pm-4.1.x-dev/src/Service/PmHierarchy.php

<?php

declare(strict_types=1);

namespace Drupal\pm\Service;

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\EntityTypeManagerInterface;

/**
 * Helper service to work with hierarchy of PM Entities.
 */
final class PmHierarchy {

  /**
   * Constructs a PmHierarchy object.
   */
  public function __construct(
    private readonly PmConfig $pmConfig,
    private readonly EntityTypeManagerInterface $entityTypeManager,
  ) {}

  /**
   * Get child entities based on hierarchy.
   *
   * @param \Drupal\Core\Entity\EntityInterface $entity
   *   The entity for which the child item needs to be found.
   *
   * @return array
   *   The child entities.
   */
  public function getChildren(EntityInterface $entity): array {
    $entity_type = $entity->getEntityTypeId();
    $bundle = $entity->bundle();
    $children_ref_field = $this->pmConfig->getChildReferenceFieldName($entity_type, $bundle);
    return $entity->{$children_ref_field}?->referencedEntities() ?: [];
  }


  /**
   * Get parent of current entity based on hierarchy.
   *
   * @param \Drupal\Core\Entity\EntityInterface $entity
   *   The entity for which the parent item needs to be found.
   *
   * @return \Drupal\Core\Entity\EntityInterface|null
   *   The parent entity
   */
  public function getParent(EntityInterface $entity): ?EntityInterface {
    $entity_type = $entity->getEntityTypeId();
    $parent_ref_field = $this->pmConfig->getParentReferenceFieldName($entity_type);
    return $entity->{$parent_ref_field}?->entity;
  }

}