/*
---------------------------------------------------------------------------
Open Asset Import Library (assimp)
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Copyright (c) 2006-2012, assimp team

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  following disclaimer.

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*/

/** @file Implementation of the VertexTriangleAdjacency helper class
 */

#include "AssimpPCH.h"

// internal headers
#include "VertexTriangleAdjacency.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
VertexTriangleAdjacency::VertexTriangleAdjacency(aiFace *pcFaces,
	unsigned int iNumFaces,
	unsigned int iNumVertices /*= 0*/,
	bool bComputeNumTriangles /*= false*/)
{
	// compute the number of referenced vertices if it wasn't specified by the caller
	const aiFace* const pcFaceEnd = pcFaces + iNumFaces;
	if (!iNumVertices)	{

		for (aiFace* pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace)	{
			ai_assert(3 == pcFace->mNumIndices);
			iNumVertices = std::max(iNumVertices,pcFace->mIndices[0]);
			iNumVertices = std::max(iNumVertices,pcFace->mIndices[1]);
			iNumVertices = std::max(iNumVertices,pcFace->mIndices[2]);
		}
	}

	this->iNumVertices = iNumVertices;

	unsigned int* pi;

	// allocate storage
	if (bComputeNumTriangles)	{
		pi = mLiveTriangles = new unsigned int[iNumVertices+1];
		memset(mLiveTriangles,0,sizeof(unsigned int)*(iNumVertices+1));
		mOffsetTable = new unsigned int[iNumVertices+2]+1;
	}
	else {
		pi = mOffsetTable = new unsigned int[iNumVertices+2]+1;
		memset(mOffsetTable,0,sizeof(unsigned int)*(iNumVertices+1));
		mLiveTriangles = NULL; // important, otherwise the d'tor would crash
	}

	// get a pointer to the end of the buffer
	unsigned int* piEnd = pi+iNumVertices;
	*piEnd++ = 0u;

	// first pass: compute the number of faces referencing each vertex
	for (aiFace* pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace)
	{
		pi[pcFace->mIndices[0]]++;	
		pi[pcFace->mIndices[1]]++;	
		pi[pcFace->mIndices[2]]++;	
	}

	// second pass: compute the final offset table
	unsigned int iSum = 0;
	unsigned int* piCurOut = this->mOffsetTable;
	for (unsigned int* piCur = pi; piCur != piEnd;++piCur,++piCurOut)	{

		unsigned int iLastSum = iSum;
		iSum += *piCur; 
		*piCurOut = iLastSum;
	}
	pi = this->mOffsetTable;

	// third pass: compute the final table
	this->mAdjacencyTable = new unsigned int[iSum];
	iSum = 0;
	for (aiFace* pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace,++iSum)	{

		unsigned int idx = pcFace->mIndices[0];
		mAdjacencyTable[pi[idx]++] = iSum;

		idx = pcFace->mIndices[1];
		mAdjacencyTable[pi[idx]++] = iSum;

		idx = pcFace->mIndices[2];
		mAdjacencyTable[pi[idx]++] = iSum;
	}
	// fourth pass: undo the offset computations made during the third pass
	// We could do this in a separate buffer, but this would be TIMES slower.
	--mOffsetTable;
	*mOffsetTable = 0u;
}
// ------------------------------------------------------------------------------------------------
VertexTriangleAdjacency::~VertexTriangleAdjacency()
{
	// delete allocated storage
	delete[] mOffsetTable;
	delete[] mAdjacencyTable;
	delete[] mLiveTriangles;
}
