////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Jan Steemann
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGOD_WAL_SYNCHRONIZER_THREAD_H
#define ARANGOD_WAL_SYNCHRONIZER_THREAD_H 1

#include "Basics/Common.h"
#include "Basics/ConditionVariable.h"
#include "Basics/Thread.h"
#include "Wal/Logfile.h"

namespace arangodb {
namespace wal {

class LogfileManager;

class SynchronizerThread : public Thread {
  //////////////////////////////////////////////////////////////////////////////
  /// @brief SynchronizerThread
  //////////////////////////////////////////////////////////////////////////////

 private:
  SynchronizerThread(SynchronizerThread const&) = delete;
  SynchronizerThread& operator=(SynchronizerThread const&) = delete;

 public:
  SynchronizerThread(LogfileManager*, uint64_t);
  ~SynchronizerThread() { shutdown(); }

 public:
  void beginShutdown() override final;

 public:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief signal that a sync is needed
  //////////////////////////////////////////////////////////////////////////////

  void signalSync();

 protected:
  void run() override;

 private:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief synchronize an unsynchronized region
  //////////////////////////////////////////////////////////////////////////////

  int doSync(bool&);

  //////////////////////////////////////////////////////////////////////////////
  /// @brief get a logfile descriptor (it caches the descriptor for performance)
  //////////////////////////////////////////////////////////////////////////////

  int getLogfileDescriptor(Logfile::IdType);

 private:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief the logfile manager
  //////////////////////////////////////////////////////////////////////////////

  LogfileManager* _logfileManager;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief condition variable for the thread
  //////////////////////////////////////////////////////////////////////////////

  basics::ConditionVariable _condition;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief number of requests waiting
  //////////////////////////////////////////////////////////////////////////////

  uint32_t _waiting;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief wait interval for the synchronizer thread when idle
  //////////////////////////////////////////////////////////////////////////////

  uint64_t const _syncInterval;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief logfile descriptor cache
  //////////////////////////////////////////////////////////////////////////////

  struct {
    Logfile::IdType id;
    int fd;
  } _logfileCache;
};
}
}

#endif