/*
---------------------------------------------------------------------------
Open Asset Import Library (assimp)
---------------------------------------------------------------------------

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* Redistributions in binary form must reproduce the above
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*/

/** @file ColladaParser.cpp
 *  @brief Implementation of the Collada parser helper
 */

#ifndef ASSIMP_BUILD_NO_COLLADA_IMPORTER

#include "ColladaParser.h"
#include <assimp/ParsingUtils.h>
#include <assimp/StringUtils.h>
#include <assimp/ZipArchiveIOSystem.h>
#include <assimp/commonMetaData.h>
#include <assimp/fast_atof.h>
#include <assimp/light.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>
#include <memory>
#include <utility>

using namespace Assimp;
using namespace Assimp::Collada;
using namespace Assimp::Formatter;

// ------------------------------------------------------------------------------------------------
static void ReportWarning(const char *msg, ...) {
    ai_assert(nullptr != msg);

    va_list args;
    va_start(args, msg);

    char szBuffer[3000];
    const int iLen = vsnprintf(szBuffer, sizeof(szBuffer), msg, args);
    ai_assert(iLen > 0);

    va_end(args);
    ASSIMP_LOG_WARN("Validation warning: ", std::string(szBuffer, iLen));
}

// ------------------------------------------------------------------------------------------------
static bool FindCommonKey(const std::string &collada_key, const MetaKeyPairVector &key_renaming, size_t &found_index) {
    for (size_t i = 0; i < key_renaming.size(); ++i) {
        if (key_renaming[i].first == collada_key) {
            found_index = i;
            return true;
        }
    }
    found_index = std::numeric_limits<size_t>::max();

    return false;
}

// ------------------------------------------------------------------------------------------------
static void readUrlAttribute(XmlNode &node, std::string &url) {
    url.clear();
    if (!XmlParser::getStdStrAttribute(node, "url", url)) {
        return;
    }
    if (url[0] != '#') {
        throw DeadlyImportError("Unknown reference format");
    }
    url = url.c_str() + 1;
}

// ------------------------------------------------------------------------------------------------
// Reads a node transformation entry of the given type and adds it to the given node's transformation list.
static void ReadNodeTransformation(XmlNode &node, Node *pNode, TransformType pType) {
    if (node.empty()) {
        return;
    }

    std::string tagName = node.name();

    Transform tf;
    tf.mType = pType;

    // read SID
    if (XmlParser::hasAttribute(node, "sid")) {
        XmlParser::getStdStrAttribute(node, "sid", tf.mID);
    }

    // how many parameters to read per transformation type
    static constexpr unsigned int sNumParameters[] = { 9, 4, 3, 3, 7, 16 };
    std::string value;
    XmlParser::getValueAsString(node, value);
    const char *content = value.c_str();
    const char *end = value.c_str() + value.size();
    // read as many parameters and store in the transformation
    for (unsigned int a = 0; a < sNumParameters[pType]; a++) {
        // skip whitespace before the number
        SkipSpacesAndLineEnd(&content, end);
        // read a number
        content = fast_atoreal_move<ai_real>(content, tf.f[a]);
    }

    // place the transformation at the queue of the node
    pNode->mTransforms.push_back(tf);
}

// ------------------------------------------------------------------------------------------------
// Reads a single string metadata item
static void ReadMetaDataItem(XmlNode &node, ColladaParser::StringMetaData &metadata) {
    const MetaKeyPairVector &key_renaming = GetColladaAssimpMetaKeysCamelCase();
    const std::string name = node.name();
    if (name.empty()) {
        return;
    }

    std::string v;
    if (!XmlParser::getValueAsString(node, v)) {
        return;
    }

    v = ai_trim(v);
    aiString aistr;
    aistr.Set(v);

    std::string camel_key_str(name);
    ToCamelCase(camel_key_str);

    size_t found_index;
    if (FindCommonKey(camel_key_str, key_renaming, found_index)) {
        metadata.emplace(key_renaming[found_index].second, aistr);
    } else {
        metadata.emplace(camel_key_str, aistr);
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an animation sampler into the given anim channel
static void ReadAnimationSampler(const XmlNode &node, AnimationChannel &pChannel) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "input") {
            if (XmlParser::hasAttribute(currentNode, "semantic")) {
                std::string semantic, sourceAttr;
                XmlParser::getStdStrAttribute(currentNode, "semantic", semantic);
                if (XmlParser::hasAttribute(currentNode, "source")) {
                    XmlParser::getStdStrAttribute(currentNode, "source", sourceAttr);
                    const char *source = sourceAttr.c_str();
                    if (source[0] != '#') {
                        throw DeadlyImportError("Unsupported URL format");
                    }
                    source++;

                    if (semantic == "INPUT") {
                        pChannel.mSourceTimes = source;
                    } else if (semantic == "OUTPUT") {
                        pChannel.mSourceValues = source;
                    } else if (semantic == "IN_TANGENT") {
                        pChannel.mInTanValues = source;
                    } else if (semantic == "OUT_TANGENT") {
                        pChannel.mOutTanValues = source;
                    } else if (semantic == "INTERPOLATION") {
                        pChannel.mInterpolationValues = source;
                    }
                }
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the joint definitions for the given controller
static void ReadControllerJoints(const XmlNode &node, Controller &pController) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "input") {
            const char *attrSemantic = currentNode.attribute("semantic").as_string();
            const char *attrSource = currentNode.attribute("source").as_string();
            if (attrSource[0] != '#') {
                throw DeadlyImportError("Unsupported URL format in \"", attrSource, "\" in source attribute of <joints> data <input> element");
            }
            ++attrSource;
            // parse source URL to corresponding source
            if (strcmp(attrSemantic, "JOINT") == 0) {
                pController.mJointNameSource = attrSource;
            } else if (strcmp(attrSemantic, "INV_BIND_MATRIX") == 0) {
                pController.mJointOffsetMatrixSource = attrSource;
            } else {
                throw DeadlyImportError("Unknown semantic \"", attrSemantic, "\" in <joints> data <input> element");
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
static void ReadControllerWeightsInput(const XmlNode &currentNode, Controller &pController) {
    InputChannel channel;

    const char *attrSemantic = currentNode.attribute("semantic").as_string();
    const char *attrSource = currentNode.attribute("source").as_string();
    channel.mOffset = currentNode.attribute("offset").as_int();

