interface BookManagerInterface

interface BookManagerInterface {
    
    /**
     * Gets the data structure representing a named menu tree.
     *
     * Since this can be the full tree including hidden items, the data returned
     * may be used for generating an admin interface or a select.
     *
     * Note: based on menu_tree_all_data().
     *
     * @param int $bid
     *   The Book ID to find links for.
     * @param array|null $link
     *   (optional) A fully loaded menu link, or NULL. If a link is supplied, only
     *   the path to root will be included in the returned tree - as if this link
     *   represented the current page in a visible menu.
     * @param int|null $max_depth
     *   (optional) Maximum depth of links to retrieve. Typically useful if only
     *   one or two levels of a sub tree are needed in conjunction with a non-NULL
     *   $link, in which case $max_depth should be greater than $link['depth'].
     *
     * @return array
     *   A tree of menu links in an array, in the order they should be rendered.
     */
    public function bookTreeAllData($bid, $link = NULL, $max_depth = NULL);
    
    /**
     * Gets the active trail IDs for the specified book at the provided path.
     *
     * @param string $bid
     *   The Book ID to find links for.
     * @param array $link
     *   A fully loaded menu link.
     *
     * @return array
     *   An array containing the active trail: a list of menu link IDs.
     */
    public function getActiveTrailIds($bid, $link);
    
    /**
     * Loads a single book entry.
     *
     * The entries of a book entry is documented in
     * \Drupal\book\BookOutlineStorageInterface::loadMultiple.
     *
     * If $translate is TRUE, it also checks access ('access' key) and
     * loads the title from the node itself.
     *
     * @param int $nid
     *   The node ID of the book.
     * @param bool $translate
     *   If TRUE, set access, title, and other elements.
     *
     * @return array
     *   The book data of that node.
     *
     * @see \Drupal\book\BookOutlineStorageInterface::loadMultiple
     */
    public function loadBookLink($nid, $translate = TRUE);
    
    /**
     * Loads multiple book entries.
     *
     * The entries of a book entry is documented in
     * \Drupal\book\BookOutlineStorageInterface::loadMultiple.
     *
     * If $translate is TRUE, it also checks access ('access' key) and
     * loads the title from the node itself.
     *
     * @param int[] $nids
     *   An array of nids to load.
     * @param bool $translate
     *   If TRUE, set access, title, and other elements.
     *
     * @return array[]
     *   The book data of each node keyed by NID.
     *
     * @see \Drupal\book\BookOutlineStorageInterface::loadMultiple
     */
    public function loadBookLinks($nids, $translate = TRUE);
    
    /**
     * Returns an array of book pages in table of contents order.
     *
     * @param int $bid
     *   The ID of the book whose pages are to be listed.
     * @param int $depth_limit
     *   Any link deeper than this value will be excluded (along with its
     *   children).
     * @param array $exclude
     *   (optional) An array of menu link ID values. Any link whose menu link ID
     *   is in this array will be excluded (along with its children). Defaults to
     *   an empty array.
     *
     * @return array
     *   An array of (menu link ID, title) pairs for use as options for selecting
     *   a book page.
     */
    public function getTableOfContents($bid, $depth_limit, array $exclude = []);
    
    /**
     * Finds the depth limit for items in the parent select.
     *
     * @param array $book_link
     *   A fully loaded menu link that is part of the book hierarchy.
     *
     * @return int
     *   The depth limit for items in the parent select.
     */
    public function getParentDepthLimit(array $book_link);
    
    /**
     * Collects node links from a given menu tree recursively.
     *
     * @param array $tree
     *   The menu tree you wish to collect node links from.
     * @param array $node_links
     *   An array in which to store the collected node links.
     */
    public function bookTreeCollectNodeLinks(&$tree, &$node_links);
    
    /**
     * Provides book loading, access control and translation.
     *
     * @param array $link
     *   A book link.
     */
    public function bookLinkTranslate(&$link);
    
    /**
     * Gets the book for a page and returns it as a linear array.
     *
     * @param array $book_link
     *   A fully loaded book link that is part of the book hierarchy.
     *
     * @return array
     *   A linear array of book links in the order that the links are shown in the
     *   book, so the previous and next pages are the elements before and after the
     *   element corresponding to the current node. The children of the current node
     *   (if any) will come immediately after it in the array, and links will only
     *   be fetched as deep as one level deeper than $book_link.
     */
    public function bookTreeGetFlat(array $book_link);
    
