Add ContentSuggestionsMediator

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"
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_article_item.h"
+#import "ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h"
+#import "ios/chrome/browser/ui/content_suggestions/content_suggestions_data_source.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_expandable_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_favicon_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_stack_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
+@interface ContentSuggestionsCollectionUpdater ()<ContentSuggestionsDataSink>
+
+@property(nonatomic, strong) id<ContentSuggestionsDataSource> dataSource;

[lpromero, 2017/01/26 10:10:20]

Can we risk creating a cycle if the one creating and retaining the updater is
the data source? Worth mentioning in the header that this object has a strong
reference to the data source, so the caller should take action to break a
potential cycle when needed.

[marq (ping after 24h), 2017/01/27 12:44:55]

Does this need to be strong? Delegates usually aren't.

[gambard, 2017/01/30 15:19:17]

Yes, the data source should be kept alive by the coordinator.

+
+@end
+
 @implementation ContentSuggestionsCollectionUpdater
 
 @synthesize collectionViewController = _collectionViewController;
+@synthesize dataSource = _dataSource;
+
+- (instancetype)initWithDataSource:
+    (id<ContentSuggestionsDataSource>)dataSource {
+  self = [super init];
+  if (self) {
+    _dataSource = dataSource;
+    _dataSource.dataSink = self;
+  }
+  return self;
+}
 
 #pragma mark - Properties
 
 - (void)setCollectionViewController:
     (ContentSuggestionsViewController*)collectionViewController {
   _collectionViewController = collectionViewController;
   [collectionViewController loadModel];
   CollectionViewModel* model = collectionViewController.collectionViewModel;
+
+  // Loads the data with the dataSource instead of hard coded value.

[lpromero, 2017/01/26 10:10:20]

Mark this with // PLACEHOLDER

[marq (ping after 24h), 2017/01/27 12:44:55]

Also, clarify that this is a change that needs to be made ("change this to load
the data ... ").

[gambard, 2017/01/30 15:19:17]

Done.

+
   NSInteger sectionIdentifier = kSectionIdentifierEnumZero;
 
   // Stack Item.
   [model addSectionWithIdentifier:sectionIdentifier];
   [model addItem:[[ContentSuggestionsStackItem alloc]
                      initWithType:ItemTypeStack
                             title:@"The title"
                          subtitle:@"The subtitle"]
       toSectionWithIdentifier:sectionIdentifier++];
 
@@ skipping 38 matching lines @@
                    image:[UIImage imageNamed:@"distillation_fail"]
               detailText:@"Details shown only when the article is "
                          @"expanded. It can be displayed on "
                          @"multiple lines."];
     expandableItem.delegate = _collectionViewController;
     [model addItem:expandableItem toSectionWithIdentifier:sectionIdentifier];
     sectionIdentifier++;
   }
 }
 
+#pragma mark - ContentSuggestionsDataSink
+
+- (void)dataAvailable {
+  [self.dataSource getMoreData];

[marq (ping after 24h), 2017/01/27 12:44:55]

Either delete the dataSource call or assign the result to something; the risk
here is that looks like it's causing the dataSource to do something, but the
current method definition returns an array. Better to code defensively even in
placeholder code.

[gambard, 2017/01/30 15:19:17]

Done.

+  // Do something.
+}
+
 #pragma mark - Public methods
 
 - (void)addTextItem:(NSString*)title
            subtitle:(NSString*)subtitle
           toSection:(NSInteger)inputSection {
   DCHECK(_collectionViewController);
   ContentSuggestionsItem* item =
       [[ContentSuggestionsItem alloc] initWithType:ItemTypeText
                                              title:title
                                           subtitle:subtitle];
@@ skipping 22 matching lines @@
                                           inSection:sectionIndex] ]];
   }
                                                      completion:nil];
 }
 
 - (BOOL)shouldUseCustomStyleForSection:(NSInteger)section {
   return section == 0 || section == 1;
 }
 
 @end