/* -*-  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>

 */

#include "mac-rx-middle.h"

#include "wifi-mac-header.h"

#include "ns3/assert.h"

#include "ns3/log.h"

#include "ns3/packet.h"

#include "ns3/simulator.h"

#include <list>

NS_LOG_COMPONENT_DEFINE ("MacRxMiddle");

namespace ns3 {

class OriginatorRxStatus {

private:

  typedef std::list<Ptr<const Packet> > Fragments;

  typedef std::list<Ptr<const Packet> >::const_iterator FragmentsCI;

  bool m_defragmenting;

  uint16_t m_lastSequenceControl;

  Fragments m_fragments;

public:

  OriginatorRxStatus () {

    /* this is a magic value necessary. */

    m_lastSequenceControl = 0xffff;

    m_defragmenting = false;

  }

  ~OriginatorRxStatus () {

    m_fragments.clear ();

  }

  bool IsDeFragmenting (void) {

    return m_defragmenting;

  }

  void AccumulateFirstFragment (Ptr<const Packet> packet) {

    NS_ASSERT (!m_defragmenting);

    m_defragmenting = true;

    m_fragments.push_back (packet);

  }

  Ptr<Packet> AccumulateLastFragment (Ptr<const Packet> packet) {

    NS_ASSERT (m_defragmenting);

    m_fragments.push_back (packet);

    m_defragmenting = false;

    Ptr<Packet> full = Create<Packet> ();

    for (FragmentsCI i = m_fragments.begin (); i != m_fragments.end (); i++) 

      {

        full->AddAtEnd (*i);

      }

    m_fragments.erase (m_fragments.begin (), m_fragments.end ());

    return full;

  }

  void AccumulateFragment (Ptr<const Packet> packet) {

    NS_ASSERT (m_defragmenting);

    m_fragments.push_back (packet);

  }

  bool IsNextFragment (uint16_t sequenceControl) {

    if ((sequenceControl >> 4) == (m_lastSequenceControl >> 4) &&

        (sequenceControl & 0x0f) == ((m_lastSequenceControl & 0x0f)+1)) 

      {

        return true;

      } 

    else 

      {

        return false;

      }

  }

  uint16_t GetLastSequenceControl (void) 

  {

    return m_lastSequenceControl;

  }

  void SetSequenceControl (uint16_t sequenceControl) 

  {

    m_lastSequenceControl = sequenceControl;

  }

};

MacRxMiddle::MacRxMiddle ()

{

  NS_LOG_FUNCTION_NOARGS ();

}

MacRxMiddle::~MacRxMiddle ()

{

  NS_LOG_FUNCTION_NOARGS ();

  for (OriginatorsI i = m_originatorStatus.begin ();

       i != m_originatorStatus.end (); i++) 

    {

      delete (*i).second;

    }

  m_originatorStatus.erase (m_originatorStatus.begin (),

                            m_originatorStatus.end ());

  for (QosOriginatorsI i = m_qosOriginatorStatus.begin ();

       i != m_qosOriginatorStatus.end (); i++) 

    {

      delete (*i).second;

    }

  m_qosOriginatorStatus.erase (m_qosOriginatorStatus.begin (),

                               m_qosOriginatorStatus.end ());

}

void 

MacRxMiddle::SetForwardCallback (ForwardUpCallback callback)

{

  NS_LOG_FUNCTION_NOARGS ();

  m_callback = callback;

}

bool

MacRxMiddle::SequenceControlSmaller (uint16_t seqca, uint16_t seqcb)

{

  NS_LOG_FUNCTION (seqca << seqcb);

  int16_t seqa = seqca >> 4;

  int16_t seqb = seqcb >> 4;

  int16_t delta = seqb - seqa;

  bool sign = seqa <= seqb;

  uint16_t absDelta = (delta < 0)?-delta:delta;

  NS_LOG_DEBUG ("seqb="<<seqb<<", seqa="<<seqa<<", delta="<<delta);

  if (absDelta < 2048)

    {

      return sign;

    }

  else

    {

      return !sign;

    }

}

OriginatorRxStatus *

MacRxMiddle::Lookup (const WifiMacHeader *hdr)

{

  NS_LOG_FUNCTION (hdr);

  OriginatorRxStatus *originator;

  Mac48Address source = hdr->GetAddr2 ();

  if (hdr->IsQosData () &&

      !hdr->GetAddr2 ().IsGroup ()) 

    {

      /* only for qos data non-broadcast frames */

      originator = m_qosOriginatorStatus[std::make_pair(source, hdr->GetQosTid ())];

      if (originator == 0) 

        {

          originator = new OriginatorRxStatus ();

          m_qosOriginatorStatus[std::make_pair(source, hdr->GetQosTid ())] = originator;

