enum Constraint : String {
	
	case top = "topAnchor"
	case bottom = "bottomAnchor"
	case right = "rightAnchor"
	case left = "leftAnchor"
	case centerX = "centerXAnchor"
	case centerY = "centerYAnchor"
}
extension UIView {
	
	func constraintLeft(toLeft of: UIView, margin: CGFloat = 0) {
		self.deleteConstraints(.left)
		print(self.constraints) // prints []
		let left = leftAnchor.constraint(equalTo: of.leftAnchor, constant: margin)
		left.identifier = Constraint.left.rawValue
		NSLayoutConstraint.activate([left])
		setNeedsUpdateConstraints()
		print(self.constraints) // prints []
	}
	/* Other functions left out */
	
	func constraintLeft(toRight of: UIView, margin: CGFloat = 0) {
		self.deleteConstraints(.left)
		print(self.constraints) // prints []
		let left = leftAnchor.constraint(equalTo: of.rightAnchor, constant: margin)
		left.identifier = Constraint.left.rawValue
		NSLayoutConstraint.activate([left])
		setNeedsUpdateConstraints()
		print(self.constraints) // prints []
	}
	func constraintCenterVertical(to of: UIView) -> Void {
		self.deleteConstraints(.centerY)
		print(self.constraints) // prints []
		let cy = centerYAnchor.constraint(equalTo: of.centerYAnchor)
		cy.identifier = Constraint.centerY.rawValue
		NSLayoutConstraint.activate([cy])
		setNeedsUpdateConstraints()
		print(self.constraints) // prints []
	}
	
	func deleteConstraints(_ constraintsToRemove: Constraint...) {
		self.removeConstraints(self.constraints.filter({ c in
			guard c.identifier != nil else {
				return false
			}
			return constraintsToRemove.contains { constraint in
				constraint.rawValue.elementsEqual(c.identifier!)
			}
		}))
	}
	
}

class CustomConstraintsViewController: UIViewController {
	
	override func viewDidLoad() {
		super.viewDidLoad()
	
		let btn = createButton(icon: "cc", label: "Test")
		
		view.addSubview(btn)
		
		let g = view.safeAreaLayoutGuide
		NSLayoutConstraint.activate([
			
			btn.topAnchor.constraint(equalTo: g.topAnchor, constant: 80.0),
			btn.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 80.0),
			btn.widthAnchor.constraint(equalToConstant: 240.0),
			//btn.heightAnchor.constraint(equalToConstant: 120.0),
			
		])
		
		btn.backgroundColor = .systemYellow

		btn.constraints.forEach { c in
			print("create button view:", c)
		}
		var i = 0
		btn.subviews.forEach { v in
			i += 1
			v.constraints.forEach { c in
				print("subview:", i, c)
			}
		}

	}
	
	func createButton(icon: String, label: String) -> UIView {
		let button = UIView() // TransparentCardView()
		button.translatesAutoresizingMaskIntoConstraints = false
		
		let uiImageView = UIImageView(image: UIImage(named: icon))
		button.addSubview(uiImageView)
		uiImageView.translatesAutoresizingMaskIntoConstraints = false
		uiImageView.constraintCenterVertical(to: button) // works
		uiImageView.constraintLeft(toLeft: button, margin: 24.0) // this does not work
		//uiImageView.leftAnchor.constraint(equalTo: button.leftAnchor, constant: 24.0).isActive = true // this does
		
		let textView = UILabel()
		textView.backgroundColor = .cyan
		button.addSubview(textView)
		textView.translatesAutoresizingMaskIntoConstraints = false
		textView.constraintCenterVertical(to: button) // works
		textView.constraintLeft(toRight: uiImageView,margin: 0) // This does not work!
		//textView.leftAnchor.constraint(equalTo: uiImageView.rightAnchor,constant: 20.0).isActive = true // this does work!
		
		textView.heightAnchor.constraint(equalToConstant: 90.0).isActive = true
		textView.widthAnchor.constraint(equalToConstant: 120.0).isActive = true
		
		button.heightAnchor.constraint(equalToConstant: 160.0).isActive = true
		return button
	}
}