/// \file   X3DExporter.cpp
/// \brief  X3D-format files exporter for Assimp. Implementation.
/// \date   2016
/// \author smal.root@gmail.com

#ifndef ASSIMP_BUILD_NO_EXPORT
#ifndef ASSIMP_BUILD_NO_X3D_EXPORTER

#include "X3DExporter.hpp"

// Header files, Assimp.
#include <assimp/Exceptional.h>
#include <assimp/StringUtils.h>
#include <assimp/Exporter.hpp>
#include <assimp/IOSystem.hpp>

using namespace std;

namespace Assimp {

void ExportSceneX3D(const char *pFile, IOSystem *pIOSystem, const aiScene *pScene, const ExportProperties *pProperties) {
    X3DExporter exporter(pFile, pIOSystem, pScene, pProperties);
}

} // namespace Assimp

namespace Assimp {

void X3DExporter::IndentationStringSet(const size_t pNewLevel) {
    if (pNewLevel > mIndentationString.size()) {
        if (pNewLevel > mIndentationString.capacity()) mIndentationString.reserve(pNewLevel + 1);

        for (size_t i = 0, i_e = pNewLevel - mIndentationString.size(); i < i_e; i++)
            mIndentationString.push_back('\t');
    } else if (pNewLevel < mIndentationString.size()) {
        mIndentationString.resize(pNewLevel);
    }
}

void X3DExporter::XML_Write(const string &pData) {
    if (pData.size() == 0) return;
    if (mOutFile->Write((void *)pData.data(), pData.length(), 1) != 1) throw DeadlyExportError("Failed to write scene data!");
}

aiMatrix4x4 X3DExporter::Matrix_GlobalToCurrent(const aiNode &pNode) const {
    aiNode *cur_node;
    std::list<aiMatrix4x4> matr;
    aiMatrix4x4 out_matr;

    // starting walk from current element to root
    matr.push_back(pNode.mTransformation);
    cur_node = pNode.mParent;
    if (cur_node != nullptr) {
        do {
            matr.push_back(cur_node->mTransformation);
            cur_node = cur_node->mParent;
        } while (cur_node != nullptr);
    }

    // multiplicate all matrices in reverse order
    for (std::list<aiMatrix4x4>::reverse_iterator rit = matr.rbegin(); rit != matr.rend(); ++rit)
        out_matr = out_matr * (*rit);

    return out_matr;
}

void X3DExporter::AttrHelper_FloatToString(const float pValue, std::string &pTargetString) {
    pTargetString = to_string(pValue);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Vec3DArrToString(const aiVector3D *pArray, const size_t pArray_Size, string &pTargetString) {
    pTargetString.clear();
    pTargetString.reserve(pArray_Size * 6); // (Number + space) * 3.
    for (size_t idx = 0; idx < pArray_Size; idx++)
        pTargetString.append(to_string(pArray[idx].x) + " " + to_string(pArray[idx].y) + " " + to_string(pArray[idx].z) + " ");

    // remove last space symbol.
    pTargetString.resize(pTargetString.length() - 1);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Vec2DArrToString(const aiVector2D *pArray, const size_t pArray_Size, std::string &pTargetString) {
    pTargetString.clear();
    pTargetString.reserve(pArray_Size * 4); // (Number + space) * 2.
    for (size_t idx = 0; idx < pArray_Size; idx++)
        pTargetString.append(to_string(pArray[idx].x) + " " + to_string(pArray[idx].y) + " ");

    // remove last space symbol.
    pTargetString.resize(pTargetString.length() - 1);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Vec3DAsVec2fArrToString(const aiVector3D *pArray, const size_t pArray_Size, string &pTargetString) {
    pTargetString.clear();
    pTargetString.reserve(pArray_Size * 4); // (Number + space) * 2.
    for (size_t idx = 0; idx < pArray_Size; idx++)
        pTargetString.append(to_string(pArray[idx].x) + " " + to_string(pArray[idx].y) + " ");

    // remove last space symbol.
    pTargetString.resize(pTargetString.length() - 1);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Col4DArrToString(const aiColor4D *pArray, const size_t pArray_Size, string &pTargetString) {
    pTargetString.clear();
    pTargetString.reserve(pArray_Size * 8); // (Number + space) * 4.
    for (size_t idx = 0; idx < pArray_Size; idx++)
        pTargetString.append(to_string(pArray[idx].r) + " " + to_string(pArray[idx].g) + " " + to_string(pArray[idx].b) + " " +
                             to_string(pArray[idx].a) + " ");

