text: /*
   
   MIT License (MIT)
   
   Copyright (c) 2015 Clement CN Tsang
   
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files (the "Software"), to deal
   in the Software without restriction, including without limitation the rights
   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   copies of the Software, and to permit persons to whom the Software is
   furnished to do so, subject to the following conditions:
   
   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.
   
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   THE SOFTWARE.
   
   */
  
  #import "CTAssetsPickerDefines.h"
  #import "CTAssetsPickerController.h"
  #import "CTAssetsPickerController+Internal.h"
  #import "CTAssetCollectionViewController.h"
  #import "CTAssetCollectionViewCell.h"
  #import "CTAssetsGridViewController.h"
  #import "PHAssetCollection+CTAssetsPickerController.h"
  #import "PHAsset+CTAssetsPickerController.h"
  #import "PHImageManager+CTAssetsPickerController.h"
  #import "NSBundle+CTAssetsPickerController.h"
  
  
  
  
  
  @interface CTAssetCollectionViewController()
  <PHPhotoLibraryChangeObserver, CTAssetsGridViewControllerDelegate>
  
  @property (nonatomic, weak) CTAssetsPickerController *picker;
  
  @property (nonatomic, strong) UIBarButtonItem *cancelButton;
  @property (nonatomic, strong) UIBarButtonItem *doneButton;
  
  @property (nonatomic, copy) NSArray *fetchResults;
  @property (nonatomic, copy) NSArray *assetCollections;
  @property (nonatomic, strong) PHCachingImageManager *imageManager;
  
  @property (nonatomic, strong) PHAssetCollection *defaultAssetCollection;
  @property (nonatomic, assign) BOOL didShowDefaultAssetCollection;
  @property (nonatomic, assign) BOOL didSelectDefaultAssetCollection;
  
  @end
  
  
  
  
  
  @implementation CTAssetCollectionViewController
  
  - (instancetype)init
  {
      if (self = [super initWithStyle:UITableViewStylePlain])
      {
          _imageManager = [PHCachingImageManager new];
          [self addNotificationObserver];
      }
      
      return self;
  }
  
  - (void)viewDidLoad
  {
      [super viewDidLoad];
      [self setupViews];
      [self localize];
      [self setupDefaultAssetCollection];
      [self setupFetchResults];
      [self registerChangeObserver];
  }
  
  - (void)viewWillAppear:(BOOL)animated
  {
      [super viewWillAppear:animated];
      [self setupButtons];
      [self updateTitle:self.picker.selectedAssets];
      [self updateButton:self.picker.selectedAssets];
      [self selectDefaultAssetCollection];
  }
  
  - (void)dealloc
  {
      [self unregisterChangeObserver];
      [self removeNotificationObserver];
  }
  
  
  #pragma mark - Reload user interface
  
  - (void)reloadUserInterface
  {
      [self setupViews];
      [self setupButtons];
      [self localize];
      [self setupDefaultAssetCollection];
      [self setupFetchResults];
  }
  
  
  #pragma mark - Accessors
  
  - (CTAssetsPickerController *)picker
  {
      return (CTAssetsPickerController *)self.splitViewController.parentViewController;
  }
  
  - (NSIndexPath *)indexPathForAssetCollection:(PHAssetCollection *)assetCollection
  {
      NSInteger row = [self.assetCollections indexOfObject:assetCollection];
  
      if (row != NSNotFound)
          return [NSIndexPath indexPathForRow:row inSection:0];
      else
          return nil;
  }
  
  
  #pragma mark - Setup
  
  - (void)setupViews
  {
      self.tableView.rowHeight = UITableViewAutomaticDimension;
      
      self.tableView.estimatedRowHeight =
      self.picker.assetCollectionThumbnailSize.height +
      self.tableView.layoutMargins.top +
      self.tableView.layoutMargins.bottom;
  
      self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
  }
  
  - (void)setupButtons
  {
      if (self.doneButton == nil)
      {
          NSString *title = (self.picker.doneButtonTitle) ?
          self.picker.doneButtonTitle : CTAssetsPickerLocalizedString(@"Done", nil);
          
          self.doneButton =
          [[UIBarButtonItem alloc] initWithTitle:title
                                           style:UIBarButtonItemStyleDone
                                          target:self.picker
                                          action:@selector(finishPickingAssets:)];
      }
      
      if (self.cancelButton == nil)
      {
          self.cancelButton =
          [[UIBarButtonItem alloc] initWithTitle:CTAssetsPickerLocalizedString(@"Cancel", nil)
                                           style:UIBarButtonItemStylePlain
                                          target:self.picker
                                          action:@selector(dismiss:)];
      }
  }
  
