Swift translation (WIP) of LOActivityAlertController

LOActivityAlertController.swift

//
//  LOActivityAlertController.swift
//  
//  Created by riccardo on 12/10/2020
//  
// Swift Translation of LOActivityAlertController found in this SO answer: https://stackoverflow.com/a/48730050

import Foundation
import UIKit

class LOActivityAlertController: UIViewController, UIViewControllerTransitioningDelegate {
    
    var activityIndicatorView: UIActivityIndicatorView!
    var titleLabel: UILabel!
    var messageLabel: UILabel!
    
    var alertTitle: String
    var alertMessage: String
    
    init(title: String, message: String) {
        self.alertTitle = title
        self.alertMessage = message
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("Not implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.transitioningDelegate = self
        self.modalPresentationStyle = .custom
        self.titleLabel = UILabel()
        self.messageLabel = UILabel()
        self.titleLabel.text = self.alertTitle
        self.messageLabel.text = self.alertMessage
        
        self.activityIndicatorView = UIActivityIndicatorView(style: .medium)
        
        let currentFrame = self.view.frame
        let alertFrame = CGRect(x: 0, y: 0, width: currentFrame.width / 2.0, height: currentFrame.height / 2.0)
        
        let stackView = UIStackView(frame: alertFrame)
        stackView.backgroundColor = .gray
        stackView.axis = .vertical
        stackView.alignment = .center
        stackView.distribution = .fillProportionally
        stackView.addArrangedSubview(self.titleLabel)
        stackView.addArrangedSubview(self.messageLabel)
        stackView.addArrangedSubview(self.activityIndicatorView)
        
        self.activityIndicatorView.startAnimating()
        
        self.view.addSubview(stackView)
    }
    
    override func viewDidAppear(_ animated: Bool) {
        
    }
    
    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        let presentationController = LOActivityAlertControllerPresentationController(presentedViewController: presented, presenting: presenting)
        return presentationController
    }
    
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        let transitioning = LOActivityAlertControllerAnimatedTransitioning(presentation: true)
        return transitioning
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        let transitioning = LOActivityAlertControllerAnimatedTransitioning(presentation: false)
        return transitioning
    }
}

class LOActivityAlertControllerPresentationController: UIPresentationController {
    
    var dimmerView: UIView!
    
    override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?) {
        self.dimmerView = UIView()
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
        dimmerView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        dimmerView.backgroundColor = UIColor.init(white: 0, alpha: 0.4)
        
        guard let presentedView = self.presentedView else { return }
        presentedView.layer.cornerRadius = 8.0
        
        let centerXMotionEffect: UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.x", type: .tiltAlongHorizontalAxis)
        centerXMotionEffect.minimumRelativeValue = -10.0
        centerXMotionEffect.maximumRelativeValue = 10.0
        
        let centerYMotionEffect: UIInterpolatingMotionEffect = UIInterpolatingMotionEffect(keyPath: "center.y", type: .tiltAlongVerticalAxis)
        centerYMotionEffect.minimumRelativeValue = -10.0
        centerYMotionEffect.maximumRelativeValue = 10.0
        
        let group: UIMotionEffectGroup = UIMotionEffectGroup()
        group.motionEffects = [centerXMotionEffect, centerYMotionEffect]
        
        presentedView.addMotionEffect(group)
    }
    
    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerView = self.containerView, let presentedView = self.presentedView else { return .zero }
        
        let size = presentedView.systemLayoutSizeFitting(UIView.layoutFittingCompressedSize)
        var frame = CGRect.zero
        
        frame.origin = CGPoint(x: containerView.frame.midX - (size.width / 2.0), y: containerView.frame.midY - (size.height / 2.0))
        
        frame.size = size
        
        return frame
    }
    
    override func presentationTransitionWillBegin() {
        guard let containerView: UIView = self.containerView, let presentedView: UIView = self.presentedView, let dimmerView = self.dimmerView else { return }
        let presentingViewController: UIViewController = self.presentingViewController
        
        dimmerView.alpha = 0.0
        dimmerView.frame = containerView.bounds
        containerView.insertSubview(dimmerView, at: 0)
        
        presentedView.center = containerView.center
        
        guard let transitionCoordinator = presentingViewController.transitionCoordinator else { return }
        
        transitionCoordinator.animate(
            alongsideTransition: { _ in
                dimmerView.alpha = 1.0
            },
            completion: nil
        )
    }
    
    override func containerViewWillLayoutSubviews() {
        super.containerViewWillLayoutSubviews()
        
        guard let containerView: UIView = self.containerView, let presentedView: UIView = self.presentedView, let dimmerView = self.dimmerView else { return }
        
        dimmerView.frame = containerView.bounds
        presentedView.frame = self.frameOfPresentedViewInContainerView
    }
    
    override func dismissalTransitionWillBegin() {
        guard let dimmerView = self.dimmerView, let transitionCoordinator = self.presentingViewController.transitionCoordinator else { return }
        
        transitionCoordinator.animate(
            alongsideTransition: { _ in
                dimmerView.alpha = 0.0
            },
            completion: nil
        )
    }

}

class LOActivityAlertControllerAnimatedTransitioning: NSObject, UIViewControllerAnimatedTransitioning {
    
    var presentation: Bool
    
    init(presentation: Bool) {
        self.presentation = presentation
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let containerView = transitionContext.containerView
        guard let fromView = transitionContext.view(forKey: .from), let toView = transitionContext.view(forKey: .to) else { return }
        if self.presentation {
            containerView.addSubview(toView)
            toView.transform = CGAffineTransform(scaleX: 1.6, y: 1.6)
            toView.alpha = 0.0
            UIView.animate(
                withDuration: 0.2,
                animations: {
                    toView.alpha = 1.0
                    toView.transform = .identity
                },
                completion: { finished in
                    transitionContext.completeTransition(true)
                }
            )
        } else {
            UIView.animate(
                withDuration: 0.2,
                animations: {
                    fromView.alpha = 0.0
                },
                completion: { finished in
                    fromView.removeFromSuperview()
                    transitionContext.completeTransition(true)
                }
            )
        }
    }
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.2
    }
    
}