class BookController

class BookController extends ControllerBase {
    
    /**
     * The book manager.
     *
     * @var \Drupal\book\BookManagerInterface
     */
    protected $bookManager;
    
    /**
     * The book export service.
     *
     * @var \Drupal\book\BookExport
     */
    protected $bookExport;
    
    /**
     * The renderer.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * Constructs a BookController object.
     *
     * @param \Drupal\book\BookManagerInterface $bookManager
     *   The book manager.
     * @param \Drupal\book\BookExport $bookExport
     *   The book export service.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer.
     */
    public function __construct(BookManagerInterface $bookManager, BookExport $bookExport, RendererInterface $renderer) {
        $this->bookManager = $bookManager;
        $this->bookExport = $bookExport;
        $this->renderer = $renderer;
    }
    
    /**
     * Returns an administrative overview of all books.
     *
     * @return array
     *   A render array representing the administrative page content.
     */
    public function adminOverview() {
        $rows = [];
        $headers = [
            t('Book'),
            t('Operations'),
        ];
        // Add any recognized books to the table list.
        foreach ($this->bookManager
            ->getAllBooks() as $book) {
            
            /** @var \Drupal\Core\Url $url */
            $url = $book['url'];
            if (isset($book['options'])) {
                $url->setOptions($book['options']);
            }
            $row = [
                Link::fromTextAndUrl($book['title'], $url),
            ];
            $links = [];
            $links['edit'] = [
                'title' => t('Edit order and titles'),
                'url' => Url::fromRoute('book.admin_edit', [
                    'node' => $book['nid'],
                ]),
            ];
            $row[] = [
                'data' => [
                    '#type' => 'operations',
                    '#links' => $links,
                ],
            ];
            $rows[] = $row;
        }
        return [
            '#type' => 'table',
            '#header' => $headers,
            '#rows' => $rows,
            '#empty' => t('No books available.'),
        ];
    }
    
    /**
     * Prints a listing of all books.
     *
     * @return array
     *   A render array representing the listing of all books content.
     */
    public function bookRender() {
        $book_list = [];
        foreach ($this->bookManager
            ->getAllBooks() as $book) {
            $book_list[] = Link::fromTextAndUrl($book['title'], $book['url']);
        }
        return [
            '#theme' => 'item_list',
            '#items' => $book_list,
            '#cache' => [
                'tags' => $this->entityTypeManager()
                    ->getDefinition('node')
                    ->getListCacheTags(),
            ],
        ];
    }
    
    /**
     * Generates representations of a book page and its children.
     *
     * The method delegates the generation of output to helper methods. The method
     * name is derived by prepending 'bookExport' to the camelized form of given
     * output type. For example, a type of 'html' results in a call to the method
     * bookExportHtml().
     *
     * @param string $type
     *   A string encoding the type of output requested. The following types are
     *   currently supported in book module:
     *   - html: Printer-friendly HTML.
     *   Other types may be supported in contributed modules.
     * @param \Drupal\node\NodeInterface $node
     *   The node to export.
     *
     * @return array
     *   A render array representing the node and its children in the book
     *   hierarchy in a format determined by the $type parameter.
     *
     * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
     */
    public function bookExport($type, NodeInterface $node) {
        $method = 'bookExport' . Container::camelize($type);
        // @todo Convert the custom export functionality to serializer.
        if (!method_exists($this->bookExport, $method)) {
            $this->messenger()
                ->addStatus(t('Unknown export format.'));
            throw new NotFoundHttpException();
        }
        $exported_book = $this->bookExport
            ->{$method}($node);
        return new Response($this->renderer
            ->renderRoot($exported_book));
    }

}