class ImageToolkitManager

class ImageToolkitManager extends DefaultPluginManager {
    
    /**
     * The config factory.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * Constructs the ImageToolkitManager object.
     *
     * @param \Traversable $namespaces
     *   An object that implements \Traversable which contains the root paths
     *   keyed by the corresponding namespace to look for plugin implementations.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend instance to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The config factory.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, ConfigFactoryInterface $config_factory) {
        parent::__construct('Plugin/ImageToolkit', $namespaces, $module_handler, 'Drupal\\Core\\ImageToolkit\\ImageToolkitInterface', 'Drupal\\Core\\ImageToolkit\\Annotation\\ImageToolkit');
        $this->setCacheBackend($cache_backend, 'image_toolkit_plugins');
        $this->configFactory = $config_factory;
    }
    
    /**
     * Gets the default image toolkit ID.
     *
     * @return string|bool
     *   ID of the default toolkit, or FALSE on error.
     */
    public function getDefaultToolkitId() {
        $toolkit_id = $this->configFactory
            ->get('system.image')
            ->get('toolkit');
        $toolkits = $this->getAvailableToolkits();
        if (!isset($toolkits[$toolkit_id]) || !class_exists($toolkits[$toolkit_id]['class'])) {
            // The selected toolkit isn't available so return the first one found. If
            // none are available this will return FALSE.
            reset($toolkits);
            $toolkit_id = key($toolkits);
        }
        return $toolkit_id;
    }
    
    /**
     * Gets the default image toolkit.
     *
     * @return \Drupal\Core\ImageToolkit\ImageToolkitInterface
     *   Object of the default toolkit, or FALSE on error.
     */
    public function getDefaultToolkit() {
        if ($toolkit_id = $this->getDefaultToolkitId()) {
            return $this->createInstance($toolkit_id);
        }
        return FALSE;
    }
    
    /**
     * Gets a list of available toolkits.
     *
     * @return array
     *   An array with the toolkit names as keys and the descriptions as values.
     */
    public function getAvailableToolkits() {
        // Use plugin system to get list of available toolkits.
        $toolkits = $this->getDefinitions();
        $output = [];
        foreach ($toolkits as $id => $definition) {
            // Only allow modules that aren't marked as unavailable.
            if (call_user_func($definition['class'] . '::isAvailable')) {
                $output[$id] = $definition;
            }
        }
        return $output;
    }

}