////////////////////////////////////////////////////////////////////////////////
/// 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_UNLOCKER_H
#define LIB_BASICS_WRITE_UNLOCKER_H 1

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


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

#define WRITE_UNLOCKER_VAR_A(a) _write_unlock_variable##a
#define WRITE_UNLOCKER_VAR_B(a) WRITE_UNLOCKER_VAR_A(a)

#define WRITE_UNLOCKER(b)                                                   \
  triagens::basics::WriteUnlocker<std::remove_reference<decltype(b)>::type> \
      WRITE_UNLOCKER_VAR_B(__LINE__)(&b, __FILE__, __LINE__)


namespace triagens {
namespace basics {

////////////////////////////////////////////////////////////////////////////////
/// @brief write unlocker
///
/// A WriteUnlocker unlocks a read-write lock during its lifetime and reaquires
/// the write lock when it is destroyed.
////////////////////////////////////////////////////////////////////////////////

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

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

  explicit WriteUnlocker(T* readWriteLock)
      : WriteUnlocker(readWriteLock, nullptr, 0) {}

  //////////////////////////////////////////////////////////////////////////////
  /// @brief unlocks the lock
  ///
  /// The constructor unlocks the lock, the destructors aquires a write-lock.
  //////////////////////////////////////////////////////////////////////////////

  WriteUnlocker(T* readWriteLock, char const* file, int line);
          : _readWriteLock(readWriteLock), _file(file), _line(line) {
            _readWriteLock->unlock();
          }

          ////////////////////////////////////////////////////////////////////////////////
          /// @brief aquires the write-lock
          ////////////////////////////////////////////////////////////////////////////////

          ~WriteUnlocker() { _readWriteLock->writeLock(); }

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

          T* _readWriteLock;

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

          char const* _file;

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

          int _line;
};
}
}

#endif