WIP: Add EventBus abstraction

src/plugin/scripts/index.js

@@ -1,5 +1,8 @@
+import { EventBus } from '../../shared/event-bus';
+
 const startImportButton = document.getElementById( 'try-wordpress-import' );
 if ( startImportButton ) {
+	const eventBus = new EventBus( { targetWindow: window.parent } );
 	window.addEventListener( 'message', handleStartImportResponse );
 	window.addEventListener( 'message', handleMessage );
 	startImportButton.addEventListener( 'click', startImport );

src/shared/event-bus.js

@@ -0,0 +1,24 @@
+export class EventBus {
+	#window;
+	#targetWindow;
+	#listeners;
+
+	constructor( options = {} ) {
+		if ( ! options.targetWindow ) {
+			throw Error( 'targetWindow option must be set' );
+		}
+		this.#targetWindow = options.window;
+		this.#window = options.window || window;
+		this.#listeners = [];
+		this.#window.addEventListener( 'message', this.handleEvent );
+	}
+
+	addListener( type, callback ) {
+		// TODO.
+	}
+
+	handleEvent( event ) {
+		// TODO.
+		console.log( event.target );
+	}
+}