  - (void)localize
  {
      [self resetTitle];
  }
  
  - (void)setupFetchResults
  {
      NSMutableArray *fetchResults = [NSMutableArray new];
  
      for (NSNumber *subtypeNumber in self.picker.assetCollectionSubtypes)
      {
          PHAssetCollectionType type       = [PHAssetCollection ctassetPickerAssetCollectionTypeOfSubtype:subtypeNumber.integerValue];
          PHAssetCollectionSubtype subtype = subtypeNumber.integerValue;
          
          PHFetchResult *fetchResult =
          [PHAssetCollection fetchAssetCollectionsWithType:type
                                                   subtype:subtype
                                                   options:self.picker.assetCollectionFetchOptions];
          
          [fetchResults addObject:fetchResult];
      }
      
      self.fetchResults = [NSMutableArray arrayWithArray:fetchResults];
      
      [self updateAssetCollections];
      [self reloadData];
      [self showDefaultAssetCollection];
  }
  
  - (void)updateAssetCollections
  {
      NSMutableArray *assetCollections = [NSMutableArray new];
  
      for (PHFetchResult *fetchResult in self.fetchResults)
      {
          for (PHAssetCollection *assetCollection in fetchResult)
          {
              BOOL showsAssetCollection = YES;
              
              if (!self.picker.showsEmptyAlbums)
              {
                  PHFetchOptions *options = [PHFetchOptions new];
                  options.predicate = self.picker.assetsFetchOptions.predicate;
                  
                  if ([options respondsToSelector:@selector(setFetchLimit:)])
                      options.fetchLimit = 1;
                  
                  NSInteger count = [assetCollection ctassetPikcerCountOfAssetsFetchedWithOptions:options];
                  
                  showsAssetCollection = (count > 0);
              }
              
              if (showsAssetCollection)
                  [assetCollections addObject:assetCollection];
          }
      }
  
      self.assetCollections = [NSMutableArray arrayWithArray:assetCollections];
  }
  
  - (void)setupDefaultAssetCollection
  {
      if (!self.picker || self.picker.defaultAssetCollection == PHAssetCollectionSubtypeAny) {
          self.defaultAssetCollection = nil;
          return;
      }
      
      PHAssetCollectionType type = [PHAssetCollection ctassetPickerAssetCollectionTypeOfSubtype:self.picker.defaultAssetCollection];
      PHFetchResult *fetchResult = [PHAssetCollection fetchAssetCollectionsWithType:type subtype:self.picker.defaultAssetCollection options:self.picker.assetCollectionFetchOptions];
      
      self.defaultAssetCollection = fetchResult.firstObject;
  }
  
  
  #pragma mark - Rotation
  
  - (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
  {
      [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
      
      [coordinator animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) {
          [self updateTitle:self.picker.selectedAssets];
          [self updateButton:self.picker.selectedAssets];
      } completion:nil];
  }
  
  #pragma mark - Notifications
  
  - (void)addNotificationObserver
  {
      NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
      
      [center addObserver:self
                 selector:@selector(selectedAssetsChanged:)
                     name:CTAssetsPickerSelectedAssetsDidChangeNotification
                   object:nil];
      
      [center addObserver:self
                 selector:@selector(contentSizeCategoryChanged:)
                     name:UIContentSizeCategoryDidChangeNotification
                   object:nil];
  }
  
  - (void)removeNotificationObserver
  {
      [[NSNotificationCenter defaultCenter] removeObserver:self name:CTAssetsPickerSelectedAssetsDidChangeNotification object:nil];
      [[NSNotificationCenter defaultCenter] removeObserver:self name:UIContentSizeCategoryDidChangeNotification object:nil];
  }
  
  
  #pragma mark - Photo library change observer
  
  - (void)registerChangeObserver
  {
      [[PHPhotoLibrary sharedPhotoLibrary] registerChangeObserver:self];
  }
  
  - (void)unregisterChangeObserver
  {
      [[PHPhotoLibrary sharedPhotoLibrary] unregisterChangeObserver:self];
  }
  
