[admob][android] Interstitial; Handle JS events from native

lib/modules/admob/Interstitial.js

@@ -1,29 +1,82 @@
 import { NativeModules } from 'react-native';
+import { statics } from './';
+import { nativeToJSError } from '../../utils';
 
 const FirebaseAdMob = NativeModules.RNFirebaseAdmob;
 
 export default class Interstitial {
 
-  constructor(admob: Object, eventListener: Object, adunit: string) {
+  constructor(admob: Object, adunit: string) {
     this.admob = admob;
     this.adUnit = adunit;
-
-    eventListener.addListener('interstitial_event', this._onInterstitialEvent.bind(this));
+    this.loaded = false;
+    this.admob.on(`interstitial_${adunit}`, this._onInterstitialEvent.bind(this));
   }
 
+  /**
+   * Handle a JS emit event
+   * @param event
+   * @private
+   */
   _onInterstitialEvent(event) {
+    const eventType = `interstitial:${this.adUnit}:${event.type}`;
 
+    let emitData = Object.assign({}, event);
+
+    switch (event.type) {
+      case 'onAdLoaded':
+        this.loaded = true;
+        break;
+      case 'onAdFailedToLoad':
+        emitData = nativeToJSError(event.payload.code, event.payload.message);
+        emitData.type = event.type;
+        break;
+      default:
+    }
+
+    this.admob.emit(eventType, emitData);
+    this.admob.emit(`interstitial:${this.adUnit}:*`, emitData);
   }
 
+  /**
+   * Load an ad with an instance of AdRequest
+   * @param request
+   * @returns {*}
+   */
   loadAd(request: AdRequest) {
     return FirebaseAdMob.interstitialLoadAd(this.adUnit, request);
   }
 
+  /**
+   * Return a local instance of isLoaded
+   * @returns {boolean}
+   */
   isLoaded() {
-    return true;
+    return this.loaded;
   }
 
+  /**
+   * Show the advert - will only show if loaded
+   * @returns {*}
+   */
   show() {
-    return FirebaseAdMob.interstitialShowAd(this.adUnit);
+    if (this.loaded) {
+      FirebaseAdMob.interstitialShowAd(this.adUnit);
+    }
+  }
+
+  /**
+   * Listen to an Ad event
+   * @param eventType
+   * @param listenerCb
+   * @returns {null}
+   */
+  on(eventType, listenerCb) {
+    if (!statics.EventTypes[eventType]) {
+      console.warn(`Invalid event type provided, must be one of: ${Object.keys(statics.EventTypes).join(', ')}`);
+      return null;
+    }
+
+    return this.admob.on(`interstitial:${this.adUnit}:${eventType}`, listenerCb);
   }
 }