Add back service worker

3 files changed, 212 insertions, 0 deletions

diff --git a/modern/src/index.js b/modern/src/index.js
index 4a5a9e4b..dbbf2da4 100644
--- a/modern/src/index.js
+++ b/modern/src/index.js
@@ -12,6 +12,7 @@ import SocketController from './SocketController';
 import theme from './common/theme';
 import Navigation from './Navigation';
 import preloadImages from './map/core/preloadImages';
+import * as serviceWorkerRegistration from './serviceWorkerRegistration';
 
 preloadImages();
 
@@ -36,3 +37,5 @@ ReactDOM.render(
     </Provider>
   ), document.getElementById('root'),
 );
+
+serviceWorkerRegistration.register();
diff --git a/modern/src/service-worker.js b/modern/src/service-worker.js
new file mode 100644
index 00000000..0f1e0ce0
--- /dev/null
+++ b/modern/src/service-worker.js
@@ -0,0 +1,72 @@
+/* eslint-disable no-restricted-globals */
+
+// This service worker can be customized!
+// See https://developers.google.com/web/tools/workbox/modules
+// for the list of available Workbox modules, or add any other
+// code you'd like.
+// You can also remove this file if you'd prefer not to use a
+// service worker, and the Workbox build step will be skipped.
+
+import { clientsClaim } from 'workbox-core';
+import { ExpirationPlugin } from 'workbox-expiration';
+import { precacheAndRoute, createHandlerBoundToURL } from 'workbox-precaching';
+import { registerRoute } from 'workbox-routing';
+import { StaleWhileRevalidate } from 'workbox-strategies';
+
+clientsClaim();
+
+// Precache all of the assets generated by your build process.
+// Their URLs are injected into the manifest variable below.
+// This variable must be present somewhere in your service worker file,
+// even if you decide not to use precaching. See https://cra.link/PWA
+precacheAndRoute(self.__WB_MANIFEST);
+
+// Set up App Shell-style routing, so that all navigation requests
+// are fulfilled with your index.html shell. Learn more at
+// https://developers.google.com/web/fundamentals/architecture/app-shell
+const fileExtensionRegexp = new RegExp('/[^/?]+\\.[^/]+$');
+registerRoute(
+  // Return false to exempt requests from being fulfilled by index.html.
+  ({ request, url }) => {
+    // If this isn't a navigation, skip.
+    if (request.mode !== 'navigate') {
+      return false;
+    } // If this is a URL that starts with /_, skip.
+
+    if (url.pathname.startsWith('/_')) {
+      return false;
+    } // If this looks like a URL for a resource, because it contains // a file extension, skip.
+
+    if (url.pathname.match(fileExtensionRegexp)) {
+      return false;
+    } // Return true to signal that we want to use the handler.
+
+    return true;
+  },
+  createHandlerBoundToURL(process.env.PUBLIC_URL + '/index.html')
+);
+
+// An example runtime caching route for requests that aren't handled by the
+// precache, in this case same-origin .png requests like those from in public/
+registerRoute(
+  // Add in any other file extensions or routing criteria as needed.
+  ({ url }) => url.origin === self.location.origin && url.pathname.endsWith('.png'), // Customize this strategy as needed, e.g., by changing to CacheFirst.
+  new StaleWhileRevalidate({
+    cacheName: 'images',
+    plugins: [
+      // Ensure that once this runtime cache reaches a maximum size the
+      // least-recently used images are removed.
+      new ExpirationPlugin({ maxEntries: 50 }),
+    ],
+  })
+);
+
+// This allows the web app to trigger skipWaiting via
+// registration.waiting.postMessage({type: 'SKIP_WAITING'})
+self.addEventListener('message', (event) => {
+  if (event.data && event.data.type === 'SKIP_WAITING') {
+    self.skipWaiting();
+  }
+});
+
+// Any other custom service worker logic can go here.
diff --git a/modern/src/serviceWorkerRegistration.js b/modern/src/serviceWorkerRegistration.js
new file mode 100644
index 00000000..2262ecdb
--- /dev/null
+++ b/modern/src/serviceWorkerRegistration.js
@@ -0,0 +1,137 @@
+// This optional code is used to register a service worker.
+// register() is not called by default.
+
+// This lets the app load faster on subsequent visits in production, and gives
+// it offline capabilities. However, it also means that developers (and users)
+// will only see deployed updates on subsequent visits to a page, after all the
+// existing tabs open on the page have been closed, since previously cached
+// resources are updated in the background.
+
+// To learn more about the benefits of this model and instructions on how to
+// opt-in, read https://cra.link/PWA
+
