[ios] Add free function to (de)serialise WebStateList.

ios/shared/chrome/browser/tabs/web_state_list_serialization.mm

Index: ios/shared/chrome/browser/tabs/web_state_list_serialization.mm
diff --git a/ios/shared/chrome/browser/tabs/web_state_list_serialization.mm b/ios/shared/chrome/browser/tabs/web_state_list_serialization.mm
new file mode 100644
index 0000000000000000000000000000000000000000..0662f3ab5f0a4f0e5eb59ef928baef35b3d35ac5
--- /dev/null
+++ b/ios/shared/chrome/browser/tabs/web_state_list_serialization.mm
@@ -0,0 +1,175 @@
+// 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/shared/chrome/browser/tabs/web_state_list_serialization.h"
+
+#include <memory>
+#include <unordered_map>
+
+#include "base/callback.h"
+#include "base/logging.h"
+#import "base/mac/foundation_util.h"
+#import "ios/shared/chrome/browser/tabs/web_state_list.h"
+#import "ios/shared/chrome/browser/tabs/web_state_opener.h"
+#import "ios/web/public/serializable_user_data_manager.h"
+#import "ios/web/public/web_state/web_state.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace {
+// Keys used to store information about the opener-opened relationship between
+// the WebStates stored in the WebStateList.
+NSString* const kOpenerIndexKey = @"OpenerIndex";
+NSString* const kOpenerNavigationIndexKey = @"OpenerNavigationIndex";
+
+// Legacy keys used to store information about the opener-opener relationship
+// before the M-60 release. Remove once M-70 has shipped.
+NSString* const kObjectIDKey = @"TabID";
+NSString* const kOpenerIDKey = @"OpenerID";
+
+// Returns whether the opener-opener relationship is encoded with legacy format.
+// The legacy format (pre M-59) references the opener by id while the new format
+// references it by index.
+// TODO(crbug.com/704941): remove once no sessions uses the old format.
+bool IsSessionUsingLegacyFormat(WebStateList* web_state_list, int old_count) {
+  for (int index = old_count; index < web_state_list->count(); ++index) {
+    web::WebState* web_state = web_state_list->GetWebStateAt(index);
+    web::SerializableUserDataManager* user_data_manager =
+        web::SerializableUserDataManager::FromWebState(web_state);
+
+    if (!user_data_manager->GetValueForSerializationKey(kOpenerIndexKey))
+      return true;
+  }
+  return false;
+}
+
+// Restores the WebStates opener-opened relationship. The relationship is
+// encoded using legacy format.
+// TODO(crbug.com/704941): remove once no sessions uses the old format.
+void RestoreRelationshipLegacy(WebStateList* web_state_list, int old_count) {
+  NSMutableDictionary<NSString*, NSValue*>* id_to_web_state =
+      [NSMutableDictionary dictionary];
+
+  for (int index = old_count; index < web_state_list->count(); ++index) {
+    web::WebState* web_state = web_state_list->GetWebStateAt(index);
+    web::SerializableUserDataManager* user_data_manager =
+        web::SerializableUserDataManager::FromWebState(web_state);
+
+    NSString* object_id = base::mac::ObjCCast<NSString>(
+        user_data_manager->GetValueForSerializationKey(kObjectIDKey));
+
+    if (!object_id || ![object_id length])
+      continue;
+
+    if (id_to_web_state[object_id] != nil)
+      continue;
+
+    id_to_web_state[object_id] = [NSValue valueWithPointer:web_state];
+  }
+
+  for (int index = old_count; index < web_state_list->count(); ++index) {
+    web::WebState* web_state = web_state_list->GetWebStateAt(index);
+    web::SerializableUserDataManager* user_data_manager =
+        web::SerializableUserDataManager::FromWebState(web_state);
+
+    NSString* opener_id = base::mac::ObjCCast<NSString>(
+        user_data_manager->GetValueForSerializationKey(kOpenerIDKey));
+
+    NSNumber* boxed_opener_navigation_index = base::mac::ObjCCast<NSNumber>(
+        user_data_manager->GetValueForSerializationKey(
+            kOpenerNavigationIndexKey));
+
+    if (!opener_id || !boxed_opener_navigation_index || ![opener_id length])
+      continue;
+
+    if (id_to_web_state[opener_id] == nil)
+      continue;
+
+    web::WebState* opener_web_state =
+        static_cast<web::WebState*>(id_to_web_state[opener_id].pointerValue);
+
+    web_state_list->SetOpenerOfWebStateAt(
+        index, WebStateOpener(opener_web_state,
+                              [boxed_opener_navigation_index intValue]));
+  }
+}
+
+// Restores the WebStates opener-opened relationship.
