Upstream Chrome on iOS source code [4/11].

ios/chrome/browser/ui/collection_view/collection_view_model.h

Index: ios/chrome/browser/ui/collection_view/collection_view_model.h
diff --git a/ios/chrome/browser/ui/collection_view/collection_view_model.h b/ios/chrome/browser/ui/collection_view/collection_view_model.h
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+// 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.
+
+#ifndef IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_MODEL_H_
+#define IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_MODEL_H_
+
+#include <UIKit/UIKit.h>
+
+@class CollectionViewItem;
+
+// Use these as the starting value for section identifier and item type enums.
+// These are provided to help not mix between indexPath's section/item and the
+// model section identifier / item type.
+//
+// For example:
+// typedef NS_ENUM(NSInteger, SectionIdentifier) {
+//   SectionIdentifierFoo = kSectionIdentifierEnumZero,
+//   SectionIdentifierBar,
+// };
+//
+// typedef NS_ENUM(NSInteger, ItemType) {
+//   ItemTypeBaz = kItemTypeEnumZero,
+//   ItemTypeQux,
+// };
+//
+// These values are chosen to try to prevent overlapping.
+const NSInteger kSectionIdentifierEnumZero = 10;
+const NSInteger kItemTypeEnumZero = 100;
+
+// CollectionViewModel acts as a model class for collection view controllers.
+// It provides methods to map from collection view index paths (aka collection
+// view section and collection view item) to model coordinates. These are
+// useful when the contents of a collection view are dynamic (for example, based
+// on experimental flags), so that there is not a static mapping between index
+// paths and section items.
+// Model coordinates have 3 dimensions: section identifier, item type and index
+// in item type.
+// Disclaimer: CollectionViewModel doesn't support a batch update logic. All
+// changes are immediately processed (contrary to the reload/delete/add order of
+// UICollectionView's |performBatchUpdates:completion:|).
+
+@interface CollectionViewModel : NSObject
+
+#pragma mark Modification methods
+
+// Adds a new section tagged with the given identifier. This method must not be
+// called multiple times with the same identifier.
+- (void)addSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Inserts a new section tagged with the given identifier at the given index.
+// This method must not be called multiple times with the same identifier.
+- (void)insertSectionWithIdentifier:(NSInteger)sectionIdentifier
+                            atIndex:(NSUInteger)index;
+
+// Adds an item to the section with the given identifier. Adding several times
+// the same item is undefined behavior.
+- (void)addItem:(CollectionViewItem*)item
+    toSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Inserts an item to the section with the given identifier at the given index.
+// |index| must not be greater than the count of elements in the section.
+- (void)insertItem:(CollectionViewItem*)item
+    inSectionWithIdentifier:(NSInteger)sectionIdentifier
+                    atIndex:(NSUInteger)index;
+
+// Removes the item for |itemType| from the section for |sectionIdentifier|.
+// If there are multiple entries with the same item type, this will remove the
+// first occurrence, but to selectively delete an item for a given index, use
+// -removeItemWithType:fromSectionWithIdentifier:atIndex:.
+- (void)removeItemWithType:(NSInteger)itemType
+    fromSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Removes the item for |itemType| from the section for |sectionIdentifier| at
+// |index|.
+- (void)removeItemWithType:(NSInteger)itemType
+    fromSectionWithIdentifier:(NSInteger)sectionIdentifier
+                      atIndex:(NSUInteger)index;
+
+// Removes the section for |sectionIdentifier|. If there are still items left in
+// the section, they are removed.
+- (void)removeSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Sets the header item for the section with the given |sectionIdentifier|.
+- (void)setHeader:(CollectionViewItem*)header
+    forSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Sets the footer item for the section with the given |sectionIdentifier|.
+- (void)setFooter:(CollectionViewItem*)footer
+    forSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+#pragma mark Query model coordinates from index paths
+
+// Returns the section identifier for the given section.
+- (NSInteger)sectionIdentifierForSection:(NSInteger)section;
+
+// Returns the item type for the given index path.
+- (NSInteger)itemTypeForIndexPath:(NSIndexPath*)indexPath;
+
+// Returns the index in item type for the given index path.
+// It corresponds to the index of the item at index path, among all the items if
+// the same type in the given section.
+// For example, let [A, B, B, B] a section, where A and B are item identifiers.
+// -indexInItemTypeForIndexPath:{0, 0} would return 0.
+// -indexInItemTypeForIndexPath:{0, 1} would return 0.
+// -indexInItemTypeForIndexPath:{0, 3} would return 2.
+- (NSUInteger)indexInItemTypeForIndexPath:(NSIndexPath*)indexPath;
+
+#pragma mark Query items from index paths
+
+// Returns whether there is an item at the given index path.
+- (BOOL)hasItemAtIndexPath:(NSIndexPath*)indexPath;
+
+// Returns the item at the given index path.
+- (CollectionViewItem*)itemAtIndexPath:(NSIndexPath*)indexPath;
+
+// Returns the header for the given |section|.
+- (CollectionViewItem*)headerForSection:(NSInteger)section;
+
+// Returns the footer for the given |section|.
+- (CollectionViewItem*)footerForSection:(NSInteger)section;
+
+// Returns an array of items in the section with the given identifier.
+- (NSArray*)itemsInSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns the header for the section with the given |sectionIdentifier|.
+- (CollectionViewItem*)headerForSectionWithIdentifier:
+    (NSInteger)sectionIdentifier;
+
+// Returns the footer for the section with the given |sectionIdentifier|.
+- (CollectionViewItem*)footerForSectionWithIdentifier:
+    (NSInteger)sectionIdentifier;
+
+#pragma mark Query index paths from model coordinates
+
+// Returns whether there is a section at the given section identifier.
+- (BOOL)hasSectionForSectionIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns the index path's section for the given section identifier.
+- (NSInteger)sectionForSectionIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns whether there is an item of type |itemType| at the given
+// |sectionIdentifier|.
+- (BOOL)hasItemForItemType:(NSInteger)itemType
+         sectionIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns the index path for |itemType| in the section for |sectionIdentifier|.
+// If there are multiple entries with the same item type, use
+// -indexPathForItemType:sectionIdentifier:atIndex:.
+- (NSIndexPath*)indexPathForItemType:(NSInteger)itemType
+                   sectionIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns whether there is an item of type |itemType| at the given
+// |sectionIdentifier| and |index|.
+- (BOOL)hasItemForItemType:(NSInteger)itemType
+         sectionIdentifier:(NSInteger)sectionIdentifier
+                   atIndex:(NSUInteger)index;
+
+// Returns the index path for |itemType| in the section for |sectionIdentifier|
+// at |index|.
+- (NSIndexPath*)indexPathForItemType:(NSInteger)itemType
+                   sectionIdentifier:(NSInteger)sectionIdentifier
+                             atIndex:(NSUInteger)index;
+
+#pragma mark Query index paths from items
+
+// Returns whether |item| exists in section for |sectionIdentifier|.
+- (BOOL)hasItem:(CollectionViewItem*)item
+    inSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns the index path corresponding to the given |item|.
+- (NSIndexPath*)indexPathForItem:(CollectionViewItem*)itemType
+         inSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+#pragma mark UICollectionView data sourcing
+
+// Returns the number of collection view sections.
+- (NSInteger)numberOfSections;
+
+// Returns the number of collection view items in the given section.
+- (NSInteger)numberOfItemsInSection:(NSInteger)section;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_MODEL_H_