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 comment storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $storage;
    
    /**
     * Constructs the CommentBreadcrumbBuilder.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager) {
        $this->storage = $entity_type_manager->getStorage('comment');
    }
    
    /**
     * {@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 = $this->storage
            ->load($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;
    }

}