comparison core/modules/book/src/BookManager.php @ 0:4c8ae668cc8c

Initial import (non-working)

+<?php
+
+namespace Drupal\book;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\StringTranslation\TranslationInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Template\Attribute;
+use Drupal\node\NodeInterface;
+
+/**
+ * Defines a book manager.
+ */
+class BookManager implements BookManagerInterface {
+  use StringTranslationTrait;
+
+  /**
+   * Defines the maximum supported depth of the book tree.
+   */
+  const BOOK_MAX_DEPTH = 9;
+
+  /**
+   * Entity manager Service Object.
+   *
+   * @var \Drupal\Core\Entity\EntityManagerInterface
+   */
+  protected $entityManager;
+
+  /**
+   * Config Factory Service Object.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * Books Array.
+   *
+   * @var array
+   */
+  protected $books;
+
+  /**
+   * Book outline storage.
+   *
+   * @var \Drupal\book\BookOutlineStorageInterface
+   */
+  protected $bookOutlineStorage;
+
+  /**
+   * Stores flattened book trees.
+   *
+   * @var array
+   */
+  protected $bookTreeFlattened;
+
+  /**
+   * The renderer.
+   *
+   * @var \Drupal\Core\Render\RendererInterface
+   */
+  protected $renderer;
+
+  /**
+   * Constructs a BookManager object.
+   */
+  public function __construct(EntityManagerInterface $entity_manager, TranslationInterface $translation, ConfigFactoryInterface $config_factory, BookOutlineStorageInterface $book_outline_storage, RendererInterface $renderer) {
+    $this->entityManager = $entity_manager;
+    $this->stringTranslation = $translation;
+    $this->configFactory = $config_factory;
+    $this->bookOutlineStorage = $book_outline_storage;
+    $this->renderer = $renderer;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getAllBooks() {
+    if (!isset($this->books)) {
+      $this->loadBooks();
+    }
+    return $this->books;
+  }
+
+  /**
+   * Loads Books Array.
+   */
+  protected function loadBooks() {
+    $this->books = [];
+    $nids = $this->bookOutlineStorage->getBooks();
+
+    if ($nids) {
+      $book_links = $this->bookOutlineStorage->loadMultiple($nids);
+      $nodes = $this->entityManager->getStorage('node')->loadMultiple($nids);
+      // @todo: Sort by weight and translated title.
+
+      // @todo: use route name for links, not system path.
+      foreach ($book_links as $link) {
+        $nid = $link['nid'];
+        if (isset($nodes[$nid]) && $nodes[$nid]->status) {
+          $link['url'] = $nodes[$nid]->urlInfo();
+          $link['title'] = $nodes[$nid]->label();
+          $link['type'] = $nodes[$nid]->bundle();
+          $this->books[$link['bid']] = $link;
+        }
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getLinkDefaults($nid) {
+    return [
+      'original_bid' => 0,
+      'nid' => $nid,
+      'bid' => 0,
+      'pid' => 0,
+      'has_children' => 0,
+      'weight' => 0,
+      'options' => [],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getParentDepthLimit(array $book_link) {
+    return static::BOOK_MAX_DEPTH - 1 - (($book_link['bid'] && $book_link['has_children']) ? $this->findChildrenRelativeDepth($book_link) : 0);
+  }
+
+  /**
+   * Determine the relative depth of the children of a given book link.
+   *
+   * @param array $book_link
+   *   The book link.
+   *
+   * @return int
+   *   The difference between the max depth in the book tree and the depth of
+   *   the passed book link.
+   */
+  protected function findChildrenRelativeDepth(array $book_link) {
+    $max_depth = $this->bookOutlineStorage->getChildRelativeDepth($book_link, static::BOOK_MAX_DEPTH);
+    return ($max_depth > $book_link['depth']) ? $max_depth - $book_link['depth'] : 0;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addFormElements(array $form, FormStateInterface $form_state, NodeInterface $node, AccountInterface $account, $collapsed = TRUE) {
+    // If the form is being processed during the Ajax callback of our book bid
+    // dropdown, then $form_state will hold the value that was selected.
+    if ($form_state->hasValue('book')) {
+      $node->book = $form_state->getValue('book');
+    }
+    $form['book'] = [
+      '#type' => 'details',
+      '#title' => $this->t('Book outline'),
+      '#weight' => 10,
+      '#open' => !$collapsed,
+      '#group' => 'advanced',
+      '#attributes' => [
+        'class' => ['book-outline-form'],
+      ],
+      '#attached' => [
+        'library' => ['book/drupal.book'],
+      ],
+      '#tree' => TRUE,
+    ];
+    foreach (['nid', 'has_children', 'original_bid', 'parent_depth_limit'] as $key) {
+      $form['book'][$key] = [
+        '#type' => 'value',
+        '#value' => $node->book[$key],
+      ];
+    }
+
+    $form['book']['pid'] = $this->addParentSelectFormElements($node->book);
+
+    // @see \Drupal\book\Form\BookAdminEditForm::bookAdminTableTree(). The
+    // weight may be larger than 15.
