/*
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) {
    // 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);
}

// ------------------------------------------------------------------------------------------------
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
#ifdef AI_CONFIG_IMPORT_REMOVE_EMPTY_BONES 
    pMesh->mNumBones = removeEmptyBones(pMesh);
#endif // AI_CONFIG_IMPORT_REMOVE_EMPTY_BONES 

    if (!DefaultLogger::isNullLogger()) {
        ASSIMP_LOG_INFO("Removed ", removed, " weights. Input bones: ", old_bones, ". Output bones: ", pMesh->mNumBones);
    }
}

} // namespace Assimp