class KeyValueFactory

class KeyValueFactory implements KeyValueFactoryInterface {
    
    /**
     * The specific setting name prefix.
     *
     * The collection name will be prefixed with this constant and used as a
     * setting name. The setting value will be the id of a service.
     */
    const SPECIFIC_PREFIX = 'keyvalue_service_';
    
    /**
     * The default setting name.
     *
     * This is a setting name that will be used if the specific setting does not
     * exist. The setting value will be the id of a service.
     */
    const DEFAULT_SETTING = 'default';
    
    /**
     * The default service id.
     *
     * If the default setting does not exist, this is the default service id.
     */
    const DEFAULT_SERVICE = 'keyvalue.database';
    
    /**
     * Instantiated stores, keyed by collection name.
     *
     * @var array
     */
    protected $stores = [];
    
    /**
     * The service container.
     *
     * @var \Symfony\Component\DependencyInjection\ContainerInterface
     */
    protected $container;
    
    /**
     * Collection-specific storage override options.
     *
     * @var array
     */
    protected $options;
    
    /**
     * @param \Symfony\Component\DependencyInjection\ContainerInterface $container
     *   The service container.
     * @param array $options
     *   (optional) Collection-specific storage override options.
     */
    public function __construct(ContainerInterface $container, array $options = []) {
        $this->container = $container;
        $this->options = $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function get($collection) {
        if (!isset($this->stores[$collection])) {
            if (isset($this->options[$collection])) {
                $service_id = $this->options[$collection];
            }
            elseif (isset($this->options[static::DEFAULT_SETTING])) {
                $service_id = $this->options[static::DEFAULT_SETTING];
            }
            else {
                $service_id = static::DEFAULT_SERVICE;
            }
            $this->stores[$collection] = $this->container
                ->get($service_id)
                ->get($collection);
        }
        return $this->stores[$collection];
    }

}