ContentSuggestions collection adds items with animation

ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_collection_updater.h"
 
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/time/time.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller.h"
@@ skipping 69 matching lines @@
 
 @interface ContentSuggestionsCollectionUpdater ()<
     ContentSuggestionsArticleItemDelegate,
     ContentSuggestionsDataSink>
 
 @property(nonatomic, weak) id<ContentSuggestionsDataSource> dataSource;
 @property(nonatomic, strong)
     NSMutableDictionary<NSNumber*, ContentSuggestionsSectionInformation*>*
         sectionInfoBySectionIdentifier;
 
-// Adds a new section if needed and returns the section identifier.
-- (NSInteger)addSectionIfNeeded:
-    (ContentSuggestionsSectionInformation*)sectionInformation;
-// Resets the models, removing the current CollectionViewItem and the
-// SectionInfo.
-- (void)resetModels;
-
 @end
 
 @implementation ContentSuggestionsCollectionUpdater
 
 @synthesize collectionViewController = _collectionViewController;
 @synthesize dataSource = _dataSource;
 @synthesize sectionInfoBySectionIdentifier = _sectionInfoBySectionIdentifier;
 
 - (instancetype)initWithDataSource:
     (id<ContentSuggestionsDataSource>)dataSource {
@@ skipping 21 matching lines @@
   SectionIdentifier sectionIdentifier = SectionIdentifierForInfo(sectionInfo);
 
   CollectionViewModel* model =
       self.collectionViewController.collectionViewModel;
   if ([model hasSectionForSectionIdentifier:sectionIdentifier] &&
       [model itemsInSectionWithIdentifier:sectionIdentifier].count > 0) {
     // Do not dismiss the presented items.
     return;
   }
 
-  [self addSuggestions:[self.dataSource suggestionsForSection:sectionInfo]];
+  [self.collectionViewController
+      addSuggestions:[self.dataSource suggestionsForSection:sectionInfo]];
 }
 
 - (void)clearSuggestion:(ContentSuggestionIdentifier*)suggestionIdentifier {
   SectionIdentifier sectionIdentifier =
       SectionIdentifierForInfo(suggestionIdentifier.sectionInfo);
   if (![self.collectionViewController.collectionViewModel
           hasSectionForSectionIdentifier:sectionIdentifier]) {
     return;
   }
 
@@ skipping 14 matching lines @@
     return;
 
   NSIndexPath* indexPath = [self.collectionViewController.collectionViewModel
              indexPathForItem:correspondingItem
       inSectionWithIdentifier:sectionIdentifier];
   [self.collectionViewController dismissEntryAtIndexPath:indexPath];
 }
 
 - (void)reloadAllData {
   [self resetModels];
-  [self addSuggestions:[self.dataSource allSuggestions]];
+  [self.collectionViewController
+      addSuggestions:[self.dataSource allSuggestions]];
 }
 
 - (void)clearSection:(ContentSuggestionsSectionInformation*)sectionInfo {
   SectionIdentifier sectionIdentifier = SectionIdentifierForInfo(sectionInfo);
   NSInteger section = [self.collectionViewController.collectionViewModel
       sectionIdentifierForSection:sectionIdentifier];
 
   [self.collectionViewController dismissSection:section];
 }
 
 #pragma mark - Public methods
 
 - (BOOL)shouldUseCustomStyleForSection:(NSInteger)section {
   NSNumber* identifier = @([self.collectionViewController.collectionViewModel
       sectionIdentifierForSection:section]);
   ContentSuggestionsSectionInformation* sectionInformation =
       self.sectionInfoBySectionIdentifier[identifier];
   return sectionInformation.layout == ContentSuggestionsSectionLayoutCustom;
 }
 
 - (ContentSuggestionType)contentSuggestionTypeForItem:
     (CollectionViewItem*)item {
   return ContentSuggestionTypeForItemType(item.type);
 }
 
-#pragma mark - ContentSuggestionsArticleItemDelegate
-
-- (void)loadImageForArticleItem:(ContentSuggestionsArticleItem*)articleItem {
-  NSInteger sectionIdentifier =
-      SectionIdentifierForInfo(articleItem.suggestionIdentifier.sectionInfo);
-
-  __weak ContentSuggestionsCollectionUpdater* weakSelf = self;
-  __weak ContentSuggestionsArticleItem* weakArticle = articleItem;
-  void (^imageFetchedCallback)(const gfx::Image&) = ^(const gfx::Image& image) {
-    if (image.IsEmpty()) {
-      return;
-    }
-
-    ContentSuggestionsCollectionUpdater* strongSelf = weakSelf;
-    ContentSuggestionsArticleItem* strongArticle = weakArticle;
-    if (!strongSelf || !strongArticle) {
-      return;
-    }
-
-    strongArticle.image = image.CopyUIImage();
-    [strongSelf.collectionViewController
-        reconfigureCellsForItems:@[ strongArticle ]
-         inSectionWithIdentifier:sectionIdentifier];
-  };
-
-  [self.dataSource.imageFetcher
-      fetchImageForSuggestion:articleItem.suggestionIdentifier
-                     callback:imageFetchedCallback];
-}
-
-#pragma mark - Private methods
-
-// Add the |suggestions| to the model and reload the data.
-- (void)addSuggestions:(NSArray<ContentSuggestion*>*)suggestions {
+- (NSArray<NSIndexPath*>*)addSuggestionsToModel:
+    (NSArray<ContentSuggestion*>*)suggestions {
   if (suggestions.count == 0) {
-    return;
+    return [NSArray array];
   }
 
