/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2005 INRIA

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Author: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>

 */

#ifndef SCHEDULER_H

#define SCHEDULER_H

#include <stdint.h>

#include "event-id.h"

namespace ns3 {

/**

 * \brief Maintain the event list

 *

 * This base class specifies the interface used to maintain the 

 * event list. If you want to provide a new event list scheduler, 

 * you need to create a subclass of this base class and implement 

 * all the pure virtual methods defined here. Namely:

 *   - ns3::Scheduler::Insert

 *   - ns3::Scheduler::IsEmpty

 *   - ns3::Scheduler::PeekNext

 *   - ns3::Scheduler::RemoveNext

 *   - ns3::Scheduler::Remove

 *

 * If you need to provide a new event list scheduler without

 * editing the main simulator class, you need to also implement

 * a subclass of the ns3::SchedulerFactory base class and

 * feed it to ns3::Simulator::setExternal.

 * The simplest example of a scheduler is the linked-list

 * scheduler included in ns3: see the files 

 * src/simulator/scheduler-list.h and src/simulator/scheduler-list.cc

 */

class Scheduler {

 public:

  struct EventKey {

      uint64_t m_ts;

      uint32_t m_uid;

  };

  virtual ~Scheduler () = 0;

  /**

   * \param id event to store in the event list

   *

   * This method takes ownership of the event pointer.

   */

  virtual void Insert (const EventId &id) = 0;

  /**

   * \returns true if the event list is empty and false otherwise.

   */

  virtual bool IsEmpty (void) const = 0;

  /**

   * \returns a pointer to the next earliest event. The caller

   *      takes ownership of the returned pointer.

   *

   * This method cannot be invoked if the list is empty.

   */

  virtual EventId PeekNext (void) const = 0;

  /**

   * This method cannot be invoked if the list is empty.

   * Remove the next earliest event from the event list.

   */

  virtual EventId RemoveNext (void) = 0;

  /**

   * \param id the id of the event to remove

   * \returns true if the id was found and removed 

   *          successfully, false otherwise.

   *

   * This methods cannot be invoked if the list is empty.

   */

  virtual bool Remove (const EventId &id) = 0;

};

}; // namespace ns3

#endif /* SCHEDULER_H */