Add Android messaging integration (#450)

Author: joshliebe

inject/android.js

@@ -2,9 +2,18 @@
  * @module Android integration
  * @category Content Scope Scripts Integrations
  */
-import { load, init } from '../src/content-scope-features.js'
+import { load, init, update } from '../src/content-scope-features.js'
 import { processConfig, isGloballyDisabled } from './../src/utils'
 
+const allowedMessages = [
+    'getClickToLoadState',
+    'getYouTubeVideoDetails',
+    'openShareFeedbackPage',
+    'setYoutubePreviewsEnabled',
+    'unblockClickToLoadContent',
+    'updateYouTubeCTLAddedFlag'
+]
+
 function initCode () {
     // @ts-expect-error https://app.asana.com/0/1201614831475344/1203979574128023/f
     const processedConfig = processConfig($CONTENT_SCOPE$, $USER_UNPROTECTED_DOMAINS$, $USER_PREFERENCES$)
@@ -16,10 +25,53 @@ function initCode () {
         platform: processedConfig.platform
     })
 
+    const messageSecret = processedConfig.messageSecret
+    // Receives messages from the platform
+    const messageCallback = processedConfig.messageCallback
+    // Sends messages to the platform
+    const messageInterface = processedConfig.messageInterface
+
+    const wrappedUpdate = ((providedSecret, ...args) => {
+        if (providedSecret === messageSecret) {
+            update(...args)
+        }
+        // eslint-disable-next-line no-extra-bind
+    }).bind(this)
+
+    Object.defineProperty(window, messageCallback, {
+        value: wrappedUpdate
+    })
+
+    let sendMessageToAndroid
+    if (Object.prototype.hasOwnProperty.call(window, messageInterface)) {
+        // @ts-expect-error - Defined on the platform using WebView.addJavascriptInterface()
+        sendMessageToAndroid = window[messageInterface].process.bind(window[messageInterface])
+        delete window[messageInterface]
+    } else {
+        sendMessageToAndroid = () => { console.error('Android messaging interface not available') }
+    }
+
     init(processedConfig)
 
-    // Not supported:
-    // update(message)
+    window.addEventListener('sendMessageProxy' + messageSecret, event => {
+        event.stopImmediatePropagation()
+
+        if (!(event instanceof CustomEvent) || !event?.detail) {
+            return console.warn('no details in sendMessage proxy', event)
+        }
+
+        const messageType = event.detail?.messageType
+        if (!allowedMessages.includes(messageType)) {
+            return console.warn('Ignoring invalid sendMessage messageType', messageType)
+        }
+
+        const message = {
+            type: messageType,
+            options: event.detail?.options
+        }
+        const stringifiedArgs = JSON.stringify(message)
+        sendMessageToAndroid(stringifiedArgs, messageSecret)
+    })
 }
 
 initCode()