[ios] Introduces ListModel and ListItem.

These serve as common model classes that can back either
UICollectionView or UITableView.  CollectionViewModel is updated to be a
subclass of ListModel with added restrictions on permitted item types
but no functional changes.  CollectionViewController and its subclasses
are largely unchanged.

BUG=805136

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ibcfbab5bae62c5c8a37f764508294421d3d1c307
Reviewed-on: https://chromium-review.googlesource.com/916365
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536708}

ios/chrome/browser/ui/collection_view/BUILD.gn

@@ -12,6 +12,7 @@ source_set("collection_view") {
   ]
   deps = [
     "//base",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/chrome/browser/ui/material_components",
   ]
   public_deps = [
@@ -43,7 +44,6 @@ source_set("unit_tests") {
   testonly = true
   sources = [
     "collection_view_controller_unittest.mm",
-    "collection_view_model_unittest.mm",
   ]
   deps = [
     ":collection_view",

ios/chrome/browser/ui/collection_view/cells/BUILD.gn

@@ -14,7 +14,6 @@ source_set("cells") {
     "collection_view_detail_item.mm",
     "collection_view_footer_item.h",
     "collection_view_footer_item.mm",
-    "collection_view_item+collection_view_controller.h",
     "collection_view_item.h",
     "collection_view_item.mm",
     "collection_view_switch_item.h",
@@ -29,6 +28,7 @@ source_set("cells") {
     "//base",
     "//ios/chrome/app/strings",
     "//ios/chrome/browser/ui/colors",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/chrome/browser/ui/material_components",
     "//ios/chrome/browser/ui/util",
     "//ios/chrome/common",
@@ -68,6 +68,7 @@ source_set("unit_tests") {
   deps = [
     ":cells",
     ":test_support",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/third_party/material_components_ios",
     "//testing/gtest",
   ]

ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h

-// Copyright 2017 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_CELLS_COLLECTION_VIEW_ITEM_COLLECTION_VIEW_CONTROLLER_H_
-#define IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_CELLS_COLLECTION_VIEW_ITEM_COLLECTION_VIEW_CONTROLLER_H_
-
-#import <Foundation/Foundation.h>
-
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
-
-// CollectionViewItem can be created with a default item type but it needs to
-// have a valid item type to be inserted in the model. Only the
-// CollectionViewController managing the item is allowed to set the item type.
-@interface CollectionViewItem (CollectionViewController)
-
-@property(nonatomic, readwrite, assign) NSInteger type;
-
-@end
-
-#endif  // IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_CELLS_COLLECTION_VIEW_ITEM_COLLECTION_VIEW_CONTROLLER_H_

ios/chrome/browser/ui/collection_view/cells/collection_view_item.h

@@ -7,18 +7,12 @@
 
 #import <UIKit/UIKit.h>
 
+#import "ios/chrome/browser/ui/list_model/list_item.h"
+
 @class MDCCollectionViewCell;
 
 // CollectionViewItem holds the model data for a given collection view item.
-@interface CollectionViewItem : NSObject<UIAccessibilityIdentification>
-
-// A client-defined value. It should be unique among items of a given collection
-// view model.
-@property(nonatomic, readonly, assign) NSInteger type;
-
-// The cell class to use in conjunction with this item. Must be a subclass of
-// MDCCollectionViewCell. The default is MDCCollectionViewCell.
-@property(nonatomic, assign) Class cellClass;
+@interface CollectionViewItem : ListItem
 
 - (instancetype)initWithType:(NSInteger)type NS_DESIGNATED_INITIALIZER;
 

ios/chrome/browser/ui/collection_view/cells/collection_view_item.mm

@@ -5,7 +5,6 @@
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 
 #import "base/logging.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/third_party/material_components_ios/src/components/CollectionCells/src/MaterialCollectionCells.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
@@ -14,27 +13,13 @@
 
 @implementation CollectionViewItem
 
-@synthesize type = _type;
-@synthesize cellClass = _cellClass;
-@synthesize accessibilityIdentifier = _accessibilityIdentifier;
-
 - (instancetype)initWithType:(NSInteger)type {
-  if ((self = [super init])) {
-    _type = type;
-    _cellClass = [MDCCollectionViewCell class];
+  if ((self = [super initWithType:type])) {
+    self.cellClass = [MDCCollectionViewCell class];
   }
   return self;
 }
 
-- (instancetype)init {
-  return [self initWithType:0];
-}
-
-- (void)setCellClass:(Class)cellClass {
-  DCHECK([cellClass isSubclassOfClass:[MDCCollectionViewCell class]]);
-  _cellClass = cellClass;
-}
-
 - (void)configureCell:(MDCCollectionViewCell*)cell {
   DCHECK([cell class] == self.cellClass);
   cell.accessibilityTraits = self.accessibilityTraits;
@@ -42,11 +27,3 @@
 }
 
