////////////////////////////////////////////////////////////////////////////////
/// 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 Frank Celler
/// @author Achim Brandt
////////////////////////////////////////////////////////////////////////////////

#ifndef LIB_BASICS_WRITE_LOCKER_H
#define LIB_BASICS_WRITE_LOCKER_H 1

#include "Basics/Common.h"
#include "Basics/ReadWriteLock.h"

#ifdef TRI_SHOW_LOCK_TIME
#include "Basics/logging.h"
#endif


////////////////////////////////////////////////////////////////////////////////
/// @brief construct locker with file and line information
///
/// Ones needs to use macros twice to get a unique variable based on the line
/// number.
////////////////////////////////////////////////////////////////////////////////

#define WRITE_LOCKER_VAR_A(a) _write_lock_variable##a
#define WRITE_LOCKER_VAR_B(a) WRITE_LOCKER_VAR_A(a)

#ifdef TRI_SHOW_LOCK_TIME

#define WRITE_LOCKER(b)                                                   \
  triagens::basics::WriteLocker<std::remove_reference<decltype(b)>::type> \
      WRITE_LOCKER_VAR_B(__LINE__)(&b, __FILE__, __LINE__)

#define WRITE_LOCKER_EVENTUAL(b, t)                                       \
  triagens::basics::WriteLocker<std::remove_reference<decltype(b)>::type> \
      WRITE_LOCKER_VAR_B(__LINE__)(&b, t, __FILE__, __LINE__)

#else

#define WRITE_LOCKER(b)                                                   \
  triagens::basics::WriteLocker<std::remove_reference<decltype(b)>::type> \
      WRITE_LOCKER_VAR_B(__LINE__)(&b)

#define WRITE_LOCKER_EVENTUAL(b, t)                                       \
  triagens::basics::WriteLocker<std::remove_reference<decltype(b)>::type> \
      WRITE_LOCKER_VAR_B(__LINE__)(&b, t)

#endif


namespace triagens {
namespace basics {

////////////////////////////////////////////////////////////////////////////////
/// @brief write locker
///
/// A WriteLocker write-locks a read-write lock during its lifetime and unlocks
/// the lock when it is destroyed.
////////////////////////////////////////////////////////////////////////////////

template <typename T>
class WriteLocker {
  WriteLocker(WriteLocker const&);
  WriteLocker& operator=(WriteLocker const&);

  
 public:
////////////////////////////////////////////////////////////////////////////////
/// @brief aquires a write-lock
///
/// The constructors aquires a write lock, the destructors unlocks the lock.
////////////////////////////////////////////////////////////////////////////////

#ifdef TRI_SHOW_LOCK_TIME

  WriteLocker(T* readWriteLock, char const* file, int line)
      : _readWriteLock(readWriteLock), _file(file), _line(line) {
    double t = TRI_microtime();
    _readWriteLock->writeLock();
    _time = TRI_microtime() - t;
  }

#else

  explicit WriteLocker(T* readWriteLock) : _readWriteLock(readWriteLock) {
    _readWriteLock->writeLock();
  }

#endif

////////////////////////////////////////////////////////////////////////////////
/// @brief aquires a write-lock, with periodic sleeps while not acquired
/// sleep time is specified in nanoseconds
////////////////////////////////////////////////////////////////////////////////

#ifdef TRI_SHOW_LOCK_TIME

  WriteLocker(T* readWriteLock, uint64_t sleepTime, char const* file, int line)
      : _readWriteLock(readWriteLock), _file(file), _line(line) {
    double t = TRI_microtime();
    while (!_readWriteLock->tryWriteLock()) {
#ifdef _WIN32
      usleep((unsigned long)sleepTime);
#else
      usleep((useconds_t)sleepTime);
#endif
    }
    _time = TRI_microtime() - t;
  }

#else

  WriteLocker(T* readWriteLock, uint64_t sleepTime)
      : _readWriteLock(readWriteLock) {
    while (!_readWriteLock->tryWriteLock()) {
#ifdef _WIN32
      usleep((unsigned long)sleepTime);
#else
      usleep((useconds_t)sleepTime);
#endif
    }
  }

#endif

  //////////////////////////////////////////////////////////////////////////////
  /// @brief releases the write-lock
  //////////////////////////////////////////////////////////////////////////////

  ~WriteLocker() {
    _readWriteLock->unlock();

#ifdef TRI_SHOW_LOCK_TIME
    if (_time > TRI_SHOW_LOCK_THRESHOLD) {
      LOG_WARNING("WriteLocker %s:%d took %f s", _file, _line, _time);
    }
#endif
  }

  
 private:
  //////////////////////////////////////////////////////////////////////////////
  /// @brief the read-write lock
  //////////////////////////////////////////////////////////////////////////////

  T* _readWriteLock;

#ifdef TRI_SHOW_LOCK_TIME

  //////////////////////////////////////////////////////////////////////////////
  /// @brief file
  //////////////////////////////////////////////////////////////////////////////

  char const* _file;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief line number
  //////////////////////////////////////////////////////////////////////////////

  int _line;

  //////////////////////////////////////////////////////////////////////////////
  /// @brief lock time
  //////////////////////////////////////////////////////////////////////////////

  double _time;

#endif
};
}
}

#endif