Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/book/src/BookBreadcrumbBuilder.php

@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookBreadcrumbBuilder.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Access\AccessManagerInterface;
+use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\node\NodeInterface;
+
+/**
+ * Provides a breadcrumb builder for nodes in a book.
+ */
+class BookBreadcrumbBuilder implements BreadcrumbBuilderInterface {
+  use StringTranslationTrait;
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * The access manager.
+   *
+   * @var \Drupal\Core\Access\AccessManagerInterface
+   */
+  protected $accessManager;
+
+  /**
+   * The current user account.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $account;
+
+  /**
+   * Constructs the BookBreadcrumbBuilder.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager service.
+   * @param \Drupal\Core\Access\AccessManagerInterface $access_manager
+   *   The access manager.
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The current user account.
+   */
+  public function __construct(EntityManagerInterface $entity_manager, AccessManagerInterface $access_manager, AccountInterface $account) {
+    $this->nodeStorage = $entity_manager->getStorage('node');
+    $this->accessManager = $access_manager;
+    $this->account = $account;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(RouteMatchInterface $route_match) {
+    $node = $route_match->getParameter('node');
+    return $node instanceof NodeInterface && !empty($node->book);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(RouteMatchInterface $route_match) {
+    $book_nids = array();
+    $links = array(Link::createFromRoute($this->t('Home'), '<front>'));
+    $book = $route_match->getParameter('node')->book;
+    $depth = 1;
+    // We skip the current node.
+    while (!empty($book['p' . ($depth + 1)])) {
+      $book_nids[] = $book['p' . $depth];
+      $depth++;
+    }
+    $parent_books = $this->nodeStorage->loadMultiple($book_nids);
+    if (count($parent_books) > 0) {
+      $depth = 1;
+      while (!empty($book['p' . ($depth + 1)])) {
+        if (!empty($parent_books[$book['p' . $depth]]) && ($parent_book = $parent_books[$book['p' . $depth]])) {
+          if ($parent_book->access('view', $this->account)) {
+            $links[] = Link::createFromRoute($parent_book->label(), 'entity.node.canonical', array('node' => $parent_book->id()));
+          }
+        }
+        $depth++;
+      }
+    }
+    return $links;
+  }
+
+}