class MyAlertView: UIView {
	
	let titleLabel: UILabel = {
		let v = UILabel()
		v.translatesAutoresizingMaskIntoConstraints = false
		v.textAlignment = .center
		v.text = "My Alert View"
		v.font = UIFont.systemFont(ofSize: 20.0, weight: .bold)
		v.textColor = .red
		return v
	}()
	let messageLabel: UILabel = {
		let v = UILabel()
		v.translatesAutoresizingMaskIntoConstraints = false
		v.textAlignment = .center
		v.numberOfLines = 0
		v.font = UIFont.systemFont(ofSize: 15.0, weight: .regular)
		v.textColor = .blue
		return v
	}()

	override init(frame: CGRect) {
		super.init(frame: frame)
		commonInit()
	}
	required init?(coder: NSCoder) {
		super.init(coder: coder)
		commonInit()
	}
	func commonInit() -> Void {
		backgroundColor = UIColor.black.withAlphaComponent(0.25)
		layer.cornerRadius = 16
		layer.borderColor = UIColor.black.cgColor
		layer.borderWidth = 2
		addSubview(titleLabel)
		addSubview(messageLabel)
		NSLayoutConstraint.activate([
			// constrain title label to width of self, 16-pts from the top
			titleLabel.topAnchor.constraint(equalTo: topAnchor, constant: 16.0),
			titleLabel.leadingAnchor.constraint(equalTo: leadingAnchor),
			titleLabel.trailingAnchor.constraint(equalTo: trailingAnchor),
			
			// constrain Top of message label to Bottom of title label + 10-pts "spacing"
			messageLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 10.0),
			// 16-pts leading and trailing
			messageLabel.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 16.0),
			messageLabel.trailingAnchor.constraint(equalTo: trailingAnchor, constant: -16.0),
			// bottom to self bottom + 16-pts "spacing"
			messageLabel.bottomAnchor.constraint(equalTo: bottomAnchor, constant: -16.0),
		])
	}
}

class ShowMyAlertViewController: UIViewController {

	override func viewDidLoad() {
		super.viewDidLoad()
		view.backgroundColor = .white
	}
	override func viewDidAppear(_ animated: Bool) {
		super.viewDidAppear(animated)
		// 2 seconds after view appears, show the alert
		DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
			self.showMyAlert("This is a test of showing a custom \"Alert / Notification\" view, which will dismiss itself after 5 seconds.")
		}
	}
	func showMyAlert(_ msg: String) -> Void {
		// instantiate MyAlertView
		let v = MyAlertView()
		// set the label's text
		v.messageLabel.text = msg
		v.translatesAutoresizingMaskIntoConstraints = false
		// add it to self's view
		view.addSubview(v)
		// hidden constraint will place the BOTTOM of the view 10-pts above the top of self's view
		let hiddenConstraint = v.bottomAnchor.constraint(equalTo: view.topAnchor, constant: -10.0)
		// visible constraint will place the TOP of the view 10-pts below the top of self's view (respecting safe area)
		let visibleConstraint = v.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 10.0)
		NSLayoutConstraint.activate([
			// center the alert view horizontally
			v.centerXAnchor.constraint(equalTo: view.centerXAnchor),
			// make its width 80% of the view
			v.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 0.8),
			// height will be determined by the content of the view
			
			// start with view above self's view frame ("hidden")
			hiddenConstraint,
		])
		// allow the alert view to start at its hidden position
		DispatchQueue.main.async {
			// swap active constraints
			hiddenConstraint.isActive = false
			visibleConstraint.isActive = true
			// animate it into view
			UIView.animate(withDuration: 0.3, animations: {
				self.view.layoutIfNeeded()
			}, completion: { done in
				// wait 5 seconds
				DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
					// swap active constraints
					visibleConstraint.isActive = false
					hiddenConstraint.isActive = true
					// animate it out of view
					UIView.animate(withDuration: 0.3, animations: {
						self.view.layoutIfNeeded()
					}, completion: { done in
						// remove it
						v.removeFromSuperview()
					})
				}
			})
		}
	}
	
}