Adds Compose Email Settings UI for deprecating Native App Launcher

ios/chrome/browser/ui/settings/compose_email_handler_collection_view_controller.mm

+// 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.
+
+#import "ios/chrome/browser/ui/settings/compose_email_handler_collection_view_controller.h"
+
+#include "base/mac/foundation_util.h"
+#import "ios/chrome/browser/ui/collection_view/cells/collection_view_text_item.h"
+#import "ios/chrome/browser/web/mailto_handler.h"
+#import "ios/chrome/browser/web/mailto_url_rewriter.h"
+#include "ios/chrome/grit/ios_strings.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/base/l10n/l10n_util_mac.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+
+typedef NS_ENUM(NSInteger, SectionIdentifier) {
+  SectionIdentifierMailtoHandlers = kSectionIdentifierEnumZero,
+};
+
+typedef NS_ENUM(NSInteger, ItemType) {
+  ItemTypeMailtoHandlers = kItemTypeEnumZero,
+};
+
+}  // namespace
+
+@interface ComposeEmailHandlerCollectionViewController () {
+  MailtoURLRewriter* _rewriter;
+}
+@end
+
+@implementation ComposeEmailHandlerCollectionViewController
+
+- (instancetype)initWithRewriter:(MailtoURLRewriter*)rewriter {
+  self = [super initWithStyle:CollectionViewControllerStyleAppBar];
+  if (self) {
+    self.title = l10n_util::GetNSString(IDS_IOS_COMPOSE_EMAIL_SETTING);
+    self.collectionViewAccessibilityIdentifier =
+        @"compose_email_handler_view_controller";
+    _rewriter = rewriter;
+    [self loadModel];
+  }
+  return self;
+}
+
+- (void)loadModel {
+  [super loadModel];
+  CollectionViewModel* model = self.collectionViewModel;
+  [model addSectionWithIdentifier:SectionIdentifierMailtoHandlers];
+
+  // Since this is a one-of-several selection UI, there must be more than one
+  // choice available to the user. If this UI is being presented when there is
+  // only one choice, it is considered a software error.
+  NSArray<MailtoHandler*>* handlers = [_rewriter defaultHandlers];
+  DCHECK([handlers count] > 1);
+  NSString* currentHandlerID = [_rewriter defaultHandlerID];
+  for (MailtoHandler* handler in handlers) {
+    CollectionViewTextItem* item =
+        [[CollectionViewTextItem alloc] initWithType:ItemTypeMailtoHandlers];
+    [item setText:[handler appName]];
+    [item setAccessibilityTraits:UIAccessibilityTraitButton];
+    if ([currentHandlerID isEqualToString:[handler appStoreID]])
+      [item setAccessoryType:MDCCollectionViewCellAccessoryCheckmark];
+    [model addItem:item
+        toSectionWithIdentifier:SectionIdentifierMailtoHandlers];
+  }
+}
+
+#pragma mark UICollectionViewDelegate
+
+- (void)collectionView:(UICollectionView*)collectionView
+    didSelectItemAtIndexPath:(NSIndexPath*)indexPath {
+  [super collectionView:collectionView didSelectItemAtIndexPath:indexPath];
+  CollectionViewModel* model = self.collectionViewModel;
+
+  // The items created in -loadModel are all MailtoHandlers type.
+  CollectionViewTextItem* selectedItem =
+      base::mac::ObjCCastStrict<CollectionViewTextItem>(
+          [model itemAtIndexPath:indexPath]);
+  DCHECK_EQ(ItemTypeMailtoHandlers, selectedItem.type);
+
+  // Do nothing if the tapped row is already chosen as the default.
+  if (selectedItem.accessoryType == MDCCollectionViewCellAccessoryCheckmark)
+    return;
+
+  // Iterate through the rows and remove the checkmark from any that has it.
+  NSMutableArray* modifiedItems = [NSMutableArray array];
+  for (id item in
+       [model itemsInSectionWithIdentifier:SectionIdentifierMailtoHandlers]) {
+    CollectionViewTextItem* textItem =
+        base::mac::ObjCCastStrict<CollectionViewTextItem>(item);
+    DCHECK_EQ(ItemTypeMailtoHandlers, textItem.type);
+    if (textItem == selectedItem) {
+      // Shows the checkmark on the new default mailto: URL handler.
+      textItem.accessoryType = MDCCollectionViewCellAccessoryCheckmark;
+      [modifiedItems addObject:textItem];
+    } else if (textItem.accessoryType ==
+               MDCCollectionViewCellAccessoryCheckmark) {
+      // Unchecks any currently checked selection.
+      textItem.accessoryType = MDCCollectionViewCellAccessoryNone;
+      [modifiedItems addObject:textItem];
+    }
+  }
+
+  NSUInteger handlerIndex = [model indexInItemTypeForIndexPath:indexPath];
+  MailtoHandler* handler =
+      [[_rewriter defaultHandlers] objectAtIndex:handlerIndex];
+  [_rewriter setDefaultHandlerID:[handler appStoreID]];
+
+  [self reconfigureCellsForItems:modifiedItems];
+}
+
+@end