fix(entry): added battery level check

docs/src/guide/options.md

@@ -39,14 +39,16 @@ These options can be used to define the initial checks to display the [`BoosterL
 ````js
 {
   performance: true,
-  browserSupport: true
+  browserSupport: true,
+  battery: true
 }
 ````
 
  | Key              | Type      | Required | Description                                                                                                                                                                                        | Default |
  | ---------------- | --------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
  | `performance`    | `Boolean` | yes      | Checking whether the [minimum characteristic values](/guide/options#performancemetrics) have been reached. If the test is negative, the [`BoosterLayer`](/components/booster-layer) will be displayed. | `true`  |
  | `browserSupport` | `Boolean` | yes      | Check if the current browser on client side is supported. If the test is negative, the [`BoosterLayer`](/components/booster-layer) will be displayed.                                            | `true`  |
+ | `battery`        | `Boolean` | yes      | Check if the current user save power in browser. If the test is negative, the [`BoosterLayer`](/components/booster-layer) will be displayed.                                                           | `true`  |
 
 ::: info
 For the browser support detection, the default [Browserslist](https://github.com/browserslist/browserslist) of the NuxtJS configuration is used.

playground/components/InfoLayer.vue

@@ -9,6 +9,7 @@
         <li id="nuxt-booster-message-unsupported-browser">outdated browser</li>
         <li id="nuxt-booster-message-reduced-bandwidth">reduced-bandwidth</li>
         <li id="nuxt-booster-message-weak-hardware">weak hardware</li>
+        <li id="nuxt-booster-message-low-battery">low battery</li>
       </ul>
       <div class="info-layer-buttons">
         <base-button

src/module.js

@@ -24,6 +24,7 @@ import { optimizePreloads } from './utils/preload';
 import { getSupportedBrowserDetector } from './utils/browser';
 import { registerAppEntry as registerAppEntryWebpack } from './hookFunctions/webpack';
 import { registerAppEntry as registerAppEntryVite } from './hookFunctions/vite';
+import { getTemplate as getBlobFileTemplate } from './utils/blob';
 
 import pluginTemplate from './tmpl/plugin.tmpl';
 import entryTemplate from './tmpl/entry.tmpl';
@@ -147,13 +148,24 @@ async function addBuildTemplates(nuxt, options) {
         entry: join(nuxt.options.appDir, 'entry'),
         runOptions: options.runOptions,
         ssr: nuxt.options.ssr,
-        ignorePerformance: !options.detection.performance,
+        ignore: {
+          battery: !options.detection.battery,
+          performance: !options.detection.performance
+        },
         performanceMetrics: JSON.stringify(options.performanceMetrics || {}),
         supportedBrowserDetector
       });
     },
     write: true
   });
+
+  const files = [['video', resolver.resolve('media/video.mp4')]];
+  const mediaContent = await getBlobFileTemplate(files);
+  addTemplate({
+    getContents: () => mediaContent,
+    filename: MODULE_NAME + '/blobs.mjs',
+    write: true
+  });
 }
 
 async function addModules(nuxt, moduleOptions) {

src/runtime/components/BoosterLayer.vue

@@ -1,6 +1,6 @@
 <template>
   <div v-if="isServer" id="nuxt-booster-layer">
     <input id="nuxt-booster-layer-close" name="close" type="checkbox" />
     <div id="nuxt-booster-layer-content">
       <slot>
         <div>
@@ -17,6 +17,8 @@
             <li id="nuxt-booster-message-reduced-bandwidth">slow connection</li>
             <!-- Displayed when user hardware are not sufficient.  -->
             <li id="nuxt-booster-message-weak-hardware">weak hardware</li>
+            <!-- Displayed when the user batteries are not sufficient.  -->
+            <li id="nuxt-booster-message-low-battery">low battery</li>
           </ul>
 
           <!-- Button to hide the layer with no javascript -->
@@ -96,5 +98,9 @@
   display: none;
 }
 
+#nuxt-speedkit-message-low-battery {
+  display: none;
+}
+
 /*! purgecss end ignore */
 </style>

src/runtime/utils/entry.js

@@ -55,3 +55,44 @@ export function initReducedView() {
     tmp.remove();
   });
 }
+
+export async function hasBatteryPerformanceIssue(videoBlob) {
+  try {
+    if (await isBatteryLow()) {
+      throw new Error('Battery is low.');
+    }
+  } catch (error) {
+    if (error.message === 'Battery is low.') {
+      throw error;
+    }
+    await canVideoPlay(videoBlob);
+  }
+}
+
+/**
+ * Checks if battery still has enough energy.
+ * This check is for Chrome and all other browsers that support this setting.
+ *
+ * Condition is: The device is not charging and Battery is below <= 20%.
+ * @see https://blog.google/products/chrome/new-chrome-features-to-save-battery-and-make-browsing-smoother/
+ * @see https://developer.chrome.com/blog/memory-and-energy-saver-mode/
+ **/
+async function isBatteryLow() {
+  const MIN_BATTERY_LEVEL = 0.2;
+  const battery = await window.navigator.getBattery();
+  return !battery.charging && battery.level <= MIN_BATTERY_LEVEL;
+}
+
+/**
+ * Checking whether a video can be played.
+ * This check is for IOS and checks if the power saving mode is enabled.
+ *
+ * In this case no video will be played automatically and play throws an error.
+ */
+export function canVideoPlay(blob) {
+  const video = document.createElement('video');
+  video.muted = true;
+  video.playsinline = true;
+  video.src = URL.createObjectURL(blob);
+  return video.play();
+}

src/tmpl/entry.tmpl.js

@@ -2,9 +2,10 @@ export default options => {
   let code = `import { ${
     options.performanceCheck ? `run, ` : ``
   }hasSufficientPerformance, setup } from '#booster/utils/performance';
-import { triggerRunCallback, observeBoosterButton, setupBoosterLayer, updateBoosterLayerMessage, initReducedView } from '#booster/utils/entry';
+import { triggerRunCallback, observeBoosterButton, setupBoosterLayer, updateBoosterLayerMessage, initReducedView, hasBatteryPerformanceIssue } from '#booster/utils/entry';
 import Deferred from '#booster/classes/Deferred';
 import { isSupportedBrowser } from '#booster/utils/browser';
+import {video as videoBlob} from './blobs.mjs';
 
 `;
 
@@ -46,15 +47,38 @@ function client () {
   const forceInit = ('__NUXT_BOOSTER_FORCE_INIT__' in window && window.__NUXT_BOOSTER_FORCE_INIT__);
 
   async function initApp(force) {
+
     if (initialized) {
       deferred.resolve();
     }
 
     document.documentElement.classList.remove('nuxt-booster-reduced-view');
 
+    `;
+
+  if (!options.ignore.battery) {
+    code += `
     try {
+      if (!force) {
+        await hasBatteryPerformanceIssue(videoBlob)
+      }
+    } catch (error) {
+
+      console.warn(error)
+
+      triggerRunCallback(false);
+
+      if (!!layerEl) {
+        // User must interact via the layer.
+        updateSpeedkitLayerMessage(layerEl, 'nuxt-speedkit-message-low-battery');
+        return null;
+      }
+    }
+    `;
+  }
 
-      `;
+  code += `
+    try {`;
 
   if (options.performanceCheck) {
     code += `
@@ -75,6 +99,9 @@ if (!force) {
       deferred.resolve();
 
     } catch (error) {
+
+      console.warn(error)
+
       triggerRunCallback(false);
 
       if (!!layerEl) {

src/utils/blob.js

@@ -0,0 +1,22 @@
+import { promises as fsPromises } from 'fs';
+import mime from 'mime-types';
+
+async function getFileInfo(name, file) {
+  return {
+    name,
+    // eslint-disable-next-line security/detect-non-literal-fs-filename
+    file: await fsPromises.readFile(file),
+    mimeType: mime.lookup(file)
+  };
+}
+
+export async function getTemplate(files) {
+  return (await Promise.all(files.map(file => getFileInfo(...file))))
+    .map(
+      ({ name, file, mimeType }) =>
+        `export const ${name} = new Blob([new Uint8Array([${[...file].join(
+          ', '
+        )}])], {type: '${mimeType}'});`
+    )
+    .join('\n');
+}

src/utils/options.js

@@ -13,7 +13,8 @@ export function getDefaultOptions() {
 
     detection: {
       performance: true,
-      browserSupport: true
+      browserSupport: true,
+      battery: true
     },
 
     performanceMetrics: {