/*

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

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 The interaction controller for the Swipe demo.  Tracks a UIScreenEdgePanGestureRecognizer

  from a specified screen edge and derives the completion percentage for the

  transition.

 */

#import "AAPLSwipeTransitionInteractionController.h"

@interface AAPLSwipeTransitionInteractionController ()

@property (nonatomic, weak) id<UIViewControllerContextTransitioning> transitionContext;

@property (nonatomic, strong, readonly) UIScreenEdgePanGestureRecognizer *gestureRecognizer;

@property (nonatomic, readonly) UIRectEdge edge;

@end

@implementation AAPLSwipeTransitionInteractionController

//| ----------------------------------------------------------------------------

- (instancetype)initWithGestureRecognizer:(UIScreenEdgePanGestureRecognizer *)gestureRecognizer edgeForDragging:(UIRectEdge)edge

{

    NSAssert(edge == UIRectEdgeTop || edge == UIRectEdgeBottom ||

             edge == UIRectEdgeLeft || edge == UIRectEdgeRight,

             @"edgeForDragging must be one of UIRectEdgeTop, UIRectEdgeBottom, UIRectEdgeLeft, or UIRectEdgeRight.");

    self = [super init];

    if (self)

    {

        _gestureRecognizer = gestureRecognizer;

        _edge = edge;

        // Add self as an observer of the gesture recognizer so that this

        // object receives updates as the user moves their finger.

        [_gestureRecognizer addTarget:self action:@selector(gestureRecognizeDidUpdate:)];

    }

    return self;

}

//| ----------------------------------------------------------------------------

- (instancetype)init

{

    @throw [NSException exceptionWithName:NSInvalidArgumentException reason:@"Use -initWithGestureRecognizer:edgeForDragging:" userInfo:nil];

}

//| ----------------------------------------------------------------------------

- (void)dealloc

{

    [self.gestureRecognizer removeTarget:self action:@selector(gestureRecognizeDidUpdate:)];

}

//| ----------------------------------------------------------------------------

- (void)startInteractiveTransition:(id<UIViewControllerContextTransitioning>)transitionContext

{

    // Save the transitionContext for later.

    self.transitionContext = transitionContext;

    [super startInteractiveTransition:transitionContext];

}

//| ----------------------------------------------------------------------------

//! Returns the offset of the pan gesture recognizer from the edge of the

//! screen as a percentage of the transition container view's width or height.

//! This is the percent completed for the interactive transition.

//

- (CGFloat)percentForGesture:(UIScreenEdgePanGestureRecognizer *)gesture

{

    // Because view controllers will be sliding on and off screen as part

    // of the animation, we want to base our calculations in the coordinate

    // space of the view that will not be moving: the containerView of the

    // transition context.

    UIView *transitionContainerView = self.transitionContext.containerView;

    CGPoint locationInSourceView = [gesture locationInView:transitionContainerView];

    // Figure out what percentage we've gone.

    CGFloat width = CGRectGetWidth(transitionContainerView.bounds);

    CGFloat height = CGRectGetHeight(transitionContainerView.bounds);

    // Return an appropriate percentage based on which edge we're dragging

    // from.

    if (self.edge == UIRectEdgeRight)

        return (width - locationInSourceView.x) / width;

    else if (self.edge == UIRectEdgeLeft)

        return locationInSourceView.x / width;

    else if (self.edge == UIRectEdgeBottom)

        return (height - locationInSourceView.y) / height;

    else if (self.edge == UIRectEdgeTop)

        return locationInSourceView.y / height;

    else

        return 0.f;

}

//| ----------------------------------------------------------------------------

//! Action method for the gestureRecognizer.

//

- (IBAction)gestureRecognizeDidUpdate:(UIScreenEdgePanGestureRecognizer *)gestureRecognizer

{

    switch (gestureRecognizer.state)

    {

        case UIGestureRecognizerStateBegan:

            // The Began state is handled by the view controllers.  In response

            // to the gesture recognizer transitioning to this state, they

            // will trigger the presentation or dismissal.

            break;

        case UIGestureRecognizerStateChanged:

            // We have been dragging! Update the transition context accordingly.

            [self updateInteractiveTransition:[self percentForGesture:gestureRecognizer]];

            break;

        case UIGestureRecognizerStateEnded:

            // Dragging has finished.

            // Complete or cancel, depending on how far we've dragged.

            if ([self percentForGesture:gestureRecognizer] >= 0.5f)

                [self finishInteractiveTransition];

            else

                [self cancelInteractiveTransition];

            break;

        default:

            // Something happened. cancel the transition.

            [self cancelInteractiveTransition];

            break;

    }

}

@end