+    $form['book']['weight'] = [
+      '#type' => 'weight',
+      '#title' => $this->t('Weight'),
+      '#default_value' => $node->book['weight'],
+      '#delta' => max(15, abs($node->book['weight'])),
+      '#weight' => 5,
+      '#description' => $this->t('Pages at a given level are ordered first by weight and then by title.'),
+    ];
+    $options = [];
+    $nid = !$node->isNew() ? $node->id() : 'new';
+    if ($node->id() && ($nid == $node->book['original_bid']) && ($node->book['parent_depth_limit'] == 0)) {
+      // This is the top level node in a maximum depth book and thus cannot be
+      // moved.
+      $options[$node->id()] = $node->label();
+    }
+    else {
+      foreach ($this->getAllBooks() as $book) {
+        $options[$book['nid']] = $book['title'];
+      }
+    }
+
+    if ($account->hasPermission('create new books') && ($nid == 'new' || ($nid != $node->book['original_bid']))) {
+      // The node can become a new book, if it is not one already.
+      $options = [$nid => $this->t('- Create a new book -')] + $options;
+    }
+    if (!$node->book['bid']) {
+      // The node is not currently in the hierarchy.
+      $options = [0 => $this->t('- None -')] + $options;
+    }
+
+    // Add a drop-down to select the destination book.
+    $form['book']['bid'] = [
+      '#type' => 'select',
+      '#title' => $this->t('Book'),
+      '#default_value' => $node->book['bid'],
+      '#options' => $options,
+      '#access' => (bool) $options,
+      '#description' => $this->t('Your page will be a part of the selected book.'),
+      '#weight' => -5,
+      '#attributes' => ['class' => ['book-title-select']],
+      '#ajax' => [
+        'callback' => 'book_form_update',
+        'wrapper' => 'edit-book-plid-wrapper',
+        'effect' => 'fade',
+        'speed' => 'fast',
+      ],
+    ];
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function checkNodeIsRemovable(NodeInterface $node) {
+    return (!empty($node->book['bid']) && (($node->book['bid'] != $node->id()) || !$node->book['has_children']));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function updateOutline(NodeInterface $node) {
+    if (empty($node->book['bid'])) {
+      return FALSE;
+    }
+
+    if (!empty($node->book['bid'])) {
+      if ($node->book['bid'] == 'new') {
+        // New nodes that are their own book.
+        $node->book['bid'] = $node->id();
+      }
+      elseif (!isset($node->book['original_bid'])) {
+        $node->book['original_bid'] = $node->book['bid'];
+      }
+    }
+
+    // Ensure we create a new book link if either the node itself is new, or the
+    // bid was selected the first time, so that the original_bid is still empty.
+    $new = empty($node->book['nid']) || empty($node->book['original_bid']);
+
+    $node->book['nid'] = $node->id();
+
+    // Create a new book from a node.
+    if ($node->book['bid'] == $node->id()) {
+      $node->book['pid'] = 0;
+    }
+    elseif ($node->book['pid'] < 0) {
+      // -1 is the default value in BookManager::addParentSelectFormElements().
+      // The node save should have set the bid equal to the node ID, but
+      // handle it here if it did not.
+      $node->book['pid'] = $node->book['bid'];
+    }
+
+    // Prevent changes to the book outline if the node being saved is not the
+    // default revision.
+    $updated = FALSE;
+    if (!$new) {
+      $original = $this->loadBookLink($node->id(), FALSE);
+      if ($node->book['bid'] != $original['bid'] || $node->book['pid'] != $original['pid'] || $node->book['weight'] != $original['weight']) {
+        $updated = TRUE;
+      }
+    }
+    if (($new || $updated) && !$node->isDefaultRevision()) {
+      return FALSE;
+    }
+
+    return $this->saveBookLink($node->book, $new);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getBookParents(array $item, array $parent = []) {
+    $book = [];
+    if ($item['pid'] == 0) {
+      $book['p1'] = $item['nid'];
+      for ($i = 2; $i <= static::BOOK_MAX_DEPTH; $i++) {
+        $parent_property = "p$i";
+        $book[$parent_property] = 0;
+      }
+      $book['depth'] = 1;
+    }
+    else {
+      $i = 1;
+      $book['depth'] = $parent['depth'] + 1;
+      while ($i < $book['depth']) {
+        $p = 'p' . $i++;
+        $book[$p] = $parent[$p];
+      }
+      $p = 'p' . $i++;
+      // The parent (p1 - p9) corresponding to the depth always equals the nid.
+      $book[$p] = $item['nid'];
+      while ($i <= static::BOOK_MAX_DEPTH) {
+        $p = 'p' . $i++;
+        $book[$p] = 0;
+      }
+    }
+    return $book;
+  }
+
+  /**
+   * Builds the parent selection form element for the node form or outline tab.
+   *
+   * This function is also called when generating a new set of options during
+   * the Ajax callback, so an array is returned that can be used to replace an
+   * existing form element.
