/*

 Copyright (C) 2016 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Zoomable image view

 */

#import "BracketStripesZoomImageView.h"

@implementation BracketStripesZoomImageView {

    BOOL _needsSizing;

    // UI

    UIScrollView *_scrollView;

    UIImageView *_imageView;

}

- (instancetype)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        self.backgroundColor = [UIColor whiteColor];

        _scrollView = [[UIScrollView alloc] initWithFrame:CGRectZero];

        _scrollView.delegate = self;

        [self addSubview:_scrollView];

        _imageView = [[UIImageView alloc] initWithFrame:CGRectZero];

        [_scrollView addSubview:_imageView];

    }

    return self;

}

- (void)layoutSubviews

{

    [super layoutSubviews];

    _scrollView.frame = self.bounds;

    if (_needsSizing) {

        [self _performSizing];

    }

}

- (void)setImage:(UIImage *)image

{

    _imageView.image = image;

    if (image) {

        [_imageView sizeToFit];

        _needsSizing = YES;

        [self setNeedsLayout];

    }

}

- (void)_performSizing

{

    _scrollView.zoomScale =

    _scrollView.minimumZoomScale =

    _scrollView.maximumZoomScale =

        1.0;

    UIImage *image = _imageView.image;

    _scrollView.contentSize = image.size;

    if (image) {

        // Aspect fit

        const CGFloat aspect = image.size.width / image.size.height;

        if (aspect*self.bounds.size.height > self.bounds.size.width) {

            // Width constrains us

            _scrollView.zoomScale =

            _scrollView.minimumZoomScale =

                self.bounds.size.width / image.size.width;

        }

        else {

            // Height constrains us

            _scrollView.zoomScale =

            _scrollView.minimumZoomScale =

            self.bounds.size.height / image.size.height;

        }

    }

    [self _centerImageInScrollView];

    _needsSizing = NO;

}

- (void)_centerImageInScrollView

{

    const CGSize boundsSize = _scrollView.bounds.size;

    CGRect frameToCenter = _imageView.frame;

    // Center horizontally

    if (frameToCenter.size.width < boundsSize.width) {

        frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2.0;

    }

    else {

        frameToCenter.origin.x = 0.0;

    }

    // Center vertically

    if (frameToCenter.size.height < boundsSize.height) {

        frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2.0;

    }

    else {

        frameToCenter.origin.y = 0.0;

    }

    _imageView.frame = frameToCenter;

}

#pragma mark - UIScrollViewDelegate

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

{

    return _imageView;

}

- (void)scrollViewDidZoom:(UIScrollView *)scrollView

{

    [self _centerImageInScrollView];

}

@end