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

/*

 * Copyright (c) 2007 University of Washington

 *

 * 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: Tom Henderson <tomhend@u.washington.edu>

 * This code has been ported from ns-2 (queue/errmodel.{cc,h}

 */

#ifndef ERROR_MODEL_H

#define ERROR_MODEL_H

#include <list>

#include "ns3/object.h"

namespace ns3 {

class Packet;

class RandomVariable;

/**

 * \brief General error model that can be used to corrupt packets

 *

 * This object is used to flag packets as being lost/errored or not.

 * It is part of the Object framework and can be aggregated to 

 * other ns3 objects and handled by the Ptr class.

 *

 * The main method is IsCorrupt(Ptr<Packet> p) which returns true if 

 * the packet is to be corrupted according to the underlying model.

 * Depending on the error model, the packet itself may have its packet

 * data buffer errored or not, or side information may be returned to

 * the client in the form of a packet tag.

 * The object can have state (resettable by Reset()).  

 * The object can also be enabled and disabled via two public member functions.

 * 

 * Typical code (simplified) to use an ErrorModel may look something like 

 * this:

 * \code 

 * Ptr<ErrorModel> rem = CreateObject<RateErrorModel> ();

 * rem->SetRandomVariable (UniformVariable ());

 * rem->SetRate (0.001);

 * ...

 * Ptr<Packet> p;

 * if (rem->IsCorrupt (p))

 *   {

 *     dropTrace(p);

 *   } else {

 *     Forward (p);

 *   }

 * \endcode

 *

 * Two practical error models, a ListErrorModel and a RateErrorModel,  

 * are currently implemented. 

 */

class ErrorModel : public Object

{

public:

  static InterfaceId iid (void);

  /**

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

   * \return an ErrorModel smart pointer that is the default ErrorModel 

   * type defined

   */

  static Ptr<ErrorModel> CreateDefault (void);

  ErrorModel ();

  virtual ~ErrorModel ();

 /**

  * \returns true if the Packet is to be considered as errored/corrupted

  * \param pkt Packet to apply error model to

  */

  bool IsCorrupt (Ptr<Packet> pkt);

 /**

  * Reset any state associated with the error model

  */

  void Reset (void);

 /**

  * Enable the error model

  */

  void Enable (void);

 /**

  * Disable the error model

  */

  void Disable (void);

  /**

   * \return true if error model is enabled; false otherwise

   */

  bool IsEnabled (void) const;

protected:

  bool m_enable;

private:

  /*

   * These methods must be implemented by subclasses

   */

  virtual bool DoCorrupt (Ptr<Packet>) = 0;

  virtual void DoReset (void) = 0;

};

enum ErrorUnit

  {   

    EU_BIT,

    EU_BYTE,

    EU_PKT

  };

/**

 * \brief Determine which packets are errored corresponding to an underlying

 * distribution, rate, and unit.

 *

 * This object is used to flag packets as being lost/errored or not.

 * The two parameters that govern the behavior are the rate (or

 * equivalently, the mean duration/spacing between errors), and the

 * unit (which may be per-bit, per-byte, and per-packet).

 * Users can optionally provide a RandomVariable object; the default

 * is to use a Uniform(0,1) distribution.

 * Reset() on this model will do nothing

 *

 * IsCorrupt() will not modify the packet data buffer

 */

class RateErrorModel : public ErrorModel

{

public:

  static InterfaceId iid (void);

  RateErrorModel ();

  virtual ~RateErrorModel ();

  /**

   * \returns the ErrorUnit being used by the underlying model

   */ 

  enum ErrorUnit GetUnit (void) const;

  /**

   * \param error_unit the ErrorUnit to be used by the underlying model

   */ 

  void SetUnit (enum ErrorUnit error_unit);

  /**

   * \returns the error rate being applied by the model

   */ 

  double GetRate (void) const;

  /**

   * \param rate the error rate to be used by the model

   */ 

  void SetRate (double rate);

  /**

   * \param ranvar A random variable distribution to generate random variates

   */ 

  void SetRandomVariable (const RandomVariable &ranvar);

private:

  virtual bool DoCorrupt (Ptr<Packet> p);

  virtual bool DoCorruptPkt (Ptr<Packet> p);

  virtual bool DoCorruptByte (Ptr<Packet> p);

  virtual bool DoCorruptBit (Ptr<Packet> p);

  virtual void DoReset (void);

  enum ErrorUnit m_unit;

  double m_rate;

  RandomVariable* m_ranvar;

};

/**

 * \brief Provide a list of Packet uids to corrupt

 *

 * This object is used to flag packets as being lost/errored or not.

 * A note on performance:  the list is assumed to be unordered, and

 * in general, Packet uids received may be unordered.  Therefore,

 * each call to IsCorrupt() will result in a walk of the list with

 * the present underlying implementation.

 * 

 * Note also that if one wants to target multiple packets from looking

 * at an (unerrored) trace file, the act of erroring a given packet may

 * cause subsequent packet uids to change.  For instance, suppose one wants 

 * to error packets 11 and 17 on a given device.  It may be that erroring

 * packet 11 will cause the subsequent uid stream to change and 17 may no

 * longer correspond to the second packet that one wants to lose.  Therefore,

 * be advised that it might take some trial and error to select the

 * right uids when multiple are provided.

 * 

 * Reset() on this model will clear the list

 *

 * IsCorrupt() will not modify the packet data buffer

 */

class ListErrorModel : public ErrorModel

{

public:

  static InterfaceId iid (void);

  ListErrorModel ();

  virtual ~ListErrorModel ();

  /**

   * \return a copy of the underlying list

   */

  std::list<uint32_t> GetList (void) const;

  /**

   * \param packetlist The list of packet uids to error.

   *

   * This method overwrites any previously provided list.

   */

  void SetList (const std::list<uint32_t> &packetlist);

private:

  virtual bool DoCorrupt (Ptr<Packet> p);

  virtual void DoReset (void);

  typedef std::list<uint32_t> PacketList;

  typedef std::list<uint32_t>::const_iterator PacketListCI;

  PacketList m_packetList;

};

} //namespace ns3

#endif