sync/api/sync_change_processor.h

// Copyright 2012 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_API_SYNC_CHANGE_PROCESSOR_H_
#define SYNC_API_SYNC_CHANGE_PROCESSOR_H_

#include <vector>

#include "sync/api/sync_data.h"
#include "sync/api/sync_error.h"
#include "sync/base/sync_export.h"
#include "sync/internal_api/public/base/model_type.h"

namespace tracked_objects {
class Location;
}  // namespace tracked_objects

namespace syncer {

class SyncChange;

typedef std::vector<SyncChange> SyncChangeList;

// An interface for services that handle receiving SyncChanges.
class SYNC_EXPORT SyncChangeProcessor {
 public:
  // Whether a context change should force a datatype refresh or not.
  enum ContextRefreshStatus { NO_REFRESH, REFRESH_NEEDED };
  typedef base::Callback<void(const SyncData&)> GetSyncDataCallback;

  SyncChangeProcessor();
  virtual ~SyncChangeProcessor();

  // Process a list of SyncChanges.
  // Returns: A default SyncError (IsSet() == false) if no errors were
  //          encountered, and a filled SyncError (IsSet() == true)
  //          otherwise.
  // Inputs:
  //   |from_here|: allows tracking of where sync changes originate.
  //   |change_list|: is the list of sync changes in need of processing.
  virtual SyncError ProcessSyncChanges(
      const tracked_objects::Location& from_here,
      const SyncChangeList& change_list) = 0;

  // Fills a list of SyncData. This should create an up to date representation
  // of all the data known to the ChangeProcessor for |datatype|, and
  // should match/be a subset of the server's view of that datatype.
  //
  // WARNING: This can be a potentially slow & memory intensive operation and
  // should only be used when absolutely necessary / sparingly.
  virtual SyncDataList GetAllSyncData(ModelType type) const = 0;

  // Retrieves the SyncData identified by |type| and |sync_tag| and invokes
  // |callback| asynchronously. If no such SyncData exists locally, IsValid on
  // the SyncData passed to |callback| will return false.
  //
  // This is an asynchronous local operation that may result in disk IO.
  //
  // Refer to sync_data.h for a description of |sync_tag|.
  //
  // TODO:(maniscalco): N.B. this method should really be pure virtual. An
  // implentation is provided here just to verify that everything compiles.
  // Update this method to be pure virtual (bug 353300).
  virtual void GetSyncData(const ModelType& type,
                           const std::string& sync_tag,
                           const GetSyncDataCallback& callback) const {}

  // Updates the context for |type|, triggering an optional context refresh.
  // Default implementation does nothing. A type's context is a per-client blob
  // that can affect all SyncData sent to/from the server, much like a cookie.
  // TODO(zea): consider pulling the refresh logic into a separate method
  // unrelated to datatype implementations.
  virtual syncer::SyncError UpdateDataTypeContext(
      ModelType type,
      ContextRefreshStatus refresh_status,
      const std::string& context);
};

}  // namespace syncer

#endif  // SYNC_API_SYNC_CHANGE_PROCESSOR_H_