DelightfulAnimations.swift

import UIKit
import PlaygroundSupport

let touchAnimationDuration: TimeInterval = 0.3
var shouldPulse = true

class Handler {
	
	@objc
	func didTouchUpInside(_ button: UIButton) {
		shouldPulse = true
		pulse(button)
	}
	
	@objc
	func flashButton() {
		flashButtonBackground()
	}
	
	@objc
	func didTouch(_ button: UIButton) {
		shouldPulse = false
		button.backgroundColor = .clear
		
		button.layer.borderWidth = 1
		
		let animation = CABasicAnimation(keyPath: "borderWidth")
		animation.fromValue = 1.5
		animation.toValue = 1
		animation.duration = touchAnimationDuration
		
		button.layer.add(animation, forKey: "borderWidthIncrease")
		
		UIView.animate(withDuration: touchAnimationDuration) {
			button.transform = CGAffineTransform(scaleX: 0.95, y: 0.95)
		}
	}
	
	@objc
	func didLift(_ button: UIButton) {
		button.layer.borderWidth = 1.5
		
		let animation = CABasicAnimation(keyPath: "borderWidth")
		animation.fromValue = 1
		animation.toValue = 1.5
		animation.duration = touchAnimationDuration
		
		button.layer.add(animation, forKey: "borderWidthDecrease")
		
		UIView.animate(withDuration: touchAnimationDuration) {
			button.transform = .identity
		}
	}
	
}

let handler = Handler()
let view = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 100))
view.backgroundColor = .white

let button = UIButton(type: .custom)
view.addSubview(button)

let tap = UITapGestureRecognizer(target: handler, action: #selector(handler.flashButton))
view.addGestureRecognizer(tap)

button.frame = CGRect(x: 40, y: 30, width: 120, height: 40)
button.setTitle("Tap me", for: .normal)
button.setTitleColor(.blue, for: .normal)

button.layer.borderWidth = 1.5
button.layer.borderColor = UIColor.blue.cgColor
button.layer.cornerRadius = 8

button.addTarget(handler, action: #selector(handler.didTouch), for: .touchDown)
button.addTarget(handler, action: #selector(handler.didTouchUpInside), for: .touchUpInside)
button.addTarget(handler, action: #selector(handler.didLift), for: .touchUpInside)
button.addTarget(handler, action: #selector(handler.didLift), for: .touchUpOutside)

// pulse(button)

PlaygroundPage.current.liveView = view
PlaygroundPage.current.needsIndefiniteExecution = true

func pulse(_ button: UIButton) {
	let breatheDuration: TimeInterval = 1.8
	let pauseDuration: TimeInterval = 1.2
	
	let increaseAnimator = UIViewPropertyAnimator(duration: breatheDuration, curve: .easeOut) {
		button.alpha = 1
		button.backgroundColor = UIColor.blue.withAlphaComponent(0.07)
		button.transform = CGAffineTransform(scaleX: 1.05, y: 1.05)
	}
	
	let decreaseAnimator = UIViewPropertyAnimator(duration: breatheDuration, curve: .easeOut) {
		button.alpha = 0.8
		button.backgroundColor = .clear
		button.transform = CGAffineTransform(scaleX: 0.95, y: 0.95)
	}
	
	increaseAnimator.addCompletion { _ in
		DispatchQueue.main.asyncAfter(deadline: .now() + pauseDuration) {
			decreaseAnimator.startAnimation()
		}
	}
	
	decreaseAnimator.addCompletion { _ in
		guard shouldPulse else { return }
		
		DispatchQueue.main.asyncAfter(deadline: .now() + pauseDuration) {
			pulse(button)
		}
	}
	
	increaseAnimator.startAnimation()
}

func flashButtonBackground() {
	let animationDuration: TimeInterval = 0.2
	
	let animatorIn = UIViewPropertyAnimator(duration: animationDuration, curve: .easeOut) {
		button.backgroundColor = UIColor.black.withAlphaComponent(0.25)
	}
	let animatorOut = UIViewPropertyAnimator(duration: animationDuration, curve: .easeOut) {
		button.backgroundColor = .white
	}
	
	animatorIn.addCompletion { _ in
		animatorOut.startAnimation()
	}
	
	animatorIn.startAnimation()
}