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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 (0 == 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 + 1;

    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 = nullptr; // 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) {

        unsigned nind = pcFace->mNumIndices;

        unsigned *ind = pcFace->mIndices;

        if (nind > 0) pi[ind[0]]++;

        if (nind > 1) pi[ind[1]]++;

        if (nind > 2) pi[ind[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 nind = pcFace->mNumIndices;

        unsigned *ind = pcFace->mIndices;

        if (nind > 0) mAdjacencyTable[pi[ind[0]]++] = iSum;

        if (nind > 1) mAdjacencyTable[pi[ind[1]]++] = iSum;

        if (nind > 2) mAdjacencyTable[pi[ind[2]]++] = 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;

}