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

/*

 * Copyright (c) 2005,2006 INRIA

 * 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

 *

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

 */

#include <iostream>

#include <cassert>

#include "ns3/debug.h"

#include "ns3/queue.h"

#include "ns3/simulator.h"

#include "ns3/composite-trace-resolver.h"

#include "p2p-net-device.h"

#include "p2p-channel.h"

NS_DEBUG_COMPONENT_DEFINE ("PointToPointNetDevice");

namespace ns3 {

: 

  NetDevice(node, MacAddress ("00:00:00:00:00:00")), 

  m_txMachineState (READY),

  m_bps (DataRate (0xffffffff)),

  m_tInterframeGap (Seconds(0)),

  m_channel (0), 

  m_queue (0),

  m_rxTrace ()

{

  NS_DEBUG ("PointToPointNetDevice::PointToPointNetDevice (" << node << ")");

  // BUGBUG FIXME

  //

  // You _must_ support broadcast to get any sort of packet from the ARP layer.

  EnableBroadcast (MacAddress ("ff:ff:ff:ff:ff:ff"));

  EnableMulticast();

  EnablePointToPoint();

}

PointToPointNetDevice::~PointToPointNetDevice()

{

  NS_DEBUG ("PointToPointNetDevice::~PointToPointNetDevice ()");

  delete m_queue;

  m_queue = 0;

}

//

// Copy constructor for PointToPointNetDevice.

//

// We use the underlying NetDevice copy constructor to get the base class

// copied.  These just remain as is (e.g. you get the same name, the same

// MAC address).  If you need to fix them up, YOU, the copier need to do 

// that.

// 

// The things we need to be careful of are the channel, the queue and the

// trace callback.  If the channel pointer is non-zero, we copy the pointer 

// and add a reference.  If the queue is non-zero, we copy it using the queue

// assignment operator.  We don't mess with the trace -- we just reset it.

// We're assuming that the tracing will be set up after the topology creation

// phase and this won't actually matter.

//

PointToPointNetDevice::PointToPointNetDevice (const PointToPointNetDevice& nd)

: 

  NetDevice(nd), 

  m_txMachineState(READY),

  m_bps (nd.m_bps),

  m_tInterframeGap (nd.m_tInterframeGap),

  m_channel(0), 

  m_queue(0),

  m_rxTrace ()

{

  NS_DEBUG ("PointToPointNetDevice::PointToPointNetDevice (" << &nd << ")");

  if (nd.m_channel)

    {

      m_channel = nd.m_channel;

      m_channel->Ref ();

    }

  if (nd.m_queue)

    {

      m_queue = nd.m_queue;

    }

}

void PointToPointNetDevice::DoDispose()

{

 if (m_channel != 0)

 {

   m_channel->Unref ();

   m_channel = 0;

 }

 NetDevice::DoDispose ();

}

//

// Assignment operator for PointToPointNetDevice.

//

// This uses the non-obvious trick of taking the source net device passed by

// value instead of by reference.  This causes the copy constructor to be

// invoked (where the real work is done -- see above).  All we have to do

// here is to return the newly constructed net device.

//

  PointToPointNetDevice&

PointToPointNetDevice::operator= (const PointToPointNetDevice nd)

{

  NS_DEBUG ("PointToPointNetDevice::operator= (" << &nd << ")");

  return *this;

}

  void 

PointToPointNetDevice::SetDataRate(DataRate bps)

{

  m_bps = bps;

}

  void 

PointToPointNetDevice::SetInterframeGap(Time t)

{

  m_tInterframeGap = t;

}

  bool

PointToPointNetDevice::SendTo (Packet& p, const MacAddress& dest)

{

  NS_DEBUG ("PointToPointNetDevice::SendTo (" << &p << ", " << &dest << ")");

  NS_DEBUG ("PointToPointNetDevice::SendTo (): UID is " << p.GetUid () << ")");

  NS_ASSERT (IsLinkUp ());

#ifdef NOTYET

    struct NetDevicePacketDestAddress tag;

    tag.address = address;

    p.AddTag (tag);

#endif

//

// This class simulates a point to point device.  In the case of a serial

// link, this means that we're simulating something like a UART.  This is

// not a requirement for a point-to-point link, but it's a typical model for

// the device.  

//

// Generally, a real device will have a list of pending packets to transmit.  

// An on-device CPU frees the main CPU(s) of the details of what is happening

// in the device and feeds the USART.  The main CPU basically just sees the 

// list of packets -- it puts packets into the list, and the device frees the

// packets when they are transmitted.

//

// In the case of our virtual device here, the queue pointed to by m_queue

// corresponds to this list.  The main CPU adds packets to the list by 

// calling this method and when the device completes a send, the packets are

// freed in an "interrupt" service routine.

//

// We're going to do the same thing here.  So first of all, the incoming packet

// goes onto our queue if possible.  If the queue can't handle it, there's

// nothing to be done.

//

    if (m_queue->Enqueue(p) == false )

      {

        return false;

      }

//

// If there's a transmission in progress, the "interrupt" will keep the

// transmission process going.  If the device is idle, we need to start a

// transmission.

//

// In the real world, the USART runs until it finishes sending bits, and then

// pulls on the device's transmit complete interrupt wire.  At the same time,

// the electrons from the last wiggle of the wire are busy propagating down

// the wire.  In the case of a long speed-of-light delay in the wire, we could

// conceivably start transmitting the next packet before the end of the 

// previously sent data has even reached the end of the wire.  This situation

// is usually avoided (like the plague) and an "interframe gap" is introduced.

// This is usually the round-trip delay on the channel plus some hard-to-

// quantify receiver turn-around time (the time required for the receiver

// to process the last frame and prepare for reception of the next).

