/*

     File: RootViewController.m

 Abstract: View controller to manage a scrollview that displays a zoomable image.

  Version: 1.1

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#import "RootViewController.h"

#define ZOOM_VIEW_TAG 100

#define ZOOM_STEP 1.5

#define THUMB_HEIGHT 150

#define THUMB_V_PADDING 10

#define THUMB_H_PADDING 10

#define CREDIT_LABEL_HEIGHT 20

#define AUTOSCROLL_THRESHOLD 30

@interface RootViewController (ViewHandlingMethods)

- (void)toggleThumbView;

- (void)pickImageNamed:(NSString *)name;

- (NSArray *)imageNames;

- (void)createThumbScrollViewIfNecessary;

- (void)createSlideUpViewIfNecessary;

@end

@interface RootViewController (AutoscrollingMethods)

- (void)maybeAutoscrollForThumb:(ThumbImageView *)thumb;

- (void)autoscrollTimerFired:(NSTimer *)timer;

- (void)legalizeAutoscrollDistance;

- (float)autoscrollDistanceForProximityToEdge:(float)proximity;

@end

@interface RootViewController (UtilityMethods)

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center;

@end

@implementation RootViewController

- (void)loadView {

    [super loadView];

    imageScrollView = [[UIScrollView alloc] initWithFrame:[[self view] bounds]];

    [imageScrollView setBackgroundColor:[UIColor blackColor]];

    [imageScrollView setDelegate:self];

    [imageScrollView setBouncesZoom:YES];

    [[self view] addSubview:imageScrollView];

    [self pickImageNamed:@"WeCanDoIt"];

}

- (void)dealloc {

    [imageScrollView release];

    [slideUpView release];

    [thumbScrollView release];

    [super dealloc];

}

#pragma mark UIScrollViewDelegate methods

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {

    UIView *view = nil;

    if (scrollView == imageScrollView) {

        view = [imageScrollView viewWithTag:ZOOM_VIEW_TAG];

    }

    return view;

}

/************************************** NOTE **************************************/

/* The following delegate method works around a known bug in zoomToRect:animated: */

/* In the next release after 3.0 this workaround will no longer be necessary      */

/**********************************************************************************/

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {

    [scrollView setZoomScale:scale+0.01 animated:NO];

    [scrollView setZoomScale:scale animated:NO];

}

#pragma mark TapDetectingImageViewDelegate methods

- (void)tapDetectingImageView:(TapDetectingImageView *)view gotSingleTapAtPoint:(CGPoint)tapPoint {

    // Single tap shows or hides drawer of thumbnails.

    [self toggleThumbView];

}

- (void)tapDetectingImageView:(TapDetectingImageView *)view gotDoubleTapAtPoint:(CGPoint)tapPoint {

    // double tap zooms in

    float newScale = [imageScrollView zoomScale] * ZOOM_STEP;

    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:tapPoint];

    [imageScrollView zoomToRect:zoomRect animated:YES];

}

- (void)tapDetectingImageView:(TapDetectingImageView *)view gotTwoFingerTapAtPoint:(CGPoint)tapPoint {

    // two-finger tap zooms out

    float newScale = [imageScrollView zoomScale] / ZOOM_STEP;

    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:tapPoint];

    [imageScrollView zoomToRect:zoomRect animated:YES];

}

#pragma mark ThumbImageViewDelegate methods

- (void)thumbImageViewWasTapped:(ThumbImageView *)tiv {

    [self pickImageNamed:[tiv imageName]];

    [self toggleThumbView];

}

- (void)thumbImageViewStartedTracking:(ThumbImageView *)tiv {

    [thumbScrollView bringSubviewToFront:tiv];

}

- (void)thumbImageViewMoved:(ThumbImageView *)draggingThumb {

    // check if we've moved close enough to an edge to autoscroll, or far enough away to stop autoscrolling

    [self maybeAutoscrollForThumb:draggingThumb];

