import UIKit

class TransitioningDelegate: NSObject, UIViewControllerTransitioningDelegate {

    var startFrame = CGRect()
    var dissmis = false




    func presentationControllerForPresentedViewController(presented: UIViewController, presentingViewController presenting: UIViewController, sourceViewController source: UIViewController) -> UIPresentationController? {
        return PresentationController(presentedViewController: presented, presentingViewController: presenting)
    }

    func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        dissmis = false
        return self
    }

    func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        dissmis = true
        return self
    }
}


extension TransitioningDelegate: UIViewControllerAnimatedTransitioning {
    func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
        return 0.4
    }

    func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
        if let toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey), let fromViewController = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey) {
            if !dissmis {
                let toView = toViewController.view
                let fromView = fromViewController.view

                transitionContext.containerView()!.addSubview(toView)

                let toSx = startFrame.width / toView.frame.width
                let toSy = startFrame.height / toView.frame.height
                let fromSx = fromView.frame.width / startFrame.width
                let fromSy = fromView.frame.height / startFrame.height

                toView.transform = CGAffineTransformMakeScale(toSx, toSy)
                toView.frame.origin = startFrame.origin
                toView.alpha = 0

                let height = fromView.frame.height - (startFrame.origin.y + startFrame.height)

                var y = -self.startFrame.origin.y * fromSy
                if height < 0 {
                    fromView.frame.size.height += -height
                } else if startFrame.origin.y < 0 {
                    fromView.frame.size.height += -startFrame.origin.y
                    fromView.frame.origin.y = startFrame.origin.y
                    y = 0
                    let collectionController = fromViewController as! UICollectionViewController
                    collectionController.collectionView?.contentOffset.y = (collectionController.collectionViewLayout as! UICollectionViewFlowLayout).sectionInset.top
                }


                UIView.animateWithDuration(transitionDuration(transitionContext), delay: 0, options: [], animations: {

                    toView.alpha = 1
                    toView.transform = CGAffineTransformIdentity
                    toView.frame.origin = CGPoint(x: 0, y: 0)

                    fromView.transform = CGAffineTransformMakeScale(fromSx, fromSy)
                    fromView.frame.origin.x = -self.startFrame.origin.x * fromSx

                    fromView.frame.origin.y = y
                    }, completion: { _ in
                        transitionContext.completeTransition(true)
                })
            } else {
                let fromView = fromViewController.view
                let toView = toViewController.view

                let fromSx = startFrame.width / fromView.frame.width
                let fromSy = startFrame.height / fromView.frame.height

                transitionContext.containerView()!.addSubview(fromView)

                fromView.alpha = 1

                UIView.animateWithDuration(transitionDuration(transitionContext), delay: 0, options: [], animations: {

                    fromView.alpha = 0
                    fromView.transform = CGAffineTransformMakeScale(fromSx, fromSy)
                    fromView.frame.origin.x = self.startFrame.origin.x
                    fromView.frame.origin.y = self.startFrame.origin.y

                    toView.transform = CGAffineTransformIdentity
                    toView.frame.origin = CGPoint(x: 0, y: 0)
                    }, completion: { _ in
                        transitionContext.completeTransition(true)
                })
            }
        }
    }
}