 @end
-
-@implementation CollectionViewItem (CollectionViewController)
-
-- (void)setType:(NSInteger)type {
-  _type = type;
-}
-
-@end

ios/chrome/browser/ui/collection_view/cells/collection_view_item_unittest.mm

@@ -4,7 +4,6 @@
 
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/third_party/material_components_ios/src/components/CollectionCells/src/MaterialCollectionCells.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
@@ -18,21 +17,6 @@ namespace {
 
 using CollectionViewItemTest = PlatformTest;
 
-TEST_F(CollectionViewItemTest, Accessors) {
-  CollectionViewItem* five = [[CollectionViewItem alloc] initWithType:5];
-  CollectionViewItem* twelve = [[CollectionViewItem alloc] initWithType:12];
-
-  EXPECT_EQ(5, [five type]);
-  EXPECT_EQ(12, [twelve type]);
-
-  // Test setting the type property used in CollectionViewController.
-  [five setType:55];
-  EXPECT_EQ(55, [five type]);
-
-  [twelve setType:1212];
-  EXPECT_EQ(1212, [twelve type]);
-}
-
 TEST_F(CollectionViewItemTest, ConfigureCellPortsAccessibilityProperties) {
   CollectionViewItem* item = [[CollectionViewItem alloc] initWithType:0];
   item.accessibilityIdentifier = @"test_identifier";

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

@@ -7,184 +7,12 @@
 
 #import <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;
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
+#import "ios/chrome/browser/ui/list_model/list_model.h"
 
 // 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:|).
-// The __covariant modifier allows an instance of CollectionViewModel<A> to be
-// assigned to an instance of CollectionViewModel<B> iff A:B (see unit test for
-// an example).
 @interface CollectionViewModel<__covariant ObjectType : CollectionViewItem*>
-    : 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:(ObjectType)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:(ObjectType)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.
-- (ObjectType)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<ObjectType>*)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:(ObjectType)item
-    inSectionWithIdentifier:(NSInteger)sectionIdentifier;
-
-// Returns whether |item| exists.
-- (BOOL)hasItem:(ObjectType)item;
-
-// Returns the index path corresponding to the given |item|.
-- (NSIndexPath*)indexPathForItem:(ObjectType)item;
-
-#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;
+    : ListModel<ObjectType, CollectionViewItem*>
 
 @end
 

ios/chrome/browser/ui/content_suggestions/BUILD.gn

@@ -122,6 +122,7 @@ source_set("content_suggestions_ui") {
     "//ios/chrome/browser/ui/content_suggestions/cells:cells_ui",
     "//ios/chrome/browser/ui/content_suggestions/identifier",
     "//ios/chrome/browser/ui/favicon:favicon_ui",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/chrome/browser/ui/ntp",
     "//ios/chrome/browser/ui/ntp:ntp_header",
     "//ios/chrome/browser/ui/overscroll_actions",

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

@@ -9,7 +9,6 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
 #include "components/strings/grit/components_strings.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_text_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
@@ -26,6 +25,7 @@
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_view_controller_audience.h"
 #import "ios/chrome/browser/ui/content_suggestions/identifier/content_suggestion_identifier.h"
 #import "ios/chrome/browser/ui/content_suggestions/identifier/content_suggestions_section_information.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 #import "ios/third_party/material_components_ios/src/components/Snackbar/src/MaterialSnackbar.h"

ios/chrome/browser/ui/list_model/BUILD.gn

+# Copyright 2018 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.
+
+source_set("list_model") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+  sources = [
+    "list_item+Controller.h",
+    "list_item.h",
+    "list_item.mm",
+    "list_model.h",
+    "list_model.mm",
+  ]
+  deps = [
+    "//base",
+  ]
+}
+
+source_set("unit_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+  testonly = true
+  sources = [
+    "list_item_unittest.mm",
+    "list_model_unittest.mm",
+  ]
+  deps = [
+    ":list_model",
+    "//base",
+    "//ios/chrome/test:test_support",
+    "//ios/chrome/test/base",
+    "//testing/gtest",
+  ]
+}

ios/chrome/browser/ui/list_model/list_item+Controller.h

+// Copyright 2018 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_LIST_MODEL_LIST_ITEM_CONTROLLER_H_
+#define IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_ITEM_CONTROLLER_H_
+
+// ListItem can be created with a default item type but it needs to
+// have a valid item type to be inserted in the model. Only the
+// UIViewControllers managing the item are allowed to set the item type.
+@interface ListItem (Controller)
+
+// Redeclared as readwrite.
+@property(nonatomic, readwrite, assign) NSInteger type;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_ITEM_CONTROLLER_H_

