CommentBreadcrumbBuilder.php

<?php

namespace Drupal\comment;

use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
use Drupal\Core\Breadcrumb\Breadcrumb;
use Drupal\Core\Entity\EntityTypeManagerInterface;
use Drupal\Core\Link;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\StringTranslation\StringTranslationTrait;

/**
 * Class to define the comment breadcrumb builder.
 */
class CommentBreadcrumbBuilder implements BreadcrumbBuilderInterface {
  use StringTranslationTrait;

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * Constructs the CommentBreadcrumbBuilder.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
    $this->entityTypeManager = $entity_type_manager;
  }

  /**
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match) {
    return $route_match
      ->getRouteName() == 'comment.reply' && $route_match
      ->getParameter('entity');
  }

  /**
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match) {
    $breadcrumb = new Breadcrumb();
    $breadcrumb
      ->addCacheContexts([
      'route',
    ]);
    $breadcrumb
      ->addLink(Link::createFromRoute($this
      ->t('Home'), '<front>'));
    $entity = $route_match
      ->getParameter('entity');
    $breadcrumb
      ->addLink(new Link($entity
      ->label(), $entity
      ->toUrl()));
    $breadcrumb
      ->addCacheableDependency($entity);
    if (($pid = $route_match
      ->getParameter('pid')) && ($comment = $this->entityTypeManager
      ->getStorage('comment')
      ->load($pid))) {

      /** @var \Drupal\comment\CommentInterface $comment */
      $breadcrumb
        ->addCacheableDependency($comment);

      // Display link to parent comment.
      // @todo Clean-up permalink in https://www.drupal.org/node/2198041
      $breadcrumb
        ->addLink(new Link($comment
        ->getSubject(), $comment
        ->toUrl()));
    }
    return $breadcrumb;
  }

}