/* -*- C++ -*-

 * lemon/concept/heap.h - Part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

///\ingroup concept

///\file

///\brief Classes for representing heaps.

///

#ifndef LEMON_CONCEPT_HEAP_H

#define LEMON_CONCEPT_HEAP_H

#include <lemon/invalid.h>

namespace lemon {

  namespace concept {

    /// \addtogroup concept

    /// @{

    /// \brief A concept structure describes the main interface of heaps.

    ///

    /// A concept structure describes the main interface of heaps.

    ///

    template <typename Item, typename Prio, typename ItemIntMap>

    class Heap {

    public:

      /// \brief Type to represent the items states.

      ///

      /// Each Item element have a state associated to it. It may be "in heap",

      /// "pre heap" or "post heap". The later two are indifferent from the

      /// heap's point of view, but may be useful to the user.

      ///

      /// The ItemIntMap _should_ be initialized in such way, that it maps

      /// PRE_HEAP (-1) to any element to be put in the heap...

      enum state_enum {

	IN_HEAP = 0,

	PRE_HEAP = -1,

	POST_HEAP = -2

      };

      /// \brief The constructor.

      ///

      /// The constructor.

      /// \param _iim should be given to the constructor, since it is used

      /// internally to handle the cross references. The value of the map

      /// should be PRE_HEAP (-1) for each element.

      explicit Heap(ItemIntMap &_iim) {}

      /// The number of items stored in the heap.

      ///

      /// \brief Returns the number of items stored in the heap.

      int size() const { return 0; }

      /// \brief Checks if the heap stores no items.

      ///

      /// Returns \c true if and only if the heap stores no items.

      bool empty() const { return false; }

      /// \brief Insert an item into the heap with the given heap.

      ///    

      /// Adds \c i to the heap with priority \c p. 

      /// \param i The item to insert.

      /// \param p The priority of the item.

      void push(const Item &i, const Prio &p) {}

      /// \brief Returns the item with minimum priority.

      ///

      /// This method returns the item with minimum priority.  

      /// \pre The heap must be nonempty.  

      Item top() const {}

      /// \brief Returns the minimum priority.

      ///

      /// It returns the minimum priority.

      /// \pre The heap must be nonempty.

      Prio prio() const {}

      /// \brief Deletes the item with minimum priority.

      ///

      /// This method deletes the item with minimum priority.

      /// \pre The heap must be non-empty.  

      void pop() {}

      /// \brief Deletes \c i from the heap.

      ///

      /// This method deletes item \c i from the heap, if \c i was

      /// already stored in the heap.

      /// \param i The item to erase. 

      void erase(const Item &i) {}

      /// \brief Returns the priority of \c i.

      ///

      /// This function returns the priority of item \c i.  

      /// \pre \c i must be in the heap.

      /// \param i The item.

      Prio operator[](const Item &i) const {}

      /// \brief \c i gets to the heap with priority \c p independently 

      /// if \c i was already there.

      ///

      /// This method calls \ref push(\c i, \c p) if \c i is not stored

      /// in the heap and sets the priority of \c i to \c p otherwise.

      /// It may throw an \e UnderFlowPriorityException. 

      /// \param i The item.

      /// \param p The priority.

      void set(const Item &i, const Prio &p) {}

      /// \brief Decreases the priority of \c i to \c p.

      ///

      /// This method decreases the priority of item \c i to \c p.

      /// \pre \c i must be stored in the heap with priority at least \c p.

      /// \param i The item.

      /// \param p The priority.

      void decrease(const Item &i, const Prio &p) {}

      /// \brief Increases the priority of \c i to \c p.

      ///

      /// This method sets the priority of item \c i to \c p. 

      /// \pre \c i must be stored in the heap with priority at most \c

      /// p relative to \c Compare.

      /// \param i The item.

      /// \param p The priority.

      void increase(const Item &i, const Prio &p) {}

      /// \brief Returns if \c item is in, has already been in, or has 

      /// never been in the heap.

      ///

      /// This method returns PRE_HEAP if \c item has never been in the

      /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP

      /// otherwise. In the latter case it is possible that \c item will

      /// get back to the heap again.

      /// \param i The item.

      state_enum state(const Item &i) const {}

      template <typename _Heap>

      struct Constraints {

      public:

	void constraints() {

	  Item item;

	  Prio prio;

	  ignore_unused_variable_warning(item);

	  ignore_unused_variable_warning(prio);

	  typedef typename _Heap::state_enum state_enum;

	  state_enum state;

	  ignore_unused_variable_warning(state);

	  _Heap heap1 = _Heap(map);

	  ignore_unused_variable_warning(heap1);

	  heap.push(item, prio);

	  prio = heap.prio();

	  item = heap.top();

	  heap.pop();

	  heap.set(item, prio);

	  heap.decrease(item, prio);

	  heap.increase(item, prio);

	  prio = heap[item];

	  heap.erase(item);

	  state = heap.state(item);

	  state = _Heap::PRE_HEAP;

	  state = _Heap::IN_HEAP;

	  state = _Heap::POST_HEAP;

	}

	_Heap& heap;

	ItemIntMap& map;

	Constraints() : heap(0), map(0) {}

      };

    };

    /// @}

  } // namespace lemon

}

#endif // LEMON_CONCEPT_PATH_H