class BookAdminEditForm

class BookAdminEditForm extends FormBase {
    
    /**
     * The node storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $nodeStorage;
    
    /**
     * The book manager.
     *
     * @var \Drupal\book\BookManagerInterface
     */
    protected $bookManager;
    
    /**
     * Constructs a new BookAdminEditForm.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
     *   The custom block storage.
     * @param \Drupal\book\BookManagerInterface $book_manager
     *   The book manager.
     */
    public function __construct(EntityStorageInterface $node_storage, BookManagerInterface $book_manager) {
        $this->nodeStorage = $node_storage;
        $this->bookManager = $book_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        $entity_type_manager = $container->get('entity_type.manager');
        return new static($entity_type_manager->getStorage('node'), $container->get('book.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'book_admin_edit';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, NodeInterface $node = NULL) {
        $form['#title'] = $node->label();
        $form['#node'] = $node;
        $this->bookAdminTable($node, $form);
        $form['save'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save book pages'),
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        if ($form_state->getValue('tree_hash') != $form_state->getValue('tree_current_hash')) {
            $form_state->setErrorByName('', $this->t('This book has been modified by another user, the changes could not be saved.'));
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        // Save elements in the same order as defined in post rather than the form.
        // This ensures parents are updated before their children, preventing orphans.
        $user_input = $form_state->getUserInput();
        if (isset($user_input['table'])) {
            $order = array_flip(array_keys($user_input['table']));
            $form['table'] = array_merge($order, $form['table']);
            foreach (Element::children($form['table']) as $key) {
                if ($form['table'][$key]['#item']) {
                    $row = $form['table'][$key];
                    $values = $form_state->getValue([
                        'table',
                        $key,
                    ]);
                    // Update menu item if moved.
                    if ($row['parent']['pid']['#default_value'] != $values['pid'] || $row['weight']['#default_value'] != $values['weight']) {
                        $link = $this->bookManager
                            ->loadBookLink($values['nid'], FALSE);
                        $link['weight'] = $values['weight'];
                        $link['pid'] = $values['pid'];
                        $this->bookManager
                            ->saveBookLink($link, FALSE);
                    }
                    // Update the title if changed.
                    if ($row['title']['#default_value'] != $values['title']) {
                        $node = $this->nodeStorage
                            ->load($values['nid']);
                        $node->revision_log = $this->t('Title changed from %original to %current.', [
                            '%original' => $node->label(),
                            '%current' => $values['title'],
                        ]);
                        $node->title = $values['title'];
                        $node->book['link_title'] = $values['title'];
                        $node->setNewRevision();
                        $node->save();
                        $this->logger('content')
                            ->notice('book: updated %title.', [
                            '%title' => $node->label(),
                            'link' => $node->toLink($this->t('View'))
                                ->toString(),
                        ]);
                    }
                }
            }
        }
        $this->messenger()
            ->addStatus($this->t('Updated book %title.', [
            '%title' => $form['#node']->label(),
        ]));
    }
    
    /**
     * Builds the table portion of the form for the book administration page.
     *
     * @param \Drupal\node\NodeInterface $node
     *   The node of the top-level page in the book.
     * @param array $form
     *   The form that is being modified, passed by reference.
     *
     * @see self::buildForm()
     */
    protected function bookAdminTable(NodeInterface $node, array &$form) {
        $form['table'] = [
            '#type' => 'table',
            '#header' => [
                $this->t('Title'),
                $this->t('Weight'),
                $this->t('Parent'),
                $this->t('Operations'),
            ],
            '#empty' => $this->t('No book content available.'),
            '#tabledrag' => [
                [
                    'action' => 'match',
                    'relationship' => 'parent',
                    'group' => 'book-pid',
                    'subgroup' => 'book-pid',
                    'source' => 'book-nid',
                    'hidden' => TRUE,
                    'limit' => BookManager::BOOK_MAX_DEPTH - 2,
                ],
                [
                    'action' => 'order',
                    'relationship' => 'sibling',
                    'group' => 'book-weight',
                ],
            ],
        ];
        $tree = $this->bookManager
            ->bookSubtreeData($node->book);
        // Do not include the book item itself.
        $tree = array_shift($tree);
        if ($tree['below']) {
            $hash = Crypt::hashBase64(serialize($tree['below']));
            // Store the hash value as a hidden form element so that we can detect
            // if another user changed the book hierarchy.
            $form['tree_hash'] = [
                '#type' => 'hidden',
                '#default_value' => $hash,
            ];
            $form['tree_current_hash'] = [
                '#type' => 'value',
                '#value' => $hash,
            ];
            $this->bookAdminTableTree($tree['below'], $form['table']);
        }
    }
    
