class TermBreadcrumbBuilder

class TermBreadcrumbBuilder implements BreadcrumbBuilderInterface {
  use StringTranslationTrait;
  
  /**
   * The entity repository manager.
   *
   * @var \Drupal\Core\Entity\EntityRepositoryInterface
   */
  protected $entityRepository;
  
  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;
  
  /**
   * Constructs the TermBreadcrumbBuilder.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
   *   The entity repository.
   */
  public function __construct(EntityTypeManagerInterface $entity_type_manager, EntityRepositoryInterface $entity_repository) {
    $this->entityTypeManager = $entity_type_manager;
    $this->entityRepository = $entity_repository;
  }
  
  /**
   * {@inheritdoc}
   */
  public function applies(RouteMatchInterface $route_match, ?CacheableMetadata $cacheable_metadata = NULL) {
    // @todo Remove null safe operator in Drupal 12.0.0, see
    //   https://www.drupal.org/project/drupal/issues/3459277.
    $cacheable_metadata?->addCacheContexts([
      'route',
    ]);
    return $route_match->getRouteName() == 'entity.taxonomy_term.canonical' && $route_match->getParameter('taxonomy_term') instanceof TermInterface;
  }
  
  /**
   * {@inheritdoc}
   */
  public function build(RouteMatchInterface $route_match) {
    $breadcrumb = new Breadcrumb();
    $breadcrumb->addLink(Link::createFromRoute($this->t('Home'), '<front>'));
    $term = $route_match->getParameter('taxonomy_term');
    // Breadcrumb needs to have terms cacheable metadata as a cacheable
    // dependency even though it is not shown in the breadcrumb because e.g. its
    // parent might have changed.
    $breadcrumb->addCacheableDependency($term);
    // @todo This overrides any other possible breadcrumb and is a pure
    //   hard-coded presumption. Make this behavior configurable per
    //   vocabulary or term.
    $parents = $this->entityTypeManager
      ->getStorage('taxonomy_term')
      ->loadAllParents($term->id());
    // Remove current term being accessed.
    array_shift($parents);
    foreach (array_reverse($parents) as $term) {
      $term = $this->entityRepository
        ->getTranslationFromContext($term);
      $breadcrumb->addCacheableDependency($term);
      $breadcrumb->addLink(Link::createFromRoute($term->getName(), 'entity.taxonomy_term.canonical', [
        'taxonomy_term' => $term->id(),
      ]));
    }
    // @todo Remove in Drupal 12.0.0, will be added from ::applies(). See
    //   https://www.drupal.org/project/drupal/issues/3459277
    $breadcrumb->addCacheContexts([
      'route',
    ]);
    return $breadcrumb;
  }

}