/*

     File: ImageScrollView.m

 Abstract: Centers image within the scroll view and configures image sizing and display.

  Version: 1.1

 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) 2013 Apple Inc. All Rights Reserved.

 */

#import "ImageScrollView.h"

#import "PageViewControllerData.h"

@interface ImageScrollView () <UIScrollViewDelegate>

@property (nonatomic, strong) UIImageView *zoomView;  // contains the full image

@property CGSize imageSize;

@property CGPoint pointToCenterAfterResize;

@property CGFloat scaleToRestoreAfterResize;

@end

#pragma mark -

@implementation ImageScrollView

- (id)initWithFrame:(CGRect)frame {

    self = [super initWithFrame:frame];

    if (self) {

        self.showsVerticalScrollIndicator = NO;

        self.showsHorizontalScrollIndicator = NO;

        self.bouncesZoom = YES;

        self.decelerationRate = UIScrollViewDecelerationRateFast;

        self.delegate = self;        

    }

    return self;

}

- (void)setIndex:(NSUInteger)index {

    _index = index;

    UIImage *image = [[PageViewControllerData sharedInstance] photoAtIndex:index];

    [self displayImage:image];

}

+ (NSUInteger)imageCount {

    return [[PageViewControllerData sharedInstance] photoCount];

}

- (void)layoutSubviews  {

    [super layoutSubviews];

    // center the zoom view as it becomes smaller than the size of the screen

    CGSize boundsSize = self.bounds.size;

    CGRect frameToCenter = _zoomView.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;

    _zoomView.frame = frameToCenter;

}

- (void)setFrame:(CGRect)frame {

    BOOL sizeChanging = !CGSizeEqualToSize(frame.size, self.frame.size);

    if (sizeChanging) {

        [self prepareToResize];

    }

    [super setFrame:frame];

    if (sizeChanging) {

        [self recoverFromResizing];

    }

}

#pragma mark - UIScrollViewDelegate

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

    return _zoomView;

}

#pragma mark - Configure scrollView to display new image

- (void)displayImage:(UIImage *)image {

    // clear the previous image

    [_zoomView removeFromSuperview];

    _zoomView = nil;

    // reset our zoomScale to 1.0 before doing any further calculations

    self.zoomScale = 1.0;

    // make a new UIImageView for the new image

    _zoomView = [[UIImageView alloc] initWithImage:image];

    [self addSubview:_zoomView];

    [self configureForImageSize:image.size];

}

- (void)configureForImageSize:(CGSize)imageSize {

    _imageSize = imageSize;

    self.contentSize = imageSize;

    [self setMaxMinZoomScalesForCurrentBounds];

    self.zoomScale = self.minimumZoomScale;

}

- (void)setMaxMinZoomScalesForCurrentBounds {

    CGSize boundsSize = self.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

    // fill width if the image and phone are both portrait or both landscape; otherwise take smaller scale

    BOOL imagePortrait = _imageSize.height > _imageSize.width;

    BOOL phonePortrait = boundsSize.height > boundsSize.width;

    CGFloat minScale = imagePortrait == phonePortrait ? xScale : MIN(xScale, yScale);

    // 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 - Methods called during rotation to preserve the zoomScale and the visible portion of the image

- (void)prepareToResize {

    CGPoint boundsCenter = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));

    _pointToCenterAfterResize = [self convertPoint:boundsCenter toView:_zoomView];

    _scaleToRestoreAfterResize = 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 (_scaleToRestoreAfterResize <= self.minimumZoomScale + FLT_EPSILON)

        _scaleToRestoreAfterResize = 0;

}

- (void)recoverFromResizing {

    [self setMaxMinZoomScalesForCurrentBounds];

    // Step 1: restore zoom scale, first making sure it is within the allowable range.

    CGFloat maxZoomScale = MAX(self.minimumZoomScale, _scaleToRestoreAfterResize);

    self.zoomScale = MIN(self.maximumZoomScale, maxZoomScale);

    // 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:_pointToCenterAfterResize fromView:_zoomView];

    // 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];

    CGFloat realMaxOffset = MIN(maxOffset.x, offset.x);

    offset.x = MAX(minOffset.x, realMaxOffset);

    realMaxOffset = MIN(maxOffset.y, offset.y);

    offset.y = MAX(minOffset.y, realMaxOffset);

    self.contentOffset = offset;

}

- (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;

}

@end