/*
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Open Asset Import Library (assimp)
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*/

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

// internal headers
#include "VertexTriangleAdjacency.h"
#include <assimp/mesh.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( nullptr != 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]);
        }
    }

    mNumVertices = 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;
}