//
//  ViewController.m
//

#import "ViewController.h"
#import <Photos/Photos.h>

@interface ImageCollectionViewCell: UICollectionViewCell

- (void)configureWithImage:(UIImage *)image;

@end

@implementation ImageCollectionViewCell
{
  UIImageView *_imageView;
}

- (instancetype)initWithFrame:(CGRect)frame
{
  if (self = [super initWithFrame:frame]) {
    _imageView = [UIImageView new];
    [self.contentView addSubview:_imageView];
  }
  return self;
}

- (void)layoutSubviews
{
  [super layoutSubviews];
  _imageView.frame = self.contentView.bounds;
}

- (void)configureWithImage:(UIImage *)image
{
  _imageView.image = image;
}

@end

@interface ViewController ()
<
UICollectionViewDataSource
>
@end

@implementation ViewController
{
  UICollectionView *_collectionView;
  NSMutableArray<UIImage *> *_images;
}

- (instancetype)init
{
  if (self = [super initWithNibName:nil bundle:nil]) {
    _images = [NSMutableArray array];
  }
  return self;
}

- (void)viewDidLayoutSubviews
{
  [super viewDidLayoutSubviews];
  _collectionView.frame = self.view.bounds;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  
  UICollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
  layout.itemSize = CGSizeMake(300, 300);
  _collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
  _collectionView.dataSource = self;
  [_collectionView registerClass:[ImageCollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];
  [self.view addSubview:_collectionView];
  
  // Do any additional setup after loading the view.
  [PHPhotoLibrary requestAuthorizationForAccessLevel:PHAccessLevelReadWrite handler:^(PHAuthorizationStatus status) {
    dispatch_async(dispatch_get_main_queue(), ^{
      if (status == PHAuthorizationStatusDenied) {
        return;
      }
      
      [self fetchPhotos];
    });
  }];
}

- (void)fetchPhotos
{
  NSMutableArray<UIImage *> *images = [NSMutableArray array];
  
  PHFetchOptions *const options = [PHFetchOptions new];
  PHFetchResult<PHAsset *> *const fetchResult = [PHAsset fetchAssetsWithOptions:options];
  [fetchResult enumerateObjectsUsingBlock:^(PHAsset * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    PHImageRequestOptions *const requestOptions = [PHImageRequestOptions new];
    requestOptions.synchronous = YES;
    [[PHImageManager defaultManager] requestImageForAsset:obj
                                               targetSize:CGSizeMake(2000, 2000)
                                              contentMode:PHImageContentModeDefault
                                                  options:requestOptions
                                            resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
      if (result) {
        [images addObject:result];
      }
    }];
  }];
  
  _images = images;
  [_collectionView reloadData];
}

#pragma mark - UICollectionViewDataSource

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
  return _images.count;
}

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
  ImageCollectionViewCell *cell = (ImageCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"Cell" forIndexPath:indexPath];
  [cell configureWithImage:_images[indexPath.item]];
  return cell;
}

@end