/* -*- 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
 */

#include "ns3/log.h"
#include "ns3/enum.h"
#include "ns3/uinteger.h"
#include "reorder-queue.h"

namespace ns3 {

NS_LOG_COMPONENT_DEFINE ("ReorderQueue");

NS_OBJECT_ENSURE_REGISTERED (ReorderQueue);

TypeId ReorderQueue::GetTypeId (void)
{
  static TypeId tid = TypeId ("ns3::ReorderQueue")
    .SetParent<Queue> ()
    .SetGroupName ("Network")
    .AddConstructor<ReorderQueue> ()
    .AddAttribute ("ReorderDepth",
                   "The number of packets that will bypass a held packet",
                   UintegerValue (3),
                   MakeUintegerAccessor (&ReorderQueue::m_reorderDepth),
                   MakeUintegerChecker<uint32_t> ())
    .AddAttribute ("InSequenceLength",
                   "The number of packets until a reordering event",
                   UintegerValue (10),
                   MakeUintegerAccessor (&ReorderQueue::m_inSequenceLength),
                   MakeUintegerChecker<uint32_t> ())
  ;

  return tid;
}

ReorderQueue::ReorderQueue ()
  : Queue (),
    m_packets (),
    m_bytesInQueue (0),
    m_holdCount (0),
    m_inSequenceCount (0),
    m_held (0)
{
  NS_LOG_FUNCTION (this);
}

ReorderQueue::~ReorderQueue ()
{
  NS_LOG_FUNCTION (this);
}

bool
ReorderQueue::DoEnqueue (Ptr<QueueItem> item)
{
  NS_LOG_FUNCTION (this << item);

  if (GetMode () == QUEUE_MODE_PACKETS && (m_packets.size () >= GetMaxPackets ()))
    {
      NS_LOG_LOGIC ("Queue full (at max packets) -- droppping pkt");
      Drop (item->GetPacket ());
      return false;
    }

  if (GetMode () == QUEUE_MODE_BYTES && (m_bytesInQueue + item->GetPacket ()->GetSize () >= GetMaxBytes ()))
    {
      NS_LOG_LOGIC ("Queue full (packet would exceed max bytes) -- droppping pkt");
      Drop (item->GetPacket ());
      return false;
    }

  m_bytesInQueue += item->GetPacket ()->GetSize ();
  m_packets.push (item);

  NS_LOG_LOGIC ("Number packets " << m_packets.size ());
  NS_LOG_LOGIC ("Number bytes " << m_bytesInQueue);

  return true;
}

Ptr<QueueItem>
ReorderQueue::DoDequeue (void)
{
  NS_LOG_FUNCTION (this);

  if (m_packets.empty ())
    {
      NS_LOG_LOGIC ("Queue empty");
      return 0;
    }

  Ptr<QueueItem> item;
  if (m_holdCount == m_reorderDepth && m_held)
    {
      item = m_held;
      m_held = 0;
      m_bytesInQueue -= item->GetPacket ()->GetSize ();
      NS_LOG_LOGIC ("Released " << item->GetPacket ()->GetUid ());
      m_inSequenceCount = 0;
      m_holdCount = 0;
    }
  else
    {
      if (m_inSequenceCount == m_inSequenceLength)
        {
          m_held = m_packets.front ();
          NS_LOG_LOGIC ("Hold " << m_held->GetPacket ()->GetUid ());
          m_packets.pop ();
          m_inSequenceCount = 0;
          m_holdCount = 0;
          if (m_packets.empty ())
            {
              // We need to release this packet since no others to reorder with
              NS_LOG_LOGIC ("Release " << m_held->GetPacket ()->GetUid () << " anyway");
              item = m_held;
              m_held = 0;
              m_bytesInQueue -= item->GetPacket ()->GetSize ();
              return item;
            }
        }
      item = m_packets.front ();
      m_packets.pop ();
      m_bytesInQueue -= item->GetPacket ()->GetSize ();
      NS_LOG_LOGIC ("Popped " << item->GetPacket ());
      if (m_held)
        {
          m_holdCount++;
        }
      else
        {
          m_inSequenceCount++;
        }
    }

  NS_LOG_LOGIC ("Number packets " << m_packets.size ());
  NS_LOG_LOGIC ("Number bytes " << m_bytesInQueue);

  return item;
}

Ptr<const QueueItem>
ReorderQueue::DoPeek (void) const
{
  NS_LOG_FUNCTION (this);

  if (m_packets.empty ())
    {
      NS_LOG_LOGIC ("Queue empty");
      return 0;
    }

  Ptr<QueueItem> item = m_packets.front ();

  NS_LOG_LOGIC ("Number packets " << m_packets.size ());
  NS_LOG_LOGIC ("Number bytes " << m_bytesInQueue);

  return item;
}

} // namespace ns3