class ToolbarController

class ToolbarController extends ControllerBase implements TrustedCallbackInterface {
    
    /**
     * Returns an AJAX response to render the toolbar subtrees.
     *
     * @return \Drupal\Core\Ajax\AjaxResponse
     */
    public function subtreesAjax() {
        list($subtrees, $cacheability) = toolbar_get_rendered_subtrees();
        $response = new AjaxResponse();
        $response->addCommand(new SetSubtreesCommand($subtrees));
        // The Expires HTTP header is the heart of the client-side HTTP caching. The
        // additional server-side page cache only takes effect when the client
        // accesses the callback URL again (e.g., after clearing the browser cache
        // or when force-reloading a Drupal page).
        $max_age = 365 * 24 * 60 * 60;
        $response->setPrivate();
        $response->setMaxAge($max_age);
        $expires = new \DateTime();
        $expires->setTimestamp(REQUEST_TIME + $max_age);
        $response->setExpires($expires);
        return $response;
    }
    
    /**
     * Checks access for the subtree controller.
     *
     * @param string $hash
     *   The hash of the toolbar subtrees.
     *
     * @return \Drupal\Core\Access\AccessResultInterface
     *   The access result.
     */
    public function checkSubTreeAccess($hash) {
        $expected_hash = _toolbar_get_subtrees_hash()[0];
        return AccessResult::allowedIf($this->currentUser()
            ->hasPermission('access toolbar') && hash_equals($expected_hash, $hash))
            ->cachePerPermissions();
    }
    
    /**
     * Renders the toolbar's administration tray.
     *
     * @param array $element
     *   A renderable array.
     *
     * @return array
     *   The updated renderable array.
     *
     * @see \Drupal\Core\Render\RendererInterface::render()
     */
    public static function preRenderAdministrationTray(array $element) {
        $menu_tree = \Drupal::service('toolbar.menu_tree');
        // Load the administrative menu. The first level is the "Administration"
        // link. In order to load the children of that link, start and end on the
        // second level.
        $parameters = new MenuTreeParameters();
        $parameters->setMinDepth(2)
            ->setMaxDepth(2)
            ->onlyEnabledLinks();
        // @todo Make the menu configurable in https://www.drupal.org/node/1869638.
        $tree = $menu_tree->load('admin', $parameters);
        $manipulators = [
            [
                'callable' => 'menu.default_tree_manipulators:checkAccess',
            ],
            [
                'callable' => 'menu.default_tree_manipulators:generateIndexAndSort',
            ],
            [
                'callable' => 'toolbar_menu_navigation_links',
            ],
        ];
        $tree = $menu_tree->transform($tree, $manipulators);
        $element['administration_menu'] = $menu_tree->build($tree);
        return $element;
    }
    
    /**
     * #pre_render callback for toolbar_get_rendered_subtrees().
     *
     * @internal
     */
    public static function preRenderGetRenderedSubtrees(array $data) {
        $menu_tree = \Drupal::service('toolbar.menu_tree');
        // Load the administration menu. The first level is the "Administration"
        // link. In order to load the children of that link and the subsequent two
        // levels, start at the second level and end at the fourth.
        $parameters = new MenuTreeParameters();
        $parameters->setMinDepth(2)
            ->setMaxDepth(4)
            ->onlyEnabledLinks();
        // @todo Make the menu configurable in https://www.drupal.org/node/1869638.
        $tree = $menu_tree->load('admin', $parameters);
        $manipulators = [
            [
                'callable' => 'menu.default_tree_manipulators:checkAccess',
            ],
            [
                'callable' => 'menu.default_tree_manipulators:generateIndexAndSort',
            ],
            [
                'callable' => 'toolbar_menu_navigation_links',
            ],
        ];
        $tree = $menu_tree->transform($tree, $manipulators);
        $subtrees = [];
        // Calculated the combined cacheability of all subtrees.
        $cacheability = new CacheableMetadata();
        foreach ($tree as $element) {
            
            /** @var \Drupal\Core\Menu\MenuLinkInterface $link */
            $link = $element->link;
            if ($element->subtree) {
                $subtree = $menu_tree->build($element->subtree);
                $output = \Drupal::service('renderer')->renderPlain($subtree);
                $cacheability = $cacheability->merge(CacheableMetadata::createFromRenderArray($subtree));
            }
            else {
                $output = '';
            }
            // Many routes have dots as route name, while some special ones like
            // <front> have <> characters in them.
            $url = $link->getUrlObject();
            $id = str_replace([
                '.',
                '<',
                '>',
            ], [
                '-',
                '',
                '',
            ], $url->isRouted() ? $url->getRouteName() : $url->getUri());
            $subtrees[$id] = $output;
        }
        // Store the subtrees, along with the cacheability metadata.
        $cacheability->applyTo($data);
        $data['#subtrees'] = $subtrees;
        return $data;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function trustedCallbacks() {
        return [
            'preRenderAdministrationTray',
            'preRenderGetRenderedSubtrees',
        ];
    }

}