class ManagedStorage

final class ManagedStorage implements StorageInterface {
    
    /**
     * The decorated storage.
     *
     * @var \Drupal\Core\Config\StorageInterface
     */
    protected $storage;
    
    /**
     * The storage manager to get the storage to decorate.
     *
     * @var \Drupal\Core\Config\StorageManagerInterface
     */
    protected $manager;
    
    /**
     * ManagedStorage constructor.
     *
     * @param \Drupal\Core\Config\StorageManagerInterface $manager
     *   The storage manager.
     */
    public function __construct(StorageManagerInterface $manager) {
        $this->manager = $manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public function exists($name) {
        return $this->getStorage()
            ->exists($name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function read($name) {
        return $this->getStorage()
            ->read($name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function readMultiple(array $names) {
        return $this->getStorage()
            ->readMultiple($names);
    }
    
    /**
     * {@inheritdoc}
     */
    public function write($name, array $data) {
        return $this->getStorage()
            ->write($name, $data);
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete($name) {
        return $this->getStorage()
            ->delete($name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function rename($name, $new_name) {
        return $this->getStorage()
            ->rename($name, $new_name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function encode($data) {
        return $this->getStorage()
            ->encode($data);
    }
    
    /**
     * {@inheritdoc}
     */
    public function decode($raw) {
        return $this->getStorage()
            ->decode($raw);
    }
    
    /**
     * {@inheritdoc}
     */
    public function listAll($prefix = '') {
        return $this->getStorage()
            ->listAll($prefix);
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteAll($prefix = '') {
        return $this->getStorage()
            ->deleteAll($prefix);
    }
    
    /**
     * {@inheritdoc}
     */
    public function createCollection($collection) {
        // We return the collection directly.
        // This means that the collection will not be an instance of ManagedStorage
        // But this doesn't matter because the storage is retrieved from the
        // manager only the first time it is accessed.
        return $this->getStorage()
            ->createCollection($collection);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAllCollectionNames() {
        return $this->getStorage()
            ->getAllCollectionNames();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCollectionName() {
        return $this->getStorage()
            ->getCollectionName();
    }
    
    /**
     * Get the decorated storage from the manager if necessary.
     *
     * @return \Drupal\Core\Config\StorageInterface
     *   The config storage.
     */
    protected function getStorage() {
        // Get the storage from the manager the first time it is needed.
        if (!isset($this->storage)) {
            $this->storage = $this->manager
                ->getStorage();
        }
        return $this->storage;
    }

}