class ThemeSettings

class ThemeSettings extends DestinationBase implements ContainerFactoryPluginInterface {
    
    /**
     * The configuration factory.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * Constructs a theme settings destination object.
     *
     * @param array $configuration
     *   Plugin configuration.
     * @param string $plugin_id
     *   The plugin ID.
     * @param mixed $plugin_definition
     *   The plugin definition.
     * @param \Drupal\migrate\Plugin\MigrationInterface $migration
     *   The current migration.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The configuration factory.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, ConfigFactoryInterface $config_factory) {
        parent::__construct($configuration, $plugin_id, $plugin_definition, $migration);
        $this->configFactory = $config_factory;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
        return new static($configuration, $plugin_id, $plugin_definition, $migration, $container->get('config.factory'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function import(Row $row, array $old_destination_id_values = []) {
        $imported = FALSE;
        $config = $this->configFactory
            ->getEditable($row->getDestinationProperty('configuration_name'));
        $theme_settings = $row->getDestination();
        // Remove keys not in theme settings.
        unset($theme_settings['configuration_name']);
        unset($theme_settings['theme_name']);
        unset($theme_settings['legacy_theme_name']);
        if (isset($theme_settings)) {
            theme_settings_convert_to_config($theme_settings, $config);
            $config->save();
            $imported = TRUE;
        }
        return $imported;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['name']['type'] = 'string';
        return $ids;
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        // Theme settings vary by theme, so no specific fields are defined.
        return [];
    }

}