import UIKit

class LiveSquishButton: UIView {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        updateSquish(with: 0.05)
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event)
        updateSquish(with: touches)
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)
        updateSquish(with: 0)
    }

    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesCancelled(touches, with: event)
        updateSquish(with: 0)
    }

    private func updateSquish(with touches: Set<UITouch>) {
        guard let touch = touches.first else {
            return
        }

        let force: CGFloat
        if traitCollection.forceTouchCapability == .available, touch.force > 0 {
            force = touch.force
        } else {
            force = 1 // this occurs both when the touch moves (in which case we should not update the scale) and when using the mouse (in which case we should use a force of 1)
        }

        updateSquish(with: force + 0.05)
    }

    private func updateSquish(with force: CGFloat) {
        let scale = 1 - 0.01 * force
        transform = CGAffineTransform(scaleX: scale, y: scale)
    }
}


@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        let button = LiveSquishButton(frame: CGRect(x: 100, y: 100, width: 100, height: 100))
        button.backgroundColor = .red
        button.layer.cornerRadius = 20

        let container = UIView()
        container.backgroundColor = .lightGray
        container.addSubview(button)
        let vc = UIViewController()
        vc.view = container

        let window = UIWindow()
        self.window = window
        window.rootViewController = vc
        window.makeKeyAndVisible()

        return true
    }
}