////////////////////////////////////////////////////////////////////////////////
/// @brief generic thread pool
///
/// @file
///
/// DISCLAIMER
///
/// Copyright 2014 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
/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
/// @author Copyright 2013-2013, triAGENS GmbH, Cologne, Germany
////////////////////////////////////////////////////////////////////////////////

#ifndef ARANGODB_BASICS_THREAD_POOL_H
#define ARANGODB_BASICS_THREAD_POOL_H 1

#include "Basics/Common.h"
#include "Basics/ConditionLocker.h"
#include "Basics/ConditionVariable.h"
#include "Basics/Mutex.h"
#include <functional>

namespace triagens {
  namespace basics {

    class WorkerThread;

// -----------------------------------------------------------------------------
// --SECTION--                                                        ThreadPool
// -----------------------------------------------------------------------------

    class ThreadPool {

// -----------------------------------------------------------------------------
// --SECTION--                                        constructors / destructors
// -----------------------------------------------------------------------------

      public:

        ThreadPool (ThreadPool const&) = delete;
        ThreadPool& operator= (ThreadPool const&) = delete;

        ThreadPool (size_t,
                    std::string const&);

        ~ThreadPool ();

// -----------------------------------------------------------------------------
// --SECTION--                                                  public functions
// -----------------------------------------------------------------------------

      public:

////////////////////////////////////////////////////////////////////////////////
/// @brief return the number of threads in the pool
////////////////////////////////////////////////////////////////////////////////

        size_t numThreads () const {
          return _threads.size();
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief return the name of the pool
////////////////////////////////////////////////////////////////////////////////

        char const* name () const {
          return _name.c_str();
        }

////////////////////////////////////////////////////////////////////////////////
/// @brief dequeue a task
////////////////////////////////////////////////////////////////////////////////

        bool dequeue (std::function<void()>&);

////////////////////////////////////////////////////////////////////////////////
/// @brief enqueue a task
////////////////////////////////////////////////////////////////////////////////

        template<typename T>
        void enqueue (T task) {
          { 
            CONDITION_LOCKER(guard, _condition);
            _tasks.emplace_back(std::function<void()>(task));
          }

          _condition.signal();
        }

// -----------------------------------------------------------------------------
// --SECTION--                                                 private variables
// -----------------------------------------------------------------------------

      private:

        triagens::basics::ConditionVariable _condition;

        std::vector<triagens::basics::WorkerThread*> _threads;

        std::deque<std::function<void()>> _tasks;

        std::string _name;

        std::atomic<bool> _stopping;
    };  

  }   // namespace triagens::basics
}   // namespace triagens

#endif

// -----------------------------------------------------------------------------
// --SECTION--                                                       END-OF-FILE
// -----------------------------------------------------------------------------

// Local Variables:
// mode: outline-minor
// outline-regexp: "/// @brief\\|/// {@inheritDoc}\\|/// @page\\|// --SECTION--\\|/// @\\}"
// End: