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

/*

 * Copyright (c) 2005,2006 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>

 */

#include "ns3/assert.h"

#include "ns3/log.h"

#include "ns3/simulator.h"

#include <cmath>

#include "dcf-manager.h"

#include "wifi-phy.h"

#include "wifi-mac.h"

#include "mac-low.h"

NS_LOG_COMPONENT_DEFINE ("DcfManager");

#define MY_DEBUG(x) \

  NS_LOG_DEBUG (Simulator::Now () << " " << this << " " << x)

namespace ns3 {

/****************************************************************

 *      Implement the DCF state holder

 ****************************************************************/

DcfState::DcfState ()

  : m_backoffSlots (0),

    m_backoffStart (Seconds (0.0)),

    m_cwMin (0),

    m_cwMax (0),

    m_cw (0),

    m_accessRequested (false)

{

}

DcfState::~DcfState ()

{

}

void

DcfState::SetAifsn (uint32_t aifsn)

{

  m_aifsn = aifsn;

}

void

DcfState::SetCwMin (uint32_t minCw)

{

  m_cwMin = minCw;

  ResetCw ();

}

void

DcfState::SetCwMax (uint32_t maxCw)

{

  m_cwMax = maxCw;

  ResetCw ();

}

uint32_t

DcfState::GetAifsn (void) const

{

  return m_aifsn;

}

uint32_t

DcfState::GetCwMin (void) const

{

  return m_cwMin;

}

uint32_t

DcfState::GetCwMax (void) const

{

  return m_cwMax;

}

void

DcfState::ResetCw (void)

{

  m_cw = m_cwMin;

}

void

DcfState::UpdateFailedCw (void)

{

  // see 802.11-2012, section 9.19.2.5

  m_cw = std::min ( 2 * (m_cw + 1) - 1, m_cwMax);

}

void

DcfState::UpdateBackoffSlotsNow (uint32_t nSlots, Time backoffUpdateBound)

{

  m_backoffSlots -= nSlots;

  m_backoffStart = backoffUpdateBound;

  MY_DEBUG ("update slots=" << nSlots << " slots, backoff=" << m_backoffSlots);

}

void

DcfState::StartBackoffNow (uint32_t nSlots)

{

  NS_ASSERT (m_backoffSlots == 0);

  MY_DEBUG ("start backoff=" << nSlots << " slots");

  m_backoffSlots = nSlots;

  m_backoffStart = Simulator::Now ();

}

uint32_t

DcfState::GetCw (void) const

{

  return m_cw;

}

uint32_t

DcfState::GetBackoffSlots (void) const

{

  return m_backoffSlots;

}

Time

DcfState::GetBackoffStart (void) const

{

  return m_backoffStart;

}

bool

DcfState::IsAccessRequested (void) const

{

  return m_accessRequested;

}

void

DcfState::NotifyAccessRequested (void)

{

  m_accessRequested = true;

}

void

DcfState::NotifyAccessGranted (void)

{

  NS_ASSERT (m_accessRequested);

  m_accessRequested = false;

  DoNotifyAccessGranted ();

}

void

DcfState::NotifyCollision (void)

{

  DoNotifyCollision ();

}

void

DcfState::NotifyInternalCollision (void)

{

  DoNotifyInternalCollision ();

}

void

DcfState::NotifyChannelSwitching (void)

{

  DoNotifyChannelSwitching ();

}

/**

 * Listener for NAV events. Forwards to DcfManager

 */

class LowDcfListener : public ns3::MacLowDcfListener

{

public:

  /**

   * Create a LowDcfListener for the given DcfManager.

   *

   * \param dcf

   */

  LowDcfListener (ns3::DcfManager *dcf)

    : m_dcf (dcf)

  {

  }

  virtual ~LowDcfListener ()

  {

  }

  virtual void NavStart (Time duration)

  {

    m_dcf->NotifyNavStartNow (duration);

  }

  virtual void NavReset (Time duration)

  {

    m_dcf->NotifyNavResetNow (duration);

  }

  virtual void AckTimeoutStart (Time duration)

  {

    m_dcf->NotifyAckTimeoutStartNow (duration);

  }

  virtual void AckTimeoutReset ()

  {

    m_dcf->NotifyAckTimeoutResetNow ();

  }

  virtual void CtsTimeoutStart (Time duration)

  {

    m_dcf->NotifyCtsTimeoutStartNow (duration);

  }

  virtual void CtsTimeoutReset ()

  {

    m_dcf->NotifyCtsTimeoutResetNow ();

  }

private:

  ns3::DcfManager *m_dcf;  //!< DcfManager to forward events to

};

/**

 * Listener for PHY events. Forwards to DcfManager

 */

class PhyListener : public ns3::WifiPhyListener

{

public:

  /**

   * Create a PhyListener for the given DcfManager.

