/*
	orxonox - the future of 3D-vertical-scrollers
 
	Copyright (C) 2006 orx
 
	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2, or (at your option)
	any later version.
 
	### File Specific:
	main programmer: Marco Biasini

 */

#ifndef _BUFFERBROKER_H
#define _BUFFERBROKER_H

#include "glincl.h"
#include "debug.h"

/**
 * @brief 	Manages the streaming of the vertex buffer objects for the terrain page.
 */

struct BufferPair {
	BufferPair( int _i, int _v ) { indexName = _i; vertexName = _v; next = NULL; }
	BufferPair() { indexName = vertexName = 0; next = NULL; }
	GLuint			indexName;	
	GLuint			vertexName;
	BufferPair 		*next;
};

typedef BufferPair *pBufferPair;

class BufferBroker {
	public:
		
		BufferBroker( int _num, int _vbSize, int _ibSize )
		{
			capacity = _num;
			freeIndexBuffers = new GLuint[capacity];
			freeVertexBuffers =	new GLuint[capacity];
			lastAcquired = 0;
			vbSize = _vbSize; ibSize = _ibSize;
			glGenBuffersARB( capacity, freeIndexBuffers );
			glGenBuffersARB( capacity, freeVertexBuffers );
			for ( int i = 0; i < capacity; ++i ) {
				glBindBufferARB( GL_ARRAY_BUFFER_ARB, freeVertexBuffers[i] );
				glBufferDataARB( GL_ARRAY_BUFFER_ARB, vbSize, 
					NULL, GL_DYNAMIC_DRAW_ARB );
				glBindBufferARB( GL_ELEMENT_ARRAY_BUFFER_ARB, freeIndexBuffers[i] );
				glBufferDataARB( GL_ELEMENT_ARRAY_BUFFER_ARB, ibSize, 
					NULL, GL_DYNAMIC_DRAW_ARB );		
			}
			head = tail = NULL;
		}
		
		inline void acquire( GLuint &_vbName, GLuint &_ibName );
		
		inline void release( const GLuint &_vbName, const GLuint &_ibName );
	protected:

		int						capacity;
		
		int						vbSize,
								ibSize;
		int						lastAcquired;
		
		GLuint					*freeIndexBuffers,
								*freeVertexBuffers;						
								
		BufferPair				*head, *tail;
};

inline void BufferBroker::release( const GLuint &_vbName, const GLuint &_ibName )
{
	pBufferPair bp = head, prev = NULL;
	bool removed = false;
	
	while ( bp ) {

		if ( bp->indexName == _ibName && bp->vertexName == _vbName ) {
			if ( prev ) {
				prev->next = bp->next;					
			}
			else {
				head = bp->next;
			}
			if ( bp->next == NULL )
				tail = prev;
			int index = capacity-lastAcquired;
			lastAcquired--;
			freeIndexBuffers[index] = bp->indexName;
			freeVertexBuffers[index] = bp->vertexName;
			delete bp;
			removed = true;
			break;	
		}
		prev = bp;
		bp = bp->next;
	}
	assert( removed );
}

inline void BufferBroker::acquire( GLuint &_vbName, GLuint &_ibName )
{

	int index = capacity-lastAcquired-1;
	_vbName = freeVertexBuffers[index]; _ibName = freeIndexBuffers[index];
	lastAcquired++;
	if ( tail ) {
		tail->next = new BufferPair( _ibName, _vbName );
		tail = tail->next;
	}
	else {
		tail = head = new BufferPair( _ibName, _vbName );	
	}
}

typedef BufferBroker *pBufferBroker;

#endif