sync/internal_api/public/non_blocking_type_processor.h

// Copyright 2014 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_NON_BLOCKING_TYPE_PROCESSOR_H_
#define SYNC_ENGINE_NON_BLOCKING_TYPE_PROCESSOR_H_

#include "base/memory/weak_ptr.h"
#include "base/sequenced_task_runner.h"
#include "base/threading/non_thread_safe.h"
#include "sync/base/sync_export.h"
#include "sync/internal_api/public/base/model_type.h"
#include "sync/protocol/sync.pb.h"

namespace syncer {

class SyncCoreProxy;
class NonBlockingTypeProcessorCore;

// A sync component embedded on the synced type's thread that helps to handle
// communication between sync and model type threads.
class SYNC_EXPORT_PRIVATE NonBlockingTypeProcessor : base::NonThreadSafe {
 public:
  NonBlockingTypeProcessor(ModelType type);
  virtual ~NonBlockingTypeProcessor();

  // Returns true if this object believes that sync is preferred for this type.
  //
  // By "preferred", we mean that a policy decision has been made that this
  // type should be synced.  Most of the time this is controlled by a user
  // clicking a checkbox on the settings page.
  //
  // The canonical preferred state is based on SyncPrefs on the UI thread.  At
  // best, this value is stale and may lag behind the one set on the UI thread.
  // Before this type has registered with the UI thread, it's mostly just an
  // informed guess.
  bool IsPreferred() const;

  // Returns true if the handshake with sync thread is complete.
  bool IsConnected() const;

  // Returns the model type handled by this processor.
  ModelType GetModelType() const;

  // Starts the handshake with the sync thread.
  void Enable(SyncCoreProxy* core_proxy);

  // Severs all ties to the sync thread and may delete local sync state.
  // Another call to Enable() can be used to re-establish this connection.
  void Disable();

  // Severs all ties to the sync thread.
  // Another call to Enable() can be used to re-establish this connection.
  void Disconnect();

  // Callback used to process the handshake response.
  void OnConnect(base::WeakPtr<NonBlockingTypeProcessorCore> core,
                 scoped_refptr<base::SequencedTaskRunner> sync_thread);

  base::WeakPtr<NonBlockingTypeProcessor> AsWeakPtr();

 private:
  ModelType type_;
  sync_pb::DataTypeProgressMarker progress_marker_;

  // Whether or not sync is preferred for this type.  This is a cached copy of
  // the canonical copy information on the UI thread.
  bool is_preferred_;

  // Whether or not this object has completed its initial handshake with the
  // SyncCoreProxy.
  bool is_connected_;

  base::WeakPtr<NonBlockingTypeProcessorCore> core_;
  scoped_refptr<base::SequencedTaskRunner> sync_thread_;

  base::WeakPtrFactory<NonBlockingTypeProcessor> weak_ptr_factory_;
};

}  // namespace syncer

#endif  // SYNC_ENGINE_NON_BLOCKING_TYPE_PROCESSOR_H_