+   *
+   * @param array $book_link
+   *   A fully loaded book link that is part of the book hierarchy.
+   *
+   * @return array
+   *   A parent selection form element.
+   */
+  protected function addParentSelectFormElements(array $book_link) {
+    $config = $this->configFactory->get('book.settings');
+    if ($config->get('override_parent_selector')) {
+      return [];
+    }
+    // Offer a message or a drop-down to choose a different parent page.
+    $form = [
+      '#type' => 'hidden',
+      '#value' => -1,
+      '#prefix' => '<div id="edit-book-plid-wrapper">',
+      '#suffix' => '</div>',
+    ];
+
+    if ($book_link['nid'] === $book_link['bid']) {
+      // This is a book - at the top level.
+      if ($book_link['original_bid'] === $book_link['bid']) {
+        $form['#prefix'] .= '<em>' . $this->t('This is the top-level page in this book.') . '</em>';
+      }
+      else {
+        $form['#prefix'] .= '<em>' . $this->t('This will be the top-level page in this book.') . '</em>';
+      }
+    }
+    elseif (!$book_link['bid']) {
+      $form['#prefix'] .= '<em>' . $this->t('No book selected.') . '</em>';
+    }
+    else {
+      $form = [
+        '#type' => 'select',
+        '#title' => $this->t('Parent item'),
+        '#default_value' => $book_link['pid'],
+        '#description' => $this->t('The parent page in the book. The maximum depth for a book and all child pages is @maxdepth. Some pages in the selected book may not be available as parents if selecting them would exceed this limit.', ['@maxdepth' => static::BOOK_MAX_DEPTH]),
+        '#options' => $this->getTableOfContents($book_link['bid'], $book_link['parent_depth_limit'], [$book_link['nid']]),
+        '#attributes' => ['class' => ['book-title-select']],
+        '#prefix' => '<div id="edit-book-plid-wrapper">',
+        '#suffix' => '</div>',
+      ];
+    }
+    $this->renderer->addCacheableDependency($form, $config);
+
+    return $form;
+  }
+
+  /**
+   * Recursively processes and formats book links for getTableOfContents().
+   *
+   * This helper function recursively modifies the table of contents array for
+   * each item in the book tree, ignoring items in the exclude array or at a
+   * depth greater than the limit. Truncates titles over thirty characters and
+   * appends an indentation string incremented by depth.
+   *
+   * @param array $tree
+   *   The data structure of the book's outline tree. Includes hidden links.
+   * @param string $indent
+   *   A string appended to each node title. Increments by '--' per depth
+   *   level.
+   * @param array $toc
+   *   Reference to the table of contents array. This is modified in place, so
+   *   the function does not have a return value.
+   * @param array $exclude
+   *   Optional array of Node ID values. Any link whose node ID is in this
+   *   array will be excluded (along with its children).
+   * @param int $depth_limit
+   *   Any link deeper than this value will be excluded (along with its
+   *   children).
+   */
+  protected function recurseTableOfContents(array $tree, $indent, array &$toc, array $exclude, $depth_limit) {
+    $nids = [];
+    foreach ($tree as $data) {
+      if ($data['link']['depth'] > $depth_limit) {
+        // Don't iterate through any links on this level.
+        return;
+      }
+      if (!in_array($data['link']['nid'], $exclude)) {
+        $nids[] = $data['link']['nid'];
+      }
+    }
+
+    $nodes = $this->entityManager->getStorage('node')->loadMultiple($nids);
+
+    foreach ($tree as $data) {
+      $nid = $data['link']['nid'];
+      // Check for excluded or missing node.
+      if (empty($nodes[$nid])) {
+        continue;
+      }
+      $toc[$nid] = $indent . ' ' . Unicode::truncate($nodes[$nid]->label(), 30, TRUE, TRUE);
+      if ($data['below']) {
+        $this->recurseTableOfContents($data['below'], $indent . '--', $toc, $exclude, $depth_limit);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTableOfContents($bid, $depth_limit, array $exclude = []) {
+    $tree = $this->bookTreeAllData($bid);
+    $toc = [];
+    $this->recurseTableOfContents($tree, '', $toc, $exclude, $depth_limit);
+
+    return $toc;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deleteFromBook($nid) {
+    $original = $this->loadBookLink($nid, FALSE);
+    $this->bookOutlineStorage->delete($nid);
+
+    if ($nid == $original['bid']) {
+      // Handle deletion of a top-level post.
+      $result = $this->bookOutlineStorage->loadBookChildren($nid);
+      $children = $this->entityManager->getStorage('node')->loadMultiple(array_keys($result));
+      foreach ($children as $child) {
+        $child->book['bid'] = $child->id();
+        $this->updateOutline($child);
+      }
+    }
+    $this->updateOriginalParent($original);
+    $this->books = NULL;
+    Cache::invalidateTags(['bid:' . $original['bid']]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookTreeAllData($bid, $link = NULL, $max_depth = NULL) {
+    $tree = &drupal_static(__METHOD__, []);
+    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
+
+    // Use $nid as a flag for whether the data being loaded is for the whole
+    // tree.