    // remove last space symbol.
    pTargetString.resize(pTargetString.length() - 1);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Col3DArrToString(const aiColor3D *pArray, const size_t pArray_Size, std::string &pTargetString) {
    pTargetString.clear();
    pTargetString.reserve(pArray_Size * 6); // (Number + space) * 3.
    for (size_t idx = 0; idx < pArray_Size; idx++)
        pTargetString.append(to_string(pArray[idx].r) + " " + to_string(pArray[idx].g) + " " + to_string(pArray[idx].b) + " ");

    // remove last space symbol.
    pTargetString.resize(pTargetString.length() - 1);
    AttrHelper_CommaToPoint(pTargetString);
}

void X3DExporter::AttrHelper_Color3ToAttrList(std::list<SAttribute> &pList, const std::string &pName, const aiColor3D &pValue, const aiColor3D &pDefaultValue) {
    string tstr;

    if (pValue == pDefaultValue) return;

    AttrHelper_Col3DArrToString(&pValue, 1, tstr);
    pList.emplace_back( pName, tstr );
}

void X3DExporter::AttrHelper_FloatToAttrList(std::list<SAttribute> &pList, const string &pName, const float pValue, const float pDefaultValue) {
    string tstr;

    if (pValue == pDefaultValue) return;

    AttrHelper_FloatToString(pValue, tstr);
    pList.emplace_back( pName, tstr );
}

void X3DExporter::NodeHelper_OpenNode(const string &pNodeName, const size_t pTabLevel, const bool pEmptyElement, const list<SAttribute> &pAttrList) {
    // Write indentation.
    IndentationStringSet(pTabLevel);
    XML_Write(mIndentationString);
    // Begin of the element
    XML_Write("<" + pNodeName);
    // Write attributes
    for (const SAttribute &attr : pAttrList) {
        XML_Write(" " + attr.Name + "='" + attr.Value + "'");
    }

    // End of the element
    if (pEmptyElement) {
        XML_Write("/>\n");
    } else {
        XML_Write(">\n");
    }
}

void X3DExporter::NodeHelper_OpenNode(const string &pNodeName, const size_t pTabLevel, const bool pEmptyElement) {
    const list<SAttribute> attr_list;

    NodeHelper_OpenNode(pNodeName, pTabLevel, pEmptyElement, attr_list);
}

void X3DExporter::NodeHelper_CloseNode(const string &pNodeName, const size_t pTabLevel) {
    // Write indentation.
    IndentationStringSet(pTabLevel);
    XML_Write(mIndentationString);
    // Write element
    XML_Write("</" + pNodeName + ">\n");
}

void X3DExporter::Export_Node(const aiNode *pNode, const size_t pTabLevel) {
    bool transform = false;
    list<SAttribute> attr_list;

    // In Assimp lights is stored in next way: light source store in mScene->mLights and in node tree must present aiNode with name same as
    // light source has. Considering it we must compare every aiNode name with light sources names. Why not to look where ligths is present
    // and save them to fili? Because corresponding aiNode can be already written to file and we can only add information to file not to edit.
    if (CheckAndExport_Light(*pNode, pTabLevel)) return;

    // Check if need DEF.
    if (pNode->mName.length) attr_list.emplace_back( "DEF", pNode->mName.C_Str() );

    // Check if need <Transformation> node against <Group>.
    if (!pNode->mTransformation.IsIdentity()) {
        auto Vector2String = [this](const aiVector3D pVector) -> string {
            string tstr = to_string(pVector.x) + " " + to_string(pVector.y) + " " + to_string(pVector.z);

            AttrHelper_CommaToPoint(tstr);

            return tstr;
        };

        auto Rotation2String = [this](const aiVector3D pAxis, const ai_real pAngle) -> string {
            string tstr = to_string(pAxis.x) + " " + to_string(pAxis.y) + " " + to_string(pAxis.z) + " " + to_string(pAngle);

