class Entity

abstract class Entity extends DestinationBase implements ContainerFactoryPluginInterface, DependentPluginInterface {
    use DependencyTrait;
    use EntityFieldDefinitionTrait;
    
    /**
     * The entity storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $storage;
    
    /**
     * The list of the bundles of this entity type.
     *
     * @var array
     */
    protected $bundles;
    
    /**
     * Construct a new entity.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\migrate\Plugin\MigrationInterface $migration
     *   The migration.
     * @param \Drupal\Core\Entity\EntityStorageInterface $storage
     *   The storage for this entity type.
     * @param array $bundles
     *   The list of bundles this entity type has.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, EntityStorageInterface $storage, array $bundles) {
        $plugin_definition += [
            'label' => $storage->getEntityType()
                ->getPluralLabel(),
        ];
        parent::__construct($configuration, $plugin_id, $plugin_definition, $migration);
        $this->storage = $storage;
        $this->bundles = $bundles;
        $this->supportsRollback = TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
        $entity_type_id = static::getEntityTypeId($plugin_id);
        return new static($configuration, $plugin_id, $plugin_definition, $migration, $container->get('entity_type.manager')
            ->getStorage($entity_type_id), array_keys($container->get('entity_type.bundle.info')
            ->getBundleInfo($entity_type_id)));
    }
    
    /**
     * Gets the bundle for the row taking into account the default.
     *
     * @param \Drupal\migrate\Row $row
     *   The current row we're importing.
     *
     * @return string
     *   The bundle for this row.
     */
    public function getBundle(Row $row) {
        $default_bundle = isset($this->configuration['default_bundle']) ? $this->configuration['default_bundle'] : '';
        $bundle_key = $this->getKey('bundle');
        return $row->getDestinationProperty($bundle_key) ?: $default_bundle;
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields(MigrationInterface $migration = NULL) {
        // TODO: Implement fields() method.
    }
    
    /**
     * Creates or loads an entity.
     *
     * @param \Drupal\migrate\Row $row
     *   The row object.
     * @param array $old_destination_id_values
     *   The old destination IDs.
     *
     * @return \Drupal\Core\Entity\EntityInterface
     *   The entity we are importing into.
     */
    protected function getEntity(Row $row, array $old_destination_id_values) {
        $entity_id = reset($old_destination_id_values) ?: $this->getEntityId($row);
        if (!empty($entity_id) && ($entity = $this->storage
            ->load($entity_id))) {
            // Allow updateEntity() to change the entity.
            $entity = $this->updateEntity($entity, $row) ?: $entity;
        }
        else {
            // Attempt to ensure we always have a bundle.
            if ($bundle = $this->getBundle($row)) {
                $row->setDestinationProperty($this->getKey('bundle'), $bundle);
            }
            // Stubs might need some required fields filled in.
            if ($row->isStub()) {
                $this->processStubRow($row);
            }
            $entity = $this->storage
                ->create($row->getDestination());
            $entity->enforceIsNew();
        }
        return $entity;
    }
    
    /**
     * Gets the entity ID of the row.
     *
     * @param \Drupal\migrate\Row $row
     *   The row of data.
     *
     * @return string
     *   The entity ID for the row that we are importing.
     */
    protected function getEntityId(Row $row) {
        return $row->getDestinationProperty($this->getKey('id'));
    }
    
    /**
     * Returns a specific entity key.
     *
     * @param string $key
     *   The name of the entity key to return.
     *
     * @return string|bool
     *   The entity key, or FALSE if it does not exist.
     *
     * @see \Drupal\Core\Entity\EntityTypeInterface::getKeys()
     */
    protected function getKey($key) {
        return $this->storage
            ->getEntityType()
            ->getKey($key);
    }
    
    /**
     * {@inheritdoc}
     */
    public function rollback(array $destination_identifier) {
        // Delete the specified entity from Drupal if it exists.
        $entity = $this->storage
            ->load(reset($destination_identifier));
        if ($entity) {
            $entity->delete();
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $this->addDependency('module', $this->storage
            ->getEntityType()
            ->getProvider());
        return $this->dependencies;
    }

}