//

// So, if the transmit machine is ready, we need to schedule a transmit 

// complete event (at which time we tell the channel we're no longer sending

// bits).  A separate transmit ready event (at which time the transmitter 

// becomes ready to start sending bits again is scheduled there).  Finally, 

// we tell the channel (via TransmitStart ()) that we've started wiggling the 

// wire and bits are coming out.

//

// If the transmit machine is not ready, we just leave and the transmit ready

// event we know is coming will kick-start the transmit process.

//

    if (m_txMachineState == READY) 

      {

        return TransmitStart (p);

      }

    return true;

}

  bool

PointToPointNetDevice::TransmitStart (Packet &p)

{

  NS_DEBUG ("PointToPointNetDevice::TransmitStart (" << &p << ")");

  NS_DEBUG (

    "PointToPointNetDevice::TransmitStart (): UID is " << p.GetUid () << ")");

//

// This function is called to start the process of transmitting a packet.

// We need to tell the channel that we've started wiggling the wire and

// schedule an event that will be executed when it's time to tell the 

// channel that we're done wiggling the wire.

//

  NS_ASSERT_MSG(m_txMachineState == READY, "Must be READY to transmit");

  m_txMachineState = BUSY;

  Time tEvent = Seconds (m_bps.CalculateTxTime(p.GetSize()));

  NS_DEBUG ("PointToPointNetDevice::TransmitStart (): " <<

    "Schedule TransmitCompleteEvent in " << 

    tEvent.GetSeconds () << "sec");

  Simulator::Schedule (tEvent, 

                       &PointToPointNetDevice::TransmitCompleteEvent, 

                       this);

  return m_channel->TransmitStart (p, this); 

}

  void

PointToPointNetDevice::TransmitCompleteEvent (void)

{

  NS_DEBUG ("PointToPointNetDevice::TransmitCompleteEvent ()");

//

// This function is called to finish the  process of transmitting a packet.

// We need to tell the channel that we've stopped wiggling the wire and

// schedule an event that will be executed when it's time to re-enable

// the transmitter after the interframe gap.

//

  NS_ASSERT_MSG(m_txMachineState == BUSY, "Must be BUSY if transmitting");

  m_txMachineState = GAP;

  Packet p;

  bool found;

  found = m_queue->Dequeue (p);

  NS_ASSERT_MSG(found, "Packet must be on queue if transmitted");

  NS_DEBUG ("PointToPointNetDevice::TransmitCompleteEvent (): Pkt UID is " << 

            p.GetUid () << ")");

  m_channel->TransmitEnd (p, this); 

  NS_DEBUG (

    "PointToPointNetDevice::TransmitCompleteEvent (): " <<

    "Schedule TransmitReadyEvent in "

    << m_tInterframeGap.GetSeconds () << "sec");

  Simulator::Schedule (m_tInterframeGap, 

                       &PointToPointNetDevice::TransmitReadyEvent, 

                       this);

}

  void

PointToPointNetDevice::TransmitReadyEvent (void)

{

  NS_DEBUG ("PointToPointNetDevice::TransmitReadyEvent ()");

//

// This function is called to enable the transmitter after the interframe

// gap has passed.  If there are pending transmissions, we use this opportunity

// to start the next transmit.

//

  NS_ASSERT_MSG(m_txMachineState == GAP, "Must be in interframe gap");

  m_txMachineState = READY;

  if (m_queue->IsEmpty())

    {

      return;

    }

  else

    {

      Packet p;

      bool found;

      found = m_queue->Peek (p);

      NS_ASSERT_MSG(found, "IsEmpty false but no Packet on queue?");

      TransmitStart (p);

    }

}

TraceResolver *

PointToPointNetDevice::DoCreateTraceResolver (TraceContext const &context)

{

  CompositeTraceResolver *resolver = new CompositeTraceResolver (context);

  resolver->Add ("queue", 

                 MakeCallback (&Queue::CreateTraceResolver, m_queue),

                 PointToPointNetDevice::QUEUE);

  resolver->Add ("rx",

                 m_rxTrace,

                 PointToPointNetDevice::RX);

  return resolver;

}

bool

PointToPointNetDevice::Attach (PointToPointChannel* ch)

{

  NS_DEBUG ("PointToPointNetDevice::Attach (" << &ch << ")");

  if (m_channel)

    {

      m_channel->Unref ();

      m_channel = 0;

    }

  m_channel = ch;

  m_channel->Ref ();

  m_channel->Attach(this);

  m_bps = m_channel->GetDataRate ();

  m_tInterframeGap = m_channel->GetDelay ();

  /* 

   * For now, this device is up whenever a channel is attached to it.

   * In fact, it should become up only when the second device

   * is attached to the channel. So, there should be a way for

   * a PointToPointChannel to notify both of its attached devices

   * that the channel is 'complete', hence that the devices are

   * up, hence that they can call NotifyLinkUp. 

   */

  NotifyLinkUp ();

  return true;

}

void

PointToPointNetDevice::AddQueue (Queue* q)

{

  NS_DEBUG ("PointToPointNetDevice::AddQueue (" << q << ")");

  m_queue = q;

}

void

PointToPointNetDevice::Receive (Packet& p)

{

  // ignore return value for now.

  NS_DEBUG ("PointToPointNetDevice::Receive (" << &p << ")");

  m_rxTrace (p);

  ForwardUp (p);

}

Queue* 

PointToPointNetDevice::GetQueue(void) const 

{ 

    return m_queue;

}

Channel* 

PointToPointNetDevice::DoGetChannel(void) const 

{ 

    m_channel->Ref();

    return m_channel;

}

bool 

PointToPointNetDevice::DoNeedsArp (void) const

{

  return false;

}

} // namespace ns3