    // local URLS always start with a '#'. We don't support global URLs
    if (attrSource[0] != '#') {
        throw DeadlyImportError("Unsupported URL format in \"", attrSource, "\" in source attribute of <vertex_weights> data <input> element");
    }
    channel.mAccessor = attrSource + 1;

    // parse source URL to corresponding source
    if (strcmp(attrSemantic, "JOINT") == 0) {
        pController.mWeightInputJoints = channel;
    } else if (strcmp(attrSemantic, "WEIGHT") == 0) {
        pController.mWeightInputWeights = channel;
    } else {
        throw DeadlyImportError("Unknown semantic \"", attrSemantic, "\" in <vertex_weights> data <input> element");
    }
}

// ------------------------------------------------------------------------------------------------
static void ReadControllerWeightsVCount(const XmlNode &currentNode, Controller &pController) {
    const std::string stdText = currentNode.text().as_string();
    const char *text = stdText.c_str();
    const char *end = text + stdText.size();
    size_t numWeights = 0;
    for (auto it = pController.mWeightCounts.begin(); it != pController.mWeightCounts.end(); ++it) {
        if (*text == 0) {
            throw DeadlyImportError("Out of data while reading <vcount>");
        }

        *it = strtoul10(text, &text);
        numWeights += *it;
        SkipSpacesAndLineEnd(&text, end);
    }
    // reserve weight count
    pController.mWeights.resize(numWeights);
}

// ------------------------------------------------------------------------------------------------
static void ReadControllerWeightsJoint2verts(XmlNode &currentNode, Controller &pController) {
    // read JointIndex - WeightIndex pairs
    std::string stdText;
    XmlParser::getValueAsString(currentNode, stdText);
    const char *text = stdText.c_str();
    const char *end = text + stdText.size();
    for (auto it = pController.mWeights.begin(); it != pController.mWeights.end(); ++it) {
        if (text == nullptr) {
            throw DeadlyImportError("Out of data while reading <vertex_weights>");
        }
        SkipSpacesAndLineEnd(&text, end);
        it->first = strtoul10(text, &text);
        SkipSpacesAndLineEnd(&text, end);
        if (*text == 0) {
            throw DeadlyImportError("Out of data while reading <vertex_weights>");
        }
        it->second = strtoul10(text, &text);
        SkipSpacesAndLineEnd(&text, end);
    }

}

// ------------------------------------------------------------------------------------------------
// Reads the joint weights for the given controller
static void ReadControllerWeights(XmlNode &node, Controller &pController) {
    // Read vertex count from attributes and resize the array accordingly
    int vertexCount = 0;
    XmlParser::getIntAttribute(node, "count", vertexCount);
    pController.mWeightCounts.resize(vertexCount);

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "input") {
            ReadControllerWeightsInput(currentNode, pController);
        } else if (currentName == "vcount" && vertexCount > 0) {
            ReadControllerWeightsVCount(currentNode, pController);
        } else if (currentName == "v" && vertexCount > 0) {
            ReadControllerWeightsJoint2verts(currentNode, pController);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a material entry into the given material
static void ReadMaterial(const XmlNode &node, Material &pMaterial) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "instance_effect") {
            std::string url;
            readUrlAttribute(currentNode, url);
            pMaterial.mEffect = url;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a light entry into the given light
static void ReadLight(XmlNode &node, Light &pLight) {
    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    // TODO: Check the current technique and skip over unsupported extra techniques

    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "spot") {
            pLight.mType = aiLightSource_SPOT;
        } else if (currentName == "ambient") {
            pLight.mType = aiLightSource_AMBIENT;
        } else if (currentName == "directional") {
            pLight.mType = aiLightSource_DIRECTIONAL;
        } else if (currentName == "point") {
            pLight.mType = aiLightSource_POINT;
        } else if (currentName == "color") {
            // text content contains 3 floats
            std::string v;
            XmlParser::getValueAsString(currentNode, v);
            const char *content = v.c_str();
            const char *end = content + v.size();

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pLight.mColor.r);
            SkipSpacesAndLineEnd(&content, end);

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pLight.mColor.g);
            SkipSpacesAndLineEnd(&content, end);

