fix: cache pwa static assets offline

public/sw.js

@@ -1,4 +1,10 @@
-const CACHE_NAME = "wtr-shell-v5";
+const CACHE_VERSION = "v6";
+const CACHE_PREFIX = "wtr-";
+const SHELL_CACHE = `${CACHE_PREFIX}shell-${CACHE_VERSION}`;
+const RUNTIME_CACHE = `${CACHE_PREFIX}runtime-${CACHE_VERSION}`;
+const API_CACHE = `${CACHE_PREFIX}api-${CACHE_VERSION}`;
+const ACTIVE_CACHES = new Set([SHELL_CACHE, RUNTIME_CACHE, API_CACHE]);
+
 const SHELL = [
   "/",
   "/settings",
@@ -11,8 +17,75 @@ const SHELL = [
   "/icons/maskable-512.png",
 ];
 
+function isCacheableResponse(response) {
+  return response && response.ok && response.type !== "opaque";
+}
+
+async function putInCache(cacheName, request, response) {
+  if (!isCacheableResponse(response)) return;
+  const cache = await caches.open(cacheName);
+  await cache.put(request, response.clone());
+}
+
+function isWeatherApiRequest(url) {
+  return (
+    url.pathname.startsWith("/api/imgw/") ||
+    url.pathname === "/api/imgw-current" ||
+    url.pathname === "/api/current-weather" ||
+    url.pathname === "/api/forecast"
+  );
+}
+
+function isStaticAssetRequest(request, url) {
+  return (
+    url.origin === self.location.origin &&
+    (url.pathname.startsWith("/_next/static/") ||
+      url.pathname.startsWith("/icons/") ||
+      url.pathname === "/manifest.json" ||
+      ["font", "image", "script", "style", "worker"].includes(request.destination))
+  );
+}
+
+async function cacheFirst(request) {
+  const cached = await caches.match(request);
+  if (cached) return cached;
+  const response = await fetch(request);
+  await putInCache(RUNTIME_CACHE, request, response);
+  return response;
+}
+
+async function networkFirst(request, cacheName) {
+  try {
+    const response = await fetch(request);
+    await putInCache(cacheName, request, response);
+    return response;
+  } catch {
+    return (
+      (await caches.match(request)) ||
+      new Response(JSON.stringify({ error: "Offline." }), {
+        status: 503,
+        headers: { "Content-Type": "application/json" },
+      })
+    );
+  }
+}
+
+async function handleNavigation(request) {
+  try {
+    const response = await fetch(request);
+    await putInCache(SHELL_CACHE, request, response);
+    return response;
+  } catch {
+    return (await caches.match(request)) || (await caches.match("/")) || (await caches.match("/offline"));
+  }
+}
+
 self.addEventListener("install", (event) => {
-  event.waitUntil(caches.open(CACHE_NAME).then((cache) => cache.addAll(SHELL)));
+  event.waitUntil(
+    caches
+      .open(SHELL_CACHE)
+      .then((cache) => Promise.allSettled(SHELL.map((url) => cache.add(new Request(url, { cache: "reload" }))))),
+  );
   self.skipWaiting();
 });
 
@@ -20,44 +93,42 @@ self.addEventListener("activate", (event) => {
   event.waitUntil(
     caches
       .keys()
-      .then((keys) => Promise.all(keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key)))),
+      .then((keys) =>
+        Promise.all(
+          keys
+            .filter((key) => key.startsWith(CACHE_PREFIX) && !ACTIVE_CACHES.has(key))
+            .map((key) => caches.delete(key)),
+        ),
+      ),
   );
   self.clients.claim();
 });
 
 self.addEventListener("fetch", (event) => {
   if (event.request.method !== "GET") return;
+
   const url = new URL(event.request.url);
-  if (
-    url.pathname.startsWith("/api/imgw/") ||
-    url.pathname === "/api/imgw-current" ||
-    url.pathname === "/api/current-weather" ||
-    url.pathname === "/api/forecast"
-  ) {
-    event.respondWith(
-      fetch(event.request)
-        .then((response) => {
-          const copy = response.clone();
-          caches.open(CACHE_NAME).then((cache) => cache.put(event.request, copy));
-          return response;
-        })
-        .catch(() => caches.match(event.request)),
-    );
+  if (url.origin !== self.location.origin) return;
+
+  if (isWeatherApiRequest(url)) {
+    event.respondWith(networkFirst(event.request, API_CACHE));
     return;
   }
+
   if (event.request.mode === "navigate") {
-    event.respondWith(
-      fetch(event.request).catch(() =>
-        caches.match(event.request).then((response) => response || caches.match("/offline")),
-      ),
-    );
+    event.respondWith(handleNavigation(event.request));
+    return;
+  }
+
+  if (isStaticAssetRequest(event.request, url)) {
+    event.respondWith(cacheFirst(event.request));
   }
 });
 
 self.addEventListener("push", (event) => {
   const fallbackPayload = {
     title: "IMGW",
-    body: "Nowe ostrzeżenie meteorologiczne.",
+    body: "Nowe ostrze\u017cenie meteorologiczne.",
     url: "/warnings",
   };
   let payload = fallbackPayload;