        }

    } 

  else

    {

      /* - management frames

       * - qos data broadcast frames

       * - nqos data frames

       * see section 7.1.3.4.1

       */

      originator = m_originatorStatus[source];

      if (originator == 0) 

        {

          originator = new OriginatorRxStatus ();

          m_originatorStatus[source] = originator;

        }

    }

  return originator;

}

bool

MacRxMiddle::IsDuplicate (const WifiMacHeader* hdr, 

                          OriginatorRxStatus *originator) const

{

  NS_LOG_FUNCTION (hdr << originator);

  if (hdr->IsRetry () &&

      originator->GetLastSequenceControl () == hdr->GetSequenceControl ()) 

    {

      return true;

    }

  return false;

}

Ptr<Packet>

MacRxMiddle::HandleFragments (Ptr<Packet> packet, const WifiMacHeader *hdr,

                              OriginatorRxStatus *originator)

{

  NS_LOG_FUNCTION (packet << hdr << originator);

  if (originator->IsDeFragmenting ()) 

    {

      if (hdr->IsMoreFragments ()) 

        {

          if (originator->IsNextFragment (hdr->GetSequenceControl ())) 

            {

              NS_LOG_DEBUG ("accumulate fragment seq="<<hdr->GetSequenceNumber ()<<

                     ", frag="<<hdr->GetFragmentNumber ()<<

                     ", size="<<packet->GetSize ());

              originator->AccumulateFragment (packet);

              originator->SetSequenceControl (hdr->GetSequenceControl ());

            } 

          else 

            {

              NS_LOG_DEBUG ("non-ordered fragment");

            }

          return 0;

        } 

      else 

        {

          if (originator->IsNextFragment (hdr->GetSequenceControl ())) 

            {

              NS_LOG_DEBUG ("accumulate last fragment seq="<<hdr->GetSequenceNumber ()<<

                     ", frag="<<hdr->GetFragmentNumber ()<<

                     ", size="<<hdr->GetSize ());

              Ptr<Packet> p = originator->AccumulateLastFragment (packet);

              originator->SetSequenceControl (hdr->GetSequenceControl ());

              return p;

            } 

          else 

            {

              NS_LOG_DEBUG ("non-ordered fragment");

              return 0;

            }

        }

    } 

  else 

    {

      if (hdr->IsMoreFragments ()) 

        {

          NS_LOG_DEBUG ("accumulate first fragment seq="<<hdr->GetSequenceNumber ()<<

                 ", frag="<<hdr->GetFragmentNumber ()<<

                 ", size="<<packet->GetSize ());

          originator->AccumulateFirstFragment (packet);

          originator->SetSequenceControl (hdr->GetSequenceControl ());

          return 0;

        } 

      else 

        {

          return packet;

        }

    }

}

void

MacRxMiddle::Receive (Ptr<Packet> packet, const WifiMacHeader *hdr)

{

  NS_LOG_FUNCTION (packet << hdr);

  NS_ASSERT (hdr->IsData () || hdr->IsMgt ());

  OriginatorRxStatus *originator = Lookup (hdr);

  /**

   * The check below is really uneeded because it can fail in a lot of

   * normal cases. Specifically, it is possible for sequence numbers to 

   * loop back to zero once they reach 0xfff0 and to go up to 0xf7f0 in 

   * which case the check below will report the two sequence numbers to 

   * not have the correct order relationship.

   * So, this check cannot be used to discard old duplicate frames. It is

   * thus here only for documentation purposes.

   */

  if (!SequenceControlSmaller (originator->GetLastSequenceControl (), 

                               hdr->GetSequenceControl ()))

    {

      NS_LOG_DEBUG ("Sequence numbers have looped back. last recorded="<<originator->GetLastSequenceControl ()<<

                    " currently seen="<< hdr->GetSequenceControl ());

    }

  // filter duplicates.

  if (IsDuplicate (hdr, originator)) 

    {

      NS_LOG_DEBUG ("duplicate from="<<hdr->GetAddr2 ()<<

                    ", seq="<<hdr->GetSequenceNumber ()<<

                    ", frag="<<hdr->GetFragmentNumber ());

      return;

    }

  Ptr<Packet> agregate = HandleFragments (packet, hdr, originator);

  if (agregate == 0) 

    {

      return;

    }

  NS_LOG_DEBUG ("forwarding data from="<<hdr->GetAddr2 ()<<

                ", seq="<<hdr->GetSequenceNumber ()<<

                ", frag="<<hdr->GetFragmentNumber ());

  if (!hdr->GetAddr1 ().IsGroup ())

    {

      originator->SetSequenceControl (hdr->GetSequenceControl ());

    }

  m_callback (agregate, hdr);

}

} // namespace ns3