/// Snaps nearest cell to center of collection view

SingleItemCarouselFlowLayout.swift

final class SingleItemCarouselFlowLayout: UICollectionViewFlowLayout {

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

        guard let collectionView = collectionView else {
            return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
        }

        var offsetAdjustment: CGFloat = .greatestFiniteMagnitude
        let horizontalCenter = proposedContentOffset.x + (collectionView.bounds.width / 2)

        let targetRect = CGRect(x: proposedContentOffset.x, y: 0.0, width: collectionView.bounds.width, height: collectionView.bounds.height)

        super.layoutAttributesForElements(in: targetRect)?.forEach{ layoutAttributes in
            let itemHorizontalCenter = layoutAttributes.center.x

            if abs(itemHorizontalCenter - horizontalCenter) < abs(offsetAdjustment) {
                offsetAdjustment = itemHorizontalCenter - horizontalCenter
            }
        }

        return CGPoint(x: proposedContentOffset.x + offsetAdjustment, y: proposedContentOffset.y)
    }
}