+    $nid = isset($link['nid']) ? $link['nid'] : 0;
+    // Generate a cache ID (cid) specific for this $bid, $link, $language, and
+    // depth.
+    $cid = 'book-links:' . $bid . ':all:' . $nid . ':' . $language_interface->getId() . ':' . (int) $max_depth;
+
+    if (!isset($tree[$cid])) {
+      // If the tree data was not in the static cache, build $tree_parameters.
+      $tree_parameters = [
+        'min_depth' => 1,
+        'max_depth' => $max_depth,
+      ];
+      if ($nid) {
+        $active_trail = $this->getActiveTrailIds($bid, $link);
+        $tree_parameters['expanded'] = $active_trail;
+        $tree_parameters['active_trail'] = $active_trail;
+        $tree_parameters['active_trail'][] = $nid;
+      }
+
+      // Build the tree using the parameters; the resulting tree will be cached.
+      $tree[$cid] = $this->bookTreeBuild($bid, $tree_parameters);
+    }
+
+    return $tree[$cid];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getActiveTrailIds($bid, $link) {
+    // The tree is for a single item, so we need to match the values in its
+    // p columns and 0 (the top level) with the plid values of other links.
+    $active_trail = [0];
+    for ($i = 1; $i < static::BOOK_MAX_DEPTH; $i++) {
+      if (!empty($link["p$i"])) {
+        $active_trail[] = $link["p$i"];
+      }
+    }
+    return $active_trail;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookTreeOutput(array $tree) {
+    $items = $this->buildItems($tree);
+
+    $build = [];
+
+    if ($items) {
+      // Make sure drupal_render() does not re-order the links.
+      $build['#sorted'] = TRUE;
+      // Get the book id from the last link.
+      $item = end($items);
+      // Add the theme wrapper for outer markup.
+      // Allow menu-specific theme overrides.
+      $build['#theme'] = 'book_tree__book_toc_' . $item['original_link']['bid'];
+      $build['#items'] = $items;
+      // Set cache tag.
+      $build['#cache']['tags'][] = 'config:system.book.' . $item['original_link']['bid'];
+    }
+
+    return $build;
+  }
+
+  /**
+   * Builds the #items property for a book tree's renderable array.
+   *
+   * Helper function for ::bookTreeOutput().
+   *
+   * @param array $tree
+   *   A data structure representing the tree.
+   *
+   * @return array
+   *   The value to use for the #items property of a renderable menu.
+   */
+  protected function buildItems(array $tree) {
+    $items = [];
+
+    foreach ($tree as $data) {
+      $element = [];
+
+      // Generally we only deal with visible links, but just in case.
+      if (!$data['link']['access']) {
+        continue;
+      }
+      // Set a class for the <li> tag. Since $data['below'] may contain local
+      // tasks, only set 'expanded' to true if the link also has children within
+      // the current book.
+      $element['is_expanded'] = FALSE;
+      $element['is_collapsed'] = FALSE;
+      if ($data['link']['has_children'] && $data['below']) {
+        $element['is_expanded'] = TRUE;
+      }
+      elseif ($data['link']['has_children']) {
+        $element['is_collapsed'] = TRUE;
+      }
+
+      // Set a helper variable to indicate whether the link is in the active
+      // trail.
+      $element['in_active_trail'] = FALSE;
+      if ($data['link']['in_active_trail']) {
+        $element['in_active_trail'] = TRUE;
+      }
+
+      // Allow book-specific theme overrides.
+      $element['attributes'] = new Attribute();
+      $element['title'] = $data['link']['title'];
+      $node = $this->entityManager->getStorage('node')->load($data['link']['nid']);
+      $element['url'] = $node->urlInfo();
+      $element['localized_options'] = !empty($data['link']['localized_options']) ? $data['link']['localized_options'] : [];
+      $element['localized_options']['set_active_class'] = TRUE;
+      $element['below'] = $data['below'] ? $this->buildItems($data['below']) : [];
+      $element['original_link'] = $data['link'];
+      // Index using the link's unique nid.
+      $items[$data['link']['nid']] = $element;
+    }
+
+    return $items;
+  }
+
+  /**
+   * Builds a book tree, translates links, and checks access.
+   *
+   * @param int $bid
+   *   The Book ID to find links for.
+   * @param array $parameters
+   *   (optional) An associative array of build parameters. Possible keys:
+   *   - expanded: An array of parent link IDs to return only book links that
+   *     are children of one of the parent link IDs in this list. If empty,
+   *     the whole outline is built, unless 'only_active_trail' is TRUE.
+   *   - active_trail: An array of node IDs, representing the currently active
+   *     book link.
+   *   - only_active_trail: Whether to only return links that are in the active
+   *     trail. This option is ignored if 'expanded' is non-empty.
+   *   - min_depth: The minimum depth of book links in the resulting tree.