   CollectionViewModel* model =
       self.collectionViewController.collectionViewModel;
 
+  NSMutableArray<NSIndexPath*>* indexPaths = [NSMutableArray array];
   for (ContentSuggestion* suggestion in suggestions) {
     NSInteger sectionIdentifier =
-        [self addSectionIfNeeded:suggestion.suggestionIdentifier.sectionInfo];
+        SectionIdentifierForInfo(suggestion.suggestionIdentifier.sectionInfo);
+
     ContentSuggestionsArticleItem* articleItem =
         [[ContentSuggestionsArticleItem alloc]
             initWithType:ItemTypeForContentSuggestionType(suggestion.type)
                    title:suggestion.title
                 subtitle:suggestion.text
                 delegate:self
                      url:suggestion.url];
 
     articleItem.publisher = suggestion.publisher;
     articleItem.publishDate = suggestion.publishDate;
 
     articleItem.suggestionIdentifier = suggestion.suggestionIdentifier;
 
+    NSInteger section = [model sectionForSectionIdentifier:sectionIdentifier];
+    NSInteger itemNumber = [model numberOfItemsInSection:section];
     [model addItem:articleItem toSectionWithIdentifier:sectionIdentifier];
+
+    [indexPaths
+        addObject:[NSIndexPath indexPathForItem:itemNumber inSection:section]];
   }
 
-  if ([self.collectionViewController isViewLoaded]) {
-    [self.collectionViewController.collectionView reloadData];
-  }
+  return indexPaths;
 }
 
-- (NSInteger)addSectionIfNeeded:
-    (ContentSuggestionsSectionInformation*)sectionInformation {
-  NSInteger sectionIdentifier = SectionIdentifierForInfo(sectionInformation);
+- (NSIndexSet*)addSectionsForSuggestionsToModel:
+    (NSArray<ContentSuggestion*>*)suggestions {
+  NSMutableIndexSet* indexSet = [NSMutableIndexSet indexSet];
 
   CollectionViewModel* model =
       self.collectionViewController.collectionViewModel;
-  if (![model hasSectionForSectionIdentifier:sectionIdentifier]) {
-    [model addSectionWithIdentifier:sectionIdentifier];
-    self.sectionInfoBySectionIdentifier[@(sectionIdentifier)] =
-        sectionInformation;
-    [self.sectionInfoBySectionIdentifier setObject:sectionInformation
-                                            forKey:@(sectionIdentifier)];
+  for (ContentSuggestion* suggestion in suggestions) {
+    ContentSuggestionsSectionInformation* sectionInfo =
+        suggestion.suggestionIdentifier.sectionInfo;
+    NSInteger sectionIdentifier = SectionIdentifierForInfo(sectionInfo);
+
+    if (![model hasSectionForSectionIdentifier:sectionIdentifier]) {
+      [model addSectionWithIdentifier:sectionIdentifier];
+      self.sectionInfoBySectionIdentifier[@(sectionIdentifier)] = sectionInfo;
+      [indexSet addIndex:[model sectionForSectionIdentifier:sectionIdentifier]];
+    }
   }
-  return sectionIdentifier;
+  return indexSet;
 }
 
+#pragma mark - ContentSuggestionsArticleItemDelegate
+
+- (void)loadImageForArticleItem:(ContentSuggestionsArticleItem*)articleItem {
+  NSInteger sectionIdentifier =
+      SectionIdentifierForInfo(articleItem.suggestionIdentifier.sectionInfo);
+
+  __weak ContentSuggestionsCollectionUpdater* weakSelf = self;
+  __weak ContentSuggestionsArticleItem* weakArticle = articleItem;
+  void (^imageFetchedCallback)(const gfx::Image&) = ^(const gfx::Image& image) {
+    if (image.IsEmpty()) {
+      return;
+    }
+
+    ContentSuggestionsCollectionUpdater* strongSelf = weakSelf;
+    ContentSuggestionsArticleItem* strongArticle = weakArticle;
+    if (!strongSelf || !strongArticle) {
+      return;
+    }
+
+    strongArticle.image = image.CopyUIImage();
+    [strongSelf.collectionViewController
+        reconfigureCellsForItems:@[ strongArticle ]
+         inSectionWithIdentifier:sectionIdentifier];
+  };
+
+  [self.dataSource.imageFetcher
+      fetchImageForSuggestion:articleItem.suggestionIdentifier
+                     callback:imageFetchedCallback];
+}
+
+#pragma mark - Private methods
+
+// Resets the models, removing the current CollectionViewItem and the
+// SectionInfo.
 - (void)resetModels {
   [self.collectionViewController loadModel];
   self.sectionInfoBySectionIdentifier = [[NSMutableDictionary alloc] init];
 }
 
 @end