lib: Add PermittedMenuItemFilter ...

... for iterating over menu items the user is allowed to display

refs #8720

library/Icinga/Web/Menu/PermittedMenuItemFilter.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Icinga\Web\Menu;
+
+use RecursiveFilterIterator;
+use Icinga\Authentication\Manager;
+use Icinga\Web\Menu;
+
+class PermittedMenuItemFilter extends RecursiveFilterIterator
+{
+    /**
+     * Accept menu items that are permitted to the user
+     *
+     * @return bool Whether the user has the required permission granted to display the menu item
+     */
+    public function accept()
+    {
+        $item = $this->current();
+        /** @var Menu $item */
+        if (($permission = $item->getPermission()) !== null) {
+            $auth = Manager::getInstance();
+            if (! $auth->isAuthenticated()) {
+                // Don't accept menu item because user is not authenticated and the menu item requires a permission
+                return false;
+            }
+            if (! $auth->getUser()->can($permission)) {
+                return false;
+            }
+        }
+        // Accept menu item if it does not require a permission
+        return true;
+    }
+}