/*

    Copyright (C) 2015 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    This is the "LoopLayout" class implementation.

*/

#import "AAPLLoopLayout.h"

@implementation AAPLLoopLayout

- (void)prepareLayout {

    [super prepareLayout];

    CGFloat halfItemWidth = 0.5 * itemSize.width;

    CGFloat halfItemHeight = 0.5 * itemSize.height;

    CGFloat radiusInset = sqrt(halfItemWidth * halfItemWidth + halfItemHeight * halfItemHeight);

    loopCenter = NSMakePoint(NSMidX(box), NSMidY(box));

    loopSize = NSMakeSize(0.5 * (box.size.width - 2.0 * radiusInset), 0.5 * (box.size.height - 2.0 * radiusInset));

}

- (NSCollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {

    NSInteger count = [[self collectionView] numberOfItemsInSection:0];

    if (count == 0) {

        return nil;

    }

    NSUInteger itemIndex = [indexPath item];

    CGFloat angleInRadians = ((CGFloat)itemIndex / (CGFloat)count) * (2.0 * M_PI);

    NSPoint subviewCenter;

    subviewCenter.x = loopCenter.x + loopSize.width * cos(angleInRadians);

    subviewCenter.y = loopCenter.y + loopSize.height * sin(2.0 * angleInRadians);

    NSRect itemFrame = NSMakeRect(subviewCenter.x - 0.5 * itemSize.width, subviewCenter.y - 0.5 * itemSize.height, itemSize.width, itemSize.height);

    NSCollectionViewLayoutAttributes *attributes = [[[self class] layoutAttributesClass] layoutAttributesForItemWithIndexPath:indexPath];

    [attributes setFrame:NSRectToCGRect(itemFrame)];

    [attributes setZIndex:[indexPath item]];

    return attributes;

}

@end