/*
 * Copyright (c) 1999-2005 Mark D. Hill and David A. Wood
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef PRIOHEAP_H
#define PRIOHEAP_H

#include <iostream>

#include "mem/gems_common/Vector.hh"

typedef unsigned int HeapIndex;

template <class TYPE>
class PrioHeap {
public:
  // Constructors
  PrioHeap() { init(); }

  // Destructor
  //~PrioHeap();

  // Public Methods
  void init() { m_current_size = 0; }
  int size() const { return m_current_size; }
  void insert(const TYPE& key);
  const TYPE& peekMin() const;
  const TYPE& peekElement(int index) const;
  TYPE extractMin();
  void print(std::ostream& out) const;
private:
  // Private Methods
  bool verifyHeap() const;
  bool verifyHeap(HeapIndex index) const;
  void heapify();

  // Private copy constructor and assignment operator
  PrioHeap(const PrioHeap& obj);
  PrioHeap<TYPE>& operator=(const PrioHeap& obj);

  // Data Members (m_ prefix)
  Vector<TYPE> m_heap;
  HeapIndex m_current_size;
};

// Output operator declaration
template <class TYPE>
std::ostream& operator<<(std::ostream& out, const PrioHeap<TYPE>& obj);

// ******************* Helper Functions *******************
inline
HeapIndex get_parent(HeapIndex i)
{
  //  return (i/2);
  return (i>>1);
}

inline
HeapIndex get_right(HeapIndex i)
{
  //  return (2*i) + 1;
  return (i<<1) | 1;
}

inline
HeapIndex get_left(HeapIndex i)
{
  //  return (2*i);
  return (i<<1);
}

template <class TYPE>
void prio_heap_swap(TYPE& n1, TYPE& n2)
{
  TYPE temp = n1;
  n1 = n2;
  n2 = temp;
}

// ******************* Definitions *******************

template <class TYPE>
void PrioHeap<TYPE>::insert(const TYPE& key)
{
  int i;
  // grow the vector size
  m_current_size++;
  m_heap.setSize(m_current_size+1);

  if(m_current_size == 1){      // HACK: need to initialize index 0 to avoid purify UMCs
    m_heap[0] = key;
  }

  i = m_current_size;
  while ((i > 1) && (node_less_then_eq(key, m_heap[get_parent(i)]))) {
    m_heap[i] = m_heap[get_parent(i)];
    i = get_parent(i);
  }
  m_heap[i] = key;
  //  assert(verifyHeap());
}

template <class TYPE>
const TYPE& PrioHeap<TYPE>::peekMin() const
{
  assert(size() > 0);
  return m_heap[1]; // 1, not 0, is the first element
}

template <class TYPE>
const TYPE& PrioHeap<TYPE>::peekElement(int index) const
{
  assert(size() > 0);
  return m_heap[index];
}

template <class TYPE>
TYPE PrioHeap<TYPE>::extractMin()
{
  //  TYPE temp;
  assert(size() > 0);
  TYPE temp = m_heap[1]; // 1, not 0, is the first element
  m_heap[1] = m_heap[m_current_size];
  m_current_size--;
  heapify();
  return temp;
}

template <class TYPE>
bool PrioHeap<TYPE>::verifyHeap() const
{
  return verifyHeap(1);
}

template <class TYPE>
bool PrioHeap<TYPE>::verifyHeap(HeapIndex index) const
{
  // Recursively verify that each node is <= its parent
  if(index > m_current_size) {
    return true;
  } else if (index == 1) {
    return
      verifyHeap(get_right(index)) &&
      verifyHeap(get_left(index));
  } else if (node_less_then_eq(m_heap[get_parent(index)], m_heap[index])) {
    return
      verifyHeap(get_right(index)) &&
      verifyHeap(get_left(index));
  } else {
    // Heap property violation
    return false;
  }
}

template <class TYPE>
void PrioHeap<TYPE>::heapify()
{
  HeapIndex current_node = 1;
  HeapIndex left, right, smallest;
  //  HeapIndex size = m_current_size;

  while(true) {
    left = get_left(current_node);
    right = get_right(current_node);

    // Find the smallest of the current node and children
    if (left <= m_current_size && node_less_then_eq(m_heap[left], m_heap[current_node])) {
      smallest = left;
    } else {
      smallest = current_node;
    }

    if (right <= m_current_size && node_less_then_eq(m_heap[right], m_heap[smallest])) {
      smallest = right;
    }

    // Check to see if we are done
    if (smallest == current_node) {
      // We are done
      break;
    } else {
      // Not done, heapify on the smallest child
      prio_heap_swap(m_heap[current_node], m_heap[smallest]);
      current_node = smallest;
    }
  }
  //  assert(verifyHeap());
}

template <class TYPE>
void PrioHeap<TYPE>::print(std::ostream& out) const
{
  Vector<TYPE> copyHeap(m_heap);

  // sort copyHeap (inefficient, but will not be done often)

  for(HeapIndex i=0;i<m_current_size; i++){
    for(HeapIndex j=0; j< m_current_size; j++){
      if(copyHeap[i].m_time < copyHeap[j].m_time){
        prio_heap_swap(copyHeap[i], copyHeap[j]);
      }
    }
  }

  out << "[PrioHeap: ";

  for(HeapIndex i=1; i<= m_current_size; i++){
    out << copyHeap[i];

    if(i != m_current_size-1){
      out << ",";
    }
    out << " ";
  }
  out << "]";
}

// Output operator definition
template <class TYPE>
std::ostream& operator<<(std::ostream& out, const PrioHeap<TYPE>& obj)
{
  obj.print(out);
  out << std::flush;
  return out;
}

#endif //PRIOHEAP_H