    /* The rest of this method handles the reordering of thumbnails in the thumbScrollView. See  */

    /* ThumbImageView.h and ThumbImageView.m for more information about how this works.          */

    // we'll reorder only if the thumb is overlapping the scroll view

    if (CGRectIntersectsRect([draggingThumb frame], [thumbScrollView bounds])) {        

        BOOL draggingRight = [draggingThumb frame].origin.x > [draggingThumb home].origin.x ? YES : NO;

        /* we're going to shift over all the thumbs who live between the home of the moving thumb */

        /* and the current touch location. A thumb counts as living in this area if the midpoint  */

        /* of its home is contained in the area.                                                  */

        NSMutableArray *thumbsToShift = [[NSMutableArray alloc] init];

        // get the touch location in the coordinate system of the scroll view

        CGPoint touchLocation = [draggingThumb convertPoint:[draggingThumb touchLocation] toView:thumbScrollView];

        // calculate minimum and maximum boundaries of the affected area

        float minX = draggingRight ? CGRectGetMaxX([draggingThumb home]) : touchLocation.x;

        float maxX = draggingRight ? touchLocation.x : CGRectGetMinX([draggingThumb home]);

        // iterate through thumbnails and see which ones need to move over

        for (ThumbImageView *thumb in [thumbScrollView subviews]) {

            // skip the thumb being dragged

            if (thumb == draggingThumb) continue;

            // skip non-thumb subviews of the scroll view (such as the scroll indicators)

            if (! [thumb isMemberOfClass:[ThumbImageView class]]) continue;

            float thumbMidpoint = CGRectGetMidX([thumb home]);

            if (thumbMidpoint >= minX && thumbMidpoint <= maxX) {

                [thumbsToShift addObject:thumb];

            }

        }

        // shift over the other thumbs to make room for the dragging thumb. (if we're dragging right, they shift to the left)

        float otherThumbShift = ([draggingThumb home].size.width + THUMB_H_PADDING) * (draggingRight ? -1 : 1);

        // as we shift over the other thumbs, we'll calculate how much the dragging thumb's home is going to move

        float draggingThumbShift = 0.0;

        // send each of the shifting thumbs to its new home

        for (ThumbImageView *otherThumb in thumbsToShift) {

            CGRect home = [otherThumb home];

            home.origin.x += otherThumbShift;

            [otherThumb setHome:home];

            [otherThumb goHome];

            draggingThumbShift += ([otherThumb frame].size.width + THUMB_H_PADDING) * (draggingRight ? 1 : -1);

        }

        [thumbsToShift release];

        // change the home of the dragging thumb, but don't send it there because it's still being dragged

        CGRect home = [draggingThumb home];

        home.origin.x += draggingThumbShift;

        [draggingThumb setHome:home];

    }

}

- (void)thumbImageViewStoppedTracking:(ThumbImageView *)tiv {

    // if the user lets go of the thumb image view, stop autoscrolling

    [autoscrollTimer invalidate];

    autoscrollTimer = nil;

}

#pragma mark Autoscrolling methods

- (void)maybeAutoscrollForThumb:(ThumbImageView *)thumb {

    autoscrollDistance = 0;

    // only autoscroll if the thumb is overlapping the thumbScrollView

    if (CGRectIntersectsRect([thumb frame], [thumbScrollView bounds])) {

        CGPoint touchLocation = [thumb convertPoint:[thumb touchLocation] toView:thumbScrollView];

        float distanceFromLeftEdge  = touchLocation.x - CGRectGetMinX([thumbScrollView bounds]);

        float distanceFromRightEdge = CGRectGetMaxX([thumbScrollView bounds]) - touchLocation.x;

        if (distanceFromLeftEdge < AUTOSCROLL_THRESHOLD) {

            autoscrollDistance = [self autoscrollDistanceForProximityToEdge:distanceFromLeftEdge] * -1; // if scrolling left, distance is negative

