class NavigationUserBlock

final class NavigationUserBlock extends BlockBase {
    const NAVIGATION_LINKS_MENU = 'navigation-user-links';
    
    /**
     * {@inheritdoc}
     */
    public function build() : array {
        return [
            '#create_placeholder' => TRUE,
            '#lazy_builder' => [
                static::class . '::buildLinks',
                [
                    $this->configuration['label'],
                ],
            ],
            '#cache' => [
                'keys' => [
                    'navigation_user_block',
                ],
            ],
        ];
    }
    
    /**
     * Lazy builder callback.
     */
    public static function buildLinks(string $label) : array {
        $parameters = new MenuTreeParameters();
        $parameters->setMinDepth(0)
            ->setMaxDepth(2)
            ->onlyEnabledLinks();
        
        /** @var \Drupal\Core\Menu\MenuLinkTreeInterface $menu_tree */
        $menu_tree = \Drupal::service('navigation.menu_tree');
        $subtree = $menu_tree->load(static::NAVIGATION_LINKS_MENU, $parameters);
        // Load the current user so that they can be added as a cacheable dependency
        // of the final render array.
        $account = User::load(\Drupal::currentUser()->id());
        $menu_definition = [
            'menu_name' => static::NAVIGATION_LINKS_MENU,
            'route_name' => 'user.page',
            'route_parameters' => [],
            'title' => $account->getDisplayName(),
            'description' => '',
            'options' => [],
            'provider' => 'navigation',
            'enabled' => '1',
        ];
        // Create a parent link that serves as a wrapper.
        // If the menu is removed for any reason, this item shows a link to the
        // user profile page as a fallback.
        $link = MenuLinkDefault::create(\Drupal::getContainer(), [], 'navigation.user_links.user.wrapper', $menu_definition);
        $tree = new MenuLinkTreeElement($link, TRUE, 1, FALSE, $subtree);
        $manipulators = [
            [
                'callable' => 'menu.default_tree_manipulators:checkAccess',
            ],
            [
                'callable' => 'menu.default_tree_manipulators:generateIndexAndSort',
            ],
        ];
        $tree = $menu_tree->transform([
            $tree,
        ], $manipulators);
        $build = $menu_tree->build($tree);
        $build['#title'] = $label;
        $build['#cache']['contexts'][] = 'user';
        $cacheable_metadata = CacheableMetadata::createFromRenderArray($build);
        $cacheable_metadata->addCacheableDependency($account);
        $cacheable_metadata->applyTo($build);
        return $build;
    }

}