/*

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

See LICENSE.txt for this sample’s licensing information

Abstract:

Custom UICollectionViewLayout to represent Circle Layout design.

*/

#import "CircleLayout.h"

#define ITEM_SIZE 70

@interface CircleLayout ()

@property (nonatomic, assign) CGPoint center;

@property (nonatomic, assign) CGFloat radius;

@property (nonatomic, assign) NSInteger cellCount;

@end

@implementation CircleLayout

-(void)prepareLayout

{

    [super prepareLayout];

    CGSize size = self.collectionView.frame.size;

    _cellCount = [[self collectionView] numberOfItemsInSection:0];

    _center = CGPointMake(size.width / 2.0, size.height / 2.0);

    _radius = MIN(size.width, size.height) / 2.5;

}

-(CGSize)collectionViewContentSize

{

    return [self collectionView].frame.size;

}

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)path

{

    UICollectionViewLayoutAttributes* attributes = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:path];

    attributes.size = CGSizeMake(ITEM_SIZE, ITEM_SIZE);

    attributes.center = CGPointMake(_center.x + _radius * cosf(2 * path.item * M_PI / _cellCount),

                                    _center.y + _radius * sinf(2 * path.item * M_PI / _cellCount));

    return attributes;

}

-(NSArray*)layoutAttributesForElementsInRect:(CGRect)rect

{

    NSMutableArray* attributes = [NSMutableArray array];

    for (NSInteger i=0 ; i < self.cellCount; i++) {

        NSIndexPath* indexPath = [NSIndexPath indexPathForItem:i inSection:0];

        [attributes addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];

    }

    return attributes;

}

- (UICollectionViewLayoutAttributes *)initialLayoutAttributesForInsertedItemAtIndexPath:(NSIndexPath *)itemIndexPath

{

    UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];

    attributes.alpha = 0.0;

    attributes.center = CGPointMake(_center.x, _center.y);

    return attributes;

}

- (UICollectionViewLayoutAttributes *)finalLayoutAttributesForDeletedItemAtIndexPath:(NSIndexPath *)itemIndexPath

{

    UICollectionViewLayoutAttributes* attributes = [self layoutAttributesForItemAtIndexPath:itemIndexPath];

    attributes.alpha = 0.0;

    attributes.center = CGPointMake(_center.x, _center.y);

    attributes.transform3D = CATransform3DMakeScale(0.1, 0.1, 1.0);

    return attributes;

}

@end