/* Copyright (C) 2009 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. 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 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * =========================================================================
 * File        : VertexBuffer.cpp
 * Project     : 0 A.D.
 * Description : encapsulation of VBOs with batching and sharing
 * =========================================================================
 */

#include "precompiled.h"
#include "ps/Errors.h"
#include "lib/ogl.h"
#include "Renderer.h"
#include "VertexBuffer.h"
#include "VertexBufferManager.h"
#include "ps/CLogger.h"

ERROR_GROUP(Renderer);
ERROR_TYPE(Renderer, VBOFailed);

///////////////////////////////////////////////////////////////////////////////
// shared list of all free batch objects
std::vector<CVertexBuffer::Batch *> CVertexBuffer::m_FreeBatches;
// NOTE: This global variable is here (as opposed to in VertexBufferManager.cpp,
// as would be logical) to make sure that m_FreeBatches is freed in the right
// order relative to the VertexBufferManager
CVertexBufferManager g_VBMan;

///////////////////////////////////////////////////////////////////////////////
// Call at shutdown to free memory
void CVertexBuffer::Shutdown()
{
	for(std::vector<Batch*>::iterator iter=m_FreeBatches.begin();iter!=m_FreeBatches.end();++iter)
	{
		delete *iter;
	}
}

///////////////////////////////////////////////////////////////////////////////
// CVertexBuffer constructor 
CVertexBuffer::CVertexBuffer(size_t vertexSize,bool dynamic) 
	: m_VertexSize(vertexSize), m_Handle(0), m_SysMem(0), m_Dynamic(dynamic)
{
	size_t size = MAX_VB_SIZE_BYTES;

	// allocate raw buffer
	if (g_Renderer.m_Caps.m_VBO) {

		// TODO: Detect when VBO failed, then fall back to system memory
		// (and copy all old VBOs into there, because it needs to be
		// consistent).

		// (PT: Disabled the VBOFailed test because it's not very useful at the
		// moment (it'll just cause the program to terminate, and I don't think
		// it has ever helped to discover any problems, and a later ogl_WarnIfError()
		// will tell us if there were any VBO issues anyway), and so it's a
		// waste of time to call glGetError so frequently.)
		// glGetError(); // clear the error state

		pglGenBuffersARB(1,&m_Handle);
		pglBindBufferARB(GL_ARRAY_BUFFER_ARB,m_Handle);
		// if (glGetError() != GL_NO_ERROR) throw PSERROR_Renderer_VBOFailed();

		pglBufferDataARB(GL_ARRAY_BUFFER_ARB,size,0,m_Dynamic ? GL_DYNAMIC_DRAW_ARB : GL_STATIC_DRAW_ARB);
		// if (glGetError() != GL_NO_ERROR) throw PSERROR_Renderer_VBOFailed();

	} else {
		m_SysMem=new u8[size];
	}

	// store max/free vertex counts
	m_MaxVertices=m_FreeVertices=size/vertexSize;
	
	// create sole free chunk
	VBChunk* chunk=new VBChunk;
	chunk->m_Owner=this;
	chunk->m_Count=m_FreeVertices;
	chunk->m_Index=0;
	m_FreeList.push_front(chunk);
}

///////////////////////////////////////////////////////////////////////////////
// CVertexBuffer destructor
CVertexBuffer::~CVertexBuffer()
{
	if (m_Handle) {
		pglDeleteBuffersARB(1,&m_Handle);
	} else if (m_SysMem) {
		delete[] m_SysMem;
	}

	// janwas 2004-06-14: release freelist
	typedef std::list<VBChunk*>::iterator Iter;
	for(Iter iter=m_FreeList.begin();iter!=m_FreeList.end();++iter)
		delete *iter;
}

///////////////////////////////////////////////////////////////////////////////
// Allocate: try to allocate a buffer of given number of vertices (each of 
// given size), with the given type, and using the given texture - return null 
// if no free chunks available
CVertexBuffer::VBChunk* CVertexBuffer::Allocate(size_t vertexSize,size_t numVertices,bool dynamic)
{
	// check this is the right kind of buffer
	if (dynamic!=m_Dynamic || vertexSize!=m_VertexSize) return 0;

	// quick check there's enough vertices spare to allocate
	if (numVertices>m_FreeVertices) return 0;