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pLight.mColor.b);
            SkipSpacesAndLineEnd(&content, end);
        } else if (currentName == "constant_attenuation") {
            XmlParser::getValueAsReal(currentNode, pLight.mAttConstant);
        } else if (currentName == "linear_attenuation") {
            XmlParser::getValueAsReal(currentNode, pLight.mAttLinear);
        } else if (currentName == "quadratic_attenuation") {
            XmlParser::getValueAsReal(currentNode, pLight.mAttQuadratic);
        } else if (currentName == "falloff_angle") {
            XmlParser::getValueAsReal(currentNode, pLight.mFalloffAngle);
        } else if (currentName == "falloff_exponent") {
            XmlParser::getValueAsReal(currentNode, pLight.mFalloffExponent);
        }
        // FCOLLADA extensions
        // -------------------------------------------------------
        else if (currentName == "outer_cone") {
            XmlParser::getValueAsReal(currentNode, pLight.mOuterAngle);
        } else if (currentName == "penumbra_angle") { // this one is deprecated, now calculated using outer_cone
            XmlParser::getValueAsReal(currentNode, pLight.mPenumbraAngle);
        } else if (currentName == "intensity") {
            XmlParser::getValueAsReal(currentNode, pLight.mIntensity);
        } else if (currentName == "falloff") {
            XmlParser::getValueAsReal(currentNode, pLight.mOuterAngle);
        } else if (currentName == "hotspot_beam") {
            XmlParser::getValueAsReal(currentNode, pLight.mFalloffAngle);
        }
        // OpenCOLLADA extensions
        // -------------------------------------------------------
        else if (currentName == "decay_falloff") {
            XmlParser::getValueAsReal(currentNode, pLight.mOuterAngle);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a camera entry into the given light
static void ReadCamera(XmlNode &node, Camera &camera) {
    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "orthographic") {
            camera.mOrtho = true;
        } else if (currentName == "xfov" || currentName == "xmag") {
            XmlParser::getValueAsReal(currentNode, camera.mHorFov);
        } else if (currentName == "yfov" || currentName == "ymag") {
            XmlParser::getValueAsReal(currentNode, camera.mVerFov);
        } else if (currentName == "aspect_ratio") {
            XmlParser::getValueAsReal(currentNode, camera.mAspect);
        } else if (currentName == "znear") {
            XmlParser::getValueAsReal(currentNode, camera.mZNear);
        } else if (currentName == "zfar") {
            XmlParser::getValueAsReal(currentNode, camera.mZFar);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
ColladaParser::ColladaParser(IOSystem *pIOHandler, const std::string &pFile) :
        mFileName(pFile),
        mRootNode(nullptr),
        mUnitSize(1.0f),
        mUpDirection(UP_Y),
        mFormat(FV_1_5_n) {
    if (nullptr == pIOHandler) {
        throw DeadlyImportError("IOSystem is nullptr.");
    }

    std::unique_ptr<IOStream> daeFile;
    std::unique_ptr<ZipArchiveIOSystem> zip_archive;

    // Determine type
    const std::string extension = BaseImporter::GetExtension(pFile);
    if (extension != "dae") {
        zip_archive = std::make_unique<ZipArchiveIOSystem>(pIOHandler, pFile);
    }

    if (zip_archive && zip_archive->isOpen()) {
        std::string dae_filename = ReadZaeManifest(*zip_archive);

        if (dae_filename.empty()) {
            throw DeadlyImportError("Invalid ZAE");
        }

        daeFile.reset(zip_archive->Open(dae_filename.c_str()));
        if (daeFile == nullptr) {
            throw DeadlyImportError("Invalid ZAE manifest: '", dae_filename, "' is missing");
        }
    } else {
        // attempt to open the file directly
        daeFile.reset(pIOHandler->Open(pFile));
        if (daeFile == nullptr) {
            throw DeadlyImportError("Failed to open file '", pFile, "'.");
        }
    }

    // generate a XML reader for it
    if (!mXmlParser.parse(daeFile.get())) {
        throw DeadlyImportError("Unable to read file, malformed XML");
    }
    // start reading
    const XmlNode node = mXmlParser.getRootNode();
    XmlNode colladaNode = node.child("COLLADA");
    if (colladaNode.empty()) {
        return;
    }

    // Read content and embedded textures
    ReadContents(colladaNode);
    if (zip_archive && zip_archive->isOpen()) {
        ReadEmbeddedTextures(*zip_archive);
    }
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
ColladaParser::~ColladaParser() {
    for (auto &it : mNodeLibrary) {
        delete it.second;
    }
    for (auto &it : mMeshLibrary) {
        delete it.second;
    }
}

// ------------------------------------------------------------------------------------------------
// Read a ZAE manifest and return the filename to attempt to open
std::string ColladaParser::ReadZaeManifest(ZipArchiveIOSystem &zip_archive) {
    // Open the manifest
    std::unique_ptr<IOStream> manifestfile(zip_archive.Open("manifest.xml"));
    if (manifestfile == nullptr) {
        // No manifest, hope there is only one .DAE inside
        std::vector<std::string> file_list;
        zip_archive.getFileListExtension(file_list, "dae");

        if (file_list.empty()) {
            return {};
        }

        return file_list.front();
    }
    XmlParser manifestParser;
    if (!manifestParser.parse(manifestfile.get())) {
        return {};
    }

    XmlNode root = manifestParser.getRootNode();
    const std::string &name = root.name();
    if (name != "dae_root") {
        root = *manifestParser.findNode("dae_root");
        if (nullptr == root) {
            return {};
        }
        std::string v;
        XmlParser::getValueAsString(root, v);
        aiString ai_str(v);
        UriDecodePath(ai_str);
        return std::string(ai_str.C_Str());
    }

    return {};
}

// ------------------------------------------------------------------------------------------------
// Convert a path read from a collada file to the usual representation
void ColladaParser::UriDecodePath(aiString &ss) {
    // TODO: collada spec, p 22. Handle URI correctly.
    // For the moment we're just stripping the file:// away to make it work.
    // Windows doesn't seem to be able to find stuff like
    // 'file://..\LWO\LWO2\MappingModes\earthSpherical.jpg'
    if (0 == strncmp(ss.data, "file://", 7)) {
        ss.length -= 7;
        memmove(ss.data, ss.data + 7, ss.length);
        ss.data[ss.length] = '\0';
    }

