Refactor preference syncing.

chrome/browser/prefs/pref_model_associator.h

Index: chrome/browser/prefs/pref_model_associator.h
diff --git a/chrome/browser/prefs/pref_model_associator.h b/chrome/browser/prefs/pref_model_associator.h
new file mode 100644
index 0000000000000000000000000000000000000000..7b24153216600fa4a810de7ae9f5c66b7c0880ba
--- /dev/null
+++ b/chrome/browser/prefs/pref_model_associator.h
@@ -0,0 +1,152 @@
+// Copyright (c) 2011 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 CHROME_BROWSER_PREFS_PREF_MODEL_ASSOCIATOR_H_
+#define CHROME_BROWSER_PREFS_PREF_MODEL_ASSOCIATOR_H_
+#pragma once
+
+#include <map>
+#include <set>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/threading/non_thread_safe.h"
+#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/sync/syncable_service.h"
+#include "chrome/browser/sync/unrecoverable_error_handler.h"
+
+class Profile;
+class ProfileSyncService;
+class Value;
+
+namespace sync_api {
+class WriteNode;
+class WriteTransaction;
+}
+
+namespace browser_sync {
+class ChangeProcessor;
+class GenericChangeProcessor;
+}
+
+// Contains all model association related logic:
+// * Algorithm to associate preferences model and sync model.
+// TODO(sync): Rewrite to use change processor instead of transactions.
+// TODO(sync): Merge this into PrefService. We don't actually need the id_map
+// mapping since the sync node tags are the same as the pref names.
+class PrefModelAssociator
+    : public SyncableService,
+      public base::NonThreadSafe {
+ public:
+  explicit PrefModelAssociator(PrefService* pref_service);
+  virtual ~PrefModelAssociator();
+
+  // SyncableService implementation.
+  virtual bool AssociateModels() OVERRIDE;
+  virtual bool DisassociateModels() OVERRIDE;
+  virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes) OVERRIDE;
+  virtual void AbortAssociation() OVERRIDE;  // Not implemented.
+  virtual bool CryptoReadyIfNecessary() OVERRIDE;
+  virtual void ApplyChangesFromSync(
+      const sync_api::BaseTransaction* trans,
+      const sync_api::SyncManager::ChangeRecord* changes,
+      int change_count) OVERRIDE;
+  virtual void SetupSync(
+      ProfileSyncService* sync_service,
+      browser_sync::GenericChangeProcessor* change_processor) OVERRIDE;
+
+  // Returns the list of preference names that should be monitored for changes.
+  // Only preferences that are registered will be in this list.
+  std::set<std::string> synced_preferences() const;
+
+  // Register a preference with the specified name for syncing. We do not care
+  // about the type at registration time, but when changes arrive from the
+  // syncer, we check if they can be applied and if not drop them.
+  virtual void RegisterPref(const char* name);
+
+  // Returns true if the specified preference is registered for syncing.
+  virtual bool IsPrefRegistered(const char* name);
+
+  // Process a local preference change.
+  virtual void ProcessPrefChange(const std::string& name);
+
+  // Merges the value of local_pref into the supplied server_value and returns
+  // the result (caller takes ownership). If there is a conflict, the server
+  // value always takes precedence. Note that only certain preferences will
+  // actually be merged, all others will return a copy of the server value. See
+  // the method's implementation for details.
+  static Value* MergePreference(const PrefService::Preference& local_pref,
+                                const Value& server_value);
+
+  // Writes the value of pref into the specified node. Returns true
+  // upon success.
+  static bool WritePreferenceToNode(const std::string& name,
+                                    const Value& value,
+                                    sync_api::WriteNode* node);
+
+  // Extract preference value and name from sync specifics.
+  Value* ReadPreferenceSpecifics(
+      const sync_pb::PreferenceSpecifics& specifics,
+      std::string* name);
+
+  // Returns the sync id for the given preference name, or sync_api::kInvalidId
+  // if the preference name is not associated to any sync id.
+  int64 GetSyncIdFromChromeId(const std::string& node_id);
+ protected:
+  friend class ProfileSyncServicePreferenceTest;
+
+  // For testing.
+  PrefModelAssociator();
+
+  // Create an association for a given preference. A sync node is created if
+  // necessary and the value is read from or written to the node as appropriate.
+  bool InitPrefNodeAndAssociate(sync_api::WriteTransaction* trans,
+                                const sync_api::BaseNode& root,
+                                const PrefService::Preference* pref);
+
+  // Associates the given preference name with the given sync id.
+  void Associate(const PrefService::Preference* node, int64 sync_id);
+
+  // Remove the association that corresponds to the given sync id.
+  void Disassociate(int64 sync_id);
+
+  // Returns whether a node with the given permanent tag was found and update
+  // |sync_id| with that node's id.
+  bool GetSyncIdForTaggedNode(const std::string& tag, int64* sync_id);
+
+  // Perform any additional operations that need to happen after a preference
+  // has been updated.
+  void SendUpdateNotificationsIfNecessary(const std::string& pref_name);
+
+  typedef std::map<std::string, int64> PreferenceNameToSyncIdMap;
+  typedef std::map<int64, std::string> SyncIdToPreferenceNameMap;
+
+  static Value* MergeListValues(const Value& from_value, const Value& to_value);
+  static Value* MergeDictionaryValues(const Value& from_value,
+                                      const Value& to_value);
+
+  PrefService* pref_service_;
+  ProfileSyncService* sync_service_;
+
+  // Do we have an active association between the preferences and sync models?
+  // Set by AssociateModels, reset by DisassociateModels.
+  bool models_associated_;
+
+  // Whether we're currently processing changes from the syncer. While this is
+  // true, we ignore any pref changes, since we triggered them.
+  bool processing_syncer_changes_;
+
+  PreferenceNameToSyncIdMap id_map_;
+  SyncIdToPreferenceNameMap id_map_inverse_;
+  std::set<std::string> synced_preferences_;
+
+  // TODO(zea): Get rid of this and use one owned by the PSS.
+  // We create, but don't own this (will be destroyed by data type controller).
+  browser_sync::GenericChangeProcessor* change_processor_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefModelAssociator);
+};
+
+#endif  // CHROME_BROWSER_PREFS_PREF_MODEL_ASSOCIATOR_H_