class EntitySchemaSubscriber

class EntitySchemaSubscriber implements EntityTypeListenerInterface, EventSubscriberInterface {
    use EntityTypeEventSubscriberTrait;
    use StringTranslationTrait;
    
    /**
     * The definition update manager.
     *
     * @var \Drupal\Core\Entity\EntityDefinitionUpdateManagerInterface
     */
    protected $entityDefinitionUpdateManager;
    
    /**
     * The last installed schema definitions.
     *
     * @var \Drupal\Core\Entity\EntityLastInstalledSchemaRepositoryInterface
     */
    protected $entityLastInstalledSchemaRepository;
    
    /**
     * The workspace information service.
     *
     * @var \Drupal\workspaces\WorkspaceInformationInterface
     */
    protected $workspaceInfo;
    
    /**
     * Constructs a new EntitySchemaSubscriber.
     *
     * @param \Drupal\Core\Entity\EntityDefinitionUpdateManagerInterface $entityDefinitionUpdateManager
     *   Definition update manager.
     * @param \Drupal\Core\Entity\EntityLastInstalledSchemaRepositoryInterface $entityLastInstalledSchemaRepository
     *   Last definitions.
     * @param \Drupal\workspaces\WorkspaceInformationInterface $workspace_information
     *   The workspace information service.
     */
    public function __construct(EntityDefinitionUpdateManagerInterface $entityDefinitionUpdateManager, EntityLastInstalledSchemaRepositoryInterface $entityLastInstalledSchemaRepository, WorkspaceInformationInterface $workspace_information) {
        $this->entityDefinitionUpdateManager = $entityDefinitionUpdateManager;
        $this->entityLastInstalledSchemaRepository = $entityLastInstalledSchemaRepository;
        $this->workspaceInfo = $workspace_information;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        return static::getEntityTypeEvents();
    }
    
    /**
     * {@inheritdoc}
     */
    public function onEntityTypeCreate(EntityTypeInterface $entity_type) {
        // If the entity type is supported by Workspaces, add the revision metadata
        // field.
        if ($this->workspaceInfo
            ->isEntityTypeSupported($entity_type)) {
            $this->addRevisionMetadataField($entity_type);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function onFieldableEntityTypeCreate(EntityTypeInterface $entity_type, array $field_storage_definitions) {
        $this->onEntityTypeCreate($entity_type);
    }
    
    /**
     * {@inheritdoc}
     */
    public function onEntityTypeUpdate(EntityTypeInterface $entity_type, EntityTypeInterface $original) {
        // If the entity type is now supported by Workspaces, add the revision
        // metadata field.
        if ($this->workspaceInfo
            ->isEntityTypeSupported($entity_type) && !$this->workspaceInfo
            ->isEntityTypeSupported($original)) {
            $this->addRevisionMetadataField($entity_type);
        }
        // If the entity type is no longer supported by Workspaces, remove the
        // revision metadata field.
        if ($this->workspaceInfo
            ->isEntityTypeSupported($original) && !$this->workspaceInfo
            ->isEntityTypeSupported($entity_type)) {
            $revision_metadata_keys = $original->get('revision_metadata_keys');
            $field_storage_definition = $this->entityLastInstalledSchemaRepository
                ->getLastInstalledFieldStorageDefinitions($entity_type->id())[$revision_metadata_keys['workspace']];
            $this->entityDefinitionUpdateManager
                ->uninstallFieldStorageDefinition($field_storage_definition);
            // We are only removing a revision metadata key so we don't need to go
            // through the entity update process.
            $entity_type->setRevisionMetadataKey('workspace', NULL);
            $this->entityLastInstalledSchemaRepository
                ->setLastInstalledDefinition($entity_type);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function onFieldableEntityTypeUpdate(EntityTypeInterface $entity_type, EntityTypeInterface $original, array $field_storage_definitions, array $original_field_storage_definitions, ?array &$sandbox = NULL) {
        $this->onEntityTypeUpdate($entity_type, $original);
    }
    
    /**
     * {@inheritdoc}
     */
    public function onEntityTypeDelete(EntityTypeInterface $entity_type) {
        // Nothing to do here.
    }
    
    /**
     * Adds the 'workspace' revision metadata field to an entity type.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type that has been installed or updated.
     */
    protected function addRevisionMetadataField(EntityTypeInterface $entity_type) {
        if (!$entity_type->hasRevisionMetadataKey('workspace')) {
            // Bail out if there's an existing field called 'workspace'.
            if ($this->entityDefinitionUpdateManager
                ->getFieldStorageDefinition('workspace', $entity_type->id())) {
                throw new \RuntimeException("An existing 'workspace' field was found for the '{$entity_type->id()}' entity type. Set the 'workspace' revision metadata key to use a different field name and run this update function again.");
            }
            // We are only adding a revision metadata key so we don't need to go
            // through the entity update process.
            $entity_type->setRevisionMetadataKey('workspace', 'workspace');
            $this->entityLastInstalledSchemaRepository
                ->setLastInstalledDefinition($entity_type);
        }
        $this->entityDefinitionUpdateManager
            ->installFieldStorageDefinition($entity_type->getRevisionMetadataKey('workspace'), $entity_type->id(), 'workspaces', $this->getWorkspaceFieldDefinition());
    }
    
    /**
     * Gets the base field definition for the 'workspace' revision metadata field.
     *
     * @return \Drupal\Core\Field\BaseFieldDefinition
     *   The base field definition.
     */
    protected function getWorkspaceFieldDefinition() {
        return BaseFieldDefinition::create('entity_reference')->setLabel($this->t('Workspace'))
            ->setDescription($this->t('Indicates the workspace that this revision belongs to.'))
            ->setSetting('target_type', 'workspace')
            ->setInternal(TRUE)
            ->setTranslatable(FALSE)
            ->setRevisionable(TRUE);
    }

}