1 files changed, 45 insertions, 16 deletions

diff --git a/serviceWorker.js b/serviceWorker.js
index ba9ca7a..ce8ed7e 100644
--- a/serviceWorker.js
+++ b/serviceWorker.js
@@ -23,30 +23,59 @@ self.addEventListener('activate', e => {
     e.waitUntil(self.clients.claim())
 })
 
+const checkChange = (r1, r2) => {
+    const h1 = r1.headers
+    const h2 = r2.headers
+    if (h1.get('etag') && h2.get('etag')) return h1.get('etag') !== h2.get('etag')
+    if (h1.get('last-modified') && h2.get('last-modified')) return h1.get('last-modified') !== h2.get('last-modified')
+    return h1.get('content-length') !== h2.get('content-length')
+}
+
 self.addEventListener('fetch', e => {
     const url = new URL(e.request.url)
     const isTarget = ASSETS.includes(url.pathname) || url.pathname.startsWith('/fonts/')
 
     if (!isTarget) return
 
-    e.respondWith(
-        caches.open(CACHE_NAME).then(async cache => {
-            const cachedResponse = await cache.match(e.request)
+    e.respondWith((async () => {
+        const cache = await caches.open(CACHE_NAME)
+        const cachedResponse = await cache.match(e.request)
+
+        const networkFetch = fetch(e.request, { cache: 'no-cache' }).then(async networkResponse => {
+            if (!networkResponse.ok) return networkResponse
+
+            const freshCopy = networkResponse.clone()
+            let changed = false
 
-            if (cachedResponse) console.log(`cache ${url.pathname}`)
-            else console.log(`fetch ${url.pathname}`)
+            if (cachedResponse) {
+                changed = checkChange(cachedResponse, networkResponse)
+            } else {
+                console.log(`fetch ${url.pathname}`)
+            }
 
-            const networkFetch = fetch(e.request).then(networkResponse => {
-                if (networkResponse.ok) {
-                    console.log(`updating ${url.pathname}`)
-                    cache.put(e.request, networkResponse.clone())
-                }
-                return networkResponse
-            }).catch(err => {
-                console.error(`failed ${url.pathname}:`, err)
-            })
+            await cache.put(e.request, freshCopy)
 
-            return cachedResponse || networkFetch
+            if (changed) {
+                console.log(`content changed, signaling refresh: ${url.pathname}`)
+                const clients = await self.clients.matchAll()
+                clients.forEach(client => {
+                    client.postMessage({
+                        type: 'REFRESH',
+                        url: url.pathname
+                    })
+                })
+            }
+            return networkResponse
+        }).catch(err => {
+            console.error(`failed ${url.pathname}:`, err)
         })
-    )
+
+        if (cachedResponse) {
+            console.log(`cache ${url.pathname}`)
+            e.waitUntil(networkFetch)
+            return cachedResponse
+        }
+
+        return networkFetch
+    })())
 })
\ No newline at end of file