   *

   * \param dcf

   */

  PhyListener (ns3::DcfManager *dcf)

    : m_dcf (dcf)

  {

  }

  virtual ~PhyListener ()

  {

  }

  virtual void NotifyRxStart (Time duration)

  {

    m_dcf->NotifyRxStartNow (duration);

  }

  virtual void NotifyRxEndOk (void)

  {

    m_dcf->NotifyRxEndOkNow ();

  }

  virtual void NotifyRxEndError (void)

  {

    m_dcf->NotifyRxEndErrorNow ();

  }

  {

    m_dcf->NotifyTxStartNow (duration);

  }

  virtual void NotifyMaybeCcaBusyStart (Time duration)

  {

    m_dcf->NotifyMaybeCcaBusyStartNow (duration);

  }

  virtual void NotifySwitchingStart (Time duration)

  {

    m_dcf->NotifySwitchingStartNow (duration);

  }

private:

  ns3::DcfManager *m_dcf;  //!< DcfManager to forward events to

};

/****************************************************************

 *      Implement the DCF manager of all DCF state holders

 ****************************************************************/

DcfManager::DcfManager ()

  : m_lastAckTimeoutEnd (MicroSeconds (0)),

    m_lastCtsTimeoutEnd (MicroSeconds (0)),

    m_lastNavStart (MicroSeconds (0)),

    m_lastNavDuration (MicroSeconds (0)),

    m_lastRxStart (MicroSeconds (0)),

    m_lastRxDuration (MicroSeconds (0)),

    m_lastRxReceivedOk (true),

    m_lastRxEnd (MicroSeconds (0)),

    m_lastTxStart (MicroSeconds (0)),

    m_lastTxDuration (MicroSeconds (0)),

    m_lastBusyStart (MicroSeconds (0)),

    m_lastBusyDuration (MicroSeconds (0)),

    m_lastSwitchingStart (MicroSeconds (0)),

    m_lastSwitchingDuration (MicroSeconds (0)),

    m_rxing (false),

    m_slotTimeUs (0),

    m_sifs (Seconds (0.0)),

    m_phyListener (0),

    m_lowListener (0)

{

  NS_LOG_FUNCTION (this);

}

DcfManager::~DcfManager ()

{

  delete m_phyListener;

  delete m_lowListener;

  m_phyListener = 0;

  m_lowListener = 0;

}

void

DcfManager::SetupPhyListener (Ptr<WifiPhy> phy)

{

  NS_LOG_FUNCTION (this << phy);

  if (m_phyListener != 0)

    {

      delete m_phyListener;

    }

  m_phyListener = new PhyListener (this);

  phy->RegisterListener (m_phyListener);

}

void

DcfManager::SetupLowListener (Ptr<MacLow> low)

{

  NS_LOG_FUNCTION (this << low);

  if (m_lowListener != 0)

    {

      delete m_lowListener;

    }

  m_lowListener = new LowDcfListener (this);

  low->RegisterDcfListener (m_lowListener);

}

void

DcfManager::SetSlot (Time slotTime)

{

  NS_LOG_FUNCTION (this << slotTime);

  m_slotTimeUs = slotTime.GetMicroSeconds ();

}

void

DcfManager::SetSifs (Time sifs)

{

  NS_LOG_FUNCTION (this << sifs);

  m_sifs = sifs;

}

void

DcfManager::SetEifsNoDifs (Time eifsNoDifs)

{

  NS_LOG_FUNCTION (this << eifsNoDifs);

  m_eifsNoDifs = eifsNoDifs;

}

Time

DcfManager::GetEifsNoDifs () const

{

  NS_LOG_FUNCTION (this);

  return m_eifsNoDifs;