+   *     Defaults to 1, which is to build the whole tree for the book.
+   *   - max_depth: The maximum depth of book links in the resulting tree.
+   *   - conditions: An associative array of custom database select query
+   *     condition key/value pairs; see
+   *     \Drupal\book\BookOutlineStorage::getBookMenuTree() for the actual
+   *     query.
+   *
+   * @return array
+   *   A fully built book tree.
+   */
+  protected function bookTreeBuild($bid, array $parameters = []) {
+    // Build the book tree.
+    $data = $this->doBookTreeBuild($bid, $parameters);
+    // Check access for the current user to each item in the tree.
+    $this->bookTreeCheckAccess($data['tree'], $data['node_links']);
+    return $data['tree'];
+  }
+
+  /**
+   * Builds a book tree.
+   *
+   * This function may be used build the data for a menu tree only, for example
+   * to further massage the data manually before further processing happens.
+   * _menu_tree_check_access() needs to be invoked afterwards.
+   *
+   * @param int $bid
+   *   The book ID to find links for.
+   * @param array $parameters
+   *   (optional) An associative array of build parameters. Possible keys:
+   *   - expanded: An array of parent link IDs to return only book links that
+   *     are children of one of the parent link IDs in this list. If empty,
+   *     the whole outline is built, unless 'only_active_trail' is TRUE.
+   *   - active_trail: An array of node IDs, representing the currently active
+   *     book link.
+   *   - only_active_trail: Whether to only return links that are in the active
+   *     trail. This option is ignored if 'expanded' is non-empty.
+   *   - min_depth: The minimum depth of book links in the resulting tree.
+   *     Defaults to 1, which is to build the whole tree for the book.
+   *   - max_depth: The maximum depth of book links in the resulting tree.
+   *   - conditions: An associative array of custom database select query
+   *     condition key/value pairs; see
+   *     \Drupal\book\BookOutlineStorage::getBookMenuTree() for the actual
+   *     query.
+   *
+   * @return array
+   *   An array with links representing the tree structure of the book.
+   *
+   * @see \Drupal\book\BookOutlineStorageInterface::getBookMenuTree()
+   */
+  protected function doBookTreeBuild($bid, array $parameters = []) {
+    // Static cache of already built menu trees.
+    $trees = &drupal_static(__METHOD__, []);
+    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
+
+    // Build the cache id; sort parents to prevent duplicate storage and remove
+    // default parameter values.
+    if (isset($parameters['expanded'])) {
+      sort($parameters['expanded']);
+    }
+    $tree_cid = 'book-links:' . $bid . ':tree-data:' . $language_interface->getId() . ':' . hash('sha256', serialize($parameters));
+
+    // If we do not have this tree in the static cache, check {cache_data}.
+    if (!isset($trees[$tree_cid])) {
+      $cache = \Drupal::cache('data')->get($tree_cid);
+      if ($cache && $cache->data) {
+        $trees[$tree_cid] = $cache->data;
+      }
+    }
+
+    if (!isset($trees[$tree_cid])) {
+      $min_depth = (isset($parameters['min_depth']) ? $parameters['min_depth'] : 1);
+      $result = $this->bookOutlineStorage->getBookMenuTree($bid, $parameters, $min_depth, static::BOOK_MAX_DEPTH);
+
+      // Build an ordered array of links using the query result object.
+      $links = [];
+      foreach ($result as $link) {
+        $link = (array) $link;
+        $links[$link['nid']] = $link;
+      }
+      $active_trail = (isset($parameters['active_trail']) ? $parameters['active_trail'] : []);
+      $data['tree'] = $this->buildBookOutlineData($links, $active_trail, $min_depth);
+      $data['node_links'] = [];
+      $this->bookTreeCollectNodeLinks($data['tree'], $data['node_links']);
+
+      // Cache the data, if it is not already in the cache.
+      \Drupal::cache('data')->set($tree_cid, $data, Cache::PERMANENT, ['bid:' . $bid]);
+      $trees[$tree_cid] = $data;
+    }
+
+    return $trees[$tree_cid];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookTreeCollectNodeLinks(&$tree, &$node_links) {
+    // All book links are nodes.
+    // @todo clean this up.
+    foreach ($tree as $key => $v) {
+      $nid = $v['link']['nid'];
+      $node_links[$nid][$tree[$key]['link']['nid']] = &$tree[$key]['link'];
+      $tree[$key]['link']['access'] = FALSE;
+      if ($tree[$key]['below']) {
+        $this->bookTreeCollectNodeLinks($tree[$key]['below'], $node_links);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookTreeGetFlat(array $book_link) {
+    if (!isset($this->bookTreeFlattened[$book_link['nid']])) {
+      // Call $this->bookTreeAllData() to take advantage of caching.
+      $tree = $this->bookTreeAllData($book_link['bid'], $book_link, $book_link['depth'] + 1);
+      $this->bookTreeFlattened[$book_link['nid']] = [];
+      $this->flatBookTree($tree, $this->bookTreeFlattened[$book_link['nid']]);
+    }
+
+    return $this->bookTreeFlattened[$book_link['nid']];
+  }
+
+  /**
+   * Recursively converts a tree of menu links to a flat array.