            AttrHelper_CommaToPoint(tstr);

            return tstr;
        };

        aiVector3D scale, translate, rotate_axis;
        ai_real rotate_angle;

        transform = true;
        pNode->mTransformation.Decompose(scale, rotate_axis, rotate_angle, translate);
        // Check if values different from default
        if ((rotate_angle != 0) && (rotate_axis.Length() > 0))
            attr_list.emplace_back( "rotation", Rotation2String(rotate_axis, rotate_angle) );

        if (!scale.Equal({ 1.0, 1.0, 1.0 })) {
            attr_list.emplace_back( "scale", Vector2String(scale) );
        }
        if (translate.Length() > 0) {
            attr_list.emplace_back( "translation", Vector2String(translate) );
        }
    }

    // Begin node if need.
    if (transform)
        NodeHelper_OpenNode("Transform", pTabLevel, false, attr_list);
    else
        NodeHelper_OpenNode("Group", pTabLevel);

    // Export metadata
    if (pNode->mMetaData != nullptr) {
        for (size_t idx_prop = 0; idx_prop < pNode->mMetaData->mNumProperties; idx_prop++) {
            const aiString *key;
            const aiMetadataEntry *entry;

            if (pNode->mMetaData->Get(idx_prop, key, entry)) {
                switch (entry->mType) {
                case AI_BOOL:
                    Export_MetadataBoolean(*key, *static_cast<bool *>(entry->mData), pTabLevel + 1);
                    break;
                case AI_DOUBLE:
                    Export_MetadataDouble(*key, *static_cast<double *>(entry->mData), pTabLevel + 1);
                    break;
                case AI_FLOAT:
                    Export_MetadataFloat(*key, *static_cast<float *>(entry->mData), pTabLevel + 1);
                    break;
                case AI_INT32:
                    Export_MetadataInteger(*key, *static_cast<int32_t *>(entry->mData), pTabLevel + 1);
                    break;
                case AI_AISTRING:
                    Export_MetadataString(*key, *static_cast<aiString *>(entry->mData), pTabLevel + 1);
                    break;
                default:
                    LogError("Unsupported metadata type: " + to_string(entry->mType));
                    break;
                } // switch(entry->mType)
            }
        }
    } // if(pNode->mMetaData != nullptr)

    // Export meshes.
    for (size_t idx_mesh = 0; idx_mesh < pNode->mNumMeshes; idx_mesh++)
        Export_Mesh(pNode->mMeshes[idx_mesh], pTabLevel + 1);
    // Export children.
    for (size_t idx_node = 0; idx_node < pNode->mNumChildren; idx_node++)
        Export_Node(pNode->mChildren[idx_node], pTabLevel + 1);

    // End node if need.
    if (transform)
        NodeHelper_CloseNode("Transform", pTabLevel);
    else
        NodeHelper_CloseNode("Group", pTabLevel);
}

void X3DExporter::Export_Mesh(const size_t pIdxMesh, const size_t pTabLevel) {
    const char *NodeName_IFS = "IndexedFaceSet";
    const char *NodeName_Shape = "Shape";

    list<SAttribute> attr_list;
    aiMesh &mesh = *mScene->mMeshes[pIdxMesh]; // create alias for convenience.

    // Check if mesh already defined early.
    if (mDEF_Map_Mesh.find(pIdxMesh) != mDEF_Map_Mesh.end()) {
        // Mesh already defined, just refer to it
        attr_list.emplace_back( "USE", mDEF_Map_Mesh.at(pIdxMesh) );
        NodeHelper_OpenNode(NodeName_Shape, pTabLevel, true, attr_list);

        return;
    }

    string mesh_name(mesh.mName.C_Str() + string("_IDX_") + to_string(pIdxMesh)); // Create mesh name

    // Define mesh name.
    attr_list.emplace_back( "DEF", mesh_name );
    mDEF_Map_Mesh[pIdxMesh] = mesh_name;

    //
    // "Shape" node.
    //
    NodeHelper_OpenNode(NodeName_Shape, pTabLevel, false, attr_list);
    attr_list.clear();

    //
    // "Appearance" node.
    //
    Export_Material(mesh.mMaterialIndex, pTabLevel + 1);

    //
    // "IndexedFaceSet" node.
    //
    // Fill attributes which differ from default. In Assimp for colors, vertices and normals used one indices set. So, only "coordIndex" must be set.
    string coordIndex;

