MWGridViewController.m

//
//  MWGridViewController.m
//  MWPhotoBrowser
//
//  Created by Michael Waterfall on 08/10/2013.
//
//

#import "MWGridViewController.h"
#import "MWGridCell.h"
#import "MWPhotoBrowserPrivate.h"
#import "MWCommon.h"

@interface MWGridViewController () {
    
    // Store margins for current setup
    CGFloat _margin, _gutter, _marginL, _gutterL, _columns, _columnsL;
    
}

@end

@implementation MWGridViewController

- (id)init {
    if ((self = [super initWithCollectionViewLayout:[UICollectionViewFlowLayout new]])) {
        
        // Defaults
        _columns = 3, _columnsL = 4;
        _margin = 0, _gutter = 1;
        _marginL = 0, _gutterL = 1;
        
        // For pixel perfection...
        if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
            // iPad
            _columns = 6, _columnsL = 8;
            _margin = 1, _gutter = 2;
            _marginL = 1, _gutterL = 2;
        } else if ([UIScreen mainScreen].bounds.size.height == 480) {
            // iPhone 3.5 inch
            _columns = 3, _columnsL = 4;
            _margin = 0, _gutter = 1;
            _marginL = 1, _gutterL = 2;
        } else {
            // iPhone 4 inch
            _columns = 3, _columnsL = 5;
            _margin = 0, _gutter = 1;
            _marginL = 0, _gutterL = 2;
        }

        _initialContentOffset = CGPointMake(0, CGFLOAT_MAX);
 
    }
    return self;
}

#pragma mark - View

- (void)viewDidLoad {
    [super viewDidLoad];
    [self.collectionView registerClass:[MWGridCell class] forCellWithReuseIdentifier:@"GridCell"];
    self.collectionView.alwaysBounceVertical = YES;
    self.collectionView.backgroundColor = [UIColor blackColor];
}

- (void)viewWillDisappear:(BOOL)animated {
    // Cancel outstanding loading
    NSArray *visibleCells = [self.collectionView visibleCells];
    if (visibleCells) {
        for (MWGridCell *cell in visibleCells) {
            [cell.photo cancelAnyLoading];
        }
    }
    [super viewWillDisappear:animated];
}

- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];
    [self performLayout];
}

- (void)viewDidLayoutSubviews {
    [super viewDidLayoutSubviews];
}

- (void)adjustOffsetsAsRequired {
    
    // Move to previous content offset
    if (_initialContentOffset.y != CGFLOAT_MAX) {
        self.collectionView.contentOffset = _initialContentOffset;
        [self.collectionView layoutIfNeeded]; // Layout after content offset change
    }
    
    // Check if current item is visible and if not, make it so!
    if (_browser.numberOfPhotos > 0) {
        NSIndexPath *currentPhotoIndexPath = [NSIndexPath indexPathForItem:_browser.currentIndex inSection:0];
        NSArray *visibleIndexPaths = [self.collectionView indexPathsForVisibleItems];
        BOOL currentVisible = NO;
        for (NSIndexPath *indexPath in visibleIndexPaths) {
            if ([indexPath isEqual:currentPhotoIndexPath]) {
                currentVisible = YES;
                break;
            }
        }
        if (!currentVisible) {
            [self.collectionView scrollToItemAtIndexPath:currentPhotoIndexPath atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
        }
    }
    
}

- (void)performLayout {
    UINavigationBar *navBar = self.navigationController.navigationBar;
    self.collectionView.contentInset = UIEdgeInsetsMake(navBar.frame.origin.y + navBar.frame.size.height + [self getGutter], 0, 0, 0);
}

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    [self.collectionView reloadData];
    [self performLayout]; // needed for iOS 5 & 6
}

#pragma mark - Layout

- (CGFloat)getColumns {
    if ((UIInterfaceOrientationIsPortrait(self.interfaceOrientation))) {
        return _columns;
    } else {
        return _columnsL;
    }
}

- (CGFloat)getMargin {
    if ((UIInterfaceOrientationIsPortrait(self.interfaceOrientation))) {
        return _margin;
    } else {
        return _marginL;
    }
}

- (CGFloat)getGutter {
    if ((UIInterfaceOrientationIsPortrait(self.interfaceOrientation))) {
        return _gutter;
    } else {
        return _gutterL;
    }
}

#pragma mark - Collection View

- (NSInteger)collectionView:(UICollectionView *)view numberOfItemsInSection:(NSInteger)section {
    return [_browser numberOfPhotos];
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    MWGridCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"GridCell" forIndexPath:indexPath];
    if (!cell) {
        cell = [[MWGridCell alloc] init];
    }
    id <MWPhoto> photo = [_browser thumbPhotoAtIndex:indexPath.row];
    cell.photo = photo;
    cell.gridController = self;
    cell.selectionMode = _selectionMode;
    cell.isSelected = [_browser photoIsSelectedAtIndex:indexPath.row];
    cell.index = indexPath.row;
    UIImage *img = [_browser imageForPhoto:photo];
    if (img) {
        [cell displayImage];
    } else {
        [photo loadUnderlyingImageAndNotify];
    }
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    [_browser setCurrentPhotoIndex:indexPath.row];
    [_browser hideGrid];
}

- (void)collectionView:(UICollectionView *)collectionView didEndDisplayingCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath {
    [((MWGridCell *)cell).photo cancelAnyLoading];
}

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    CGFloat margin = [self getMargin];
    CGFloat gutter = [self getGutter];
    CGFloat columns = [self getColumns];
    CGFloat value = floorf(((self.view.bounds.size.width - (columns - 1) * gutter - 2 * margin) / columns));
    return CGSizeMake(value, value);
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section {
    return [self getGutter];
}

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section {
    return [self getGutter];
}

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
    CGFloat margin = [self getMargin];
    return UIEdgeInsetsMake(margin, margin, margin, margin);
}

@end