/*

     File: ThumbImageView.m

 Abstract: UIImageView subclass to display a thumbnail image; notifies a delegate of various interactions.

  Version: 1.1

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 */

#import "ThumbImageView.h"

#define DRAG_THRESHOLD 10

float distanceBetweenPoints(CGPoint a, CGPoint b);

@implementation ThumbImageView

@synthesize delegate;

@synthesize imageName;

@synthesize home;

@synthesize touchLocation;

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

    self = [super initWithImage:image];

    if (self) {

        [self setUserInteractionEnabled:YES];

        [self setExclusiveTouch:YES];  // block other touches while dragging a thumb view

    }

    return self;

}

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

    // store the location of the starting touch so we can decide when we've moved far enough to drag

    touchLocation = [[touches anyObject] locationInView:self];

    if ([delegate respondsToSelector:@selector(thumbImageViewStartedTracking:)])

        [delegate thumbImageViewStartedTracking:self];

}

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

    // we want to establish a minimum distance that the touch has to move before it counts as dragging,

    // so that the slight movement involved in a tap doesn't cause the frame to move.

    CGPoint newTouchLocation = [[touches anyObject] locationInView:self];

    // if we're already dragging, move our frame

    if (dragging) {

        float deltaX = newTouchLocation.x - touchLocation.x;

        float deltaY = newTouchLocation.y - touchLocation.y;

        [self moveByOffset:CGPointMake(deltaX, deltaY)];

    }

    // if we're not dragging yet, check if we've moved far enough from the initial point to start

    else if (distanceBetweenPoints(touchLocation, newTouchLocation) > DRAG_THRESHOLD) {

        touchLocation = newTouchLocation;

        dragging = YES;

    }

}

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

    if (dragging) {

        [self goHome];

        dragging = NO;

    } else if ([[touches anyObject] tapCount] == 1) {

        if ([delegate respondsToSelector:@selector(thumbImageViewWasTapped:)])

            [delegate thumbImageViewWasTapped:self];

    }

    if ([delegate respondsToSelector:@selector(thumbImageViewStoppedTracking:)]) 

        [delegate thumbImageViewStoppedTracking:self];

}

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

    [self goHome];

    dragging = NO;

    if ([delegate respondsToSelector:@selector(thumbImageViewStoppedTracking:)]) 

        [delegate thumbImageViewStoppedTracking:self];

}

- (void)goHome {

    // distance is in pixels

    float distanceFromHome = distanceBetweenPoints([self frame].origin, [self home].origin);  

    // duration is in seconds, so each additional pixel adds only 1/1000th of a second.

    float animationDuration = 0.1 + distanceFromHome * 0.001; 

    [UIView beginAnimations:nil context:NULL];

    [UIView setAnimationDuration:animationDuration];

    [self setFrame:[self home]];

    [UIView commitAnimations];

}

- (void)moveByOffset:(CGPoint)offset {

    CGRect frame = [self frame];

    frame.origin.x += offset.x;

    frame.origin.y += offset.y;

    [self setFrame:frame];

    if ([delegate respondsToSelector:@selector(thumbImageViewMoved:)])

        [delegate thumbImageViewMoved:self];

}    

@end

float distanceBetweenPoints(CGPoint a, CGPoint b) {

    float deltaX = a.x - b.x;

    float deltaY = a.y - b.y;

    return sqrtf( (deltaX * deltaX) + (deltaY * deltaY) );

}