+   *
+   * @param array $tree
+   *   A tree of menu links in an array.
+   * @param array $flat
+   *   A flat array of the menu links from $tree, passed by reference.
+   *
+   * @see static::bookTreeGetFlat()
+   */
+  protected function flatBookTree(array $tree, array &$flat) {
+    foreach ($tree as $data) {
+      $flat[$data['link']['nid']] = $data['link'];
+      if ($data['below']) {
+        $this->flatBookTree($data['below'], $flat);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadBookLink($nid, $translate = TRUE) {
+    $links = $this->loadBookLinks([$nid], $translate);
+    return isset($links[$nid]) ? $links[$nid] : FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadBookLinks($nids, $translate = TRUE) {
+    $result = $this->bookOutlineStorage->loadMultiple($nids, $translate);
+    $links = [];
+    foreach ($result as $link) {
+      if ($translate) {
+        $this->bookLinkTranslate($link);
+      }
+      $links[$link['nid']] = $link;
+    }
+
+    return $links;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function saveBookLink(array $link, $new) {
+    // Keep track of Book IDs for cache clear.
+    $affected_bids[$link['bid']] = $link['bid'];
+    $link += $this->getLinkDefaults($link['nid']);
+    if ($new) {
+      // Insert new.
+      $parents = $this->getBookParents($link, (array) $this->loadBookLink($link['pid'], FALSE));
+      $this->bookOutlineStorage->insert($link, $parents);
+
+      // Update the has_children status of the parent.
+      $this->updateParent($link);
+    }
+    else {
+      $original = $this->loadBookLink($link['nid'], FALSE);
+      // Using the Book ID as the key keeps this unique.
+      $affected_bids[$original['bid']] = $original['bid'];
+      // Handle links that are moving.
+      if ($link['bid'] != $original['bid'] || $link['pid'] != $original['pid']) {
+        // Update the bid for this page and all children.
+        if ($link['pid'] == 0) {
+          $link['depth'] = 1;
+          $parent = [];
+        }
+        // In case the form did not specify a proper PID we use the BID as new
+        // parent.
+        elseif (($parent_link = $this->loadBookLink($link['pid'], FALSE)) && $parent_link['bid'] != $link['bid']) {
+          $link['pid'] = $link['bid'];
+          $parent = $this->loadBookLink($link['pid'], FALSE);
+          $link['depth'] = $parent['depth'] + 1;
+        }
+        else {
+          $parent = $this->loadBookLink($link['pid'], FALSE);
+          $link['depth'] = $parent['depth'] + 1;
+        }
+        $this->setParents($link, $parent);
+        $this->moveChildren($link, $original);
+
+        // Update the has_children status of the original parent.
+        $this->updateOriginalParent($original);
+        // Update the has_children status of the new parent.
+        $this->updateParent($link);
+      }
+      // Update the weight and pid.
+      $this->bookOutlineStorage->update($link['nid'], [
+        'weight' => $link['weight'],
+        'pid' => $link['pid'],
+        'bid' => $link['bid'],
+      ]);
+    }
+    $cache_tags = [];
+    foreach ($affected_bids as $bid) {
+      $cache_tags[] = 'bid:' . $bid;
+    }
+    Cache::invalidateTags($cache_tags);
+    return $link;
+  }
+
+  /**
+   * Moves children from the original parent to the updated link.
+   *
+   * @param array $link
+   *   The link being saved.
+   * @param array $original
+   *   The original parent of $link.
+   */
+  protected function moveChildren(array $link, array $original) {
+    $p = 'p1';
+    $expressions = [];
+    for ($i = 1; $i <= $link['depth']; $p = 'p' . ++$i) {
+      $expressions[] = [$p, ":p_$i", [":p_$i" => $link[$p]]];
+    }
+    $j = $original['depth'] + 1;
+    while ($i <= static::BOOK_MAX_DEPTH && $j <= static::BOOK_MAX_DEPTH) {
+      $expressions[] = ['p' . $i++, 'p' . $j++, []];
+    }
+    while ($i <= static::BOOK_MAX_DEPTH) {
+      $expressions[] = ['p' . $i++, 0, []];
+    }
+
+    $shift = $link['depth'] - $original['depth'];
+    if ($shift > 0) {
+      // The order of expressions must be reversed so the new values don't
+      // overwrite the old ones before they can be used because "Single-table
+      // UPDATE assignments are generally evaluated from left to right"
+      // @see http://dev.mysql.com/doc/refman/5.0/en/update.html
+      $expressions = array_reverse($expressions);
+    }
+
+    $this->bookOutlineStorage->updateMovedChildren($link['bid'], $original, $expressions, $shift);
+  }
+
+  /**
+   * Sets the has_children flag of the parent of the node.