  
  #pragma mark - Photo library changed
  
  - (void)photoLibraryDidChange:(PHChange *)changeInstance
  {
      // Call might come on any background queue. Re-dispatch to the main queue to handle it.
      dispatch_async(dispatch_get_main_queue(), ^{
          
          NSMutableArray *updatedFetchResults = nil;
          
          for (PHFetchResult *fetchResult in self.fetchResults)
          {
              PHFetchResultChangeDetails *changeDetails = [changeInstance changeDetailsForFetchResult:fetchResult];
              
              if (changeDetails)
              {
                  if (!updatedFetchResults)
                      updatedFetchResults = [self.fetchResults mutableCopy];
                  
                  updatedFetchResults[[self.fetchResults indexOfObject:fetchResult]] = changeDetails.fetchResultAfterChanges;
              }
          }
          
          if (updatedFetchResults)
          {
              self.fetchResults = updatedFetchResults;
              [self updateAssetCollections];
              [self reloadData];
          }
          
      });
  }
  
  
  #pragma mark - Selected assets changed
  
  - (void)selectedAssetsChanged:(NSNotification *)notification
  {
      NSArray *selectedAssets = (NSArray *)notification.object;
      [self updateTitle:selectedAssets];
      [self updateButton:selectedAssets];
  }
  
  - (void)updateTitle:(NSArray *)selectedAssets
  {
      if ([self isTopViewController] && selectedAssets.count > 0)
          self.title = self.picker.selectedAssetsString;
      else
          [self resetTitle];
  }
  
  - (void)updateButton:(NSArray *)selectedAssets
  {
      self.navigationItem.leftBarButtonItem = (self.picker.showsCancelButton) ? self.cancelButton : nil;
      self.navigationItem.rightBarButtonItem = [self isTopViewController] ? self.doneButton : nil;
      
      if (self.picker.alwaysEnableDoneButton)
          self.navigationItem.rightBarButtonItem.enabled = YES;
      else
          self.navigationItem.rightBarButtonItem.enabled = (self.picker.selectedAssets.count > 0);
  }
  
  - (BOOL)isTopViewController
  {
      UIViewController *vc = self.splitViewController.viewControllers.lastObject;
      
      if ([vc isMemberOfClass:[UINavigationController class]])
          return (self == ((UINavigationController *)vc).topViewController);
      else
          return NO;
  }
  
  - (void)resetTitle
  {
      if (!self.picker.title)
          self.title = CTAssetsPickerLocalizedString(@"Photos", nil);
      else
          self.title = self.picker.title;
  }
  
  
  #pragma mark - Content size category changed
  
  - (void)contentSizeCategoryChanged:(NSNotification *)notification
  {
      [self reloadData];
  }
  
  
  #pragma mark - Reload data
  
  - (void)reloadData
  {
      if (self.assetCollections.count > 0)
          [self.tableView reloadData];
      else
          [self.picker showNoAssets];
  }
  
  
  #pragma mark - Table view data source
  
  - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
  {
      return 1;
  }
  
  - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
  {
      return self.assetCollections.count;
  }
  
  - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
  {
      PHAssetCollection *collection = self.assetCollections[indexPath.row];
      NSUInteger count;
      
      if (self.picker.showsNumberOfAssets)
          count = [collection ctassetPikcerCountOfAssetsFetchedWithOptions:self.picker.assetsFetchOptions];
      else
          count = NSNotFound;
      
      static NSString *cellIdentifier = @"CellIdentifier";
      
      CTAssetCollectionViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
      
      if (cell == nil)
          cell = [[CTAssetCollectionViewCell alloc] initWithThumbnailSize:self.picker.assetCollectionThumbnailSize
                                                              reuseIdentifier:cellIdentifier];
      
      [cell bind:collection count:count];
      [self requestThumbnailsForCell:cell assetCollection:collection];
      
      return cell;
  }
  
  - (void)requestThumbnailsForCell:(CTAssetCollectionViewCell *)cell assetCollection:(PHAssetCollection *)collection
  {
      NSUInteger count    = cell.thumbnailStacks.thumbnailViews.count;
      NSArray *assets     = [self posterAssetsFromAssetCollection:collection count:count];
      CGSize targetSize   = [self.picker imageSizeForContainerSize:self.picker.assetCollectionThumbnailSize];
      
      for (NSUInteger index = 0; index < count; index++)
      {
          CTAssetThumbnailView *thumbnailView = [cell.thumbnailStacks thumbnailAtIndex:index];
          thumbnailView.hidden = (assets.count > 0) ? YES : NO;
          
          if (index < assets.count)
          {
              PHAsset *asset = assets[index];
              [self.imageManager ctassetsPickerRequestImageForAsset:asset
                                           targetSize:targetSize
                                          contentMode:PHImageContentModeAspectFill
                                              options:self.picker.thumbnailRequestOptions
                                        resultHandler:^(UIImage *image, NSDictionary *info){
                                            [thumbnailView setHidden:NO];
                                            [thumbnailView bind:image assetCollection:collection];
                                        }];
          }
      }
  }
  