    /**
     * Returns an array of all books.
     *
     * This list may be used for generating a list of all the books, or for
     * building the options for a form select.
     *
     * @return array
     *   An array of all books.
     */
    public function getAllBooks();
    
    /**
     * Handles additions and updates to the book outline.
     *
     * This common helper function performs all additions and updates to the book
     * outline through node addition, node editing, node deletion, or the outline
     * tab.
     *
     * @param \Drupal\node\NodeInterface $node
     *   The node that is being saved, added, deleted, or moved.
     *
     * @return bool
     *   TRUE if the book link was saved; FALSE otherwise.
     */
    public function updateOutline(NodeInterface $node);
    
    /**
     * Saves a link for a single book entry to the book.
     *
     * @param array $link
     *   The link data to save. $link['nid'] must be set. Other keys in this array
     *   get default values from
     *   \Drupal\book\BookManagerInterface::getLinkDefaults(). The array keys
     *   available to be set are documented in
     *   \Drupal\book\BookOutlineStorageInterface::loadMultiple().
     * @param bool $new
     *   Whether this is a link to a new book entry.
     *
     * @return array
     *   The book entry link information. This is $link with values added or
     *   updated.
     *
     * @see \Drupal\book\BookManagerInterface::getLinkDefaults()
     * @see \Drupal\book\BookOutlineStorageInterface::loadMultiple()
     */
    public function saveBookLink(array $link, $new);
    
    /**
     * Returns an array with default values for a book page's menu link.
     *
     * @param string|int $nid
     *   The ID of the node whose menu link is being created.
     *
     * @return array
     *   The default values for the menu link.
     */
    public function getLinkDefaults($nid);
    public function getBookParents(array $item, array $parent = []);
    
    /**
     * Builds the common elements of the book form for the node and outline forms.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     * @param \Drupal\node\NodeInterface $node
     *   The node whose form is being viewed.
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The account viewing the form.
     * @param bool $collapsed
     *   If TRUE, the fieldset starts out collapsed.
     *
     * @return array
     *   The form structure, with the book elements added.
     */
    public function addFormElements(array $form, FormStateInterface $form_state, NodeInterface $node, AccountInterface $account, $collapsed = TRUE);
    
    /**
     * Deletes node's entry from book table.
     *
     * @param int $nid
     *   The nid to delete.
     */
    public function deleteFromBook($nid);
    
    /**
     * Returns a rendered menu tree.
     *
     * The menu item's LI element is given one of the following classes:
     * - expanded: The menu item is showing its submenu.
     * - collapsed: The menu item has a submenu which is not shown.
     *
     * @param array $tree
     *   A data structure representing the tree as returned from buildBookOutlineData.
     *
     * @return array
     *   A structured array to be rendered by
     *   \Drupal\Core\Render\RendererInterface::render().
     *
     * @see \Drupal\Core\Menu\MenuLinkTree::build
     */
    public function bookTreeOutput(array $tree);
    
    /**
     * Checks access and performs dynamic operations for each link in the tree.
     *
     * @param array $tree
     *   The book tree you wish to operate on.
     * @param array $node_links
     *   A collection of node link references generated from $tree by
     *   menu_tree_collect_node_links().
     */
    public function bookTreeCheckAccess(&$tree, $node_links = []);
    
    /**
     * Gets the data representing a subtree of the book hierarchy.
     *
     * The root of the subtree will be the link passed as a parameter, so the
     * returned tree will contain this item and all its descendants in the menu
     * tree.
     *
     * @param array $link
     *   A fully loaded book link.
     *
     * @return array
     *   A subtree of book links in an array, in the order they should be rendered.
     */
    public function bookSubtreeData($link);
    
    /**
     * Determines if a node can be removed from the book.
     *
     * A node can be removed from a book if it is actually in a book and it either
     * is not a top-level page or is a top-level page with no children.
     *
     * @param \Drupal\node\NodeInterface $node
     *   The node to remove from the outline.
     *
     * @return bool
     *   TRUE if a node can be removed from the book, FALSE otherwise.
     */
    public function checkNodeIsRemovable(NodeInterface $node);

}