/* <!-- copyright */
/*
 * aria2 - The high speed download utility
 *
 * Copyright (C) 2009 Tatsuhiro Tsujikawa
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * In addition, as a special exception, the copyright holders give
 * permission to link the code of portions of this program with the
 * OpenSSL library under certain conditions as described in each
 * individual source file, and distribute linked combinations
 * including the two.
 * You must obey the GNU General Public License in all respects
 * for all of the code used other than OpenSSL.  If you modify
 * file(s) with this exception, you may extend this exception to your
 * version of the file(s), but you are not obligated to do so.  If you
 * do not wish to do so, delete this exception statement from your
 * version.  If you delete this exception statement from all source
 * files in the program, then also delete it here.
 */
/* copyright --> */
#ifndef D_SEQUENTIAL_PICKER_H
#define D_SEQUENTIAL_PICKER_H

#include "common.h"

#include <deque>
#include <memory>

namespace aria2 {

template<typename T>
class SequentialPicker {
private:
  std::deque<std::shared_ptr<T> > entries_;
  std::shared_ptr<T> pickedEntry_;
public:
  bool isPicked() const
  {
    return pickedEntry_.get();
  }

  const std::shared_ptr<T>& getPickedEntry() const
  {
    return pickedEntry_;
  }

  void dropPickedEntry()
  {
    pickedEntry_.reset();
  }

  bool hasNext() const
  {
    return !entries_.empty();
  }

  std::shared_ptr<T> pickNext()
  {
    std::shared_ptr<T> r;
    if(hasNext()) {
      r = entries_.front();
      entries_.pop_front();
      pickedEntry_ = r;
    }
    return r;
  }

  void pushEntry(const std::shared_ptr<T>& entry)
  {
    entries_.push_back(entry);
  }

  size_t countEntryInQueue() const
  {
    return entries_.size();
  }
};

} // namespace aria2

#endif // D_SEQUENTIAL_PICKER_H