Spring animation with stiffness and damping for the old UIView animation API

UIView+SpringAnimation.swift

extension UIView {
    @MainActor class func animate(
        springStiffness stiffness: CGFloat,
        damping: CGFloat,
        initialSpringVelocity: CGFloat = 0.0,
        delay: TimeInterval = 0.0,
        options: UIView.AnimationOptions = [],
        animations: () -> Void,
        completion: ((Bool) -> Void)? = nil
    ) {
        let (duration, bounce) = durationAndBounce(forStiffness: stiffness, damping: damping)
        animate(
            springDuration: duration,
            bounce: bounce,
            initialSpringVelocity: initialSpringVelocity,
            delay: delay,
            options: options,
            animations: animations,
            completion: completion,
        )
    }

    private class func durationAndBounce(forStiffness stiffness: CGFloat, damping: CGFloat) -> (duration: TimeInterval, bounce: CGFloat) {
        let duration = 2 * .pi / sqrt(stiffness)
        let dampingThreshold = 4 * .pi / duration
        let bounce: CGFloat
        if damping < dampingThreshold {
            bounce = 1 - damping * duration / (4 * .pi)
        } else {
            bounce = (4 * .pi) / (damping * duration) - 1
        }
        return (duration: TimeInterval(duration), bounce: bounce)
    }
}