text: <?php
  
  namespace Drupal\content_moderation\Plugin\Field;
  
  use Drupal\Core\Entity\ContentEntityInterface;
  use Drupal\Core\Entity\EntityPublishedInterface;
  use Drupal\Core\Field\FieldItemList;
  use Drupal\Core\TypedData\ComputedItemListTrait;
  
  /**
   * A computed field that provides a content entity's moderation state.
   *
   * It links content entities to a moderation state configuration entity via a
   * moderation state content entity.
   */
  class ModerationStateFieldItemList extends FieldItemList {
  
    use ComputedItemListTrait {
      get as traitGet;
    }
  
    /**
     * {@inheritdoc}
     */
    protected function computeValue() {
      $moderation_state = $this->getModerationStateId();
      // Do not store NULL values, in the case where an entity does not have a
      // moderation workflow associated with it, we do not create list items for
      // the computed field.
      if ($moderation_state) {
        // An entity can only have a single moderation state.
        $this->list[0] = $this->createItem(0, $moderation_state);
      }
    }
  
    /**
     * Gets the moderation state ID linked to a content entity revision.
     *
     * @return string|null
     *   The moderation state ID linked to a content entity revision.
     */
    protected function getModerationStateId() {
      $entity = $this->getEntity();
  
      /** @var \Drupal\content_moderation\ModerationInformationInterface $moderation_info */
      $moderation_info = \Drupal::service('content_moderation.moderation_information');
      if (!$moderation_info->shouldModerateEntitiesOfBundle($entity->getEntityType(), $entity->bundle())) {
        return NULL;
      }
  
      // Existing entities will have a corresponding content_moderation_state
      // entity associated with them.
      if (!$entity->isNew() && $content_moderation_state = $this->loadContentModerationStateRevision($entity)) {
        return $content_moderation_state->moderation_state->value;
      }
  
      // It is possible that the bundle does not exist at this point. For example,
      // the node type form creates a fake Node entity to get default values.
      // @see \Drupal\node\NodeTypeForm::form()
      $workflow = $moderation_info->getWorkFlowForEntity($entity);
      return $workflow ? $workflow->getTypePlugin()->getInitialState($entity)->id() : NULL;
    }
  
    /**
     * Load the content moderation state revision associated with an entity.
     *
     * @param \Drupal\Core\Entity\ContentEntityInterface $entity
     *   The entity the content moderation state entity will be loaded from.
     *
     * @return \Drupal\content_moderation\Entity\ContentModerationStateInterface|null
     *   The content_moderation_state revision or FALSE if none exists.
     */
    protected function loadContentModerationStateRevision(ContentEntityInterface $entity) {
      $moderation_info = \Drupal::service('content_moderation.moderation_information');
      $content_moderation_storage = \Drupal::entityTypeManager()->getStorage('content_moderation_state');
  
      $revisions = $content_moderation_storage->getQuery()
        ->condition('content_entity_type_id', $entity->getEntityTypeId())
        ->condition('content_entity_id', $entity->id())
        // Ensure the correct revision is loaded in scenarios where a revision is
        // being reverted.
        ->condition('content_entity_revision_id', $entity->isNewRevision() ? $entity->getLoadedRevisionId() : $entity->getRevisionId())
        ->condition('workflow', $moderation_info->getWorkflowForEntity($entity)->id())
        ->condition('langcode', $entity->language()->getId())
        ->allRevisions()
        ->sort('revision_id', 'DESC')
        ->execute();
      if (empty($revisions)) {
        return NULL;
      }
  
      /** @var \Drupal\content_moderation\Entity\ContentModerationStateInterface $content_moderation_state */
      $content_moderation_state = $content_moderation_storage->loadRevision(key($revisions));
      if ($entity->getEntityType()->hasKey('langcode')) {
        $langcode = $entity->language()->getId();
        if (!$content_moderation_state->hasTranslation($langcode)) {
          $content_moderation_state->addTranslation($langcode, $content_moderation_state->toArray());
        }
        if ($content_moderation_state->language()->getId() !== $langcode) {
          $content_moderation_state = $content_moderation_state->getTranslation($langcode);
        }
      }
      return $content_moderation_state;
    }
  
    /**
     * {@inheritdoc}
     */
    public function get($index) {
      if ($index !== 0) {
        throw new \InvalidArgumentException('An entity can not have multiple moderation states at the same time.');
      }
      return $this->traitGet($index);
    }
  
    /**
     * {@inheritdoc}
     */
    public function onChange($delta) {
      $this->updateModeratedEntity($this->list[$delta]->value);
  
      parent::onChange($delta);
    }
  
    /**
     * {@inheritdoc}
     */
    public function setValue($values, $notify = TRUE) {
      parent::setValue($values, $notify);
      $this->valueComputed = TRUE;
  
      // If the parent created a field item and if the parent should be notified
      // about the change (e.g. this is not initialized with the current value),
      // update the moderated entity.
      if (isset($this->list[0]) && $notify) {
        $this->updateModeratedEntity($this->list[0]->value);
      }
    }
  
    /**
     * Updates the default revision flag and the publishing status of the entity.
     *
     * @param string $moderation_state_id
     *   The ID of the new moderation state.
     */
    protected function updateModeratedEntity($moderation_state_id) {
      $entity = $this->getEntity();
  
      /** @var \Drupal\content_moderation\ModerationInformationInterface $content_moderation_info */
      $content_moderation_info = \Drupal::service('content_moderation.moderation_information');
      $workflow = $content_moderation_info->getWorkflowForEntity($entity);
  
      // Change the entity's default revision flag and the publishing status only
      // if the new workflow state is a valid one.
      if ($workflow && $workflow->getTypePlugin()->hasState($moderation_state_id)) {
        /** @var \Drupal\content_moderation\ContentModerationState $current_state */
        $current_state = $workflow->getTypePlugin()->getState($moderation_state_id);
  
        // This entity is default if it is new, the default revision state, or the
        // default revision is not published.
        if (!$entity->isSyncing()) {
          $update_default_revision = $entity->isNew()
            || $current_state->isDefaultRevisionState()
            || !$content_moderation_info->isDefaultRevisionPublished($entity);
  
          $entity->isDefaultRevision($update_default_revision);
        }
  
        // Update publishing status if it can be updated and if it needs updating.
        $published_state = $current_state->isPublishedState();
        if (($entity instanceof EntityPublishedInterface) && $entity->isPublished() !== $published_state) {
          $published_state ? $entity->setPublished() : $entity->setUnpublished();
        }
      }
    }
  
  }
  