contacts_events-8.x-1.x-dev/src/Plugin/Validation/Constraint/UniqueFieldValueForGivenReferenceFieldValidator.php

<?php

namespace Drupal\contacts_events\Plugin\Validation\Constraint;

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Entity\Query\QueryInterface;
use Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates that a reference field is unique for a given entity type and field.
 */
class UniqueFieldValueForGivenReferenceFieldValidator extends ConstraintValidator {

  /**
   * {@inheritdoc}
   */
  public function validate($items, Constraint $constraint) {
    /** @var \Drupal\Core\Field\FieldItemInterface $item */
    if (!$item = $items->first()) {
      return;
    }
    $field_name = $items->getFieldDefinition()->getName();
    /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
    $entity = $items->getEntity();
    /** @var \Drupal\contacts_events\Plugin\Validation\Constraint\UniqueFieldValueForGivenReferenceField $constraint */
    $grouping_field = $constraint->getGroupingFieldOption();
    $grouping_entity = $entity->get($grouping_field)->target_id;
    $entity_type_id = $entity->getEntityTypeId();
    $id_key = $entity->getEntityType()->getKey('id');

    // Field main property is not always 'value', eg entity reference.
    $field_value_property = $item->mainPropertyName();
    $field_value = $item->{$field_value_property};
    if ($field_value) {
      $query = \Drupal::entityQuery($entity_type_id)
        // The id could be NULL, so we cast it to 0 in that case.
        ->accessCheck(TRUE)
        ->condition($id_key, (int) $items->getEntity()->id(), '<>')
        ->condition($field_name, $field_value)
        ->condition($grouping_field, $grouping_entity)
        ->range(0, 1)
        ->count();
      $this->alterQuery($query);
      $value_taken = (bool) $query->execute();

      if ($value_taken) {
        $params = [
          '%value' => $field_value,
          '@entity_type' => $entity->getEntityType()->getSingularLabel(),
          '@field_name' => mb_strtolower($items->getFieldDefinition()->getLabel()),
        ];

        // Get entity label if grouping field is an entity reference.
        if ($item instanceof EntityReferenceItem) {
          $reference_entity = $item->entity;

          if ($reference_entity && $reference_entity instanceof EntityInterface) {
            $params['%value_label'] = $reference_entity->label();
          }
        }
        $this->context->addViolation($constraint->getMessage(), $params);
      }
    }
  }

  /**
   * Alter the query checking for existing values.
   *
   * @param \Drupal\Core\Entity\Query\QueryInterface $query
   *   The query.
   */
  protected function alterQuery(QueryInterface $query) {
    // Allows extending validators to add custom conditions and alter the query.
  }

}