        } else if (distanceFromRightEdge < AUTOSCROLL_THRESHOLD) {

            autoscrollDistance = [self autoscrollDistanceForProximityToEdge:distanceFromRightEdge];

        }        

    }

    // if no autoscrolling, stop and clear timer

    if (autoscrollDistance == 0) {

        [autoscrollTimer invalidate];

        autoscrollTimer = nil;

    } 

    // otherwise create and start timer (if we don't already have a timer going)

    else if (autoscrollTimer == nil) {

        autoscrollTimer = [NSTimer scheduledTimerWithTimeInterval:(1.0 / 60.0)

                                                           target:self 

                                                         selector:@selector(autoscrollTimerFired:) 

                                                         userInfo:thumb 

                                                          repeats:YES];

    } 

}

- (float)autoscrollDistanceForProximityToEdge:(float)proximity {

    // the scroll distance grows as the proximity to the edge decreases, so that moving the thumb

    // further over results in faster scrolling.

    return ceilf((AUTOSCROLL_THRESHOLD - proximity) / 5.0);

}

- (void)legalizeAutoscrollDistance {

    // makes sure the autoscroll distance won't result in scrolling past the content of the scroll view

    float minimumLegalDistance = [thumbScrollView contentOffset].x * -1;

    float maximumLegalDistance = [thumbScrollView contentSize].width - ([thumbScrollView frame].size.width + [thumbScrollView contentOffset].x);

    autoscrollDistance = MAX(autoscrollDistance, minimumLegalDistance);

    autoscrollDistance = MIN(autoscrollDistance, maximumLegalDistance);

}

- (void)autoscrollTimerFired:(NSTimer*)timer {

    [self legalizeAutoscrollDistance];

    // autoscroll by changing content offset

    CGPoint contentOffset = [thumbScrollView contentOffset];

    contentOffset.x += autoscrollDistance;

    [thumbScrollView setContentOffset:contentOffset];

    // adjust thumb position so it appears to stay still

    ThumbImageView *thumb = (ThumbImageView *)[timer userInfo];

    [thumb moveByOffset:CGPointMake(autoscrollDistance, 0)];

}

#pragma mark View handling methods

- (void)toggleThumbView {

    [self createSlideUpViewIfNecessary]; // no-op if slideUpView has already been created

    CGRect frame = [slideUpView frame];

    if (thumbViewShowing) {

        frame.origin.y += frame.size.height;

    } else {

        frame.origin.y -= frame.size.height;

    }

    [UIView beginAnimations:nil context:nil];

    [UIView setAnimationDuration:0.3];

    [slideUpView setFrame:frame];

    [UIView commitAnimations];

    thumbViewShowing = !thumbViewShowing;

}

- (void)pickImageNamed:(NSString *)name {

    // first remove previous image view, if any

    [[imageScrollView viewWithTag:ZOOM_VIEW_TAG] removeFromSuperview];

    UIImage *image = [UIImage imageNamed:[NSString stringWithFormat:@"%@.png", name]];

    TapDetectingImageView *zoomView = [[TapDetectingImageView alloc] initWithImage:image];

    [zoomView setDelegate:self];

    [zoomView setTag:ZOOM_VIEW_TAG];

    [imageScrollView addSubview:zoomView];

    [imageScrollView setContentSize:[zoomView frame].size];

    [zoomView release];

    // choose minimum scale so image width fits screen

    float minScale  = [imageScrollView frame].size.width  / [zoomView frame].size.width;

    [imageScrollView setMinimumZoomScale:minScale];

    [imageScrollView setZoomScale:minScale];

    [imageScrollView setContentOffset:CGPointZero];

}

- (NSArray *)imageNames {

    // the filenames are stored in a plist in the app bundle, so create array by reading this plist

    NSString *path = [[NSBundle mainBundle] pathForResource:@"Images" ofType:@"plist"];

