start of the refactoring to widget system

src/public/javascripts/widgets/basic_widget.js

@@ -0,0 +1,41 @@
+class BasicWidget {
+    /**
+     * @param {AppContext} appContext
+     */
+    constructor(appContext) {
+        this.appContext = appContext;
+        this.widgetId = `widget-${this.constructor.name}`;
+    }
+
+    render() {
+        const $widget = $('<div>').attr('id', this.widgetId);
+
+        // actual rendering is async
+        this.doRender($widget);
+
+        return $widget;
+    }
+
+    /**
+     * for overriding
+     *
+     * @param {JQuery} $widget
+     */
+    async doRender($widget) {}
+
+    eventReceived(name, data) {
+        const fun = this[name + 'Listener'];
+
+        if (typeof fun === 'function') {
+            fun.call(this, data);
+        }
+    }
+
+    trigger(name, data) {
+        this.appContext.trigger(name, data);
+    }
+
+    cleanup() {}
+}
+
+export default BasicWidget;