/*

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

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 The interaction controller for the Slide demo.

 */

#import "AAPLSlideTransitionInteractionController.h"

@interface AAPLSlideTransitionInteractionController ()

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

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

@property (nonatomic, readwrite) CGPoint initialLocationInContainerView;

@property (nonatomic, readwrite) CGPoint initialTranslationInContainerView;

@end

@implementation AAPLSlideTransitionInteractionController

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

- (instancetype)initWithGestureRecognizer:(UIPanGestureRecognizer *)gestureRecognizer

{

    self = [super init];

    if (self)

    {

        _gestureRecognizer = gestureRecognizer;

        // 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:" userInfo:nil];

}

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

- (void)dealloc

{

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

}

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

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

{

    // Save the transitionContext, initial location, and the translation within

    // the containing view.

    self.transitionContext = transitionContext;

    self.initialLocationInContainerView = [self.gestureRecognizer locationInView:transitionContext.containerView];

    self.initialTranslationInContainerView = [self.gestureRecognizer translationInView:transitionContext.containerView];

    [super startInteractiveTransition:transitionContext];

}

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

//! Returns the offset of the pan gesture recognizer from its initial location

//! as a percentage of the transition container view's width.  This is

//! the percent completed for the interactive transition.

//

- (CGFloat)percentForGesture:(UIPanGestureRecognizer *)gesture

{

    UIView *transitionContainerView = self.transitionContext.containerView;

    CGPoint translationInContainerView = [gesture translationInView:transitionContainerView];

    // If the direction of the current touch along the horizontal axis does not

    // match the initial direction, then the current touch position along

    // the horizontal axis has crossed over the initial position.  See the

    // comment in the -beginInteractiveTransitionIfPossible: method of

    // AAPLSlideTransitionDelegate.

    if ((translationInContainerView.x > 0.f && self.initialTranslationInContainerView.x < 0.f) ||

        (translationInContainerView.x < 0.f && self.initialTranslationInContainerView.x > 0.f))

        return -1.f;

    // Figure out what percentage we've traveled.

    return fabs(translationInContainerView.x) / CGRectGetWidth(transitionContainerView.bounds);

}

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

//! Action method for the gestureRecognizer.

//

- (IBAction)gestureRecognizeDidUpdate:(UIScreenEdgePanGestureRecognizer *)gestureRecognizer

{

    switch (gestureRecognizer.state) {

        case UIGestureRecognizerStateBegan:

            // The Began state is handled by AAPLSlideTransitionDelegate.  In

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

            // it will trigger the transition.

            break;

        case UIGestureRecognizerStateChanged:

            // -percentForGesture returns -1.f if the current position of the

            // touch along the horizontal axis has crossed over the initial

            // position.  See the comment in the

            // -beginInteractiveTransitionIfPossible: method of

            // AAPLSlideTransitionDelegate for details.

            if ([self percentForGesture:gestureRecognizer] < 0.f) {

                [self cancelInteractiveTransition];

                // Need to remove our action from the gesture recognizer to

                // ensure it will not be called again before deallocation.

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

            } else {

                // 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] >= 0.4f)

                [self finishInteractiveTransition];

            else

                [self cancelInteractiveTransition];

            break;

        default:

            // Something happened. cancel the transition.

            [self cancelInteractiveTransition];

            break;

    }

}

@end