From https://once.com/writebook

app/javascript/controllers/edit_mode_controller.js

@@ -0,0 +1,32 @@
+import { Controller } from "@hotwired/stimulus"
+import { readCookie, setCookie } from "helpers/cookie_helpers"
+
+export default class extends Controller {
+  static values = { targetUrl: String }
+  static classes = [ "editing" ]
+  static outlets = [ "autosave" ]
+
+  connect() {
+    document.body.classList.toggle(this.editingClass, this.#savedCheckedState)
+  }
+
+  async change({ target: { checked } }) {
+    if (!checked) {
+      await this.#submitAutosaveControllers()
+    }
+
+    setCookie("edit_mode", checked)
+    Turbo.visit(this.targetUrlValue)
+  }
+
+
+  async #submitAutosaveControllers() {
+    for (const autosave of this.autosaveOutlets) {
+      await autosave.submit()
+    }
+  }
+
+  get #savedCheckedState() {
+    return readCookie("edit_mode") === "true"
+  }
+}