    // Maxon Cinema Collada Export writes "file:///C:\andsoon" with three slashes...
    // I need to filter it without destroying linux paths starting with "/somewhere"
    if (ss.data[0] == '/' && isalpha((unsigned char)ss.data[1]) && ss.data[2] == ':') {
        --ss.length;
        ::memmove(ss.data, ss.data + 1, ss.length);
        ss.data[ss.length] = 0;
    }

    // find and convert all %xy special chars
    char *out = ss.data;
    for (const char *it = ss.data; it != ss.data + ss.length; /**/) {
        if (*it == '%' && (it + 3) < ss.data + ss.length) {
            // separate the number to avoid dragging in chars from behind into the parsing
            char mychar[3] = { it[1], it[2], 0 };
            size_t nbr = strtoul16(mychar);
            it += 3;
            *out++ = static_cast<char>(nbr & 0xFF);
        } else {
            *out++ = *it++;
        }
    }

    // adjust length and terminator of the shortened string
    *out = 0;
    ai_assert(out > ss.data);
    ss.length = static_cast<ai_uint32>(out - ss.data);
}

// ------------------------------------------------------------------------------------------------
// Reads the contents of the file
void ColladaParser::ReadContents(XmlNode &node) {
    if (const std::string name = node.name(); name == "COLLADA") {
        std::string version;
        if (XmlParser::getStdStrAttribute(node, "version", version)) {
            aiString v;
            v.Set(version);
            mAssetMetaData.emplace(AI_METADATA_SOURCE_FORMAT_VERSION, v);
            if (!::strncmp(version.c_str(), "1.5", 3)) {
                mFormat = FV_1_5_n;
                ASSIMP_LOG_DEBUG("Collada schema version is 1.5.n");
            } else if (!::strncmp(version.c_str(), "1.4", 3)) {
                mFormat = FV_1_4_n;
                ASSIMP_LOG_DEBUG("Collada schema version is 1.4.n");
            } else if (!::strncmp(version.c_str(), "1.3", 3)) {
                mFormat = FV_1_3_n;
                ASSIMP_LOG_DEBUG("Collada schema version is 1.3.n");
            }
        }
        ReadStructure(node);
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the structure of the file
void ColladaParser::ReadStructure(XmlNode &node) {
    for (XmlNode &currentNode : node.children()) {
        if (const std::string &currentName = currentNode.name(); currentName == "asset") {
            ReadAssetInfo(currentNode);
        } else if (currentName == "library_animations") {
            ReadAnimationLibrary(currentNode);
        } else if (currentName == "library_animation_clips") {
            ReadAnimationClipLibrary(currentNode);
        } else if (currentName == "library_controllers") {
            ReadControllerLibrary(currentNode);
        } else if (currentName == "library_images") {
            ReadImageLibrary(currentNode);
        } else if (currentName == "library_materials") {
            ReadMaterialLibrary(currentNode);
        } else if (currentName == "library_effects") {
            ReadEffectLibrary(currentNode);
        } else if (currentName == "library_geometries") {
            ReadGeometryLibrary(currentNode);
        } else if (currentName == "library_visual_scenes") {
            ReadSceneLibrary(currentNode);
        } else if (currentName == "library_lights") {
            ReadLightLibrary(currentNode);
        } else if (currentName == "library_cameras") {
            ReadCameraLibrary(currentNode);
        } else if (currentName == "library_nodes") {
            ReadSceneNode(currentNode, nullptr); /* some hacking to reuse this piece of code */
        } else if (currentName == "scene") {
            ReadScene(currentNode);
        }
    }

    PostProcessRootAnimations();
    PostProcessControllers();
}

// ------------------------------------------------------------------------------------------------
// Reads asset information such as coordinate system information and legal blah
void ColladaParser::ReadAssetInfo(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        if (const std::string &currentName = currentNode.name(); currentName == "unit") {
            mUnitSize = 1.f;
            std::string tUnitSizeString;
            if (XmlParser::getStdStrAttribute(currentNode, "meter", tUnitSizeString)) {
                try {
                    fast_atoreal_move<ai_real>(tUnitSizeString.data(), mUnitSize);
                } catch (const DeadlyImportError& die) {
                    std::string warning("Collada: Failed to parse meter parameter to real number. Exception:\n");
                    warning.append(die.what());
                    ASSIMP_LOG_WARN(warning.data());
                }
            }
        } else if (currentName == "up_axis") {
            std::string v;
            if (!XmlParser::getValueAsString(currentNode, v)) {
                continue;
            }
            if (v == "X_UP") {
                mUpDirection = UP_X;
            } else if (v == "Z_UP") {
                mUpDirection = UP_Z;
            } else {
                mUpDirection = UP_Y;
            }
        } else if (currentName == "contributor") {
            for (XmlNode currentChildNode : currentNode.children()) {
                ReadMetaDataItem(currentChildNode, mAssetMetaData);
            }
        } else {
            ReadMetaDataItem(currentNode, mAssetMetaData);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the animation clips
void ColladaParser::ReadAnimationClipLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    std::string animName;
    if (!XmlParser::getStdStrAttribute(node, "name", animName)) {
        if (!XmlParser::getStdStrAttribute(node, "id", animName)) {
            animName = std::string("animation_") + ai_to_string(mAnimationClipLibrary.size());
        }
    }

    std::pair<std::string, std::vector<std::string>> clip;
    clip.first = animName;