    NSData *plistData = [NSData dataWithContentsOfFile:path];

    NSString *error; NSPropertyListFormat format;

    NSArray *imageNames = [NSPropertyListSerialization propertyListFromData:plistData

                                                           mutabilityOption:NSPropertyListImmutable

                                                                     format:&format

                                                           errorDescription:&error];

    if (!imageNames) {

        NSLog(@"Failed to read image names. Error: %@", error);

        [error release];

    }

    return imageNames;

}

- (void)createSlideUpViewIfNecessary {

    if (!slideUpView) {

        [self createThumbScrollViewIfNecessary];

        CGRect bounds = [[self view] bounds];

        float thumbHeight = [thumbScrollView frame].size.height;

        float labelHeight = CREDIT_LABEL_HEIGHT;

        // create label giving credit for images

        UILabel *creditLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, thumbHeight, bounds.size.width, labelHeight)];

        [creditLabel setBackgroundColor:[UIColor clearColor]];

        [creditLabel setTextColor:[UIColor whiteColor]];

        [creditLabel setFont:[UIFont fontWithName:@"AmericanTypewriter" size:14]];

        [creditLabel setText:@"images courtesy of the american legion"];

        [creditLabel setTextAlignment:UITextAlignmentCenter];        

        // create container view that will hold scroll view and label

        CGRect frame = CGRectMake(CGRectGetMinX(bounds), CGRectGetMaxY(bounds), bounds.size.width, thumbHeight + labelHeight);

        slideUpView = [[UIView alloc] initWithFrame:frame];

        [slideUpView setBackgroundColor:[UIColor blackColor]];

        [slideUpView setOpaque:NO];

        [slideUpView setAlpha:0.75];

        [[self view] addSubview:slideUpView];

        // add subviews to container view

        [slideUpView addSubview:thumbScrollView];

        [slideUpView addSubview:creditLabel];

        [creditLabel release];        

    }    

}

- (void)createThumbScrollViewIfNecessary {

    if (!thumbScrollView) {        

        float scrollViewHeight = THUMB_HEIGHT + THUMB_V_PADDING;

        float scrollViewWidth  = [[self view] bounds].size.width;

        thumbScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, scrollViewWidth, scrollViewHeight)];

        [thumbScrollView setCanCancelContentTouches:NO];

        [thumbScrollView setClipsToBounds:NO];

        // now place all the thumb views as subviews of the scroll view 

        // and in the course of doing so calculate the content width

        float xPosition = THUMB_H_PADDING;

        for (NSString *name in [self imageNames]) {

            UIImage *thumbImage = [UIImage imageNamed:[NSString stringWithFormat:@"%@_thumb.png", name]];

            if (thumbImage) {

                ThumbImageView *thumbView = [[ThumbImageView alloc] initWithImage:thumbImage];

                [thumbView setDelegate:self];

                [thumbView setImageName:name];

                CGRect frame = [thumbView frame];

                frame.origin.y = THUMB_V_PADDING;

                frame.origin.x = xPosition;

                [thumbView setFrame:frame];

                [thumbView setHome:frame];

                [thumbScrollView addSubview:thumbView];

                [thumbView release];

                xPosition += (frame.size.width + THUMB_H_PADDING);

            }

        }

        [thumbScrollView setContentSize:CGSizeMake(xPosition, scrollViewHeight)];

    }    

}

#pragma mark Utility methods

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center {

    CGRect zoomRect;

    // the zoom rect is in the content view's coordinates. 

    //    At a zoom scale of 1.0, it would be the size of the imageScrollView's bounds.

    //    As the zoom scale decreases, so more content is visible, the size of the rect grows.

    zoomRect.size.height = [imageScrollView frame].size.height / scale;

    zoomRect.size.width  = [imageScrollView frame].size.width  / scale;

    // choose an origin so as to get the right center.

    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);

    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);

    return zoomRect;

}

@end