    // fill coordinates index.
    coordIndex.reserve(mesh.mNumVertices * 4); // Index + space + Face delimiter
    for (size_t idx_face = 0; idx_face < mesh.mNumFaces; idx_face++) {
        const aiFace &face_cur = mesh.mFaces[idx_face];

        for (size_t idx_vert = 0; idx_vert < face_cur.mNumIndices; idx_vert++) {
            coordIndex.append(to_string(face_cur.mIndices[idx_vert]) + " ");
        }

        coordIndex.append("-1 "); // face delimiter.
    }

    // remove last space symbol.
    coordIndex.resize(coordIndex.length() - 1);
    attr_list.emplace_back( "coordIndex", coordIndex );
    // create node
    NodeHelper_OpenNode(NodeName_IFS, pTabLevel + 1, false, attr_list);
    attr_list.clear();
    // Child nodes for "IndexedFaceSet" needed when used colors, textures or normals.
    string attr_value;

    // Export <Coordinate>
    AttrHelper_Vec3DArrToString(mesh.mVertices, mesh.mNumVertices, attr_value);
    attr_list.emplace_back( "point", attr_value );
    NodeHelper_OpenNode("Coordinate", pTabLevel + 2, true, attr_list);
    attr_list.clear();

    // Export <ColorRGBA>
    if (mesh.HasVertexColors(0)) {
        AttrHelper_Col4DArrToString(mesh.mColors[0], mesh.mNumVertices, attr_value);
        attr_list.emplace_back( "color", attr_value );
        NodeHelper_OpenNode("ColorRGBA", pTabLevel + 2, true, attr_list);
        attr_list.clear();
    }

    // Export <TextureCoordinate>
    if (mesh.HasTextureCoords(0)) {
        AttrHelper_Vec3DAsVec2fArrToString(mesh.mTextureCoords[0], mesh.mNumVertices, attr_value);
        attr_list.emplace_back( "point", attr_value );
        NodeHelper_OpenNode("TextureCoordinate", pTabLevel + 2, true, attr_list);
        attr_list.clear();
    }

    // Export <Normal>
    if (mesh.HasNormals()) {
        AttrHelper_Vec3DArrToString(mesh.mNormals, mesh.mNumVertices, attr_value);
        attr_list.emplace_back( "vector", attr_value );
        NodeHelper_OpenNode("Normal", pTabLevel + 2, true, attr_list);
        attr_list.clear();
    }

    //
    // Close opened nodes.
    //
    NodeHelper_CloseNode(NodeName_IFS, pTabLevel + 1);
    NodeHelper_CloseNode(NodeName_Shape, pTabLevel);
}

void X3DExporter::Export_Material(const size_t pIdxMaterial, const size_t pTabLevel) {
    const char *NodeName_A = "Appearance";

    list<SAttribute> attr_list;
    aiMaterial &material = *mScene->mMaterials[pIdxMaterial]; // create alias for convenience.

    // Check if material already defined early.
    if (mDEF_Map_Material.find(pIdxMaterial) != mDEF_Map_Material.end()) {
        // Material already defined, just refer to it
        attr_list.emplace_back( "USE", mDEF_Map_Material.at(pIdxMaterial) );
        NodeHelper_OpenNode(NodeName_A, pTabLevel, true, attr_list);

        return;
    }

    string material_name(string("_IDX_") + to_string(pIdxMaterial)); // Create material name
    aiString ai_mat_name;

    if (material.Get(AI_MATKEY_NAME, ai_mat_name) == AI_SUCCESS) material_name.insert(0, ai_mat_name.C_Str());

    // Define material name.
    attr_list.emplace_back( "DEF", material_name );
    mDEF_Map_Material[pIdxMaterial] = material_name;

    //
    // "Appearance" node.
    //
    NodeHelper_OpenNode(NodeName_A, pTabLevel, false, attr_list);
    attr_list.clear();

    //
    // "Material" node.
    //
    {
        auto Color4ToAttrList = [&](const string &pAttrName, const aiColor4D &pAttrValue, const aiColor3D &pAttrDefaultValue) {
            string tstr;

            if (aiColor3D(pAttrValue.r, pAttrValue.g, pAttrValue.b) != pAttrDefaultValue) {
                AttrHelper_Col4DArrToString(&pAttrValue, 1, tstr);
                attr_list.emplace_back( pAttrName, tstr );
            }
        };

        float tvalf;
        aiColor3D color3;
        aiColor4D color4;