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "instance_animation") {
            std::string url;
            readUrlAttribute(currentNode, url);
            clip.second.push_back(url);
        }

        if (clip.second.size() > 0) {
            mAnimationClipLibrary.push_back(clip);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// The controller post processing step
void ColladaParser::PostProcessControllers() {
    for (auto &it : mControllerLibrary) {
        std::string meshId = it.second.mMeshId;
        if (meshId.empty()) {
            continue;
        }

        auto findItr = mControllerLibrary.find(meshId);
        while (findItr != mControllerLibrary.end()) {
            meshId = findItr->second.mMeshId;
            findItr = mControllerLibrary.find(meshId);
        }

        it.second.mMeshId = meshId;
    }
}

// ------------------------------------------------------------------------------------------------
// Re-build animations from animation clip library, if present, otherwise combine single-channel animations
void ColladaParser::PostProcessRootAnimations() {
    if (mAnimationClipLibrary.empty()) {
        mAnims.CombineSingleChannelAnimations();
        return;
    }

    Animation temp;
    for (auto &it : mAnimationClipLibrary) {
        std::string clipName = it.first;

        auto *clip = new Animation();
        clip->mName = clipName;

        temp.mSubAnims.push_back(clip);

        for (const std::string &animationID : it.second) {
            auto animation = mAnimationLibrary.find(animationID);

            if (animation != mAnimationLibrary.end()) {
                Animation *pSourceAnimation = animation->second;
                pSourceAnimation->CollectChannelsRecursively(clip->mChannels);
            }
        }
    }

    mAnims = temp;

    // Ensure no double deletes.
    temp.mSubAnims.clear();
}

// ------------------------------------------------------------------------------------------------
// Reads the animation library
void ColladaParser::ReadAnimationLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "animation") {
            ReadAnimation(currentNode, &mAnims);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an animation into the given parent structure
void ColladaParser::ReadAnimation(XmlNode &node, Collada::Animation *pParent) {
    if (node.empty()) {
        return;
    }

    // an <animation> element may be a container for grouping sub-elements or an animation channel
    // this is the channel collection by ID, in case it has channels
    using ChannelMap = std::map<std::string, AnimationChannel>;
    ChannelMap channels;
    // this is the anim container in case we're a container
    Animation *anim = nullptr;

    // optional name given as an attribute
    std::string animName;
    if (!XmlParser::getStdStrAttribute(node, "name", animName)) {
        animName = "animation";
    }

    std::string animID;
    pugi::xml_attribute idAttr = node.attribute("id");
    if (idAttr) {
        animID = idAttr.as_string();
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "animation") {
            if (!anim) {
                anim = new Animation;
                anim->mName = animName;
                pParent->mSubAnims.push_back(anim);
            }

            // recurse into the sub-element
            ReadAnimation(currentNode, anim);
        } else if (currentName == "source") {
            ReadSource(currentNode);
        } else if (currentName == "sampler") {
            std::string id;
            if (XmlParser::getStdStrAttribute(currentNode, "id", id)) {
                // have it read into a channel
                auto newChannel = channels.insert(std::make_pair(id, AnimationChannel())).first;
                ReadAnimationSampler(currentNode, newChannel->second);
            }
        } else if (currentName == "channel") {
            std::string source_name, target;
            XmlParser::getStdStrAttribute(currentNode, "source", source_name);
            XmlParser::getStdStrAttribute(currentNode, "target", target);
            if (source_name[0] == '#') {
                source_name = source_name.substr(1, source_name.size() - 1);
            }
            auto cit = channels.find(source_name);
            if (cit != channels.end()) {
                cit->second.mTarget = target;
            }
        }
    }

    // it turned out to have channels - add them
    if (!channels.empty()) {
        if (nullptr == anim) {
            anim = new Animation;
            anim->mName = animName;
            pParent->mSubAnims.push_back(anim);
        }

        for (const auto &channel : channels) {
            anim->mChannels.push_back(channel.second);
        }

        if (idAttr) {
            mAnimationLibrary[animID] = anim;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the skeleton controller library
void ColladaParser::ReadControllerLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName != "controller") {
            continue;
        }
        if (std::string id; XmlParser::getStdStrAttribute(currentNode, "id", id)) {
            mControllerLibrary[id] = Controller();
            ReadController(currentNode, mControllerLibrary[id]);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a controller into the given mesh structure
void ColladaParser::ReadController(XmlNode &node, Collada::Controller &controller) {
    // initial values
    controller.mType = Skin;
    controller.mMethod = Normalized;

    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        if (const std::string &currentName = currentNode.name(); currentName == "morph") {
            controller.mType = Morph;
            std::string id = currentNode.attribute("source").as_string();
            controller.mMeshId = id.substr(1, id.size() - 1);
            if (const int methodIndex = currentNode.attribute("method").as_int(); methodIndex > 0) {
                std::string method;
                XmlParser::getValueAsString(currentNode, method);

