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<?php

/**
 * Implements hook_entity_presave().
 *
 * This hook autamatically sets an unpublish date for events so that they are no
 * longer indexed by search engines after event has occurred.
 */
function unpublisher_entity_presave(Drupal\Core\Entity\EntityInterface $entity) {
  if ($entity instanceof NodeInterface) {
    if ($entity->getType() == 'event') {
      $start_date = date('U', strtotime($entity->field_start_date->value));
      $end_date = date('U', strtotime($entity->field_end_date->value));

      if ($start_date > $end_date) {
        $entity->unpublish_on->value = strtotime('+1 day', $start_date);
      }
      else {
        $entity->unpublish_on->value = strtotime('+1 day', $end_date);
      }
    }
  }
}