+   *
+   * This method is mostly called when a book link is moved/created etc. So we
+   * want to update the has_children flag of the new parent book link.
+   *
+   * @param array $link
+   *   The book link, data reflecting its new position, whose new parent we want
+   *   to update.
+   *
+   * @return bool
+   *   TRUE if the update was successful (either there is no parent to update,
+   *   or the parent was updated successfully), FALSE on failure.
+   */
+  protected function updateParent(array $link) {
+    if ($link['pid'] == 0) {
+      // Nothing to update.
+      return TRUE;
+    }
+    return $this->bookOutlineStorage->update($link['pid'], ['has_children' => 1]);
+  }
+
+  /**
+   * Updates the has_children flag of the parent of the original node.
+   *
+   * This method is called when a book link is moved or deleted. So we want to
+   * update the has_children flag of the parent node.
+   *
+   * @param array $original
+   *   The original link whose parent we want to update.
+   *
+   * @return bool
+   *   TRUE if the update was successful (either there was no original parent to
+   *   update, or the original parent was updated successfully), FALSE on
+   *   failure.
+   */
+  protected function updateOriginalParent(array $original) {
+    if ($original['pid'] == 0) {
+      // There were no parents of this link. Nothing to update.
+      return TRUE;
+    }
+    // Check if $original had at least one child.
+    $original_number_of_children = $this->bookOutlineStorage->countOriginalLinkChildren($original);
+
+    $parent_has_children = ((bool) $original_number_of_children) ? 1 : 0;
+    // Update the parent. If the original link did not have children, then the
+    // parent now does not have children. If the original had children, then the
+    // the parent has children now (still).
+    return $this->bookOutlineStorage->update($original['pid'], ['has_children' => $parent_has_children]);
+  }
+
+  /**
+   * Sets the p1 through p9 properties for a book link being saved.
+   *
+   * @param array $link
+   *   The book link to update, passed by reference.
+   * @param array $parent
+   *   The parent values to set.
+   */
+  protected function setParents(array &$link, array $parent) {
+    $i = 1;
+    while ($i < $link['depth']) {
+      $p = 'p' . $i++;
+      $link[$p] = $parent[$p];
+    }
+    $p = 'p' . $i++;
+    // The parent (p1 - p9) corresponding to the depth always equals the nid.
+    $link[$p] = $link['nid'];
+    while ($i <= static::BOOK_MAX_DEPTH) {
+      $p = 'p' . $i++;
+      $link[$p] = 0;
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookTreeCheckAccess(&$tree, $node_links = []) {
+    if ($node_links) {
+      // @todo Extract that into its own method.
+      $nids = array_keys($node_links);
+
+      // @todo This should be actually filtering on the desired node status
+      //   field language and just fall back to the default language.
+      $nids = \Drupal::entityQuery('node')
+        ->condition('nid', $nids, 'IN')
+        ->condition('status', 1)
+        ->execute();
+
+      foreach ($nids as $nid) {
+        foreach ($node_links[$nid] as $mlid => $link) {
+          $node_links[$nid][$mlid]['access'] = TRUE;
+        }
+      }
+    }
+    $this->doBookTreeCheckAccess($tree);
+  }
+
+  /**
+   * Sorts the menu tree and recursively checks access for each item.
+   *
+   * @param array $tree
+   *   The book tree to operate on.
+   */
+  protected function doBookTreeCheckAccess(&$tree) {
+    $new_tree = [];
+    foreach ($tree as $key => $v) {
+      $item = &$tree[$key]['link'];
+      $this->bookLinkTranslate($item);
+      if ($item['access']) {
+        if ($tree[$key]['below']) {
+          $this->doBookTreeCheckAccess($tree[$key]['below']);
+        }
+        // The weights are made a uniform 5 digits by adding 50000 as an offset.
+        // After calling $this->bookLinkTranslate(), $item['title'] has the
+        // translated title. Adding the nid to the end of the index insures that
+        // it is unique.
+        $new_tree[(50000 + $item['weight']) . ' ' . $item['title'] . ' ' . $item['nid']] = $tree[$key];
+      }
+    }
+    // Sort siblings in the tree based on the weights and localized titles.
+    ksort($new_tree);
+    $tree = $new_tree;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookLinkTranslate(&$link) {
+    $node = NULL;
+    // Access will already be set in the tree functions.
+    if (!isset($link['access'])) {
+      $node = $this->entityManager->getStorage('node')->load($link['nid']);
+      $link['access'] = $node && $node->access('view');
+    }
+    // For performance, don't localize a link the user can't access.
+    if ($link['access']) {
+      // @todo - load the nodes en-mass rather than individually.
+      if (!$node) {
+        $node = $this->entityManager->getStorage('node')
+          ->load($link['nid']);
+      }
+      // The node label will be the value for the current user's language.
+      $link['title'] = $node->label();
+      $link['options'] = [];
+    }
+    return $link;
+  }
+
+  /**
+   * Sorts and returns the built data representing a book tree.