                if (method == "RELATIVE") {
                    controller.mMethod = Relative;
                }
            }
        } else if (currentName == "skin") {
            if (std::string id; XmlParser::getStdStrAttribute(currentNode, "source", id)) {
                controller.mMeshId = id.substr(1, id.size() - 1);
            }
        } else if (currentName == "bind_shape_matrix") {
            std::string v;
            XmlParser::getValueAsString(currentNode, v);
            const char *content = v.c_str();
            const char *end = content + v.size();
            for (auto & a : controller.mBindShapeMatrix) {
                SkipSpacesAndLineEnd(&content, end);
                // read a number
                content = fast_atoreal_move<ai_real>(content, a);
                // skip whitespace after it
                SkipSpacesAndLineEnd(&content, end);
            }
        } else if (currentName == "source") {
            ReadSource(currentNode);
        } else if (currentName == "joints") {
            ReadControllerJoints(currentNode, controller);
        } else if (currentName == "vertex_weights") {
            ReadControllerWeights(currentNode, controller);
        } else if (currentName == "targets") {
            for (XmlNode currentChildNode = node.first_child(); currentNode; currentNode = currentNode.next_sibling()) {
                const std::string &currentChildName = currentChildNode.name();
                if (currentChildName == "input") {
                    const char *semantics = currentChildNode.attribute("semantic").as_string();
                    const char *source = currentChildNode.attribute("source").as_string();
                    if (strcmp(semantics, "MORPH_TARGET") == 0) {
                        controller.mMorphTarget = source + 1;
                    } else if (strcmp(semantics, "MORPH_WEIGHT") == 0) {
                        controller.mMorphWeight = source + 1;
                    }
                }
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the image library contents
void ColladaParser::ReadImageLibrary(const XmlNode &node) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "image") {
            if (std::basic_string<char> id; XmlParser::getStdStrAttribute(currentNode, "id", id)) {
                mImageLibrary[id] = Image();
                // read on from there
                ReadImage(currentNode, mImageLibrary[id]);
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an image entry into the given image
void ColladaParser::ReadImage(const XmlNode &node, Collada::Image &pImage) const {
    for (XmlNode &currentNode : node.children()) {
        const std::string currentName = currentNode.name();
        if (currentName == "image") {
            // Ignore
            continue;
        } else if (currentName == "init_from") {
            if (mFormat == FV_1_4_n) {
                // FIX: C4D exporter writes empty <init_from/> tags
                if (!currentNode.empty()) {
                    // element content is filename - hopefully
                    const char *sz = currentNode.text().as_string();
                    if (nullptr != sz) {
                        aiString filepath(sz);
                        UriDecodePath(filepath);
                        pImage.mFileName = filepath.C_Str();
                    }
                }
                if (!pImage.mFileName.length()) {
                    pImage.mFileName = "unknown_texture";
                }
            } else if (mFormat == FV_1_5_n) {
                std::string value;
                XmlNode refChild = currentNode.child("ref");
                XmlNode hexChild = currentNode.child("hex");
                if (refChild) {
                    // element content is filename - hopefully
                    if (XmlParser::getValueAsString(refChild, value)) {
                        aiString filepath(value);
                        UriDecodePath(filepath);
                        pImage.mFileName = filepath.C_Str();
                    }
                } else if (hexChild && !pImage.mFileName.length()) {
                    // embedded image. get format
                    pImage.mEmbeddedFormat = hexChild.attribute("format").as_string();
                    if (pImage.mEmbeddedFormat.empty()) {
                        ASSIMP_LOG_WARN("Collada: Unknown image file format");
                    }

                    XmlParser::getValueAsString(hexChild, value);
                    const char *data = value.c_str();
                    // hexadecimal-encoded binary octets. First of all, find the
                    // required buffer size to reserve enough storage.
                    const char *cur = data;
                    while (!IsSpaceOrNewLine(*cur)) {
                        ++cur;
                    }

                    const unsigned int size = (unsigned int)(cur - data) * 2;
                    pImage.mImageData.resize(size);
                    for (unsigned int i = 0; i < size; ++i) {
                        pImage.mImageData[i] = HexOctetToDecimal(data + (i << 1));
                    }
                }
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the material library
void ColladaParser::ReadMaterialLibrary(XmlNode &node) {
    std::map<std::string, int> names;
    for (const XmlNode &currentNode : node.children()) {
        std::string id = currentNode.attribute("id").as_string();
        std::string name = currentNode.attribute("name").as_string();
        mMaterialLibrary[id] = Material();

        if (!name.empty()) {
            auto it = names.find(name);
            if (it != names.end()) {
                std::ostringstream strStream;
                strStream << ++it->second;
                name.append(" " + strStream.str());
            } else {
                names[name] = 0;
            }

            mMaterialLibrary[id].mName = name;
        }

        ReadMaterial(currentNode, mMaterialLibrary[id]);
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the light library
void ColladaParser::ReadLightLibrary(XmlNode &node) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "light") {
            std::string id;
            if (XmlParser::getStdStrAttribute(currentNode, "id", id)) {
                ReadLight(currentNode, mLightLibrary[id] = Light());
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the camera library
void ColladaParser::ReadCameraLibrary(XmlNode &node) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "camera") {
            std::string id;
            if (!XmlParser::getStdStrAttribute(currentNode, "id", id)) {
                continue;
            }

            // create an entry and store it in the library under its ID
            Camera &cam = mCameraLibrary[id];
            std::string name;
            if (!XmlParser::getStdStrAttribute(currentNode, "name", name)) {
                continue;
            }
            if (!name.empty()) {
                cam.mName = name;
            }
            ReadCamera(currentNode, cam);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the effect library
void ColladaParser::ReadEffectLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "effect") {
            // read ID. Do I have to repeat my ranting about "optional" attributes?
            std::string id;
            XmlParser::getStdStrAttribute(currentNode, "id", id);

            // create an entry and store it in the library under its ID
            mEffectLibrary[id] = Effect();

            // read on from there
            ReadEffect(currentNode, mEffectLibrary[id]);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry into the given effect
void ColladaParser::ReadEffect(XmlNode &node, Collada::Effect &pEffect) {
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "profile_COMMON") {
            ReadEffectProfileCommon(currentNode, pEffect);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an COMMON effect profile
void ColladaParser::ReadEffectProfileCommon(XmlNode &node, Collada::Effect &pEffect) {
    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string currentName = currentNode.name();
        if (currentName == "newparam") {
            // save ID
            std::string sid = currentNode.attribute("sid").as_string();
            pEffect.mParams[sid] = EffectParam();
            ReadEffectParam(currentNode, pEffect.mParams[sid]);
        } else if (currentName == "technique" || currentName == "extra") {
            // just syntactic sugar
        } else if (mFormat == FV_1_4_n && currentName == "image") {
            // read ID. Another entry which is "optional" by design but obligatory in reality
            std::string id = currentNode.attribute("id").as_string();