  - (NSArray *)posterAssetsFromAssetCollection:(PHAssetCollection *)collection count:(NSUInteger)count;
  {
      PHFetchOptions *options = [PHFetchOptions new];
      options.predicate       = self.picker.assetsFetchOptions.predicate; // aligned specified predicate
      options.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:YES]];
      
      PHFetchResult *result = [PHAsset fetchKeyAssetsInAssetCollection:collection options:options];
      
      NSUInteger location = 0;
      NSUInteger length   = (result.count < count) ? result.count : count;
      NSArray *assets     = [self itemsFromFetchResult:result range:NSMakeRange(location, length)];
      
      return assets;
  }
  
  - (NSArray *)itemsFromFetchResult:(PHFetchResult *)result range:(NSRange)range
  {
      if (result.count == 0)
          return nil;
      
      NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:range];
      NSArray *array = [result objectsAtIndexes:indexSet];
      
      return array;
  }
  
  
  #pragma mark - Table view delegate
  
  - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
  {
      PHAssetCollection *collection = self.assetCollections[indexPath.row];
      
      CTAssetsGridViewController *vc = [CTAssetsGridViewController new];
      vc.title = self.picker.selectedAssetsString ? : collection.localizedTitle;
      vc.assetCollection = collection;
      vc.delegate = self;
      
      UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
      nav.delegate = (id<UINavigationControllerDelegate>)self.picker;
      
      [self.picker setShouldCollapseDetailViewController:NO];
      [self.splitViewController showDetailViewController:nav sender:nil];
  }
  
  
  #pragma mark - Show / select default asset collection
  
  - (void)showDefaultAssetCollection
  {
      if (self.defaultAssetCollection && !self.didShowDefaultAssetCollection)
      {
          CTAssetsGridViewController *vc = [CTAssetsGridViewController new];
          vc.title = self.picker.selectedAssetsString ? : self.defaultAssetCollection.localizedTitle;
          vc.assetCollection = self.defaultAssetCollection;
          vc.delegate = self;
          
          UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
          nav.delegate = (id<UINavigationControllerDelegate>)self.picker;
          
          [self.picker setShouldCollapseDetailViewController:(self.picker.modalPresentationStyle == UIModalPresentationFormSheet)];
          [self.splitViewController showDetailViewController:nav sender:nil];
  
          NSIndexPath *indexPath = [self indexPathForAssetCollection:self.defaultAssetCollection];
          [self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionTop];
          
          self.didShowDefaultAssetCollection = YES;
      }
  }
  
  - (void)selectDefaultAssetCollection
  {
      if (self.defaultAssetCollection && !self.didSelectDefaultAssetCollection)
      {
          NSIndexPath *indexPath = [self indexPathForAssetCollection:self.defaultAssetCollection];
          
          if (indexPath)
          {
              [UIView animateWithDuration:0.0f
                               animations:^{
                                   [self.tableView selectRowAtIndexPath:indexPath
                                                               animated:(!self.splitViewController.collapsed)
                                                         scrollPosition:UITableViewScrollPositionTop];
                           }
                           completion:^(BOOL finished){
                               // mimic clearsSelectionOnViewWillAppear
                               if (finished && self.splitViewController.collapsed)
                                   [self.tableView deselectRowAtIndexPath:indexPath animated:YES];
                           }];
          }
          
          self.didSelectDefaultAssetCollection = YES;
      }
  }
  
  
  #pragma mark - Grid view controller delegate
  
  - (void)assetsGridViewController:(CTAssetsGridViewController *)picker photoLibraryDidChangeForAssetCollection:(PHAssetCollection *)assetCollection
  {
      NSIndexPath *indexPath = [self indexPathForAssetCollection:assetCollection];
      
      if (indexPath)
      {
          [self.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];
          [self.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
      }
  }
  
  @end