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

core/modules/book/src/BookExport.php

@@ -0,0 +1,151 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookExport.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\node\Entity\Node;
+use Drupal\node\NodeInterface;
+
+/**
+ * Provides methods for exporting book to different formats.
+ *
+ * If you would like to add another format, swap this class in container.
+ */
+class BookExport {
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * The node view builder.
+   *
+   * @var \Drupal\Core\Entity\EntityViewBuilderInterface
+   */
+  protected $viewBuilder;
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a BookExport object.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entityManager
+   *   The entity manager.
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(EntityManagerInterface $entityManager, BookManagerInterface $book_manager) {
+    $this->nodeStorage = $entityManager->getStorage('node');
+    $this->viewBuilder = $entityManager->getViewBuilder('node');
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * Generates HTML for export when invoked by book_export().
+   *
+   * The given node is embedded to its absolute depth in a top level section. For
+   * example, a child node with depth 2 in the hierarchy is contained in
+   * (otherwise empty) <div> elements corresponding to depth 0 and depth 1.
+   * This is intended to support WYSIWYG output - e.g., level 3 sections always
+   * look like level 3 sections, no matter their depth relative to the node
+   * selected to be exported as printer-friendly HTML.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node to export.
+   *
+   * @throws \Exception
+   *   Thrown when the node was not attached to a book.
+   *
+   * @return array
+   *   A render array representing the HTML for a node and its children in the
+   *   book hierarchy.
+   */
+  public function bookExportHtml(NodeInterface $node) {
+    if (!isset($node->book)) {
+      throw new \Exception();
+    }
+
+    $tree = $this->bookManager->bookSubtreeData($node->book);
+    $contents = $this->exportTraverse($tree, array($this, 'bookNodeExport'));
+    return array(
+      '#theme' => 'book_export_html',
+      '#title' => $node->label(),
+      '#contents' => $contents,
+      '#depth' => $node->book['depth'],
+      '#cache' => [
+        'tags' => $node->getEntityType()->getListCacheTags(),
+      ],
+    );
+  }
+
+  /**
+   * Traverses the book tree to build printable or exportable output.
+   *
+   * During the traversal, the callback is applied to each node and is called
+   * recursively for each child of the node (in weight, title order).
+   *
+   * @param array $tree
+   *   A subtree of the book menu hierarchy, rooted at the current page.
+   * @param callable $callable
+   *   A callback to be called upon visiting a node in the tree.
+   *
+   * @return string
+   *   The output generated in visiting each node.
+   */
+  protected function exportTraverse(array $tree, $callable) {
+    // If there is no valid callable, use the default callback.
+    $callable = !empty($callable) ? $callable : array($this, 'bookNodeExport');
+
+    $build = array();
+    foreach ($tree as $data) {
+      // Note- access checking is already performed when building the tree.
+      if ($node = $this->nodeStorage->load($data['link']['nid'])) {
+        $children = $data['below'] ? $this->exportTraverse($data['below'], $callable) : '';
+        $build[] = call_user_func($callable, $node, $children);
+      }
+    }
+
+    return $build;
+  }
+
+  /**
+   * Generates printer-friendly HTML for a node.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node that will be output.
+   * @param string $children
+   *   (optional) All the rendered child nodes within the current node. Defaults
+   *   to an empty string.
+   *
+   * @return array
+   *   A render array for the exported HTML of a given node.
+   *
+   * @see \Drupal\book\BookExport::exportTraverse()
+   */
+  protected function bookNodeExport(NodeInterface $node, $children = '') {
+    $build = $this->viewBuilder->view($node, 'print', NULL);
+    unset($build['#theme']);
+
+    return array(
+      '#theme' => 'book_node_export_html',
+      '#content' => $build,
+      '#node' => $node,
+      '#children' => $children,
+    );
+  }
+
+}