/*

     File: TapDetectingImageView.m 

 Abstract: n/a 

  Version: 1.2 

 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple 

 Inc. ("Apple") in consideration of your agreement to the following 

 terms, and your use, installation, modification or redistribution of 

 this Apple software constitutes acceptance of these terms.  If you do 

 not agree with these terms, please do not use, install, modify or 

 redistribute this Apple software. 

 In consideration of your agreement to abide by the following terms, and 

 subject to these terms, Apple grants you a personal, non-exclusive 

 license, under Apple's copyrights in this original Apple software (the 

 "Apple Software"), to use, reproduce, modify and redistribute the Apple 

 Software, with or without modifications, in source and/or binary forms; 

 provided that if you redistribute the Apple Software in its entirety and 

 without modifications, you must retain this notice and the following 

 text and disclaimers in all such redistributions of the Apple Software. 

 Neither the name, trademarks, service marks or logos of Apple Inc. may 

 be used to endorse or promote products derived from the Apple Software 

 without specific prior written permission from Apple.  Except as 

 expressly stated in this notice, no other rights or licenses, express or 

 implied, are granted by Apple herein, including but not limited to any 

 patent rights that may be infringed by your derivative works or by other 

 works in which the Apple Software may be incorporated. 

 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE 

 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION 

 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS 

 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND 

 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS. 

 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL 

 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 

 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 

 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, 

 MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED 

 AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE), 

 STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE 

 POSSIBILITY OF SUCH DAMAGE. 

 Copyright (C) 2012 Apple Inc. All Rights Reserved. 

*/

#import "TapDetectingImageView.h"

#define DOUBLE_TAP_DELAY 0.35

CGPoint midpointBetweenPoints(CGPoint a, CGPoint b);

@interface TapDetectingImageView ()

- (void)handleSingleTap;

- (void)handleDoubleTap;

- (void)handleTwoFingerTap;

@end

@implementation TapDetectingImageView

@synthesize delegate;

- (id)initWithImage:(UIImage *)image {

    self = [super initWithImage:image];

    if (self) {

        [self setUserInteractionEnabled:YES];

        [self setMultipleTouchEnabled:YES];

        twoFingerTapIsPossible = YES;

        multipleTouches = NO;

    }

    return self;

}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

{

    // cancel any pending handleSingleTap messages 

    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(handleSingleTap) object:nil];

    // update our touch state

    if ([[event touchesForView:self] count] > 1)

        multipleTouches = YES;

    if ([[event touchesForView:self] count] > 2)

        twoFingerTapIsPossible = NO;

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

{

    BOOL allTouchesEnded = ([touches count] == [[event touchesForView:self] count]);

    // first check for plain single/double tap, which is only possible if we haven't seen multiple touches

    if (!multipleTouches) {

        UITouch *touch = [touches anyObject];

        tapLocation = [touch locationInView:self];

        if ([touch tapCount] == 1) {

            [self performSelector:@selector(handleSingleTap) withObject:nil afterDelay:DOUBLE_TAP_DELAY];

        } else if([touch tapCount] == 2) {

            [self handleDoubleTap];

        }

    }    

    // check for 2-finger tap if we've seen multiple touches and haven't yet ruled out that possibility

    else if (multipleTouches && twoFingerTapIsPossible) { 

        // case 1: this is the end of both touches at once 

        if ([touches count] == 2 && allTouchesEnded) {

            int i = 0; 

            int tapCounts[2]= {0}; CGPoint tapLocations[2]={{0, 0}};

            for (UITouch *touch in touches) {

                tapCounts[i]    = [touch tapCount];

                tapLocations[i] = [touch locationInView:self];

                i++;

            }

            if (tapCounts[0] == 1 && tapCounts[1] == 1) { // it's a two-finger tap if they're both single taps

                tapLocation = midpointBetweenPoints(tapLocations[0], tapLocations[1]);

                [self handleTwoFingerTap];

            }

        }

        // case 2: this is the end of one touch, and the other hasn't ended yet

        else if ([touches count] == 1 && !allTouchesEnded) {

            UITouch *touch = [touches anyObject];

            if ([touch tapCount] == 1) {

                // if touch is a single tap, store its location so we can average it with the second touch location

                tapLocation = [touch locationInView:self];

            } else {

                twoFingerTapIsPossible = NO;

            }

        }

        // case 3: this is the end of the second of the two touches

        else if ([touches count] == 1 && allTouchesEnded) {

            UITouch *touch = [touches anyObject];

            if ([touch tapCount] == 1) {

                // if the last touch up is a single tap, this was a 2-finger tap

                tapLocation = midpointBetweenPoints(tapLocation, [touch locationInView:self]);

                [self handleTwoFingerTap];

            }

        }

    }

    // if all touches are up, reset touch monitoring state

    if (allTouchesEnded) {

        twoFingerTapIsPossible = YES;

        multipleTouches = NO;

    }

}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {

    twoFingerTapIsPossible = YES;

    multipleTouches = NO;

}

#pragma mark Private

- (void)handleSingleTap {

    if ([delegate respondsToSelector:@selector(tapDetectingImageView:gotSingleTapAtPoint:)])

        [delegate tapDetectingImageView:self gotSingleTapAtPoint:tapLocation];

}

- (void)handleDoubleTap {

    if ([delegate respondsToSelector:@selector(tapDetectingImageView:gotDoubleTapAtPoint:)])

        [delegate tapDetectingImageView:self gotDoubleTapAtPoint:tapLocation];

}

- (void)handleTwoFingerTap {

    if ([delegate respondsToSelector:@selector(tapDetectingImageView:gotTwoFingerTapAtPoint:)])

        [delegate tapDetectingImageView:self gotTwoFingerTapAtPoint:tapLocation];

}

@end

CGPoint midpointBetweenPoints(CGPoint a, CGPoint b) {

    CGFloat x = (a.x + b.x) / 2.0;

    CGFloat y = (a.y + b.y) / 2.0;

    return CGPointMake(x, y);

}