Merge pull request 'service worker stuff' (#40) from v.1.2.7 into main

Reviewed-on: #40

mih_ui/web/flutter_bootstrap.js

@@ -3,47 +3,48 @@
 
 const serviceWorkerVersion = '{{flutter_service_worker_version}}';
 
-if ('serviceWorker' in navigator) {
-  window.addEventListener('load', function () {
-    const serviceWorkerUrl = 'flutter_service_worker.js?v=' + serviceWorkerVersion;
-    
-    // Manually register here so we can attach custom update listeners
-    navigator.serviceWorker.register(serviceWorkerUrl).then((reg) => {
-      if (reg.waiting) {
-        showUpdatePrompt(reg);
-      }
+// 1. Let Flutter handle the service worker registration cleanly via its native loader
+_flutter.loader.load({
+  serviceWorkerSettings: {
+    serviceWorkerVersion: serviceWorkerVersion
+  }
+});
 
-      reg.addEventListener('updatefound', () => {
-        const newWorker = reg.installing;
+// 2. Safely monitor the registration generated by Flutter without double-registering
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.ready.then((reg) => {
+    // If an updated worker is already waiting in the background
+    if (reg.waiting) {
+      showUpdatePrompt(reg);
+    }
+
+    // Listen for new updates found while the user has the app open
+    reg.addEventListener('updatefound', () => {
+      const newWorker = reg.installing;
+      if (newWorker) {
         newWorker.addEventListener('statechange', () => {
           if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
             showUpdatePrompt(reg);
           }
         });
-      });
-    });
-
-    let refreshing = false;
-    navigator.serviceWorker.addEventListener('controllerchange', () => {
-      if (!refreshing) {
-        refreshing = true;
-        window.location.reload();
       }
     });
   });
+
+  // Guard against infinite reload loops when the controller shifts
+  let refreshing = false;
+  navigator.serviceWorker.addEventListener('controllerchange', () => {
+    if (!refreshing) {
+      refreshing = true;
+      window.location.reload();
+    }
+  });
 }
 
 function showUpdatePrompt(reg) {
   if (confirm('A new version of MIH is available. Refresh now to update?')) {
     reg.unregister().then(function () {
-      window.location.reload(); // Bypass cache and reload
+      window.location.reload(); // Unregister and reload to force clear the browser's cache
     });
   }
 }
-
-// Initialize Flutter and pass the service worker version
-_flutter.loader.load({
-  serviceWorkerSettings: {
-    serviceWorkerVersion: serviceWorkerVersion
-  }
-});