/**

 * vim: set ts=4 :

 * ===============================================================

 * SourceMod (C)2004-2007 AlliedModders LLC.  All rights reserved.

 * ===============================================================

 *

 * This file is not open source and may not be copied without explicit

 * written permission of AlliedModders LLC.  This file may not be redistributed 

 * in whole or significant part.

 * For information, see LICENSE.txt or http://www.sourcemod.net/license.php

 *

 * Version: $Id$

 */

#ifndef _INCLUDE_SOURCEMOD_FASTLINK_H_

#define _INCLUDE_SOURCEMOD_FASTLINK_H_

#include <assert.h>

template <typename T>

class FastLink

{

	friend class iterator;

public:

	struct FastLinkNode

	{

		unsigned int prev;

		unsigned int next;

		unsigned int freeNode;

		T obj;

	};

public:

	FastLink(unsigned int maxsize) : m_Size(0), m_FirstLink(0), m_FreeNodes(0), m_LastLink(0)

	{

		m_MaxSize = maxsize;

		m_Nodes = new FastLinkNode[m_MaxSize+1];

	}

public:

	bool push_back(const T & obj)

	{

		unsigned int new_node = GetFreeIndex();

		if (!new_node)

		{

			return false;

		}

		m_Nodes[new_node].obj = obj;

		m_Nodes[new_node].next = 0;

		if (!m_FirstLink)

		{

			m_Nodes[new_node].prev = 0;

			m_FirstLink = new_node;

			m_LastLink = new_node;

		} else {

			m_Nodes[new_node].prev = m_LastLink;

			m_Nodes[m_LastLink].next = new_node;

			m_LastLink = new_node;

		}

		m_Size++;

		return true;

	}

	size_t size() const

	{

		return m_Size;

	}

private:

	unsigned int GetFreeIndex()

	{

		if (m_FreeNodes)

		{

			return m_Nodes[m_FreeNodes--].freeNode;

		} else {

			if (m_LastLink >= m_MaxSize)

			{

				return 0;

			}

			return m_LastLink + 1;

		}

	}

public:

	class iterator

	{

		friend class FastLink;

	public:

		iterator()

		{

			link = NULL;

			position = 0;

		}

		iterator(const FastLink *_link, unsigned int _position)

		{

			link = _link;

			position = _position;

		}

	public:

		bool operator ==(const iterator &where) const

		{

			return (link == where.link && position == where.position);

		}

		bool operator !=(const iterator &where) const

		{

			return (link != where.link || position != where.position);

		}

		T & operator *()

		{

			return link->m_Nodes[position].obj;

		}

		const T & operator *() const

		{

			return link->m_Nodes[position].obj;

		}

		iterator & operator++()

		{

			position = link->m_Nodes[position].next;

			return *this;

		}

	private:

		const FastLink *link;

		unsigned int position;

	};

public:

	iterator begin() const

	{

		return iterator(this, m_FirstLink);

	}

	iterator end() const

	{

		return iterator(this, 0);

	}

	void remove(const T & obj)

	{

		for (iterator iter=begin(); iter!=end(); ++iter)

		{

			if ((*iter) == obj)

			{

				erase(iter);

				return;

			}

		}

	}

	iterator erase(const iterator &where)

	{

		/* Whoa, this better be right! */

		assert(where.link == this);

		iterator iter(where.link, where.position);

		++iter;

		unsigned int index = where.position;

		/* Each case is different, we have no sentinel.

		 * CASE: We're the HEAD AND the TAIL */

		if (index == m_FirstLink

			&& index == m_LastLink)

		{

			m_FirstLink = 0;

			m_LastLink = 0;

		}

		/* We're the HEAD */

		else if (index == m_FirstLink)

		{

			m_FirstLink = m_Nodes[index].next;

			m_Nodes[m_FirstLink].prev = 0;

		}

		/* We're the TAIL */

		else if (index == m_LastLink)

		{

			m_LastLink = m_Nodes[index].prev;

			m_Nodes[m_LastLink].next = 0;

		}

		/* We're in the middle! */

		else

		{

			/* Patch forward reference */

			m_Nodes[m_Nodes[index].next].prev = m_Nodes[index].prev;

			/* Patch backward reference */

			m_Nodes[m_Nodes[index].prev].next = m_Nodes[index].next;

		}

		/* Add us to the free list */

		m_Nodes[++m_FreeNodes].freeNode = index;

		m_Size--;

		return iter;

	}

private:

	size_t m_Size;

	unsigned int m_FirstLink;

	unsigned int m_FreeNodes;

	unsigned int m_LastLink;

	unsigned int m_MaxSize;

	FastLinkNode *m_Nodes;

};

#endif //_INCLUDE_SOURCEMOD_FASTLINK_H_