Basic feature implemented, very basic poc

app/javascript/controllers/theme_switcher_controller.js

@@ -0,0 +1,28 @@
+import { Controller } from "@hotwired/stimulus"
+import Cookie from "../lib/cookies"
+
+// Connects to data-controller="theme-switcher"
+export default class extends Controller {
+  COOKIE_NAME = "modeTheme"
+
+  connect() {
+    console.log("connect switcher")
+  }
+
+  switch() {
+    const cookieValue = Cookie.get(this.COOKIE_NAME);
+    const newThemeValue = cookieValue == "dark" ? "light" : "dark";
+    
+    Cookie.set("modeTheme", newThemeValue);
+    window.document.getElementsByTagName("html")[0].setAttribute("data-bs-theme", newThemeValue);
+
+    const icon = this.element.getElementsByTagName("i")[0];
+    if(newThemeValue == "dark") {
+      icon.classList.remove("bi-sun-fill")
+      icon.classList.add("bi-moon-stars-fill")
+    } else {
+      icon.classList.add("bi-sun-fill")
+      icon.classList.remove("bi-moon-stars-fill")
+    }
+  }
+}