Paging viewcontroller using interactive transitioning

ViewController.swift

import UIKit

extension UIColor {
    static func randomColor() -> UIColor {
        let red = CGFloat(arc4random_uniform(255)) / 255.0
        let green = CGFloat(arc4random_uniform(255)) / 255.0
        let blue = CGFloat(arc4random_uniform(255)) / 255.0
        return UIColor(red: red, green: green, blue: blue, alpha: 1.0)
    }
}

class ViewController: UIViewController, UIViewControllerTransitioningDelegate {
    
    var interactionController: InteractionController?
    
    var gestureRecognizer: UIPanGestureRecognizer?
    
    var slidesRight = true
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = UIColor.randomColor()
        
        let panGestureRecognizer = UIPanGestureRecognizer(target: self,
                                                          action: #selector(panned))
        view.addGestureRecognizer(panGestureRecognizer)
        self.gestureRecognizer = panGestureRecognizer
        
        let tap = UITapGestureRecognizer(target: self, action: #selector(tapped))
        view.addGestureRecognizer(tap)
    }
    
    @objc
    func tapped(tapGestureRecognizer: UITapGestureRecognizer) {
        let viewController = ViewController()
        viewController.transitioningDelegate = self
        present(viewController, animated: true, completion: nil)

    }
    
    @objc
    func panned(panGestureRecognizer: UIPanGestureRecognizer) {
        switch panGestureRecognizer.state {
        case .began:
            let translation = panGestureRecognizer.translation(in: view)
            
            if fabs(translation.x) > 0 {
                
                if translation.x == 0 {
                    return;
                }
                
                if translation.x < 0 {
                    slidesRight = true
                    let viewController = ViewController()
                    viewController.transitioningDelegate = self
                    present(viewController, animated: true, completion: nil)
                } else {
                    slidesRight = false
                    let viewController = ViewController()
                    viewController.transitioningDelegate = self
                    present(viewController, animated: true, completion: nil)
                }
            }

        default:
            print("Not presenting")
        }
    }

    
    public func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) ->  UIViewControllerInteractiveTransitioning? {
        self.interactionController = InteractionController(gestureRecognizer: gestureRecognizer!)
        return self.interactionController!
    }
    
    
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        let slideDirection: SlideDirection = slidesRight ? .Right : .Left
        return AnimationController(slideDirection: slideDirection)
    }
    
}

class InteractionController: UIPercentDrivenInteractiveTransition {
    let gestureRecognizer: UIPanGestureRecognizer
    
    init(gestureRecognizer: UIPanGestureRecognizer) {
        self.gestureRecognizer = gestureRecognizer
        super.init()
        self.gestureRecognizer.addTarget(self, action: #selector(panned))
    }
    
    override var completionSpeed: CGFloat {
        get {
            return 1.0 - self.percentComplete
        }
        set {}
    }

    
    @objc
    func panned(pan: UIPanGestureRecognizer) {
        
        switch pan.state {
        case .changed:
            let translation = gestureRecognizer.translation(in: gestureRecognizer.view!)
            let ratio = (translation.x / gestureRecognizer.view!.bounds.size.width)
            update(abs(ratio))
            
        case .ended:
            let translation = gestureRecognizer.translation(in: gestureRecognizer.view!)
            let ratio = translation.x / gestureRecognizer.view!.bounds.size.width
            
            if abs(ratio) > 0.30 {
                finish()
            } else {
                cancel()
            }

        default:
            print("Unrecognized state")
        }
        
    }
    
    override func startInteractiveTransition(_ transitionContext: UIViewControllerContextTransitioning) {
        super.startInteractiveTransition(transitionContext)
        print("starting interactive transition")
    }
}

enum SlideDirection {
    
    case Left
    case Right
}

class AnimationController: NSObject, UIViewControllerAnimatedTransitioning {
    
    let slideDirection: SlideDirection
    
    init(slideDirection: SlideDirection) {
        self.slideDirection = slideDirection
    }
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.33
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let containerView = transitionContext.containerView
        
        let toView = transitionContext.view(forKey: .to)
        let fromView = transitionContext.view(forKey: .from)

        toView?.frame = containerView.bounds
        fromView?.frame = containerView.bounds
        
        var translationX: CGFloat = 0
        
        if slideDirection == .Right {
               translationX = containerView.bounds.size.width
        } else {
            translationX = -containerView.bounds.size.width
        }
        
        toView?.transform = CGAffineTransform(translationX: translationX, y: 0)
        fromView?.transform = CGAffineTransform.identity
        
        containerView.addSubview(toView!)
        
        UIView.animate(withDuration: 0.33, delay: 0, options: .curveEaseInOut, animations: {
            toView?.transform = CGAffineTransform.identity
            fromView?.transform = CGAffineTransform(translationX: -translationX, y: 0)
            

        }) { completed in

            if transitionContext.transitionWasCancelled {
                transitionContext.completeTransition(false)
                fromView?.transform = CGAffineTransform.identity
            } else {
                transitionContext.completeTransition(true)
            }
        }
    }
}