Implement frontpage theme switch

app/javascript/packs/application.ts

@@ -12,6 +12,7 @@ import initQuestion from 'retrospring/features/question';
 import initModeration from 'retrospring/features/moderation';
 import initMemes from 'retrospring/features/memes';
 import initLocales from 'retrospring/features/locales';
+import initFront from 'retrospring/features/front';
 
 start();
 document.addEventListener('DOMContentLoaded', initAnswerbox);
@@ -24,4 +25,5 @@ document.addEventListener('DOMContentLoaded', initQuestion);
 document.addEventListener('DOMContentLoaded', initModeration);
 document.addEventListener('DOMContentLoaded', initMemes);
 document.addEventListener('turbolinks:load', initAnnouncements);
-document.addEventListener('turbolinks:load', initLocales);
+document.addEventListener('turbolinks:load', initLocales);
+document.addEventListener('turbolinks:load', initFront);

app/javascript/retrospring/features/front/index.ts

@@ -0,0 +1,8 @@
+import registerEvents from 'retrospring/utilities/registerEvents';
+import { themeButtonHandler } from './theme';
+
+export default (): void => {
+  registerEvents([
+    { type: 'click', target: document.querySelectorAll('.js-theme-button'), handler: themeButtonHandler }
+  ]);
+}

app/javascript/retrospring/features/front/theme.ts

@@ -0,0 +1,14 @@
+export function themeButtonHandler(event: Event): void {
+  const button = event.currentTarget as HTMLButtonElement;
+  event.preventDefault();
+  
+  const theme = button.dataset.theme;
+
+  document.body.setAttribute('class', 'not-logged-in');
+
+  if (theme === 'reset') return;
+
+  if (!document.body.classList.contains(theme)) {
+    document.body.classList.add(theme);
+  }
+}