Cards Swipe Direction about cardslayout HOT 7 OPEN

// MARK: - Layout configuration
public var itemSize: CGSize = CGSize(width: 200, height: 100) {
    didSet{
        invalidateLayout()
    }
}

public var spacing: CGFloat = 10.0 {
    didSet{
        invalidateLayout()
    }
}

public var maximumVisibleItems: Int = 3 {
    didSet{
        invalidateLayout()
    }
}

// MARK: UICollectionViewLayout
override open var collectionView: UICollectionView {
    return super.collectionView!
}

override open var collectionViewContentSize: CGSize {
    let itemsCount = CGFloat(collectionView.numberOfItems(inSection: 0))
    return CGSize(width: collectionView.bounds.width * itemsCount, height: collectionView.bounds.height * itemsCount)
}

override open func prepare() {
    super.prepare()
    assert(collectionView.numberOfSections == 1, "Multiple sections aren't supported!")
}

override open func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
    let totalItemsCount = collectionView.numberOfItems(inSection: 0)
    let minVisibleIndex = max(Int(collectionView.contentOffset.y) / Int(collectionView.bounds.height), 0)
    let maxVisibleIndex = min(minVisibleIndex + maximumVisibleItems, totalItemsCount)
    let contentCenterX = collectionView.contentOffset.x + (collectionView.bounds.width / 2.0)
    let deltaOffset = Int(collectionView.contentOffset.y) % Int(collectionView.bounds.height)
    let percentageDeltaOffset = CGFloat(deltaOffset) / collectionView.bounds.height
    let visibleIndices = minVisibleIndex..<maxVisibleIndex
    let attributes: [UICollectionViewLayoutAttributes] = visibleIndices.map { index in
        let indexPath = IndexPath(item: index, section: 0)
        return computeLayoutAttributesForItem(indexPath: indexPath, minVisibleIndex: minVisibleIndex, contentCenterX: contentCenterX, deltaOffset: CGFloat(deltaOffset), percentageDeltaOffset: percentageDeltaOffset)
    }
    return attributes
}

override open func layoutAttributesForItem(at indexPath: IndexPath) -> UICollectionViewLayoutAttributes? {
    let contentCenterX = collectionView.contentOffset.x + (collectionView.bounds.width / 2.0)
    let minVisibleIndex = Int(collectionView.contentOffset.x) / Int(collectionView.bounds.width)
    let deltaOffset = Int(collectionView.contentOffset.y) % Int(collectionView.bounds.height)
    let percentageDeltaOffset = CGFloat(deltaOffset) / collectionView.bounds.height
    return computeLayoutAttributesForItem(indexPath: indexPath, minVisibleIndex: minVisibleIndex, contentCenterX: contentCenterX, deltaOffset: CGFloat(deltaOffset), percentageDeltaOffset: percentageDeltaOffset)
}

override open func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool {
    return true
}

private func scale(at index: Int) -> CGFloat {
    let translatedCoefficient = CGFloat(index) - CGFloat(self.maximumVisibleItems) / 2
    return CGFloat(pow(0.95, translatedCoefficient))
}

private func transform(atCurrentVisibleIndex visibleIndex: Int, percentageOffset: CGFloat) -> CGAffineTransform {
    var rawScale = visibleIndex < maximumVisibleItems ? scale(at: visibleIndex) : 1.0
    if visibleIndex != 0 {
        let previousScale = scale(at: visibleIndex - 1)
        let delta = (previousScale - rawScale) * percentageOffset
        rawScale += delta
    }
    return CGAffineTransform(scaleX: rawScale, y: rawScale)
}

func computeLayoutAttributesForItem(indexPath: IndexPath, minVisibleIndex: Int, contentCenterX: CGFloat, deltaOffset: CGFloat, percentageDeltaOffset: CGFloat) -> UICollectionViewLayoutAttributes {
    let attributes = UICollectionViewLayoutAttributes(forCellWith:indexPath)
    let visibleIndex = indexPath.row - minVisibleIndex
    //Using this to fill up screen with card with fixed % of margin
    attributes.size = CGSize(width: (collectionView.bounds.width - ((collectionView.bounds.width * 2)/100)), height: (collectionView.bounds.height - ((collectionView.bounds.height * 4)/100)))
    let midY = self.collectionView.bounds.midY
    attributes.center = CGPoint(x: contentCenterX , y: midY + spacing * CGFloat(visibleIndex)) // MARK: this x spacing value is the key to home page center cell xposition
    attributes.zIndex = maximumVisibleItems - visibleIndex
    attributes.transform = transform(atCurrentVisibleIndex: visibleIndex, percentageOffset: percentageDeltaOffset)
    switch visibleIndex {
    case 0:
        attributes.center.y -= deltaOffset
    case 1..<maximumVisibleItems:
        attributes.center.y -= spacing * percentageDeltaOffset
        if visibleIndex == maximumVisibleItems - 1 {
            attributes.alpha = percentageDeltaOffset
        }
    default:
        attributes.alpha = 0
    }
    return attributes
}