Implement new SyncAPI and convert Preferences to it.

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
index 7b24153216600fa4a810de7ae9f5c66b7c0880ba..ada7b5123bb6fc555e650d96a5b6424a1fe474fb 100644
--- a/chrome/browser/prefs/pref_model_associator.h
+++ b/chrome/browser/prefs/pref_model_associator.h
@@ -14,28 +14,18 @@
 #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"
+#include "chrome/browser/sync/api/syncable_service.h"
+#include "chrome/browser/sync/api/sync_data.h"
 
-class Profile;
-class ProfileSyncService;
-class Value;
-
-namespace sync_api {
-class WriteNode;
-class WriteTransaction;
+namespace sync_pb {
+class PreferenceSpecifics;
 }
 
-namespace browser_sync {
-class ChangeProcessor;
-class GenericChangeProcessor;
-}
+class Value;
 
-// 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.
+// Contains all preference sync related logic.
+// TODO(sync): Merge this into PrefService once we separate the profile
+// PrefService from the local state PrefService.
 class PrefModelAssociator
     : public SyncableService,
       public base::NonThreadSafe {
@@ -44,32 +34,34 @@ class PrefModelAssociator
   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.
+  virtual SyncDataList GetAllSyncData(syncable::ModelType type) OVERRIDE;
+  virtual void ProcessSyncChanges(const SyncChangeList& change_list) OVERRIDE;
+  virtual bool MergeDataAndStartSyncing(
+      syncable::ModelType type,
+      const SyncDataList& initial_sync_data,
+      SyncChangeProcessor* sync_processor) OVERRIDE;
+  virtual void StopSyncing(syncable::ModelType type) OVERRIDE;
+
+  // Returns the list of preference names that are registered as syncable, and
+  // hence should be monitored for changes.
+  std::set<std::string> registered_preferences() const;
+
+  // Returns the list of preferences actually being synced (which is a subset
+  // of those registered as syncable).
   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.
+  // Note: This should only be called at profile startup time (before sync
+  // begins).

[Mattias Nissler (ping if slow), 2011/05/21 18:17:52]

You may run into trouble regarding this. Design-wise, all prefs should be
registered at initialization time, but unfortunately some code violates that
rule. What happens if we call this after initialization time?

[Nicolas Zea, 2011/05/23 18:13:27]

It will DCHECK, so should be caught quickly. That said, as long as all syncable
preferences have registered before the sync engine starts up, which is late in
the startup process, everything should be fine.

In release mode it will simply register the preference as syncable but the
preference won't get updated unless a new sync change is received, so it should
be handled (relatively) gracefully.

[Mattias Nissler (ping if slow), 2011/05/23 20:43:08]

I have learned to not rely on this property of prefs, so don't complain later
you haven't been warned :)
That's good.

[tim (not reviewing), 2011/05/23 20:51:02]

AFAIK, the behavior was pretty similar in the old world - we'd associate prefs
at one point and expect that prefs were registered by then.  It's just that it
was happening in some dark corner of sync rather than here in prefs code so no
one who knew better realized it :|

Hope to catch more of these with the new api...

   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.
+  // Process a local preference change. This can trigger new SyncChanges being
+  // sent to the syncer.
   virtual void ProcessPrefChange(const std::string& name);
 
   // Merges the value of local_pref into the supplied server_value and returns
@@ -80,71 +72,83 @@ class PrefModelAssociator
   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);
+  // Fills |sync_data| with a sync representation of the preference data
+  // provided.
+  static bool CreatePrefSyncData(const std::string& name,
+                                 const Value& value,
+                                 SyncData* sync_data);
 
   // 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;
 
+  typedef std::map<std::string, SyncData> SyncDataMap;
+
   // 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.
+  // Create an association for a given preference. If |sync_pref| is valid,
+  // signifying that sync has data for this preference, we reconcile their data
+  // with ours and append a new UPDATE SyncChange to |sync_changes|. If
+  // sync_pref is not set, we append an ADD SyncChange to |sync_changes| with
+  // the current preference data.
+  // Note: We do not modify the sync data for preferences that are either
+  // controlled by policy (are not user modifiable) or have their default value
+  // (are not user controlled).
+  void InitPrefAndAssociate(const SyncData& sync_pref,
+                            const std::string& pref_name,
+                            SyncChangeList* sync_changes);
+
+  // Perform any additional local 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.
+  // Set when start syncing, reset in StopSyncing. While this is not set, we
+  // ignore any local preference changes (when we start syncing we will look
+  // up the most recent values anyways).
   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.
+  // true, we ignore any local preference changes, since we triggered them.
   bool processing_syncer_changes_;
 
-  PreferenceNameToSyncIdMap id_map_;
-  SyncIdToPreferenceNameMap id_map_inverse_;
-  std::set<std::string> synced_preferences_;
+  // A set of preference names.
+  typedef std::set<std::string> PreferenceSet;
+
+  // All preferences that have registered as being syncable with this profile.
+  PreferenceSet registered_preferences_;
+
+  // The preferences we are currently actually syncing (i.e. those the server
+  // is aware of). This is a subset of |registered_preferences_|, but excludes
+  // those with default values or not modifiable by the user (for example due
+  // to being controlled by policy)
+  PreferenceSet synced_preferences_;
+
+  // We keep track of the most recent sync data we've received those
+  // preferences registered as syncable but not in our synced_preferences_ list.
+  // These are used if at a later time the preference in question should be
+  // synced (for example the pref policy changes), and we need to get the
+  // most recent sync data.
+  // TODO(zea): See if we can get rid of the difference between
+  // synced_preferences_ and registered_preferences_ by always updating the
+  // local user pref store with pref data and letting the PrefStoreKeeper
+  // handle ensuring the appropriate policy value is used.
+  SyncDataMap untracked_pref_sync_data_;
+
+  // The PrefService we are syncing to.
+  PrefService* pref_service_;
 
-  // 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_;
+  // Sync's SyncChange handler. We push all our changes through this.
+  SyncChangeProcessor* sync_processor_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefModelAssociator);
 };