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

/*

 * Copyright (c) 2006 INRIA

 * Copyright (c) 2005 Mathieu Lacage

 *

 * 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 "heap-scheduler.h"

#include "event-impl.h"

#include "ns3/assert.h"

#include "ns3/log.h"

NS_LOG_COMPONENT_DEFINE ("HeapScheduler");

namespace ns3 {

NS_OBJECT_ENSURE_REGISTERED (HeapScheduler);

TypeId

HeapScheduler::GetTypeId (void)

{

  static TypeId tid = TypeId ("ns3::HeapScheduler")

    .SetParent<Scheduler> ()

    .AddConstructor<HeapScheduler> ()

  ;

  return tid;

}

HeapScheduler::HeapScheduler ()

{

  // we purposedly waste an item at the start of

  // the array to make sure the indexes in the

  // array start at one.

  m_heap.push_back (empty);

}

HeapScheduler::~HeapScheduler ()

{

}

uint32_t

HeapScheduler::Parent (uint32_t id) const

{

  return id / 2;

}

uint32_t

HeapScheduler::Sibling (uint32_t id) const

{

  return id + 1;

}

uint32_t

HeapScheduler::LeftChild (uint32_t id) const

{

  return id * 2;

}

uint32_t

HeapScheduler::RightChild (uint32_t id) const

{

  return id * 2 + 1;

}

uint32_t

HeapScheduler::Root (void) const

{

  return 1;

}

bool

HeapScheduler::IsRoot (uint32_t id) const

{

  return (id == Root ()) ? true : false;

}

uint32_t

HeapScheduler::Last (void) const

{

  return m_heap.size () - 1;

}

bool

HeapScheduler::IsBottom (uint32_t id) const

{

  return (id >= m_heap.size ()) ? true : false;

}

void

HeapScheduler::Exch (uint32_t a, uint32_t b)

{

  NS_ASSERT (b < m_heap.size () && a < m_heap.size ());

  NS_LOG_DEBUG ("Exch " << a << ", " << b);

  Event tmp (m_heap[a]);

  m_heap[a] = m_heap[b];

  m_heap[b] = tmp;

}

bool

HeapScheduler::IsLessStrictly (uint32_t a, uint32_t b) const

{

  return m_heap[a] < m_heap[b];

}

uint32_t

HeapScheduler::Smallest (uint32_t a, uint32_t b) const

{

  return IsLessStrictly (a,b) ? a : b;

}

bool

HeapScheduler::IsEmpty (void) const

{

  return (m_heap.size () == 1) ? true : false;

}

void

HeapScheduler::BottomUp (void)

{

  uint32_t index = Last ();

  while (!IsRoot (index)

         && IsLessStrictly (index, Parent (index)))

    {

      Exch (index, Parent (index));

      index = Parent (index);

    }

}

void

HeapScheduler::TopDown (uint32_t start)

{

  uint32_t index = start;

  uint32_t right = RightChild (index);

  while (!IsBottom (right))

    {

      uint32_t left = LeftChild (index);

      uint32_t tmp = Smallest (left, right);

      if (IsLessStrictly (index, tmp))

        {

          return;

        }

      Exch (index, tmp);

      index = tmp;

      right = RightChild (index);

    }

  if (IsBottom (index))

    {

      return;

    }

  NS_ASSERT (!IsBottom (index));

  uint32_t left = LeftChild (index);

  if (IsBottom (left))

    {

      return;

    }

  if (IsLessStrictly (index, left))

    {

      return;

    }

  Exch (index, left);

}

void

HeapScheduler::Insert (const Event &ev)

{

  m_heap.push_back (ev);

  BottomUp ();

}

Scheduler::Event

HeapScheduler::PeekNext (void) const

{

  return m_heap[Root ()];

}

Scheduler::Event

HeapScheduler::RemoveNext (void)

{

  Event next = m_heap[Root ()];

  Exch (Root (), Last ());

  m_heap.pop_back ();

  TopDown (Root ());

  return next;

}

void

HeapScheduler::Remove (const Event &ev)

{

  uint32_t uid = ev.key.m_uid;

  for (uint32_t i = 1; i < m_heap.size (); i++)

    {

      if (uid == m_heap[i].key.m_uid)

        {

          NS_ASSERT (m_heap[i].impl == ev.impl);

          Exch (i, Last ());

          m_heap.pop_back ();

          TopDown (i);

          return;

        }

    }

  NS_ASSERT (false);

}

} // namespace ns3