/*
     File: ImageScrollView.m
 Abstract: Centers image within the scroll view and configures image sizing and display.
  Version: 1.1
 
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 */

#import "ImageScrollView.h"
#import "TilingView.h"

@implementation ImageScrollView
@synthesize index;

- (id)initWithFrame:(CGRect)frame
{
    if ((self = [super initWithFrame:frame])) {
        self.showsVerticalScrollIndicator = NO;
        self.showsHorizontalScrollIndicator = NO;
        self.bouncesZoom = YES;
        self.decelerationRate = UIScrollViewDecelerationRateFast;
        self.delegate = self;        
    }
    return self;
}

- (void)dealloc
{
    [imageView release];
    [super dealloc];
}

#pragma mark -
#pragma mark Override layoutSubviews to center content

- (void)layoutSubviews 
{
    [super layoutSubviews];
    
    // center the image as it becomes smaller than the size of the screen
    
    CGSize boundsSize = self.bounds.size;
    CGRect frameToCenter = imageView.frame;
    
    // center horizontally
    if (frameToCenter.size.width < boundsSize.width)
        frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
    else
        frameToCenter.origin.x = 0;
    
    // center vertically
    if (frameToCenter.size.height < boundsSize.height)
        frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
    else
        frameToCenter.origin.y = 0;
    
    imageView.frame = frameToCenter;
    
    if ([imageView isKindOfClass:[TilingView class]]) {
        // to handle the interaction between CATiledLayer and high resolution screens, we need to manually set the
        // tiling view's contentScaleFactor to 1.0. (If we omitted this, it would be 2.0 on high resolution screens,
        // which would cause the CATiledLayer to ask us for tiles of the wrong scales.)
        imageView.contentScaleFactor = 1.0;
    }
}

#pragma mark -
#pragma mark UIScrollView delegate methods

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return imageView;
}

#pragma mark -
#pragma mark Configure scrollView to display new image (tiled or not)

- (void)displayImage:(UIImage *)image
{
    // clear the previous imageView
    [imageView removeFromSuperview];
    [imageView release];
    imageView = nil;
    
    // reset our zoomScale to 1.0 before doing any further calculations
    self.zoomScale = 1.0;
    
    // make a new UIImageView for the new image
    imageView = [[UIImageView alloc] initWithImage:image];
    [self addSubview:imageView];
    
    self.contentSize = [image size];
    [self setMaxMinZoomScalesForCurrentBounds];
    self.zoomScale = self.minimumZoomScale;
}

- (void)displayTiledImageNamed:(NSString *)imageName size:(CGSize)imageSize
{
    // clear the previous imageView
    [imageView removeFromSuperview];
    [imageView release];
    imageView = nil;
    
    // reset our zoomScale to 1.0 before doing any further calculations
    self.zoomScale = 1.0;
    
    // make a new TilingView for the new image
    imageView = [[TilingView alloc] initWithImageName:imageName size:imageSize];
    [(TilingView *)imageView setAnnotates:YES]; // ** remove this line to remove the white tile grid **
    [self addSubview:imageView];
    
    self.contentSize = imageSize;
    [self setMaxMinZoomScalesForCurrentBounds];
    self.zoomScale = self.minimumZoomScale;
}

- (void)setMaxMinZoomScalesForCurrentBounds
{
    CGSize boundsSize = self.bounds.size;
    CGSize imageSize = imageView.bounds.size;
    
    // calculate min/max zoomscale
    CGFloat xScale = boundsSize.width / imageSize.width;    // the scale needed to perfectly fit the image width-wise
    CGFloat yScale = boundsSize.height / imageSize.height;  // the scale needed to perfectly fit the image height-wise
    CGFloat minScale = MIN(xScale, yScale);                 // use minimum of these to allow the image to become fully visible
    
    // on high resolution screens we have double the pixel density, so we will be seeing every pixel if we limit the
    // maximum zoom scale to 0.5.
    CGFloat maxScale = 1.0 / [[UIScreen mainScreen] scale];
    
    // don't let minScale exceed maxScale. (If the image is smaller than the screen, we don't want to force it to be zoomed.) 
    if (minScale > maxScale) {
        minScale = maxScale;
    }
    
    self.maximumZoomScale = maxScale;
    self.minimumZoomScale = minScale;
}

#pragma mark -
#pragma mark Methods called during rotation to preserve the zoomScale and the visible portion of the image

// returns the center point, in image coordinate space, to try to restore after rotation. 
- (CGPoint)pointToCenterAfterRotation
{
    CGPoint boundsCenter = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));
    return [self convertPoint:boundsCenter toView:imageView];
}

// returns the zoom scale to attempt to restore after rotation. 
- (CGFloat)scaleToRestoreAfterRotation
{
    CGFloat contentScale = self.zoomScale;
    
    // If we're at the minimum zoom scale, preserve that by returning 0, which will be converted to the minimum
    // allowable scale when the scale is restored.
    if (contentScale <= self.minimumZoomScale + FLT_EPSILON)
        contentScale = 0;
    
    return contentScale;
}

- (CGPoint)maximumContentOffset
{
    CGSize contentSize = self.contentSize;
    CGSize boundsSize = self.bounds.size;
    return CGPointMake(contentSize.width - boundsSize.width, contentSize.height - boundsSize.height);
}

- (CGPoint)minimumContentOffset
{
    return CGPointZero;
}

// Adjusts content offset and scale to try to preserve the old zoomscale and center.
- (void)restoreCenterPoint:(CGPoint)oldCenter scale:(CGFloat)oldScale
{    
    // Step 1: restore zoom scale, first making sure it is within the allowable range.
    self.zoomScale = MIN(self.maximumZoomScale, MAX(self.minimumZoomScale, oldScale));
    
    
    // Step 2: restore center point, first making sure it is within the allowable range.
    
    // 2a: convert our desired center point back to our own coordinate space
    CGPoint boundsCenter = [self convertPoint:oldCenter fromView:imageView];
    // 2b: calculate the content offset that would yield that center point
    CGPoint offset = CGPointMake(boundsCenter.x - self.bounds.size.width / 2.0, 
                                 boundsCenter.y - self.bounds.size.height / 2.0);
    // 2c: restore offset, adjusted to be within the allowable range
    CGPoint maxOffset = [self maximumContentOffset];
    CGPoint minOffset = [self minimumContentOffset];
    offset.x = MAX(minOffset.x, MIN(maxOffset.x, offset.x));
    offset.y = MAX(minOffset.y, MIN(maxOffset.y, offset.y));
    self.contentOffset = offset;
}

@end
