class TopBar

class TopBar extends RenderElementBase {
    
    /**
     * {@inheritdoc}
     */
    public function getInfo() : array {
        $class = static::class;
        return [
            '#pre_render' => [
                [
                    $class,
                    'preRenderTopBar',
                ],
            ],
            '#theme' => 'top_bar',
            '#attached' => [
                'library' => [
                    'navigation/internal.navigation',
                ],
            ],
        ];
    }
    
    /**
     * Builds the TopBar as a structured array ready for rendering.
     *
     * Since building the TopBar takes some time, it is done just prior to
     * rendering to ensure that it is built only if it will be displayed.
     *
     * @param array $element
     *   A renderable array.
     *
     * @return array
     *   A renderable array.
     *
     * @see navigation_page_top()
     */
    public static function preRenderTopBar($element) : array {
        $top_bar_item_manager = static::topBarItemManager();
        // Group the items by region.
        foreach (TopBarRegion::cases() as $region) {
            $items = $top_bar_item_manager->getRenderedTopBarItemsByRegion($region);
            $element = array_merge($element, [
                $region->value => $items,
            ]);
        }
        return $element;
    }
    
    /**
     * Wraps the top bar item manager.
     *
     * @return \Drupal\navigation\TopBarItemManager
     *   The top bar item manager.
     */
    protected static function topBarItemManager() : TopBarItemManagerInterface {
        return \Drupal::service(TopBarItemManagerInterface::class);
    }

}