+void RestoreRelationship(WebStateList* web_state_list, int old_count) {
+  if (IsSessionUsingLegacyFormat(web_state_list, old_count))
+    return RestoreRelationshipLegacy(web_state_list, old_count);
+
+  for (int index = old_count; index < web_state_list->count(); ++index) {
+    web::WebState* web_state = web_state_list->GetWebStateAt(index);
+    web::SerializableUserDataManager* user_data_manager =
+        web::SerializableUserDataManager::FromWebState(web_state);
+
+    NSNumber* boxed_opener_index = base::mac::ObjCCast<NSNumber>(
+        user_data_manager->GetValueForSerializationKey(kOpenerIndexKey));
+
+    NSNumber* boxed_opener_navigation_index = base::mac::ObjCCast<NSNumber>(
+        user_data_manager->GetValueForSerializationKey(
+            kOpenerNavigationIndexKey));
+
+    if (!boxed_opener_index || !boxed_opener_navigation_index)
+      continue;
+
+    // If opener index is out of bound then assume there is no opener.
+    int opener_index = [boxed_opener_index intValue] + old_count;
+    if (opener_index < old_count || opener_index >= web_state_list->count())
+      continue;
+
+    web::WebState* opener = web_state_list->GetWebStateAt(opener_index);
+    web_state_list->SetOpenerOfWebStateAt(
+        index,
+        WebStateOpener(opener, [boxed_opener_navigation_index intValue]));
+  }
+}
+}  // namespace
+
+NSArray<CRWSessionStorage*>* SerializeWebStateList(
+    WebStateList* web_state_list) {
+  NSMutableArray<CRWSessionStorage*>* serialized_session =
+      [NSMutableArray arrayWithCapacity:web_state_list->count()];
+
+  for (int index = 0; index < web_state_list->count(); ++index) {
+    web::WebState* web_state = web_state_list->GetWebStateAt(index);
+    WebStateOpener opener = web_state_list->GetOpenerOfWebStateAt(index);
+
+    web::SerializableUserDataManager* user_data_manager =
+        web::SerializableUserDataManager::FromWebState(web_state);
+
+    int opener_index = WebStateList::kInvalidIndex;
+    if (opener.opener) {
+      opener_index = web_state_list->GetIndexOfWebState(opener.opener);
+      DCHECK_NE(opener_index, WebStateList::kInvalidIndex);
+      user_data_manager->AddSerializableData(@(opener_index), kOpenerIndexKey);
+      user_data_manager->AddSerializableData(@(opener.navigation_index),
+                                             kOpenerNavigationIndexKey);
+    } else {
+      user_data_manager->AddSerializableData([NSNull null], kOpenerIndexKey);
+      user_data_manager->AddSerializableData([NSNull null],
+                                             kOpenerNavigationIndexKey);
+    }
+
+    [serialized_session addObject:web_state->BuildSessionStorage()];
+  }
+
+  return [serialized_session copy];
+}
+
+void DeserializeWebStateList(WebStateList* web_state_list,
+                             NSArray<CRWSessionStorage*>* sessions,
+                             const WebStateFactory& web_state_factory) {
+  int old_count = web_state_list->count();
+  for (CRWSessionStorage* session in sessions) {
+    std::unique_ptr<web::WebState> web_state = web_state_factory.Run(session);
+    web_state_list->InsertWebState(web_state_list->count(),
+                                   std::move(web_state));
+  }
+
+  RestoreRelationship(web_state_list, old_count);
+}