+   *
+   * @param array $links
+   *   A flat array of book links that are part of the book. Each array element
+   *   is an associative array of information about the book link, containing
+   *   the fields from the {book} table. This array must be ordered depth-first.
+   * @param array $parents
+   *   An array of the node ID values that are in the path from the current
+   *   page to the root of the book tree.
+   * @param int $depth
+   *   The minimum depth to include in the returned book tree.
+   *
+   * @return array
+   *   An array of book links in the form of a tree. Each item in the tree is an
+   *   associative array containing:
+   *   - link: The book link item from $links, with additional element
+   *     'in_active_trail' (TRUE if the link ID was in $parents).
+   *   - below: An array containing the sub-tree of this item, where each
+   *     element is a tree item array with 'link' and 'below' elements. This
+   *     array will be empty if the book link has no items in its sub-tree
+   *     having a depth greater than or equal to $depth.
+   */
+  protected function buildBookOutlineData(array $links, array $parents = [], $depth = 1) {
+    // Reverse the array so we can use the more efficient array_pop() function.
+    $links = array_reverse($links);
+    return $this->buildBookOutlineRecursive($links, $parents, $depth);
+  }
+
+  /**
+   * Builds the data representing a book tree.
+   *
+   * The function is a bit complex because the rendering of a link depends on
+   * the next book link.
+   *
+   * @param array $links
+   *   A flat array of book links that are part of the book. Each array element
+   *   is an associative array of information about the book link, containing
+   *   the fields from the {book} table. This array must be ordered depth-first.
+   * @param array $parents
+   *   An array of the node ID values that are in the path from the current page
+   *   to the root of the book tree.
+   * @param int $depth
+   *   The minimum depth to include in the returned book tree.
+   *
+   * @return array
+   *   Book tree.
+   */
+  protected function buildBookOutlineRecursive(&$links, $parents, $depth) {
+    $tree = [];
+    while ($item = array_pop($links)) {
+      // We need to determine if we're on the path to root so we can later build
+      // the correct active trail.
+      $item['in_active_trail'] = in_array($item['nid'], $parents);
+      // Add the current link to the tree.
+      $tree[$item['nid']] = [
+        'link' => $item,
+        'below' => [],
+      ];
+      // Look ahead to the next link, but leave it on the array so it's
+      // available to other recursive function calls if we return or build a
+      // sub-tree.
+      $next = end($links);
+      // Check whether the next link is the first in a new sub-tree.
+      if ($next && $next['depth'] > $depth) {
+        // Recursively call buildBookOutlineRecursive to build the sub-tree.
+        $tree[$item['nid']]['below'] = $this->buildBookOutlineRecursive($links, $parents, $next['depth']);
+        // Fetch next link after filling the sub-tree.
+        $next = end($links);
+      }
+      // Determine if we should exit the loop and $request = return.
+      if (!$next || $next['depth'] < $depth) {
+        break;
+      }
+    }
+    return $tree;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function bookSubtreeData($link) {
+    $tree = &drupal_static(__METHOD__, []);
+
+    // Generate a cache ID (cid) specific for this $link.
+    $cid = 'book-links:subtree-cid:' . $link['nid'];
+
+    if (!isset($tree[$cid])) {
+      $tree_cid_cache = \Drupal::cache('data')->get($cid);
+
+      if ($tree_cid_cache && $tree_cid_cache->data) {
+        // If the cache entry exists, it will just be the cid for the actual
+        // data. This avoids duplication of large amounts of data.
+        $cache = \Drupal::cache('data')->get($tree_cid_cache->data);
+
+        if ($cache && isset($cache->data)) {
+          $data = $cache->data;
+        }
+      }
+
+      // If the subtree data was not in the cache, $data will be NULL.
+      if (!isset($data)) {
+        $result = $this->bookOutlineStorage->getBookSubtree($link, static::BOOK_MAX_DEPTH);
+        $links = [];
+        foreach ($result as $item) {
+          $links[] = $item;
+        }
+        $data['tree'] = $this->buildBookOutlineData($links, [], $link['depth']);
+        $data['node_links'] = [];
+        $this->bookTreeCollectNodeLinks($data['tree'], $data['node_links']);
+        // Compute the real cid for book subtree data.
+        $tree_cid = 'book-links:subtree-data:' . hash('sha256', serialize($data));
+        // Cache the data, if it is not already in the cache.
+
+        if (!\Drupal::cache('data')->get($tree_cid)) {
+          \Drupal::cache('data')->set($tree_cid, $data, Cache::PERMANENT, ['bid:' . $link['bid']]);
+        }
+        // Cache the cid of the (shared) data using the book and item-specific
+        // cid.
+        \Drupal::cache('data')->set($cid, $tree_cid, Cache::PERMANENT, ['bid:' . $link['bid']]);
+      }
+      // Check access for the current user to each item in the tree.
+      $this->bookTreeCheckAccess($data['tree'], $data['node_links']);
+      $tree[$cid] = $data['tree'];
+    }
+
+    return $tree[$cid];
+  }
+
+}