+  "./icons/icon-512.png",
+  "./index.html",
+  "./manifest.webmanifest"
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil((async () => {
+    const cache = await caches.open(CACHE);
+    // Added one at a time rather than addAll(): addAll is atomic, so a single
+    // failed asset would leave the app with no offline copy at all.
+    let failed = 0;
+    await Promise.all(ASSETS.map((url) =>
+      cache.add(new Request(url, { cache: 'reload' })).catch(() => { failed++; })));
+    if (failed) console.warn('precache: ' + failed + ' of ' + ASSETS.length + ' failed');
+    await self.skipWaiting();
+  })());
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil((async () => {
+    const keys = await caches.keys();
+    await Promise.all(keys
+      .filter((k) => k.startsWith('bible-') && k !== CACHE)
+      .map((k) => caches.delete(k)));
+    await self.clients.claim();
+  })());
+});
+
+self.addEventListener('fetch', (event) => {
+  const req = event.request;
+  if (req.method !== 'GET') return;
+  if (new URL(req.url).origin !== location.origin) return;
+  event.respondWith(respond(event));
+});
+
+// Aborted rather than raced, so a hung request is actually torn down instead
+// of leaking while the cache answers.
+async function fromNetwork(req) {
+  const controller = new AbortController();
+  const timer = setTimeout(() => controller.abort(), NETWORK_TIMEOUT_MS);
+  try {
+    return await fetch(req, { signal: controller.signal });
+  } finally {
+    clearTimeout(timer);
+  }
+}
+
+function cached(req) {
+  return caches.match(req, { ignoreSearch: true });
+}
+
+async function respond(event) {
+  const req = event.request;
+
+  if (STRATEGY === 'cache-first') {
+    const hit = await cached(req);
+    if (hit) return hit;
+  }
+
+  try {
+    const res = await fromNetwork(req);
+    if (res && res.ok && res.type === 'basic') {
+      const copy = res.clone();
+      // Not awaited: the response should not wait on the cache write.
+      event.waitUntil(caches.open(CACHE).then((c) => c.put(req, copy)));
+    }
+    return res;
+  } catch (err) {
+    const hit = await cached(req);
+    if (hit) return hit;
+    // Offline and never cached. Navigations get the index rather than the
+    // browser's error page; anything else genuinely fails.
+    if (req.mode === 'navigate') {
+      const index = await cached('./index.html');
+      if (index) return index;
+    }
+    throw err;
+  }
+}