/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    The view controllers used in the Detail storyboard.

*/

import UIKit

class NestedViewController: UIViewController {

    @IBAction func unwindToNested(_ segue: UIStoryboardSegue) {

        /* 

            Empty. Exists solely so that "unwind to nested" segues can find instances

            of this class.

            Notably, if an instance of this class is currently showing a Current

            Context presentation, unwinding to that instance via this action will

            only dismiss that presentation if the unwind source is contained within 

            the presentation.

            This is why the "Dismiss via Unwind" button in this app's storyboard

            will cause the containing presentation to be dismissed, while the "Unwind 

            to Nested" button will not.

        */

    }

}

class OuterViewController: UIViewController {

    @IBAction func unwindToOuter(_ segue: UIStoryboardSegue) {

        /*

            Empty. Exists solely so that "unwind to outer" segues can find 

            instances of this class.

        */

    }

}

class NonAnimatingSegue: UIStoryboardSegue {

    override func perform() {

        UIView.performWithoutAnimation {

            super.perform()

        }

    }

}

class CustomAnimationPresentationSegue: UIStoryboardSegue, UIViewControllerTransitioningDelegate, UIViewControllerAnimatedTransitioning {

    override func perform() {

        /*

            Because this class is used for a Present Modally segue, UIKit will 

            maintain a strong reference to this segue object for the duration of

            the presentation. That way, this segue object will still be around to

            provide an animation controller for the eventual dismissal, as well 

            as for the initial presentation.

        */

        destination.transitioningDelegate = self

        super.perform()

    }

    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {

        return self

    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {

        return self

    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {

        return 0.5

    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        let containerView = transitionContext.containerView

        let toView = transitionContext.view(forKey: UITransitionContextViewKey.to)!

        if transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to) == destination {

            // Presenting.

            UIView.performWithoutAnimation {

                toView.alpha = 0

                containerView.addSubview(toView)

            }

            let transitionContextDuration = transitionDuration(using: transitionContext)

            UIView.animate(withDuration: transitionContextDuration, animations: {

                toView.alpha = 1

            }, completion: { success in

                transitionContext.completeTransition(success)

            })

        }

        else {

            // Dismissing.

            let fromView = transitionContext.view(forKey: UITransitionContextViewKey.from)!

            UIView.performWithoutAnimation {

                containerView.insertSubview(toView, belowSubview: fromView)

            }

            let transitionContextDuration = transitionDuration(using: transitionContext)

            UIView.animate(withDuration: transitionContextDuration, animations: {

                fromView.alpha = 0

            }, completion: { success in

                transitionContext.completeTransition(success)

            })

        }

    }

}