class SuperellipseFpsTestController: UIViewController {

    let maskImage = #imageLiteral(resourceName: "superellipse_mask").resizeIfBigger(size: CGSize.init(width: 60, height: 60), opaque: false).cgImage!

    var imageIndex = 0
    let images: [UIImage] = [#imageLiteral(resourceName: "iv1"), #imageLiteral(resourceName: "iv3"), #imageLiteral(resourceName: "iv4")]
    func fetchNextImage() -> UIImage {
        imageIndex += randomInRange(1, images.count)
        imageIndex %= images.count
        return images[imageIndex]
    }

    var timer: Timer!

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .lightGray
//      timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(timerDidTick), userInfo: nil, repeats: true)
    }

    func animateChanges() {
        UIView.animate(withDuration: 0.6, animations: {
            self.installImages()
        }) { [weak self] _ in
            self?.animateChanges()
        }
    }

//  @objc func timerDidTick() {
//      installImages()
//  }

    enum Mode {
        case bezier
        case image
    }

    let mode = Mode.bezier

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        for _ in 0 ..< 60 {
            let iv = UIImageView()
            iv.contentMode = .scaleToFill
            imageViews.append(iv)
            view.addSubview(iv)

//          installBezierMask(to: iv)
//          installImageMask(to: iv)
        }
        animateChanges()
    }

    func installBezierMask(to imageView: UIImageView) {
        imageView.useSuperellipseMask = true
    }

    func installImageMask(to imageView: UIImageView) {
        let maskLayer = CALayer()
        maskLayer.contents = maskImage
        imageView.layer.mask = maskLayer
    }

    var imageViewFrame: CGRect {
        let width = CGFloat(60) // min(CGFloat(randomInRange(60, Int(view.frame.width / 2))), 120)
        let height = width
        let x = CGFloat(randomInRange(0, Int(view.frame.width - width)))
        let y = CGFloat(randomInRange(0, Int(view.frame.height - height)))
        return CGRect(x: x, y: y, width: width, height: height)
    }

    var imageViews = [UIImageView]()

    func installImages() {
        for imageView in imageViews {
            imageView.frame = self.imageViewFrame
            imageView.image = fetchNextImage()

            switch mode {
            case .bezier:
                imageView.useSuperellipseMask = false
                installBezierMask(to: imageView)
            case .image:
                imageView.layer.mask = nil
                installImageMask(to: imageView)
                imageView.layer.mask?.frame = imageView.bounds
            }
        }
    }

    func randomInRange(_ lo: Int, _ hi : Int) -> Int {
        return lo + Int(arc4random_uniform(UInt32(hi - lo + 1)))
    }

}