ios/chrome/browser/ui/list_model/list_item.h

+// Copyright 2018 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_LIST_MODEL_LIST_ITEM_H_
+#define IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_ITEM_H_
+
+#import <UIKit/UIKit.h>
+
+// ListItem holds the model data for a given list item.  This is intended to be
+// an abstract base class; callers should use one of the {collectionview,
+// tableview}-specific subclasses.
+@interface ListItem : NSObject<UIAccessibilityIdentification>
+
+// A client-defined value. It should be unique among items of a given list
+// model.
+@property(nonatomic, readonly, assign) NSInteger type;
+
+// The cell class to use in conjunction with this item.
+@property(nonatomic, assign) Class cellClass;
+
+- (instancetype)initWithType:(NSInteger)type NS_DESIGNATED_INITIALIZER;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_ITEM_H_

ios/chrome/browser/ui/list_model/list_item.mm

+// Copyright 2018 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/list_model/list_item.h"
+
+#import "base/logging.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation ListItem
+
+@synthesize type = _type;
+@synthesize cellClass = _cellClass;
+@synthesize accessibilityIdentifier = _accessibilityIdentifier;
+
+- (instancetype)initWithType:(NSInteger)type {
+  if ((self = [super init])) {
+    _type = type;
+  }
+  return self;
+}
+
+- (instancetype)init {
+  return [self initWithType:0];
+}
+
+- (void)setCellClass:(Class)cellClass {
+  _cellClass = cellClass;
+}
+
+@end
+
+@implementation ListItem (Controller)
+
+- (void)setType:(NSInteger)type {
+  _type = type;
+}
+
+@end

ios/chrome/browser/ui/list_model/list_item_unittest.mm

+// Copyright 2018 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/list_model/list_item.h"
+
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/gtest_mac.h"
+#include "testing/platform_test.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+
+using ListItemTest = PlatformTest;
+
+TEST_F(ListItemTest, Accessors) {
+  ListItem* five = [[ListItem alloc] initWithType:5];
+  ListItem* twelve = [[ListItem alloc] initWithType:12];
+
+  EXPECT_EQ(5, [five type]);
+  EXPECT_EQ(12, [twelve type]);
+
+  // Test setting the type property.
+  [five setType:55];
+  EXPECT_EQ(55, [five type]);
+
+  [twelve setType:1212];
+  EXPECT_EQ(1212, [twelve type]);
+}
+
+}  // namespace

ios/chrome/browser/ui/list_model/list_model.h

+// Copyright 2018 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_LIST_MODEL_LIST_MODEL_H_
+#define IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_MODEL_H_
+
+#import <UIKit/UIKit.h>
+
+@class ListItem;
+
+// 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;
+
+// ListModel acts as a model class for collectionview and tableview controllers.
+// It provides methods to map from index paths (aka section and item) to model
+// coordinates. These are useful when the contents of a list 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: ListModel doesn't support a batch update logic. All changes are
+// immediately processed (contrary to the reload/delete/add order of
+// |performBatchUpdates:completion:|).  The __covariant modifier allows an
+// instance of ListModel<A,B> to be assigned to an instance of ListModel<X,Y>
+// iff A:X and B:Y (see unit test for an example).
+@interface ListModel<__covariant ObjectType : ListItem*,
+                     __covariant SupplementalType : ListItem*> : 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:(ObjectType)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:(ObjectType)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:(SupplementalType)header
+    forSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Sets the footer item for the section with the given |sectionIdentifier|.
+- (void)setFooter:(SupplementalType)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.
+- (ObjectType)itemAtIndexPath:(NSIndexPath*)indexPath;
+
+// Returns the header for the given |section|.
+- (SupplementalType)headerForSection:(NSInteger)section;
+
+// Returns the footer for the given |section|.
+- (SupplementalType)footerForSection:(NSInteger)section;
+
+// Returns an array of items in the section with the given identifier.
+- (NSArray<ObjectType>*)itemsInSectionWithIdentifier:
+    (NSInteger)sectionIdentifier;
+
+// Returns the header for the section with the given |sectionIdentifier|.
+- (SupplementalType)headerForSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns the footer for the section with the given |sectionIdentifier|.
+- (SupplementalType)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:(ObjectType)item
+    inSectionWithIdentifier:(NSInteger)sectionIdentifier;
+
+// Returns whether |item| exists.
+- (BOOL)hasItem:(ObjectType)item;
+
+// Returns the index path corresponding to the given |item|.
+- (NSIndexPath*)indexPathForItem:(ObjectType)item;
+
+#pragma mark Data sourcing
+
+// Returns the number of sections.
+- (NSInteger)numberOfSections;
+
+// Returns the number of items in the given section.
+- (NSInteger)numberOfItemsInSection:(NSInteger)section;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_LIST_MODEL_LIST_MODEL_H_

