class ReadOnlyStorage

class ReadOnlyStorage implements StorageInterface {
    
    /**
     * The config storage that we are decorating.
     *
     * @var \Drupal\Core\Config\StorageInterface
     */
    protected $storage;
    
    /**
     * Create a ReadOnlyStorage decorating another storage.
     *
     * @param \Drupal\Core\Config\StorageInterface $storage
     *   The decorated storage.
     */
    public function __construct(StorageInterface $storage) {
        $this->storage = $storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public function exists($name) {
        return $this->storage
            ->exists($name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function read($name) {
        return $this->storage
            ->read($name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function readMultiple(array $names) {
        return $this->storage
            ->readMultiple($names);
    }
    
    /**
     * {@inheritdoc}
     */
    public function write($name, array $data) {
        throw new \BadMethodCallException(__METHOD__ . ' is not allowed on a ReadOnlyStorage');
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete($name) {
        throw new \BadMethodCallException(__METHOD__ . ' is not allowed on a ReadOnlyStorage');
    }
    
    /**
     * {@inheritdoc}
     */
    public function rename($name, $new_name) {
        throw new \BadMethodCallException(__METHOD__ . ' is not allowed on a ReadOnlyStorage');
    }
    
    /**
     * {@inheritdoc}
     */
    public function encode($data) {
        return $this->storage
            ->encode($data);
    }
    
    /**
     * {@inheritdoc}
     */
    public function decode($raw) {
        return $this->storage
            ->decode($raw);
    }
    
    /**
     * {@inheritdoc}
     */
    public function listAll($prefix = '') {
        return $this->storage
            ->listAll($prefix);
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteAll($prefix = '') {
        throw new \BadMethodCallException(__METHOD__ . ' is not allowed on a ReadOnlyStorage');
    }
    
    /**
     * {@inheritdoc}
     */
    public function createCollection($collection) {
        return new static($this->storage
            ->createCollection($collection));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getAllCollectionNames() {
        return $this->storage
            ->getAllCollectionNames();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCollectionName() {
        return $this->storage
            ->getCollectionName();
    }

}