        // ambientIntensity="0.2"     SFFloat [inputOutput]
        if (material.Get(AI_MATKEY_COLOR_AMBIENT, color3) == AI_SUCCESS)
            AttrHelper_FloatToAttrList(attr_list, "ambientIntensity", (color3.r + color3.g + color3.b) / 3.0f, 0.2f);
        else if (material.Get(AI_MATKEY_COLOR_AMBIENT, color4) == AI_SUCCESS)
            AttrHelper_FloatToAttrList(attr_list, "ambientIntensity", (color4.r + color4.g + color4.b) / 3.0f, 0.2f);

        // diffuseColor="0.8 0.8 0.8" SFColor [inputOutput]
        if (material.Get(AI_MATKEY_COLOR_DIFFUSE, color3) == AI_SUCCESS)
            AttrHelper_Color3ToAttrList(attr_list, "diffuseColor", color3, aiColor3D(0.8f, 0.8f, 0.8f));
        else if (material.Get(AI_MATKEY_COLOR_DIFFUSE, color4) == AI_SUCCESS)
            Color4ToAttrList("diffuseColor", color4, aiColor3D(0.8f, 0.8f, 0.8f));

        // emissiveColor="0 0 0"      SFColor [inputOutput]
        if (material.Get(AI_MATKEY_COLOR_EMISSIVE, color3) == AI_SUCCESS)
            AttrHelper_Color3ToAttrList(attr_list, "emissiveColor", color3, aiColor3D(0, 0, 0));
        else if (material.Get(AI_MATKEY_COLOR_EMISSIVE, color4) == AI_SUCCESS)
            Color4ToAttrList("emissiveColor", color4, aiColor3D(0, 0, 0));

        // shininess="0.2"            SFFloat [inputOutput]
        if (material.Get(AI_MATKEY_SHININESS, tvalf) == AI_SUCCESS) AttrHelper_FloatToAttrList(attr_list, "shininess", tvalf, 0.2f);

        // specularColor="0 0 0"      SFColor [inputOutput]
        if (material.Get(AI_MATKEY_COLOR_SPECULAR, color3) == AI_SUCCESS)
            AttrHelper_Color3ToAttrList(attr_list, "specularColor", color3, aiColor3D(0, 0, 0));
        else if (material.Get(AI_MATKEY_COLOR_SPECULAR, color4) == AI_SUCCESS)
            Color4ToAttrList("specularColor", color4, aiColor3D(0, 0, 0));

        // transparency="0"           SFFloat [inputOutput]
        if (material.Get(AI_MATKEY_OPACITY, tvalf) == AI_SUCCESS) {
            if (tvalf > 1) tvalf = 1;

            tvalf = 1.0f - tvalf;
            AttrHelper_FloatToAttrList(attr_list, "transparency", tvalf, 0);
        }

        NodeHelper_OpenNode("Material", pTabLevel + 1, true, attr_list);
        attr_list.clear();
    } // "Material" node. END.

    //
    // "ImageTexture" node.
    //
    {
        auto RepeatToAttrList = [&](const string &pAttrName, const bool pAttrValue) {
            if (!pAttrValue) attr_list.emplace_back( pAttrName, "false" );
        };

        bool tvalb;
        aiString tstring;

        // url=""         MFString
        if (material.Get(AI_MATKEY_TEXTURE_DIFFUSE(0), tstring) == AI_SUCCESS) {
            if (strncmp(tstring.C_Str(), AI_EMBEDDED_TEXNAME_PREFIX, strlen(AI_EMBEDDED_TEXNAME_PREFIX)) == 0)
                LogError("Embedded texture is not supported");
            else
                attr_list.emplace_back( "url", string("\"") + tstring.C_Str() + "\"" );
        }

        // repeatS="true" SFBool
        if (material.Get(AI_MATKEY_MAPPINGMODE_U_DIFFUSE(0), tvalb) == AI_SUCCESS) RepeatToAttrList("repeatS", tvalb);

        // repeatT="true" SFBool
        if (material.Get(AI_MATKEY_MAPPINGMODE_V_DIFFUSE(0), tvalb) == AI_SUCCESS) RepeatToAttrList("repeatT", tvalb);

        NodeHelper_OpenNode("ImageTexture", pTabLevel + 1, true, attr_list);
        attr_list.clear();
    } // "ImageTexture" node. END.

