start groupping notifications + notification click works now

service-worker.js

@@ -5,13 +5,68 @@ importScripts("/firebase-init.js")
 
 firebase.initializeApp(FIREBASE_INIT);
 
+// This method shows the notifications.
 firebase.messaging().setBackgroundMessageHandler(function(payload) {
-  let title = payload.notification.title || "New message";
+  let title = payload.data.title || "New message";
   let options = {
-    body: payload.notification.body || "",
-    icon: '/img/logo96.png'
+    body: payload.data.content || "",
+    icon: '/img/logo96.png',
+    badge: '/img/badge96.png',
+    tag: payload.data.topic || undefined,
+    data: {
+      topic: payload.data.topic
+    }
   };
-  console.log("background message", payload);
-
   return self.registration.showNotification(title, options);
 });
+
+
+// This code handles a click on notification: takes
+// the user to the browser tab with the chat or opens a new tab.
+self.addEventListener('notificationclick', function(event) {
+  console.log('On notification click: ', event.notification);
+
+  const notification = event.notification;
+  notification.close();
+
+  const urlHash = '#/' + notification.data.topic;
+
+  const promises = self.clients.matchAll({
+    type: 'window',
+    includeUncontrolled: true
+  }).then((windowClients) => {
+    let matchingClient = null;
+    let anyClient = null;
+    for (let i = 0; i < windowClients.length; i++) {
+      const url = new URL(windowClients[i].url);
+      console.log('found client with URL', url);
+      if (url.hash.includes(notification.data.topic)) {
+        matchingClient = windowClients[i];
+        break;
+      } else {
+        anyClient = windowClients[i];
+      }
+    }
+
+    // Found browser tab with the topic already open.
+    if (matchingClient) {
+      return matchingClient.focus();
+    }
+
+    // Found browser tab with Tinode on a different topic,
+    // navigate to the right topic.
+    if (anyClient) {
+      const url = new URL(anyClient.url);
+      url.hash = '#/' + notification.data.topic;
+      return anyClient.navigate(url).then(() => { return anyClient.focus(); });
+    }
+
+    // Did not find a Tinode browser tab. Open one.
+    const url = new URL(self.location.origin);
+    url.hash = '#/' + notification.data.topic;
+    return clients.openWindow(url);
+
+  });
+
+  event.waitUntil(promises);
+});