	// trawl free list looking for first free chunk with enough space
	VBChunk* chunk=0;
	typedef std::list<VBChunk*>::iterator Iter;
	for (Iter iter=m_FreeList.begin();iter!=m_FreeList.end();++iter) {
		if (numVertices<=(*iter)->m_Count) {
			chunk=*iter;
			// remove this chunk from the free list
			m_FreeList.erase(iter);
			// no need to search further ..
			break;
		}
	}

	if (!chunk) {
		// no big enough spare chunk available
		return 0;
	}

	// split chunk into two; - allocate a new chunk using all unused vertices in the 
	// found chunk, and add it to the free list
	if (chunk->m_Count > numVertices) {
		VBChunk* newchunk=new VBChunk;
		newchunk->m_Owner=this;
		newchunk->m_Count=chunk->m_Count-numVertices;
		newchunk->m_Index=chunk->m_Index+numVertices;
		m_FreeList.push_front(newchunk);

		// resize given chunk, resize total available free vertices
		chunk->m_Count=numVertices;
		m_FreeVertices-=numVertices;
	}
	
	// return found chunk
	return chunk;
}

///////////////////////////////////////////////////////////////////////////////
// Release: return given chunk to this buffer
void CVertexBuffer::Release(VBChunk* chunk)
{
	// add to free list
	// TODO, RC - need to merge available chunks where possible to avoid 
	// excessive fragmentation of vertex buffer space
	m_FreeList.push_front(chunk);
	m_FreeVertices+=chunk->m_Count;
}

///////////////////////////////////////////////////////////////////////////////
// ClearBatchIndices: clear lists of all batches 
void CVertexBuffer::ClearBatchIndices()
{
	for (size_t i=0;i<m_Batches.size();i++) {
		m_Batches[i]->m_IndexData.clear();
		m_FreeBatches.push_back(m_Batches[i]);
	}
	m_Batches.clear();
}


///////////////////////////////////////////////////////////////////////////////
// AppendBatch: add a batch to the render list for this buffer
void CVertexBuffer::AppendBatch(VBChunk* UNUSED(chunk),Handle texture,size_t numIndices,u16* indices)
{
	// try and find a batch using this texture
	size_t i;
	Batch* batch=0;
	for (i=0;i<m_Batches.size();++i) {
		if (m_Batches[i]->m_Texture==texture) {
			batch=m_Batches[i];
			break;
		}
	}
	if (!batch) {
		if (m_FreeBatches.size()) {
			batch=m_FreeBatches.back();
			m_FreeBatches.pop_back();
		} else {
			batch=new Batch();
		}
		m_Batches.push_back(batch);
		batch->m_Texture=texture;
	}

	// resize the chunk's batch to fit its indices
	batch->m_IndexData.push_back(std::pair<size_t,u16*>(numIndices,indices));
//	cpu_memcpy(&batch->m_Indices[0]+cursize,indices,sizeof(u16)*numIndices);
}


///////////////////////////////////////////////////////////////////////////////
// UpdateChunkVertices: update vertex data for given chunk
void CVertexBuffer::UpdateChunkVertices(VBChunk* chunk,void* data)
{
	if (g_Renderer.m_Caps.m_VBO) {
		debug_assert(m_Handle);
		// glGetError(); // clear the error state
		pglBindBufferARB(GL_ARRAY_BUFFER_ARB,m_Handle);
		pglBufferSubDataARB(GL_ARRAY_BUFFER_ARB,chunk->m_Index*m_VertexSize,chunk->m_Count*m_VertexSize,data);
		// if (glGetError() != GL_NO_ERROR) throw PSERROR_Renderer_VBOFailed();
	} else {
		debug_assert(m_SysMem);
		cpu_memcpy(m_SysMem+chunk->m_Index*m_VertexSize,data,chunk->m_Count*m_VertexSize);
	}
}

///////////////////////////////////////////////////////////////////////////////
// Bind: bind to this buffer; return pointer to address required as parameter
// to glVertexPointer ( + etc) calls
u8* CVertexBuffer::Bind()
{
	u8* base;

	if (g_Renderer.m_Caps.m_VBO) {
		pglBindBufferARB(GL_ARRAY_BUFFER_ARB,m_Handle);
		base=(u8*) 0;
	} else {
		base=(u8*) m_SysMem;
	}
	return base;
}