    //
    // "TextureTransform" node.
    //
    {
        auto Vec2ToAttrList = [&](const string &pAttrName, const aiVector2D &pAttrValue, const aiVector2D &pAttrDefaultValue) {
            string tstr;

            if (pAttrValue != pAttrDefaultValue) {
                AttrHelper_Vec2DArrToString(&pAttrValue, 1, tstr);
                attr_list.emplace_back( pAttrName, tstr );
            }
        };

        aiUVTransform transform;

        if (material.Get(AI_MATKEY_UVTRANSFORM_DIFFUSE(0), transform) == AI_SUCCESS) {
            Vec2ToAttrList("translation", transform.mTranslation, aiVector2D(0, 0));
            AttrHelper_FloatToAttrList(attr_list, "rotation", transform.mRotation, 0);
            Vec2ToAttrList("scale", transform.mScaling, aiVector2D(1, 1));

            NodeHelper_OpenNode("TextureTransform", pTabLevel + 1, true, attr_list);
            attr_list.clear();
        }
    } // "TextureTransform" node. END.

    //
    // Close opened nodes.
    //
    NodeHelper_CloseNode(NodeName_A, pTabLevel);
}

void X3DExporter::Export_MetadataBoolean(const aiString &pKey, const bool pValue, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    attr_list.emplace_back( "name", pKey.C_Str() );
    attr_list.emplace_back( "value", pValue ? "true" : "false" );
    NodeHelper_OpenNode("MetadataBoolean", pTabLevel, true, attr_list);
}

void X3DExporter::Export_MetadataDouble(const aiString &pKey, const double pValue, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    attr_list.emplace_back( "name", pKey.C_Str() );
    attr_list.emplace_back( "value", to_string(pValue) );
    NodeHelper_OpenNode("MetadataDouble", pTabLevel, true, attr_list);
}

void X3DExporter::Export_MetadataFloat(const aiString &pKey, const float pValue, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    attr_list.emplace_back( "name", pKey.C_Str() );
    attr_list.emplace_back( "value", to_string(pValue) );
    NodeHelper_OpenNode("MetadataFloat", pTabLevel, true, attr_list);
}

void X3DExporter::Export_MetadataInteger(const aiString &pKey, const int32_t pValue, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    attr_list.emplace_back( "name", pKey.C_Str() );
    attr_list.emplace_back( "value", to_string(pValue) );
    NodeHelper_OpenNode("MetadataInteger", pTabLevel, true, attr_list);
}

void X3DExporter::Export_MetadataString(const aiString &pKey, const aiString &pValue, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    attr_list.emplace_back( "name", pKey.C_Str() );
    attr_list.emplace_back( "value", pValue.C_Str() );
    NodeHelper_OpenNode("MetadataString", pTabLevel, true, attr_list);
}

bool X3DExporter::CheckAndExport_Light(const aiNode &pNode, const size_t pTabLevel) {
    list<SAttribute> attr_list;

    auto Vec3ToAttrList = [&](const string &pAttrName, const aiVector3D &pAttrValue, const aiVector3D &pAttrDefaultValue) {
        string tstr;

        if (pAttrValue != pAttrDefaultValue) {
            AttrHelper_Vec3DArrToString(&pAttrValue, 1, tstr);
            attr_list.emplace_back( pAttrName, tstr );
        }
    };

    size_t idx_light;
    bool found = false;

    // Name of the light source can not be empty.
    if (pNode.mName.length == 0) return false;

    // search for light with name like node has.
    for (idx_light = 0; mScene->mNumLights; idx_light++) {
        if (pNode.mName == mScene->mLights[idx_light]->mName) {
            found = true;
            break;
        }
    }

    if (!found) return false;

    // Light source is found.
    const aiLight &light = *mScene->mLights[idx_light]; // Alias for convenience.

    aiMatrix4x4 trafo_mat = Matrix_GlobalToCurrent(pNode).Inverse();

    attr_list.emplace_back( "DEF", light.mName.C_Str() );
    attr_list.emplace_back( "global", "true" ); // "false" is not supported.
    // ambientIntensity="0" SFFloat [inputOutput]
    AttrHelper_FloatToAttrList(attr_list, "ambientIntensity", aiVector3D(light.mColorAmbient.r, light.mColorAmbient.g, light.mColorAmbient.b).Length(), 0);
    // color="1 1 1"        SFColor [inputOutput]
    AttrHelper_Color3ToAttrList(attr_list, "color", light.mColorDiffuse, aiColor3D(1, 1, 1));

    switch (light.mType) {
    case aiLightSource_DIRECTIONAL: {
        aiVector3D direction = trafo_mat * light.mDirection;

        Vec3ToAttrList("direction", direction, aiVector3D(0, 0, -1));
        NodeHelper_OpenNode("DirectionalLight", pTabLevel, true, attr_list);
    }

    break;
    case aiLightSource_POINT: {
        aiVector3D attenuation(light.mAttenuationConstant, light.mAttenuationLinear, light.mAttenuationQuadratic);
        aiVector3D location = trafo_mat * light.mPosition;

        Vec3ToAttrList("attenuation", attenuation, aiVector3D(1, 0, 0));
        Vec3ToAttrList("location", location, aiVector3D(0, 0, 0));
        NodeHelper_OpenNode("PointLight", pTabLevel, true, attr_list);
    }

    break;
    case aiLightSource_SPOT: {
        aiVector3D attenuation(light.mAttenuationConstant, light.mAttenuationLinear, light.mAttenuationQuadratic);
        aiVector3D location = trafo_mat * light.mPosition;
        aiVector3D direction = trafo_mat * light.mDirection;

        Vec3ToAttrList("attenuation", attenuation, aiVector3D(1, 0, 0));
        Vec3ToAttrList("location", location, aiVector3D(0, 0, 0));
        Vec3ToAttrList("direction", direction, aiVector3D(0, 0, -1));
        AttrHelper_FloatToAttrList(attr_list, "beamWidth", light.mAngleInnerCone, 0.7854f);
        AttrHelper_FloatToAttrList(attr_list, "cutOffAngle", light.mAngleOuterCone, 1.570796f);
        NodeHelper_OpenNode("SpotLight", pTabLevel, true, attr_list);
    }

    break;
    default:
        throw DeadlyExportError("Unknown light type: " + to_string(light.mType));
    } // switch(light.mType)

    return true;
}

X3DExporter::X3DExporter(const char *pFileName, IOSystem *pIOSystem, const aiScene *pScene, const ExportProperties * /*pProperties*/) :
        mScene(pScene) {
    list<SAttribute> attr_list;

    mOutFile = pIOSystem->Open(pFileName, "wt");
    if (mOutFile == nullptr) throw DeadlyExportError("Could not open output .x3d file: " + string(pFileName));

    // Begin document
    XML_Write("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
    XML_Write("<!DOCTYPE X3D PUBLIC \"ISO//Web3D//DTD X3D 3.3//EN\" \"http://www.web3d.org/specifications/x3d-3.3.dtd\">\n");
    // Root node
    attr_list.emplace_back( "profile", "Interchange" );
    attr_list.emplace_back( "version", "3.3" );
    attr_list.emplace_back( "xmlns:xsd", "http://www.w3.org/2001/XMLSchema-instance" );
    attr_list.emplace_back( "xsd:noNamespaceSchemaLocation", "http://www.web3d.org/specifications/x3d-3.3.xsd" );
    NodeHelper_OpenNode("X3D", 0, false, attr_list);
    attr_list.clear();
    // <head>: meta data.
    NodeHelper_OpenNode("head", 1);
    XML_Write(mIndentationString + "<!-- All \"meta\" from this section tou will found in <Scene> node as MetadataString nodes. -->\n");
    NodeHelper_CloseNode("head", 1);
    // Scene node.
    NodeHelper_OpenNode("Scene", 1);
    Export_Node(mScene->mRootNode, 2);
    NodeHelper_CloseNode("Scene", 1);
    // Close Root node.
    NodeHelper_CloseNode("X3D", 0);
    // Cleanup
    pIOSystem->Close(mOutFile);
    mOutFile = nullptr;
}

} // namespace Assimp

#endif // ASSIMP_BUILD_NO_X3D_EXPORTER
#endif // ASSIMP_BUILD_NO_EXPORT