ios/chrome/browser/ui/payments/BUILD.gn

@@ -144,6 +144,7 @@ source_set("payments_ui") {
     "//ios/chrome/browser/ui/collection_view",
     "//ios/chrome/browser/ui/colors",
     "//ios/chrome/browser/ui/icons",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/chrome/browser/ui/material_components",
     "//ios/chrome/browser/ui/payments/cells",
     "//ios/third_party/material_components_ios",

ios/chrome/browser/ui/payments/payment_items_display_view_controller.mm

@@ -7,11 +7,11 @@
 #include "base/mac/foundation_util.h"
 #include "components/strings/grit/components_strings.h"
 #import "ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
 #import "ios/chrome/browser/ui/icons/chrome_icon.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/payments/cells/price_item.h"
 #import "ios/chrome/browser/ui/payments/payment_items_display_view_controller_actions.h"
 #include "ios/chrome/browser/ui/rtl_geometry.h"

ios/chrome/browser/ui/payments/payment_request_edit_view_controller.mm

@@ -12,9 +12,9 @@
 #import "ios/chrome/browser/ui/autofill/cells/autofill_edit_item.h"
 #import "ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_footer_item.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_switch_item.h"
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/payments/cells/payments_selector_edit_item.h"
 #import "ios/chrome/browser/ui/payments/cells/payments_text_item.h"
 #import "ios/chrome/browser/ui/payments/payment_request_edit_view_controller_actions.h"

ios/chrome/browser/ui/payments/payment_request_selector_view_controller.mm

@@ -8,11 +8,11 @@
 #include "components/strings/grit/components_strings.h"
 #import "ios/chrome/browser/ui/autofill/cells/status_item.h"
 #import "ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
 #import "ios/chrome/browser/ui/icons/chrome_icon.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/payments/cells/payments_is_selectable.h"
 #import "ios/chrome/browser/ui/payments/cells/payments_text_item.h"
 #import "ios/chrome/browser/ui/payments/payment_request_selector_view_controller_actions.h"

ios/chrome/browser/ui/payments/payment_request_view_controller.mm

@@ -11,10 +11,10 @@
 #import "ios/chrome/browser/ui/collection_view/cells/MDCCollectionViewCell+Chrome.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_detail_item.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_footer_item.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/payments/cells/page_info_item.h"
 #import "ios/chrome/browser/ui/payments/cells/payments_text_item.h"
 #import "ios/chrome/browser/ui/payments/cells/price_item.h"

ios/chrome/browser/ui/reading_list/BUILD.gn

@@ -96,6 +96,7 @@ source_set("reading_list_ui") {
     "//ios/chrome/browser/ui/colors",
     "//ios/chrome/browser/ui/favicon:favicon_ui",
     "//ios/chrome/browser/ui/keyboard",
+    "//ios/chrome/browser/ui/list_model",
     "//ios/chrome/browser/ui/util",
     "//ios/chrome/common",
     "//ios/third_party/material_components_ios",

ios/chrome/browser/ui/reading_list/reading_list_collection_view_controller.mm

@@ -10,9 +10,9 @@
 #include "base/metrics/user_metrics_action.h"
 #include "components/strings/grit/components_strings.h"
 #import "ios/chrome/browser/ui/alert_coordinator/action_sheet_coordinator.h"
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_item+collection_view_controller.h"
 #import "ios/chrome/browser/ui/collection_view/cells/collection_view_text_item.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
+#import "ios/chrome/browser/ui/list_model/list_item+Controller.h"
 #import "ios/chrome/browser/ui/reading_list/reading_list_collection_view_item_accessibility_delegate.h"
 #import "ios/chrome/browser/ui/reading_list/reading_list_data_sink.h"
 #import "ios/chrome/browser/ui/reading_list/reading_list_data_source.h"

ios/chrome/test/BUILD.gn

@@ -199,6 +199,7 @@ test("ios_chrome_unittests") {
     "//ios/chrome/browser/ui/icons:unit_tests",
     "//ios/chrome/browser/ui/infobars:unit_tests",
     "//ios/chrome/browser/ui/keyboard:unit_tests",
+    "//ios/chrome/browser/ui/list_model:unit_tests",
     "//ios/chrome/browser/ui/location_bar:unit_tests",
     "//ios/chrome/browser/ui/main:unit_tests",
     "//ios/chrome/browser/ui/main_content:unit_tests",