            // create an entry and store it in the library under its ID
            mImageLibrary[id] = Image();

            // read on from there
            ReadImage(currentNode, mImageLibrary[id]);
        } else if (currentName == "phong")
            pEffect.mShadeType = Shade_Phong;
        else if (currentName == "constant")
            pEffect.mShadeType = Shade_Constant;
        else if (currentName == "lambert")
            pEffect.mShadeType = Shade_Lambert;
        else if (currentName == "blinn")
            pEffect.mShadeType = Shade_Blinn;

        /* Color + texture properties */
        else if (currentName == "emission")
            ReadEffectColor(currentNode, pEffect.mEmissive, pEffect.mTexEmissive);
        else if (currentName == "ambient")
            ReadEffectColor(currentNode, pEffect.mAmbient, pEffect.mTexAmbient);
        else if (currentName == "diffuse")
            ReadEffectColor(currentNode, pEffect.mDiffuse, pEffect.mTexDiffuse);
        else if (currentName == "specular")
            ReadEffectColor(currentNode, pEffect.mSpecular, pEffect.mTexSpecular);
        else if (currentName == "reflective") {
            ReadEffectColor(currentNode, pEffect.mReflective, pEffect.mTexReflective);
        } else if (currentName == "transparent") {
            pEffect.mHasTransparency = true;
            const char *opaque = currentNode.attribute("opaque").as_string();
            //const char *opaque = mReader->getAttributeValueSafe("opaque");

            if (::strcmp(opaque, "RGB_ZERO") == 0 || ::strcmp(opaque, "RGB_ONE") == 0) {
                pEffect.mRGBTransparency = true;
            }

            // In RGB_ZERO mode, the transparency is interpreted in reverse, go figure...
            if (::strcmp(opaque, "RGB_ZERO") == 0 || ::strcmp(opaque, "A_ZERO") == 0) {
                pEffect.mInvertTransparency = true;
            }

            ReadEffectColor(currentNode, pEffect.mTransparent, pEffect.mTexTransparent);
        } else if (currentName == "shininess")
            ReadEffectFloat(currentNode, pEffect.mShininess);
        else if (currentName == "reflectivity")
            ReadEffectFloat(currentNode, pEffect.mReflectivity);

        /* Single scalar properties */
        else if (currentName == "transparency")
            ReadEffectFloat(currentNode, pEffect.mTransparency);
        else if (currentName == "index_of_refraction")
            ReadEffectFloat(currentNode, pEffect.mRefractIndex);

        // GOOGLEEARTH/OKINO extensions
        // -------------------------------------------------------
        else if (currentName == "double_sided")
            XmlParser::getValueAsBool(currentNode, pEffect.mDoubleSided);

        // FCOLLADA extensions
        // -------------------------------------------------------
        else if (currentName == "bump") {
            aiColor4D dummy;
            ReadEffectColor(currentNode, dummy, pEffect.mTexBump);
        }

        // MAX3D extensions
        // -------------------------------------------------------
        else if (currentName == "wireframe") {
            XmlParser::getValueAsBool(currentNode, pEffect.mWireframe);
        } else if (currentName == "faceted") {
            XmlParser::getValueAsBool(currentNode, pEffect.mFaceted);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Read texture wrapping + UV transform settings from a profile==Maya chunk
void ColladaParser::ReadSamplerProperties(XmlNode &node, Sampler &out) {
    if (node.empty()) {
        return;
    }

    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        // MAYA extensions
        // -------------------------------------------------------
        if (currentName == "wrapU") {
            XmlParser::getValueAsBool(currentNode, out.mWrapU);
        } else if (currentName == "wrapV") {
            XmlParser::getValueAsBool(currentNode, out.mWrapV);
        } else if (currentName == "mirrorU") {
            XmlParser::getValueAsBool(currentNode, out.mMirrorU);
        } else if (currentName == "mirrorV") {
            XmlParser::getValueAsBool(currentNode, out.mMirrorV);
        } else if (currentName == "repeatU") {
            XmlParser::getValueAsReal(currentNode, out.mTransform.mScaling.x);
        } else if (currentName == "repeatV") {
            XmlParser::getValueAsReal(currentNode, out.mTransform.mScaling.y);
        } else if (currentName == "offsetU") {
            XmlParser::getValueAsReal(currentNode, out.mTransform.mTranslation.x);
        } else if (currentName == "offsetV") {
            XmlParser::getValueAsReal(currentNode, out.mTransform.mTranslation.y);
        } else if (currentName == "rotateUV") {
            XmlParser::getValueAsReal(currentNode, out.mTransform.mRotation);
        } else if (currentName == "blend_mode") {
            std::string v;
            XmlParser::getValueAsString(currentNode, v);
            const char *sz = v.c_str();
            // http://www.feelingsoftware.com/content/view/55/72/lang,en/
            // NONE, OVER, IN, OUT, ADD, SUBTRACT, MULTIPLY, DIFFERENCE, LIGHTEN, DARKEN, SATURATE, DESATURATE and ILLUMINATE
            if (0 == ASSIMP_strincmp(sz, "ADD", 3))
                out.mOp = aiTextureOp_Add;
            else if (0 == ASSIMP_strincmp(sz, "SUBTRACT", 8))
                out.mOp = aiTextureOp_Subtract;
            else if (0 == ASSIMP_strincmp(sz, "MULTIPLY", 8))
                out.mOp = aiTextureOp_Multiply;
            else {
                ASSIMP_LOG_WARN("Collada: Unsupported MAYA texture blend mode");
            }
        }
        // OKINO extensions
        // -------------------------------------------------------
        else if (currentName == "weighting") {
            XmlParser::getValueAsReal(currentNode, out.mWeighting);
        } else if (currentName == "mix_with_previous_layer") {
            XmlParser::getValueAsReal(currentNode, out.mMixWithPrevious);
        }
        // MAX3D extensions
        // -------------------------------------------------------
        else if (currentName == "amount") {
            XmlParser::getValueAsReal(currentNode, out.mWeighting);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry containing a color or a texture defining that color
void ColladaParser::ReadEffectColor(XmlNode &node, aiColor4D &pColor, Sampler &pSampler) {
    if (node.empty()) {
        return;
    }

