class ContentModerationState

class ContentModerationState extends ContentEntityBase implements ContentModerationStateInterface {
    use EntityOwnerTrait;
    
    /**
     * {@inheritdoc}
     */
    public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
        $fields = parent::baseFieldDefinitions($entity_type);
        $fields += static::ownerBaseFieldDefinitions($entity_type);
        $fields['uid']->setLabel(t('User'))
            ->setDescription(t('The username of the entity creator.'))
            ->setRevisionable(TRUE);
        $fields['workflow'] = BaseFieldDefinition::create('entity_reference')->setLabel(t('Workflow'))
            ->setDescription(t('The workflow the moderation state is in.'))
            ->setSetting('target_type', 'workflow')
            ->setRequired(TRUE)
            ->setRevisionable(TRUE);
        $fields['moderation_state'] = BaseFieldDefinition::create('string')->setLabel(t('Moderation state'))
            ->setDescription(t('The moderation state of the referenced content.'))
            ->setRequired(TRUE)
            ->setTranslatable(TRUE)
            ->setRevisionable(TRUE);
        $fields['content_entity_type_id'] = BaseFieldDefinition::create('string')->setLabel(t('Content entity type ID'))
            ->setDescription(t('The ID of the content entity type this moderation state is for.'))
            ->setRequired(TRUE)
            ->setSetting('max_length', EntityTypeInterface::ID_MAX_LENGTH)
            ->setRevisionable(TRUE);
        $fields['content_entity_id'] = BaseFieldDefinition::create('integer')->setLabel(t('Content entity ID'))
            ->setDescription(t('The ID of the content entity this moderation state is for.'))
            ->setRequired(TRUE)
            ->setRevisionable(TRUE);
        $fields['content_entity_revision_id'] = BaseFieldDefinition::create('integer')->setLabel(t('Content entity revision ID'))
            ->setDescription(t('The revision ID of the content entity this moderation state is for.'))
            ->setRequired(TRUE)
            ->setRevisionable(TRUE);
        return $fields;
    }
    
    /**
     * Creates or updates an entity's moderation state whilst saving that entity.
     *
     * @param \Drupal\content_moderation\Entity\ContentModerationState $content_moderation_state
     *   The content moderation entity content entity to create or save.
     *
     * @internal
     *   This method should only be called as a result of saving the related
     *   content entity.
     */
    public static function updateOrCreateFromEntity(ContentModerationState $content_moderation_state) {
        $content_moderation_state->realSave();
    }
    
    /**
     * Loads a content moderation state entity.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   A moderated entity object.
     *
     * @return \Drupal\content_moderation\Entity\ContentModerationStateInterface|null
     *   The related content moderation state or NULL if none could be found.
     *
     * @internal
     *   This method should only be called by code directly handling the
     *   ContentModerationState entity objects.
     */
    public static function loadFromModeratedEntity(EntityInterface $entity) {
        $content_moderation_state = NULL;
        $moderation_info = \Drupal::service('content_moderation.moderation_information');
        if ($moderation_info->isModeratedEntity($entity)) {
            
            /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
            $storage = \Drupal::entityTypeManager()->getStorage('content_moderation_state');
            // New entities may not have a loaded revision ID at this point, but the
            // creation of a content moderation state entity may have already been
            // triggered elsewhere. In this case we have to match on the revision ID
            // (instead of the loaded revision ID).
            $revision_id = $entity->getLoadedRevisionId() ?: $entity->getRevisionId();
            $ids = $storage->getQuery()
                ->accessCheck(FALSE)
                ->condition('content_entity_type_id', $entity->getEntityTypeId())
                ->condition('content_entity_id', $entity->id())
                ->condition('workflow', $moderation_info->getWorkflowForEntity($entity)
                ->id())
                ->condition('content_entity_revision_id', $revision_id)
                ->allRevisions()
                ->execute();
            if ($ids) {
                
                /** @var \Drupal\content_moderation\Entity\ContentModerationStateInterface $content_moderation_state */
                $content_moderation_state = $storage->loadRevision(key($ids));
            }
        }
        return $content_moderation_state;
    }
    
    /**
     * {@inheritdoc}
     */
    public function save() {
        $related_entity = \Drupal::entityTypeManager()->getStorage($this->content_entity_type_id->value)
            ->loadRevision($this->content_entity_revision_id->value);
        if ($related_entity instanceof TranslatableInterface) {
            $related_entity = $related_entity->getTranslation($this->activeLangcode);
        }
        $related_entity->moderation_state = $this->moderation_state;
        return $related_entity->save();
    }
    
    /**
     * Saves an entity permanently.
     *
     * When saving existing entities, the entity is assumed to be complete,
     * partial updates of entities are not supported.
     *
     * @return int
     *   Either SAVED_NEW or SAVED_UPDATED, depending on the operation performed.
     *
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   In case of failures an exception is thrown.
     */
    protected function realSave() {
        return parent::save();
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getFieldsToSkipFromTranslationChangesCheck() {
        $field_names = parent::getFieldsToSkipFromTranslationChangesCheck();
        // We need to skip the parent entity revision ID, since that will always
        // change on every save, otherwise every translation would be marked as
        // affected regardless of actual changes.
        $field_names[] = 'content_entity_revision_id';
        return $field_names;
    }

}