feat: make roast planner mobile PWA ready

public/sw.js

@@ -0,0 +1,58 @@
+const CACHE_NAME = "roast-planner-static-v1";
+const APP_SHELL = [
+  "/",
+  "/index.html",
+  "/app.css",
+  "/worksheet.css",
+  "/manifest.webmanifest",
+  "/icon.svg",
+  "/js/main.js",
+  "/js/prefill-ui.js",
+  "/js/alog-ui.js",
+  "/js/print.js",
+  "/shared/fields.js",
+  "/shared/ledger.js",
+  "/shared/time.js",
+  "/shared/reference-data.js",
+  "/shared/curve.js",
+];
+
+self.addEventListener("install", (event) => {
+  event.waitUntil(caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)));
+  self.skipWaiting();
+});
+
+self.addEventListener("activate", (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) => Promise.all(keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key)))),
+  );
+  self.clients.claim();
+});
+
+self.addEventListener("fetch", (event) => {
+  const { request } = event;
+  let url;
+  try {
+    url = new URL(request.url);
+  } catch {
+    return;
+  }
+  if (request.method !== "GET" || url.origin !== self.location.origin || url.pathname.startsWith("/api/")) return;
+
+  if (request.mode === "navigate") {
+    event.respondWith(fetch(request).catch(() => caches.match("/index.html")));
+    return;
+  }
+
+  event.respondWith(
+    caches.match(request).then((cached) => {
+      const update = fetch(request)
+        .then((response) => {
+          if (response.ok) caches.open(CACHE_NAME).then((cache) => cache.put(request, response.clone()));
+          return response;
+        })
+        .catch(() => cached);
+      return cached ?? update;
+    }),
+  );
+});