Enhanced offline (#249)

* Notification of updates & reloading

* Using version in service worker & allowing version to appear elsewhere

* Stupid file

* Ditching changelog for now. Using package json.

* Ugh.

src/components/App/index.tsx

@@ -12,6 +12,15 @@ import '../custom-els/LoadingSpinner';
 // This is imported for TypeScript only. It isn't used.
 import Compress from '../compress';
 
+const compressPromise = import(
+  /* webpackChunkName: "main-app" */
+  '../compress',
+);
+const offlinerPromise = import(
+  /* webpackChunkName: "offliner" */
+  '../../lib/offliner',
+);
+
 export interface SourceImage {
   file: File | Fileish;
   data: ImageData;
@@ -36,16 +45,13 @@ export default class App extends Component<Props, State> {
   constructor() {
     super();
 
-    import(
-      /* webpackChunkName: "main-app" */
-      '../compress',
-    ).then((module) => {
+    compressPromise.then((module) => {
       this.setState({ Compress: module.default });
     }).catch(() => {
       this.showSnack('Failed to load app');
     });
 
-    navigator.serviceWorker.register('../../sw');
+    offlinerPromise.then(({ offliner }) => offliner(this.showSnack));
 
     // In development, persist application state across hot reloads:
     if (process.env.NODE_ENV === 'development') {

src/components/compress/index.tsx

@@ -1,5 +1,4 @@
 import { h, Component } from 'preact';
-import { get, set } from 'idb-keyval';
 
 import { bind, Fileish } from '../../lib/initial-util';
 import { blobToImg, drawableToImageData, blobToText } from '../../lib/util';
@@ -156,12 +155,6 @@ async function processSvg(blob: Blob): Promise<HTMLImageElement> {
   return blobToImg(new Blob([newSource], { type: 'image/svg+xml' }));
 }
 
-async function getMostActiveServiceWorker() {
-  const reg = await navigator.serviceWorker.getRegistration();
-  if (!reg) return null;
-  return reg.active || reg.waiting || reg.installing;
-}
-
 // These are only used in the mobile view
 const resultTitles = ['Top', 'Bottom'];
 // These are only used in the desktop view
@@ -203,16 +196,7 @@ export default class Compress extends Component<Props, State> {
     this.widthQuery.addListener(this.onMobileWidthChange);
     this.updateFile(props.file);
 
-    // If this is the first time the user has interacted with the app, tell the service worker to
-    // cache all the codecs.
-    get<boolean | undefined>('user-interacted')
-      .then(async (userInteracted: boolean | undefined) => {
-        if (userInteracted) return;
-        set('user-interacted', true);
-        const serviceWorker = await getMostActiveServiceWorker();
-        if (!serviceWorker) return; // Service worker not installing yet.
-        serviceWorker.postMessage('cache-all');
-      });
+    import('../../lib/offliner').then(({ mainAppLoaded }) => mainAppLoaded());
   }
 
   @bind

src/lib/SnackBar/index.ts

@@ -8,12 +8,9 @@ export interface SnackOptions {
 function createSnack(message: string, options: SnackOptions): [Element, Promise<string>] {
   const {
     timeout = 0,
-    actions = [],
+    actions = ['dismiss'],
   } = options;
 
-  // Provide a default 'dismiss' action
-  if (!timeout && actions.length === 0) actions.push('dismiss');
-
   const el = document.createElement('div');
   el.className = style.snackbar;
   el.setAttribute('aria-live', 'assertive');

