//
// Copyright (C) 2004 Tanguy Fautré.
// For conditions of distribution and use,
// see copyright notice in tri_stripper.h
//
//////////////////////////////////////////////////////////////////////
// SVN: $Id: heap_array.h 86 2005-06-08 17:47:27Z gpsnoopy $
//////////////////////////////////////////////////////////////////////

#ifndef TRI_STRIPPER_HEADER_GUARD_HEAP_ARRAY_H
#define TRI_STRIPPER_HEADER_GUARD_HEAP_ARRAY_H

#include <vector>




namespace triangle_stripper {

	namespace detail {




// mutable heap
// can be interfaced pretty muck like an array
template <class T, class CmpT = std::less<T> > 
class heap_array
{
public:

	// Pre = PreCondition, Post = PostCondition 

	heap_array() : m_Locked(false) { }		// Post: ((size() == 0) && ! locked())

	void clear();							// Post: ((size() == 0) && ! locked())

	void reserve(size_t Size);
	size_t size() const;

	bool empty() const;
	bool locked() const;
	bool removed(size_t i) const;			// Pre: (valid(i))
	bool valid(size_t i) const;

	size_t position(size_t i) const;		// Pre: (valid(i))

	const T & top() const;					// Pre: (! empty())
	const T & peek(size_t i) const;			// Pre: (! removed(i))
	const T & operator [] (size_t i) const;	// Pre: (! removed(i))

	void lock();							// Pre: (! locked())   Post: (locked())
	size_t push(const T & Elem);			// Pre: (! locked())

	void pop();								// Pre: (locked() && ! empty())
	void erase(size_t i);					// Pre: (locked() && ! removed(i))
	void update(size_t i, const T & Elem);	// Pre: (locked() && ! removed(i))

protected:

	heap_array(const heap_array &);
	heap_array & operator = (const heap_array &);

	class linker
	{
	public:
		linker(const T & Elem, size_t i)
			: m_Elem(Elem), m_Index(i) { }

		T		m_Elem;
		size_t	m_Index;
	};

	typedef std::vector<linker> linked_heap;
	typedef std::vector<size_t> finder;

	void Adjust(size_t i);
	void Swap(size_t a, size_t b);
	bool Less(const linker & a, const linker & b) const;

	linked_heap	m_Heap;
	finder		m_Finder;
	CmpT		m_Compare;
	bool		m_Locked;
};





//////////////////////////////////////////////////////////////////////////
// heap_indexed inline functions
//////////////////////////////////////////////////////////////////////////

template <class T, class CmpT> 
inline void heap_array<T, CmpT>::clear()
{
	m_Heap.clear();
	m_Finder.clear();
	m_Locked = false;
}


template <class T, class CmpT> 
inline bool heap_array<T, CmpT>::empty() const
{
	return m_Heap.empty();
}


template <class T, class CmpT>
inline bool heap_array<T, CmpT>::locked() const
{
	return m_Locked;
}


template <class T, class CmpT>
inline void heap_array<T, CmpT>::reserve(const size_t Size)
{
	m_Heap.reserve(Size);
	m_Finder.reserve(Size);
}


template <class T, class CmpT> 
inline size_t heap_array<T, CmpT>::size() const
{
	return m_Heap.size();
}


template <class T, class CmpT> 
inline const T & heap_array<T, CmpT>::top() const
{
	assert(! empty());

	return m_Heap.front().m_Elem;
}


template <class T, class CmpT> 
inline const T & heap_array<T, CmpT>::peek(const size_t i) const
{
	assert(! removed(i));

	return (m_Heap[m_Finder[i]].m_Elem);
}


template <class T, class CmpT> 
inline const T & heap_array<T, CmpT>::operator [] (const size_t i) const
{
	return peek(i);
}


template <class T, class CmpT> 
inline void heap_array<T, CmpT>::pop()
{
	assert(locked());
	assert(! empty());

	Swap(0, size() - 1);
	m_Heap.pop_back();

	if (! empty())
		Adjust(0);
}


template <class T, class CmpT>
inline void heap_array<T, CmpT>::lock()
{
	assert(! locked());

	m_Locked =true;
}


template <class T, class CmpT> 
inline size_t heap_array<T, CmpT>::push(const T & Elem)
{
	assert(! locked());

	const size_t Id = size();
	m_Finder.push_back(Id);
	m_Heap.push_back(linker(Elem, Id));
	Adjust(Id);

	return Id;
}


template <class T, class CmpT>
inline void heap_array<T, CmpT>::erase(const size_t i)
{
	assert(locked());
	assert(! removed(i));

	const size_t j = m_Finder[i];
	Swap(j, size() - 1);
	m_Heap.pop_back();

	if (j != size())
		Adjust(j);
}


template <class T, class CmpT>
inline bool heap_array<T, CmpT>::removed(const size_t i) const
{
	assert(valid(i));

	return (m_Finder[i] >= m_Heap.size());
}


template <class T, class CmpT>
inline bool heap_array<T, CmpT>::valid(const size_t i) const
{
	return (i < m_Finder.size());
}


template <class T, class CmpT>
inline size_t heap_array<T, CmpT>::position(const size_t i) const
{
	assert(valid(i));

	return (m_Heap[i].m_Index);
}


template <class T, class CmpT> 
inline void heap_array<T, CmpT>::update(const size_t i, const T & Elem)
{
	assert(locked());
	assert(! removed(i));

	const size_t j = m_Finder[i];
	m_Heap[j].m_Elem = Elem;
	Adjust(j);
}


template <class T, class CmpT> 
inline void heap_array<T, CmpT>::Adjust(size_t i)
{
	assert(i < m_Heap.size());

	size_t j;

	// Check the upper part of the heap
	for (j = i; (j > 0) && (Less(m_Heap[(j - 1) / 2], m_Heap[j])); j = ((j - 1) / 2))
		Swap(j, (j - 1) / 2);

	// Check the lower part of the heap
	for (i = j; (j = 2 * i + 1) < size(); i = j) {
 		if ((j + 1 < size()) && (Less(m_Heap[j], m_Heap[j + 1])))
			++j;

		if (Less(m_Heap[j], m_Heap[i]))
			return;

		Swap(i, j);
	}
}


template <class T, class CmpT> 
inline void heap_array<T, CmpT>::Swap(const size_t a, const size_t b)
{
	std::swap(m_Heap[a], m_Heap[b]);

	m_Finder[(m_Heap[a].m_Index)] = a;
	m_Finder[(m_Heap[b].m_Index)] = b;
}


template <class T, class CmpT>
inline bool heap_array<T, CmpT>::Less(const linker & a, const linker & b) const
{
	return m_Compare(a.m_Elem, b.m_Elem);
}




	} // namespace detail

} // namespace triangle_stripper




#endif // TRI_STRIPPER_HEADER_GUARD_HEAP_ARRAY_H
