Implement toggle in main controller.

src/base.scss

@@ -1,3 +1,10 @@
 * {
   font-family: verdana, sans-serif;
 }
+
+#toggle-button {
+  z-index: 2;
+  position: absolute;
+  top: 0;
+  left: 0;
+}

src/index.js

@@ -7,4 +7,47 @@ window.addEventListener('load', function () {
     } else {
         startClosedAnimation();
     }
+
+    doIfAuthorized(showToggleButton);
 });
+
+function showToggleButton() {
+    console.log('Should show toggle button.');
+    const template = `
+    <div id="toggle-button">
+        <form method="post">
+            <button name="toggle">Verander dit</button>
+        </form>
+    </div>`;
+
+    const div = document.createElement('div');
+    div.innerHTML = template.trim();
+    const content = div.firstChild;
+    div.removeChild(content);
+    document.body.appendChild(content);
+    console.log(content);
+}
+
+/**
+ * Run the specified callback if the user is authorized
+ *
+ * @param callback
+ */
+function doIfAuthorized(callback) {
+    const request = new XMLHttpRequest();
+    request.open('POST', window.location); // Post to self should work
+    request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
+    request.onreadystatechange = function () {
+        switch (request.readyState) {
+            case XMLHttpRequest.DONE:
+                if (request.status === 200) {
+                    callback();
+                }
+                break;
+            default:
+                // Wait for completion.
+                break;
+        }
+    };
+    request.send('auth_check=1');
+}