src/lib/offliner.ts

@@ -0,0 +1,91 @@
+import { get, set } from 'idb-keyval';
+
+// Just for TypeScript
+import SnackBarElement from './SnackBar';
+
+/** Tell the service worker to skip waiting */
+async function skipWaiting() {
+  const reg = await navigator.serviceWorker.getRegistration();
+  if (!reg || !reg.waiting) return;
+  reg.waiting.postMessage('skip-waiting');
+}
+
+/** Find the service worker that's 'active' or closest to 'active' */
+async function getMostActiveServiceWorker() {
+  const reg = await navigator.serviceWorker.getRegistration();
+  if (!reg) return null;
+  return reg.active || reg.waiting || reg.installing;
+}
+
+/** Wait for an installing worker */
+async function installingWorker(reg: ServiceWorkerRegistration): Promise<ServiceWorker> {
+  if (reg.installing) return reg.installing;
+  return new Promise<ServiceWorker>((resolve) => {
+    reg.addEventListener(
+      'updatefound',
+      () => resolve(reg.installing!),
+      { once: true },
+    );
+  });
+}
+
+/** Wait a service worker to become waiting */
+async function updateReady(reg: ServiceWorkerRegistration): Promise<void> {
+  if (reg.waiting) return;
+  const installing = await installingWorker(reg);
+  return new Promise<void>((resolve) => {
+    installing.addEventListener('statechange', () => {
+      if (installing.state === 'installed') resolve();
+    });
+  });
+}
+
+/** Set up the service worker and monitor changes */
+export async function offliner(showSnack: SnackBarElement['showSnackbar']) {
+  if (process.env.NODE_ENV === 'production') {
+    navigator.serviceWorker.register('../sw');
+  }
+
+  const hasController = !!navigator.serviceWorker.controller;
+
+  // Look for changes in the controller
+  navigator.serviceWorker.addEventListener('controllerchange', async () => {
+    // Is it the first install?
+    if (!hasController) {
+      showSnack('Ready to work offline', { timeout: 5000 });
+      return;
+    }
+
+    // Otherwise reload (the user will have agreed to this).
+    location.reload();
+  });
+
+  const reg = await navigator.serviceWorker.getRegistration();
+  // Service worker not registered yet.
+  if (!reg) return;
+  // Look for updates
+  await updateReady(reg);
+
+  // Ask the user if they want to update.
+  const result = await showSnack('Update available', {
+    actions: ['reload', 'dismiss'],
+  });
+
+  // Tell the waiting worker to activate, this will change the controller and cause a reload (see
+  // 'controllerchange')
+  if (result === 'reload') skipWaiting();
+}
+
+/**
+ * Tell the service worker the main app has loaded. If it's the first time the service worker has
+ * heard about this, cache the heavier assets like codecs.
+ */
+export async function mainAppLoaded() {
+  // If the user has already interacted, no need to tell the service worker anything.
+  const userInteracted = await get<boolean | undefined>('user-interacted');
+  if (userInteracted) return;
+  set('user-interacted', true);
+  const serviceWorker = await getMostActiveServiceWorker();
+  if (!serviceWorker) return; // Service worker not installing yet.
+  serviceWorker.postMessage('cache-all');
+}

src/missing-types.d.ts

@@ -32,3 +32,5 @@ declare module 'url-loader!*' {
   const value: string;
   export default value;
 }
+
+declare var VERSION: string;

src/sw/index.ts

@@ -8,8 +8,7 @@ declare var self: ServiceWorkerGlobalScope;
 // This is populated by webpack.
 declare var BUILD_ASSETS: string[];
 
-const version = '1.0.0';
-const versionedCache = 'static-' + version;
+const versionedCache = 'static-' + VERSION;
 const dynamicCache = 'dynamic';
 const expectedCaches = [versionedCache, dynamicCache];
 
@@ -28,6 +27,8 @@ self.addEventListener('install', (event) => {
 });
 
 self.addEventListener('activate', (event) => {
+  self.clients.claim();
+
   event.waitUntil(async function () {
     // Remove old caches.
     const promises = (await caches.keys()).map((cacheName) => {
@@ -57,7 +58,12 @@ self.addEventListener('fetch', (event) => {
 });
 
 self.addEventListener('message', (event) => {
-  if (event.data === 'cache-all') {
-    event.waitUntil(cacheAdditionalProcessors(versionedCache, BUILD_ASSETS));
+  switch (event.data) {
+    case 'cache-all':
+      event.waitUntil(cacheAdditionalProcessors(versionedCache, BUILD_ASSETS));
+      break;
+    case 'skip-waiting':
+      self.skipWaiting();
+      break;
   }
 });

src/sw/util.ts

@@ -60,6 +60,8 @@ export async function cacheBasics(cacheName: string, buildAssets: string[]) {
     'first-interaction.',
     // Main app JS & CSS:
     'main-app.',
+    // Service worker handler:
+    'offliner.',
     // Little icons for the demo images on the homescreen:
     'icon-demo-',
     // Site logo: