/* -*- 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>

 *

 * This code started as a c++ translation of a java-based code written in 2005

 * top of this file.

 *

 * What is smart about this code ?

 *  - it does not use the index 0 in the array to avoid having to convert

 *    C-style array indexes (which start at zero) and heap-style indexes

 *    (which start at 1). This is why _all_ indexes start at 1, and that

 *    the index of the root is 1.

 *  - It uses a slightly non-standard while loop for top-down heapify

 *    to move one if statement out of the loop.

 */

#include "scheduler-heap.h"

#include "scheduler-factory.h"

#include "event-impl.h"

#include "ns3/assert.h"

#include <string>

#define noTRACE_HEAP 1

#ifdef TRACE_HEAP

#include <iostream>

# define TRACE(x) \

std::cout << "HEAP TRACE " << x << std::endl;

#else /* TRACE_HEAP */

# define TRACE(format,...)

#endif /* TRACE_HEAP */

namespace ns3 {

static class SchedulerHeapFactory : public SchedulerFactory 

{

public:

  SchedulerHeapFactory ()

  {

    SchedulerFactory::Add (this, "BinaryHeap");

  }

private:

  virtual Scheduler *DoCreate (void) const

  {

    return new SchedulerHeap ();

  }

} g_schedulerHeapFactory;

SchedulerHeap::SchedulerHeap ()

{

  // we purposedly waste an item at the start of

  // the array to make sure the indexes in the

  // array start at one.

  Scheduler::EventKey emptyKey = {0,0};

  m_heap.push_back (std::make_pair (static_cast<EventImpl *>(0), emptyKey));

}

SchedulerHeap::~SchedulerHeap ()

{}

uint32_t 

SchedulerHeap::Parent (uint32_t id) const

{

  return id / 2;

}

uint32_t 

SchedulerHeap::Sibling (uint32_t id) const

{

  return id + 1;

}

uint32_t 

SchedulerHeap::LeftChild (uint32_t id) const

{

  return id * 2;

}

uint32_t 

SchedulerHeap::RightChild (uint32_t id) const

{

  return id * 2 + 1;

}

uint32_t

SchedulerHeap::Root (void) const

{

  return 1;

}

bool

SchedulerHeap::IsRoot (uint32_t id) const

{

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

}

uint32_t

SchedulerHeap::Last (void) const

{

  return m_heap.size () - 1;

}

bool

SchedulerHeap::IsBottom (uint32_t id) const

{

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

}

void

SchedulerHeap::Exch (uint32_t a, uint32_t b) 

{

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

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

  std::pair<EventImpl*, Scheduler::EventKey> tmp (m_heap[a]);

  m_heap[a] = m_heap[b];

  m_heap[b] = tmp;

}

bool

SchedulerHeap::IsLowerStrictly (Scheduler::EventKey const*a, Scheduler::EventKey const*b) const

{

  if (a->m_ts < b->m_ts)

    {

      return true;

    }

  else if (a->m_ts > b->m_ts)

    {

      return false;

    } 

  else if (a->m_uid < b->m_uid)

    {

      return true;

    }

  else

    {

      return false;

    }

}

bool

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

{

  return IsLowerStrictly (&m_heap[a].second, &m_heap[b].second);

}

uint32_t 

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

{

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

}

bool

SchedulerHeap::IsEmpty (void) const

{

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

}

void

SchedulerHeap::BottomUp (void)

{

  uint32_t index = Last ();

  while (!IsRoot (index) && 

         IsLessStrictly (index, Parent (index))) 

    { 

      Exch(index, Parent (index)); 

      index = Parent (index); 

    }

}

void

SchedulerHeap::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

SchedulerHeap::Insert (const EventId &id)

{

  // acquire single ref

  EventImpl *event = id.PeekEventImpl ();

  event->Ref ();

  Scheduler::EventKey key;

  key.m_ts = id.GetTs ();

  key.m_uid = id.GetUid ();

  m_heap.push_back (std::make_pair (event, key));

  BottomUp ();

}

EventId

SchedulerHeap::PeekNext (void) const

{

  std::pair<EventImpl *,Scheduler::EventKey> next = m_heap[Root ()];

  return EventId (next.first, next.second.m_ts, next.second.m_uid);

}

EventId

SchedulerHeap::RemoveNext (void)

{

  std::pair<EventImpl *,Scheduler::EventKey> next = m_heap[Root ()];

  Exch (Root (), Last ());

  m_heap.pop_back ();

  TopDown (Root ());

  return EventId (Ptr<EventImpl> (next.first, false), next.second.m_ts, next.second.m_uid);

}

bool

SchedulerHeap::Remove (const EventId &id)

{

  uint32_t uid = id.GetUid ();

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

    {

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

        {

          NS_ASSERT (m_heap[i].first == id.PeekEventImpl ());

          std::pair<EventImpl *,Scheduler::EventKey> next = m_heap[i];

          // release single ref

          next.first->Unref ();

          Exch (i, Last ());

          m_heap.pop_back ();

          TopDown (i);

          return true;

        }

    }

  NS_ASSERT (false);

  // quiet compiler

  return false;

}

}; // namespace ns3