import Viewer

override public func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    guard let collectionView = self.collectionView else { return }

    let viewerController = ViewerController(initialIndexPath: indexPath, collectionView: collectionView)
    viewerController.dataSource = self
    presentViewController(viewerController, animated: false, completion: nil)
}

extension CollectionController: ViewerControllerDataSource {
    func viewerController(_ viewerController: ViewerController, viewableAt indexPath: IndexPath) -> Viewable {
        return photos[indexPath.row]
    }
}