+const isLocalhost = Boolean(
+  window.location.hostname === 'localhost' ||
+    // [::1] is the IPv6 localhost address.
+    window.location.hostname === '[::1]' ||
+    // 127.0.0.0/8 are considered localhost for IPv4.
+    window.location.hostname.match(/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/)
+);
+
+export function register(config) {
+  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
+    // The URL constructor is available in all browsers that support SW.
+    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
+    if (publicUrl.origin !== window.location.origin) {
+      // Our service worker won't work if PUBLIC_URL is on a different origin
+      // from what our page is served on. This might happen if a CDN is used to
+      // serve assets; see https://github.com/facebook/create-react-app/issues/2374
+      return;
+    }
+
+    window.addEventListener('load', () => {
+      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
+
+      if (isLocalhost) {
+        // This is running on localhost. Let's check if a service worker still exists or not.
+        checkValidServiceWorker(swUrl, config);
+
+        // Add some additional logging to localhost, pointing developers to the
+        // service worker/PWA documentation.
+        navigator.serviceWorker.ready.then(() => {
+          console.log(
+            'This web app is being served cache-first by a service ' +
+              'worker. To learn more, visit https://cra.link/PWA'
+          );
+        });
+      } else {
+        // Is not localhost. Just register service worker
+        registerValidSW(swUrl, config);
+      }
+    });
+  }
+}
+
+function registerValidSW(swUrl, config) {
+  navigator.serviceWorker
+    .register(swUrl)
+    .then((registration) => {
+      registration.onupdatefound = () => {
+        const installingWorker = registration.installing;
+        if (installingWorker == null) {
+          return;
+        }
+        installingWorker.onstatechange = () => {
+          if (installingWorker.state === 'installed') {
+            if (navigator.serviceWorker.controller) {
+              // At this point, the updated precached content has been fetched,
+              // but the previous service worker will still serve the older
+              // content until all client tabs are closed.
+              console.log(
+                'New content is available and will be used when all ' +
+                  'tabs for this page are closed. See https://cra.link/PWA.'
+              );
+
+              // Execute callback
+              if (config && config.onUpdate) {
+                config.onUpdate(registration);
+              }
+            } else {
+              // At this point, everything has been precached.
+              // It's the perfect time to display a
+              // "Content is cached for offline use." message.
+              console.log('Content is cached for offline use.');
+
+              // Execute callback
+              if (config && config.onSuccess) {
+                config.onSuccess(registration);
+              }
+            }
+          }
+        };
+      };
+    })
+    .catch((error) => {
+      console.error('Error during service worker registration:', error);
+    });
+}
+
+function checkValidServiceWorker(swUrl, config) {
+  // Check if the service worker can be found. If it can't reload the page.
+  fetch(swUrl, {
+    headers: { 'Service-Worker': 'script' },
+  })
+    .then((response) => {
+      // Ensure service worker exists, and that we really are getting a JS file.
+      const contentType = response.headers.get('content-type');
+      if (
+        response.status === 404 ||
+        (contentType != null && contentType.indexOf('javascript') === -1)
+      ) {
+        // No service worker found. Probably a different app. Reload the page.
+        navigator.serviceWorker.ready.then((registration) => {
+          registration.unregister().then(() => {
+            window.location.reload();
+          });
+        });
+      } else {
+        // Service worker found. Proceed as normal.
+        registerValidSW(swUrl, config);
+      }
+    })
+    .catch(() => {
+      console.log('No internet connection found. App is running in offline mode.');
+    });
+}
+
+export function unregister() {
+  if ('serviceWorker' in navigator) {
+    navigator.serviceWorker.ready
+      .then((registration) => {
+        registration.unregister();
+      })
+      .catch((error) => {
+        console.error(error.message);
+      });
+  }
+}