    /**
     * Helps build the main table in the book administration page form.
     *
     * @param array $tree
     *   A subtree of the book menu hierarchy.
     * @param array $form
     *   The form that is being modified, passed by reference.
     *
     * @see self::buildForm()
     */
    protected function bookAdminTableTree(array $tree, array &$form) {
        // The delta must be big enough to give each node a distinct value.
        $count = count($tree);
        $delta = $count < 30 ? 15 : intval($count / 2) + 1;
        $access = \Drupal::currentUser()->hasPermission('administer nodes');
        $destination = $this->getDestinationArray();
        foreach ($tree as $data) {
            $nid = $data['link']['nid'];
            $id = 'book-admin-' . $nid;
            $form[$id]['#item'] = $data['link'];
            $form[$id]['#nid'] = $nid;
            $form[$id]['#attributes']['class'][] = 'draggable';
            $form[$id]['#weight'] = $data['link']['weight'];
            if (isset($data['link']['depth']) && $data['link']['depth'] > 2) {
                $indentation = [
                    '#theme' => 'indentation',
                    '#size' => $data['link']['depth'] - 2,
                ];
            }
            $form[$id]['title'] = [
                '#prefix' => !empty($indentation) ? \Drupal::service('renderer')->render($indentation) : '',
                '#type' => 'textfield',
                '#default_value' => $data['link']['title'],
                '#maxlength' => 255,
                '#size' => 40,
            ];
            $form[$id]['weight'] = [
                '#type' => 'weight',
                '#default_value' => $data['link']['weight'],
                '#delta' => max($delta, abs($data['link']['weight'])),
                '#title' => $this->t('Weight for @title', [
                    '@title' => $data['link']['title'],
                ]),
                '#title_display' => 'invisible',
                '#attributes' => [
                    'class' => [
                        'book-weight',
                    ],
                ],
            ];
            $form[$id]['parent']['nid'] = [
                '#parents' => [
                    'table',
                    $id,
                    'nid',
                ],
                '#type' => 'hidden',
                '#value' => $nid,
                '#attributes' => [
                    'class' => [
                        'book-nid',
                    ],
                ],
            ];
            $form[$id]['parent']['pid'] = [
                '#parents' => [
                    'table',
                    $id,
                    'pid',
                ],
                '#type' => 'hidden',
                '#default_value' => $data['link']['pid'],
                '#attributes' => [
                    'class' => [
                        'book-pid',
                    ],
                ],
            ];
            $form[$id]['parent']['bid'] = [
                '#parents' => [
                    'table',
                    $id,
                    'bid',
                ],
                '#type' => 'hidden',
                '#default_value' => $data['link']['bid'],
                '#attributes' => [
                    'class' => [
                        'book-bid',
                    ],
                ],
            ];
            $form[$id]['operations'] = [
                '#type' => 'operations',
            ];
            $form[$id]['operations']['#links']['view'] = [
                'title' => $this->t('View'),
                'url' => new Url('entity.node.canonical', [
                    'node' => $nid,
                ]),
            ];
            if ($access) {
                $form[$id]['operations']['#links']['edit'] = [
                    'title' => $this->t('Edit'),
                    'url' => new Url('entity.node.edit_form', [
                        'node' => $nid,
                    ]),
                    'query' => $destination,
                ];
                $form[$id]['operations']['#links']['delete'] = [
                    'title' => $this->t('Delete'),
                    'url' => new Url('entity.node.delete_form', [
                        'node' => $nid,
                    ]),
                    'query' => $destination,
                ];
            }
            if ($data['below']) {
                $this->bookAdminTableTree($data['below'], $form);
            }
        }
    }

}