Offline page URL fix

static/serviceworker.js

@@ -1,26 +1,67 @@
 let version = 'v1::';
 let cacheName = 'website';
-let offlinePage = '/offline';
+let offlinePage = '/offline/';
 let offlineFundamentals = [offlinePage, '/'];
 let maxItems = 100;
 
-self.addEventListener('install', function (event) {
-	// Cache offline fundamentals
-	event.waitUntil(caches.open(version + cacheName).then(function (cache) {
-        return cache.addAll(offlineFundamentals);
-	}));
-});
 
-function trimCache(name, maxItems) {
-  caches.open(name).then(function(cache) {
-    cache.keys().then(function(keys) {
-      if (keys.length > maxItems) {
-        cache.delete(keys[0]).then(trimCache(name, maxItems));
-      }
-    });
+function addFundamentals() {
+  return caches.open(version + cacheName)
+  .then(cache => cache.addAll(offlineFundamentals))
+}
+
+// Cache the page(s) that initiate the service worker
+function cacheClients() {
+  return clients.matchAll({
+      includeUncontrolled: true
+  })
+  .then(allClients => allClients.map(client => client.url))
+  .then(pages => Promise.all([pages, caches.open(cacheName)]))
+  .then(([pages, cache]) => cache.addAll(pages))
+}
+
+// Remove caches whose name is no longer valid
+function clearInvalidatedCaches() {
+  return caches.keys()
+  .then( keys => {
+      return Promise.all(keys
+        .filter(key => !key.includes(version))
+        .map(key => caches.delete(key))
+      );
   });
 }
 
+function trimCache(name, maxItems) {
+  return caches.open(name)
+  .then(cache => Promise.all([cache, cache.keys()]))
+  // Make sure offlineFundamentals don't get deleted
+  .then(([cache, keys]) => [
+    cache,
+    keys.filter(key => !offlineFundamentals.includes(key)),
+    keys.length - maxItems
+  ])
+  .then(([cache, possibleDelete, numToDelete]) => {
+    // Trim cache until we are of the right size
+    deleteInProgress = []
+    for (let i = 0; i < numToDelete; i++) {
+      // Keep track of each delete
+      deleteInProgress.push(cache.delete(possibleDelete[i]));
+    }
+
+    // Return when everything is resolved
+    return Promise.all(deleteInProgress);
+  })
+}
+
+self.addEventListener('install', function (event) {
+	// Cache offline fundamentals
+	event.waitUntil(
+    addFundamentals()
+    .then(() => cacheClients())
+    .then(() => skipWaiting())
+  )
+});
+
 // Listens for trimCache command which occurs on page load
 self.addEventListener('message', event => {
   if (event.data.command == 'trimCache') {
@@ -28,65 +69,68 @@ self.addEventListener('message', event => {
   }
 });
 
-
 // If the version changes, invalidate the cache
 self.addEventListener('activate', function (event) {
   event.waitUntil(
-    caches.keys()
-      .then(function (keys) {
-        // Remove caches whose name is no longer valid
-        return Promise.all(keys
-          .filter(function (key) {
-            return key.indexOf(version) !== 0;
-          })
-          .map(function (key) {
-            return caches.delete(key);
-          })
-        );
-      })
+    clearInvalidatedCaches()
+    .then(() => clients.claim())
   );
 });
 
+if (registration.navigationPreload) {
+  addEventListener('activate', event => {
+      event.waitUntil(
+          registration.navigationPreload.enable()
+      );
+  });
+}
+
 // Listen for request events
 self.addEventListener('fetch', function (event) {
-	let request = event.request;
+	const request = event.request;
+
+  let isRequestType = function(name) {
+    return request.headers
+      .get('Accept')
+      .includes(name);
+  }
 
   // Always fetch non-GET requests from the network
   if (request.method !== 'GET') {
-    event.respondWith(
-      fetch(request)
-        .catch(function () {
-          return caches.match(offlinePage);
-        })
-    );
+    // Present offline page when failed to
+    // fetch a HTML page
+    if (isRequestType('text/html')) {
+      event.respondWith(
+        fetch(request)
+        .catch(() => caches.match(offlinePage))
+      );
+    }
     return;
   }
 
-  let isRequestType = function(name) { return request.headers.get('Accept').includes(name); }
-
 	// Network-first Approach
 	event.respondWith(
     // Attepmt to grab the latest copy from the network
-		fetch(request).then(function (response) {
+    Promise.resolve(event.preloadResponse)
+    .then(preloadResponse => preloadResponse || fetch(request))
+    .then(response => {
 			// If successful, create a copy of the response
       // and save it to the cache
       // Note: Ignore badges
-      if (request.url.includes("/badges")) {
+      if (!request.url.includes("/badges")) {
         let cacheCopy = response.clone();
-        event.waitUntil(caches.open(version + cacheName).then(function (cache) {
-          return cache.put(request, cacheCopy);
-        }));
+        event.waitUntil(
+          caches.open(version + cacheName)
+          .then(cache => cache.put(request, cacheCopy))
+        );
       }
 			return response;
-		}).catch(function (error) {
-      // Otherwise, check the cache.
-      return caches.match(request).then(function (response) {
-        // Show offline page if cache misses for HTML pages.
-        if (isRequestType('text/html')) {
-          return response || caches.match(offlinePage);
-        }
-        return response;
-      });
 		})
+    // Check the cache
+    .catch(error =>
+      caches.match(request)
+      // Show offline page for HTML pages if cache miss
+      .then(response => isRequestType('text/html')? response || caches.match(offlinePage) : response)
+		)
 	);
 });