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

/*

 * Copyright (c) 2007 University of Washington

 * All rights reserved.

 *

 * 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

 */

// The queue base class does not have any limit based on the number

// of packets or number of bytes. It is, conceptually, infinite 

// by default. Only subclasses define limitations.

// The base class implements tracing and basic statistics calculations.

#ifndef QUEUE_H

#define QUEUE_H

#include <string>

#include <list>

#include "ns3/packet.h"

#include "ns3/object.h"

#include "ns3/callback-trace-source.h"

#include "ns3/trace-resolver.h"

namespace ns3 {

class StringEnumDefaultValue;

/**

 * \brief Abstract base class for packet Queues

 * 

 * This class defines the base APIs for packet queues in the ns-3 system

 */

class Queue : public Object

{

public:

  static const InterfaceId iid;

  enum TraceType {

    ENQUEUE,

    DEQUEUE,

    DROP,

  };

  Queue ();

  virtual ~Queue ();

  TraceResolver *CreateTraceResolver (TraceContext const &context);

  /**

   * \return true if the queue is empty; false otherwise

   */

  bool IsEmpty (void);

  /**

   * Place a packet into the rear of the Queue

   * \return True if the operation was successful; false otherwise

   */

  bool Enqueue (const Packet& p);

  /**

   * Remove a packet from the front of the Queue

   * \return True if the operation was successful; false otherwise

   */

  bool Dequeue (Packet &p);

  /**

   * Get a copy of the item at the front of the queue without removing it

   * \return True if the operation was successful; false otherwise

   */

  bool Peek (Packet &p);

  /**

   * XXX Doesn't do anything right now, think its supposed to flush the queue

   */

  void DequeueAll (void);

  /**

   * \return The number of packets currently stored in the Queue

   */

  uint32_t GetNPackets (void);

  /**

   * \return The number of bytes currently occupied by the packets in the Queue

   */

  uint32_t GetNBytes (void);

  /**

   * \return The total number of bytes recieved by this Queue since the

   * simulation began, or since ResetStatistics was called, according to 

   * whichever happened more recently

   * 

   */

  uint32_t GetTotalReceivedBytes (void);

  /**

   * \return The total number of packets recieved by this Queue since the

   * simulation began, or since ResetStatistics was called, according to 

   * whichever happened more recently

   */

  uint32_t GetTotalReceivedPackets (void);

  /**

   * \return The total number of bytes dropped by this Queue since the

   * simulation began, or since ResetStatistics was called, according to 

   * whichever happened more recently

   */

  uint32_t GetTotalDroppedBytes (void);

  /**

   * \return The total number of bytes dropped by this Queue since the

   * simulation began, or since ResetStatistics was called, according to 

   * whichever happened more recently

   */

  uint32_t GetTotalDroppedPackets (void);

  /**

   * Resets the counts for dropped packets, dropped bytes, recieved packets, and

   * recieved bytes.

   */

  void ResetStatistics (void);

#if 0

  // average calculation requires keeping around

  // a buffer with the date of arrival of past received packets

  // which are within the average window

  // so, it is quite costly to do it all the time.

  // Hence, it is disabled by default and must be explicitely

  // enabled with this method which specifies the size

  // of the average window in time units.

  void EnableRunningAverage (Time averageWindow);

  void DisableRunningAverage (void);

  // average

  double GetQueueSizeAverage (void);

  double GetReceivedBytesPerSecondAverage (void);

  double GetReceivedPacketsPerSecondAverage (void);

  double GetDroppedBytesPerSecondAverage (void);

  double GetDroppedPacketsPerSecondAverage (void);

  // variance

  double GetQueueSizeVariance (void);

  double GetReceivedBytesPerSecondVariance (void);

  double GetReceivedPacketsPerSecondVariance (void);

  double GetDroppedBytesPerSecondVariance (void);

  double GetDroppedPacketsPerSecondVariance (void);

#endif

private:

  virtual bool DoEnqueue (const Packet& p) = 0;

  virtual bool DoDequeue (Packet &p) = 0;

  virtual bool DoPeek (Packet &p) = 0;

protected:

  // called by subclasses to notify parent of packet drops.

  void Drop (const Packet& p);

private:

  CallbackTraceSource<const Packet &> m_traceEnqueue;

  CallbackTraceSource<const Packet &> m_traceDequeue;

  CallbackTraceSource<const Packet &> m_traceDrop;

  uint32_t m_nBytes;

  uint32_t m_nTotalReceivedBytes;

  uint32_t m_nPackets;

  uint32_t m_nTotalReceivedPackets;

  uint32_t m_nTotalDroppedBytes;

  uint32_t m_nTotalDroppedPackets;

public:

  /**

   * A factory method to generate a preconfigured default Queue for use

   * \return a Queue smart pointer that is the default Queue type defined

   */

  static Ptr<Queue> CreateDefault (void);

};

}; // namespace ns3

#endif /* QUEUE_H */