sync: Implement per-type update processing

sync/engine/sync_directory_update_handler.h

+// Copyright (c) 2013 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 SYNC_ENGINE_SYNC_DIRECTORY_UPDATE_HANDLER_H_
+#define SYNC_ENGINE_SYNC_DIRECTORY_UPDATE_HANDLER_H_
+
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"

[Nicolas Zea, 2013/10/25 21:04:41]

this isn't needed is it?

[rlarocque, 2013/10/25 22:29:47]

Nope.  Removed.

+#include "sync/base/sync_export.h"
+#include "sync/engine/process_updates_util.h"
+#include "sync/internal_api/public/base/model_type.h"
+
+namespace sync_pb {
+class DataTypeProgressMarker;
+class GetUpdatesResponse;
+}
+
+namespace syncer {
+
+namespace sessions {
+class StatusController;
+}
+
+namespace syncable {
+class Directory;
+}
+
+// This class represents the syncable::Directory's processes for requesting and
+// processing updates from the sync server.
+//
+// Each instance of this class represents a particular type in the
+// syncable::Directory.  It can store and retreive that type's progress markers.
+// It can also process a set of received SyncEntities and store their data.
+class SYNC_EXPORT_PRIVATE SyncDirectoryUpdateHandler {

[Nicolas Zea, 2013/10/25 21:04:41]

Out of curiosity, is this eventually going to implement some interface shared
with non-directory types?

[rlarocque, 2013/10/25 22:29:47]

Mostly yes.

The final interface might need to be a bit more complicated, to support features
like encryption.

The final interface will need to include functions from
SyncDirectoryUpdateHandler, SyncDirectoryCommitContributor, and the functions
for committing updates, so this class is only a piece of its implementation.

+ public:
+  SyncDirectoryUpdateHandler(syncable::Directory* dir, ModelType type);
+  ~SyncDirectoryUpdateHandler();
+
+  // Returns the stored progress marker for this type.
+  void GetDownloadProgress(

[Nicolas Zea, 2013/10/25 21:04:41]

Return rather than fill output parameter? Also, perhaps return by const ref?

[rlarocque, 2013/10/25 22:29:47]

Fixed the comment.

The syncable::Directory's function that implements this uses a pointer.  I don't
think there's any reasonable way to translate between the two styles in this
function.

I could return a const ref to a temporary, but that's kind of ugly.

+      sync_pb::DataTypeProgressMarker* progress_marker) const;
+
+  // Processes the contents of a GetUpdates response message.
+  //
+  // Should be invoked with the progress marker and set of SyncEntities from a
+  // single GetUpdates response message.  The progress marker's type must match
+  // this update processor's type, and the set of SyncEntities must include all

[Nicolas Zea, 2013/10/25 21:04:41]

s/update processor/update handler/ ?

[rlarocque, 2013/10/25 22:29:47]

Done.  (Here and elsewhere.)

+  // entities of this type found in the response message.
+  void ProcessGetUpdatesResponse(
+      const sync_pb::DataTypeProgressMarker& progress_marker,
+      const SyncEntityList& applicable_updates,
+      sessions::StatusController* status);
+
+ private:
+  friend class SyncDirectoryUpdateHandlerTest;
+
+  // Processes the given SyncEntities and stores their data in the directory.
+  // Their types must match this update processor's type.
+  void UpdateSyncEntities(
+      syncable::ModelNeutralWriteTransaction* trans,
+      const SyncEntityList& applicable_updates,
+      sessions::StatusController* status);
+
+  // Stores the given progress marker in the directory.
+  // Its type must match this update processor's type.
+  void UpdateProgressMarkers(

[Nicolas Zea, 2013/10/25 21:04:41]

Given that this only updates a single progress marker, rename
UpdateProgressMarker?

[rlarocque, 2013/10/25 22:29:47]

Done.

+      const sync_pb::DataTypeProgressMarker& progress_marker);
+
+  syncable::Directory* dir_;
+  ModelType type_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncDirectoryUpdateHandler);
+};
+
+// TODO(rlarocque): Find a better place to define this.
+typedef std::map<ModelType, SyncDirectoryUpdateHandler*> UpdateHandlerMap;
+
+}  // namespace syncer
+
+#endif  // SYNC_ENGINE_SYNC_DIRECTORY_UPDATE_HANDLER_H_