//
//  Created by Tom Baranes on 01/05/16.
//  Copyright © 2016 IBAnimatable. All rights reserved.
//

import UIKit

public class CardsAnimator: NSObject, AnimatedTransitioning {

  // MARK: - AnimatorProtocol
  public var transitionAnimationType: TransitionAnimationType
  public var transitionDuration: Duration = defaultTransitionDuration
  public var reverseAnimationType: TransitionAnimationType?
  public var interactiveGestureType: InteractiveGestureType?

  // MARK: - private
  fileprivate var fromDirection: TransitionAnimationType.Direction

  public init(from direction: TransitionAnimationType.Direction, duration: Duration) {
    transitionDuration = duration
    fromDirection = direction
    transitionAnimationType = .cards(direction: direction)
    reverseAnimationType = .cards(direction: direction.opposite)

    super.init()
  }
}

extension CardsAnimator: UIViewControllerAnimatedTransitioning {
  public func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
    return retrieveTransitionDuration(transitionContext: transitionContext)
  }

  public func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
    let (tempfromView, tempToView, tempContainerView) = retrieveViews(transitionContext: transitionContext)
    guard let fromView = tempfromView, let toView = tempToView, let containerView = tempContainerView else {
      transitionContext.completeTransition(true)
      return
    }

    if fromDirection == .forward {
      executeForwardAnimation(transitionContext: transitionContext, containerView: containerView, fromView: fromView, toView: toView)
    } else {
      executeBackwardAnimation(transitionContext: transitionContext, containerView: containerView, fromView: fromView, toView: toView)
    }
  }

}

// MARK: - Forward

private extension CardsAnimator {

  func executeBackwardAnimation(transitionContext: UIViewControllerContextTransitioning, containerView: UIView, fromView: UIView, toView: UIView) {
    let frame = fromView.frame
    var offScreenFrame = frame
    offScreenFrame.origin.y = offScreenFrame.height
    toView.frame = offScreenFrame
    containerView.insertSubview(toView, aboveSubview: fromView)
    let t1 = firstTransform()
    let t2 = secondTransformWithView(view: fromView)
    UIView.animateKeyframes(withDuration: transitionDuration, delay: 0.0, options: .calculationModeCubic, animations: {
      UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: 0.4) {
        fromView.layer.transform = t1
        fromView.alpha = 0.6
      }

      UIView.addKeyframe(withRelativeStartTime: 0.2, relativeDuration: 0.4) {
        fromView.layer.transform = t2
      }

      UIView.addKeyframe(withRelativeStartTime: 0.6, relativeDuration: 0.2) {
        toView.frame = toView.frame.offsetBy(dx: 0.0, dy: -30.0)
      }

      UIView.addKeyframe(withRelativeStartTime: 0.8, relativeDuration: 0.2) {
        toView.frame = frame
      }

    }) { _ in
      transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
    }
  }

}

// MARK: - Reverse

private extension CardsAnimator {

  func executeForwardAnimation(transitionContext: UIViewControllerContextTransitioning, containerView: UIView, fromView: UIView, toView: UIView) {
    let frame = fromView.frame
    toView.frame = frame
    let scale = CATransform3DIdentity
    toView.layer.transform = CATransform3DScale(scale, 0.6, 0.6, 1)
    toView.alpha = 0.6

    containerView.insertSubview(toView, belowSubview: fromView)
    var frameOffScreen = frame
    frameOffScreen.origin.y = frame.height
    let t1 = firstTransform()

    UIView.animateKeyframes(withDuration: transitionDuration, delay: 0.0, options: .calculationModeCubic, animations: {
      UIView.addKeyframe(withRelativeStartTime: 0.0, relativeDuration: 0.5) {
        fromView.frame = frameOffScreen
      }

      UIView.addKeyframe(withRelativeStartTime: 0.35, relativeDuration: 0.35) {
        toView.layer.transform = t1
        toView.alpha = 1.0
      }

      UIView.addKeyframe(withRelativeStartTime: 0.75, relativeDuration: 0.25) {
        toView.layer.transform = CATransform3DIdentity
      }

    }) { _ in
      if transitionContext.transitionWasCancelled {
        toView.layer.transform = CATransform3DIdentity
        toView.alpha = 1.0
      }
      transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
    }
  }

}

// MARK: - Helper

private extension CardsAnimator {

  func firstTransform() -> CATransform3D {
      var t1 = CATransform3DIdentity
      t1.m34 = 1.0 / -900
      t1 = CATransform3DScale(t1, 0.95, 0.95, 1)
      t1 = CATransform3DRotate(t1, 15.0 * .pi / 180.0, 1, 0, 0)
      return t1
  }

  func secondTransformWithView(view: UIView) -> CATransform3D {
    var t2 = CATransform3DIdentity
    t2.m34 = firstTransform().m34
    t2 = CATransform3DTranslate(t2, 0, view.frame.size.height * -0.08, 0)
    t2 = CATransform3DScale(t2, 0.8, 0.8, 1)
    return t2
  }

}