/*

Open Asset Import Library (assimp)

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---------------------------------------------------------------------- */

#include "LimitBoneWeightsProcess.h"

#include <assimp/SmallVector.h>

#include <assimp/StringUtils.h>

#include <assimp/postprocess.h>

#include <assimp/DefaultLogger.hpp>

#include <assimp/scene.h>

#include <stdio.h>

namespace Assimp {

// Make sure this value is set.

#ifndef AI_LMW_MAX_WEIGHTS

#   define AI_LMW_MAX_WEIGHTS 16

#endif

// ------------------------------------------------------------------------------------------------

// Constructor to be privately used by Importer

LimitBoneWeightsProcess::LimitBoneWeightsProcess() :

        mMaxWeights(AI_LMW_MAX_WEIGHTS), mRemoveEmptyBones(true) {

    // empty

}

// ------------------------------------------------------------------------------------------------

// Returns whether the processing step is present in the given flag field.

bool LimitBoneWeightsProcess::IsActive( unsigned int pFlags) const {

    return (pFlags & aiProcess_LimitBoneWeights) != 0;

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

void LimitBoneWeightsProcess::Execute( aiScene* pScene) {

    ai_assert(pScene != nullptr);

    ASSIMP_LOG_DEBUG("LimitBoneWeightsProcess begin");

    for (unsigned int m = 0; m < pScene->mNumMeshes; ++m) {

        ProcessMesh(pScene->mMeshes[m]);

    }

    ASSIMP_LOG_DEBUG("LimitBoneWeightsProcess end");

}

// ------------------------------------------------------------------------------------------------

// Executes the post processing step on the given imported data.

void LimitBoneWeightsProcess::SetupProperties(const Importer* pImp) {

    this->mMaxWeights = pImp->GetPropertyInteger(AI_CONFIG_PP_LBW_MAX_WEIGHTS,AI_LMW_MAX_WEIGHTS);

    this->mRemoveEmptyBones = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_REMOVE_EMPTY_BONES, 1) != 0;

}

// ------------------------------------------------------------------------------------------------

static unsigned int removeEmptyBones(aiMesh *pMesh) {

    ai_assert(pMesh != nullptr);

    unsigned int writeBone = 0;

    for (unsigned int readBone = 0; readBone< pMesh->mNumBones; ++readBone) {

        aiBone* bone = pMesh->mBones[readBone];

        if (bone->mNumWeights > 0) {

            pMesh->mBones[writeBone++] = bone;

        } else {

            delete bone;

        }

    }

    return writeBone;

}

// ------------------------------------------------------------------------------------------------

// Unites identical vertices in the given mesh

void LimitBoneWeightsProcess::ProcessMesh(aiMesh* pMesh) {

    if (!pMesh->HasBones())

        return;

    // collect all bone weights per vertex

    typedef SmallVector<Weight,8> VertexWeightArray;

    typedef std::vector<VertexWeightArray> WeightsPerVertex;

    WeightsPerVertex vertexWeights(pMesh->mNumVertices);

    size_t maxVertexWeights = 0;

    for (unsigned int b = 0; b < pMesh->mNumBones; ++b) {

        const aiBone* bone = pMesh->mBones[b];

        for (unsigned int w = 0; w < bone->mNumWeights; ++w) {

            const aiVertexWeight& vw = bone->mWeights[w];

            if (vertexWeights.size() <= vw.mVertexId)

                continue;

            vertexWeights[vw.mVertexId].push_back(Weight(b, vw.mWeight));

            maxVertexWeights = std::max(maxVertexWeights, vertexWeights[vw.mVertexId].size());

        }

    }

    if (maxVertexWeights <= mMaxWeights)

        return;

    unsigned int removed = 0, old_bones = pMesh->mNumBones;

    // now cut the weight count if it exceeds the maximum

    for (WeightsPerVertex::iterator vit = vertexWeights.begin(); vit != vertexWeights.end(); ++vit) {

        if (vit->size() <= mMaxWeights)

            continue;

        // more than the defined maximum -> first sort by weight in descending order. That's

        // why we defined the < operator in such a weird way.

        std::sort(vit->begin(), vit->end());

        // now kill everything beyond the maximum count

        unsigned int m = static_cast<unsigned int>(vit->size());

        vit->resize(mMaxWeights);

        removed += static_cast<unsigned int>(m - vit->size());

        // and renormalize the weights

        float sum = 0.0f;

        for(const Weight* it = vit->begin(); it != vit->end(); ++it) {

            sum += it->mWeight;

        }

        if (0.0f != sum) {

            const float invSum = 1.0f / sum;

            for(Weight* it = vit->begin(); it != vit->end(); ++it) {

                it->mWeight *= invSum;

            }

        }

    }

    // clear weight count for all bone

    for (unsigned int a = 0; a < pMesh->mNumBones; ++a) {

        pMesh->mBones[a]->mNumWeights = 0;

    }

    // rebuild the vertex weight array for all bones

    for (unsigned int a = 0; a < vertexWeights.size(); ++a) {

        const VertexWeightArray& vw = vertexWeights[a];

        for (const Weight* it = vw.begin(); it != vw.end(); ++it) {

            aiBone* bone = pMesh->mBones[it->mBone];

            bone->mWeights[bone->mNumWeights++] = aiVertexWeight(a, it->mWeight);

        }

    }

    // remove empty bones

    if (mRemoveEmptyBones) {

        pMesh->mNumBones = removeEmptyBones(pMesh);

    }

    if (!DefaultLogger::isNullLogger()) {

        ASSIMP_LOG_INFO("Removed ", removed, " weights. Input bones: ", old_bones, ". Output bones: ", pMesh->mNumBones);

    }

}

} // namespace Assimp