}

void

DcfManager::Add (DcfState *dcf)

{

  NS_LOG_FUNCTION (this << dcf);

  m_states.push_back (dcf);

}

Time

DcfManager::MostRecent (Time a, Time b) const

{

  NS_LOG_FUNCTION (this << a << b);

  return Max (a, b);

}

Time

DcfManager::MostRecent (Time a, Time b, Time c) const

{

  NS_LOG_FUNCTION (this << a << b << c);

  Time retval;

  retval = Max (a, b);

  retval = Max (retval, c);

  return retval;

}

Time

DcfManager::MostRecent (Time a, Time b, Time c, Time d) const

{

  NS_LOG_FUNCTION (this << a << b << c << d);

  Time e = Max (a, b);

  Time f = Max (c, d);

  Time retval = Max (e, f);

  return retval;

}

Time

DcfManager::MostRecent (Time a, Time b, Time c, Time d, Time e, Time f) const

{

  NS_LOG_FUNCTION (this << a << b << c << d << e << f);

  Time g = Max (a, b);

  Time h = Max (c, d);

  Time i = Max (e, f);

  Time k = Max (g, h);

  Time retval = Max (k, i);

  return retval;

}

Time

DcfManager::MostRecent (Time a, Time b, Time c, Time d, Time e, Time f, Time g) const

{

  NS_LOG_FUNCTION (this << a << b << c << d << e << f << g);

  Time h = Max (a, b);

  Time i = Max (c, d);

  Time j = Max (e, f);

  Time k = Max (h, i);

  Time l = Max (j, g);

  Time retval = Max (k, l);

  return retval;

}

bool

DcfManager::IsBusy (void) const

{

  NS_LOG_FUNCTION (this);

  // PHY busy

  if (m_rxing)

    {

      return true;

    }

  Time lastTxEnd = m_lastTxStart + m_lastTxDuration;

  if (lastTxEnd > Simulator::Now ())

    {

      return true;

    }

  // NAV busy

  Time lastNavEnd = m_lastNavStart + m_lastNavDuration;

  if (lastNavEnd > Simulator::Now ())

    {

      return true;

    }

  return false;

}

void

DcfManager::RequestAccess (DcfState *state)

{

  NS_LOG_FUNCTION (this << state);

  UpdateBackoff ();

  NS_ASSERT (!state->IsAccessRequested ());

  state->NotifyAccessRequested ();

  /**

   * If there is a collision, generate a backoff

   * by notifying the collision to the user.

   */

  if (state->GetBackoffSlots () == 0

      && IsBusy ())

    {

      MY_DEBUG ("medium is busy: collision");

      /* someone else has accessed the medium.

       * generate a backoff.

       */

      state->NotifyCollision ();

    }

  DoGrantAccess ();

  DoRestartAccessTimeoutIfNeeded ();

}

void

DcfManager::DoGrantAccess (void)

{

  NS_LOG_FUNCTION (this);

  uint32_t k = 0;

  for (States::const_iterator i = m_states.begin (); i != m_states.end (); k++)

    {

      DcfState *state = *i;

      if (state->IsAccessRequested ()

          && GetBackoffEndFor (state) <= Simulator::Now () )

        {

          /**

           * This is the first dcf we find with an expired backoff and which

           * needs access to the medium. i.e., it has data to send.

           */

          MY_DEBUG ("dcf " << k << " needs access. backoff expired. access granted. slots=" << state->GetBackoffSlots ());

          i++; // go to the next item in the list.

          k++;

          std::vector<DcfState *> internalCollisionStates;

          for (States::const_iterator j = i; j != m_states.end (); j++, k++)

            {

              DcfState *otherState = *j;

              if (otherState->IsAccessRequested ()

                  && GetBackoffEndFor (otherState) <= Simulator::Now ())

                {

                  MY_DEBUG ("dcf " << k << " needs access. backoff expired. internal collision. slots=" <<

                            otherState->GetBackoffSlots ());

                  /**

                   * all other dcfs with a lower priority whose backoff

                   * has expired and which needed access to the medium

                   * must be notified that we did get an internal collision.

                   */

                  internalCollisionStates.push_back (otherState);