    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "color") {
            // text content contains 4 floats
            std::string v;
            XmlParser::getValueAsString(currentNode, v);
            const char *content = v.c_str();
            const char *end = v.c_str() + v.size() + 1;

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pColor.r);
            SkipSpacesAndLineEnd(&content, end);

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pColor.g);
            SkipSpacesAndLineEnd(&content, end);

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pColor.b);
            SkipSpacesAndLineEnd(&content, end);

            content = fast_atoreal_move<ai_real>(content, (ai_real &)pColor.a);
            SkipSpacesAndLineEnd(&content, end);
        } else if (currentName == "texture") {
            // get name of source texture/sampler
            XmlParser::getStdStrAttribute(currentNode, "texture", pSampler.mName);

            // get name of UV source channel. Specification demands it to be there, but some exporters
            // don't write it. It will be the default UV channel in case it's missing.
            XmlParser::getStdStrAttribute(currentNode, "texcoord", pSampler.mUVChannel);

            // as we've read texture, the color needs to be 1,1,1,1
            pColor = aiColor4D(1.f, 1.f, 1.f, 1.f);
        } else if (currentName == "technique") {
            std::string profile;
            XmlParser::getStdStrAttribute(currentNode, "profile", profile);

            // Some extensions are quite useful ... ReadSamplerProperties processes
            // several extensions in MAYA, OKINO and MAX3D profiles.
            if (!::strcmp(profile.c_str(), "MAYA") || !::strcmp(profile.c_str(), "MAX3D") || !::strcmp(profile.c_str(), "OKINO")) {
                // get more information on this sampler
                ReadSamplerProperties(currentNode, pSampler);
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry containing a float
void ColladaParser::ReadEffectFloat(XmlNode &node, ai_real &pReal) {
    pReal = 0.f;
    XmlNode floatNode = node.child("float");
    if (floatNode.empty()) {
        return;
    }
    XmlParser::getValueAsReal(floatNode, pReal);
}

// ------------------------------------------------------------------------------------------------
// Reads an effect parameter specification of any kind
void ColladaParser::ReadEffectParam(XmlNode &node, Collada::EffectParam &pParam) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "surface") {
            // image ID given inside <init_from> tags
            XmlNode initNode = currentNode.child("init_from");
            if (initNode) {
                std::string v;
                XmlParser::getValueAsString(initNode, v);
                pParam.mType = Param_Surface;
                pParam.mReference = v.c_str();
            }
        } else if (currentName == "sampler2D" && (FV_1_4_n == mFormat || FV_1_3_n == mFormat)) {
            // surface ID is given inside <source> tags
            XmlNode source = currentNode.child("source");
            if (source) {
                std::string v;
                XmlParser::getValueAsString(source, v);
                pParam.mType = Param_Sampler;
                pParam.mReference = v.c_str();
            }
        } else if (currentName == "sampler2D") {
            // surface ID is given inside <instance_image> tags
            XmlNode instance_image = currentNode.child("instance_image");
            if (instance_image) {
                std::string url;
                XmlParser::getStdStrAttribute(instance_image, "url", url);
                if (url[0] != '#') {
                    throw DeadlyImportError("Unsupported URL format in instance_image");
                }
                pParam.mType = Param_Sampler;
                pParam.mReference = url.c_str() + 1;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the geometry library contents
void ColladaParser::ReadGeometryLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "geometry") {
            // read ID. Another entry which is "optional" by design but obligatory in reality

            std::string id;
            XmlParser::getStdStrAttribute(currentNode, "id", id);
            // create a mesh and store it in the library under its (resolved) ID
            // Skip and warn if ID is not unique
            if (mMeshLibrary.find(id) == mMeshLibrary.cend()) {
                std::unique_ptr<Mesh> mesh(new Mesh(id));

                XmlParser::getStdStrAttribute(currentNode, "name", mesh->mName);

                // read on from there
                ReadGeometry(currentNode, *mesh);
                // Read successfully, add to library
                mMeshLibrary.insert({ id, mesh.release() });
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a geometry from the geometry library.
void ColladaParser::ReadGeometry(XmlNode &node, Collada::Mesh &pMesh) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "mesh") {
            ReadMesh(currentNode, pMesh);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a mesh from the geometry library
void ColladaParser::ReadMesh(XmlNode &node, Mesh &pMesh) {
    if (node.empty()) {
        return;
    }

    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "source") {
            ReadSource(currentNode);
        } else if (currentName == "vertices") {
            ReadVertexData(currentNode, pMesh);
        } else if (currentName == "triangles" || currentName == "lines" || currentName == "linestrips" ||
                   currentName == "polygons" || currentName == "polylist" || currentName == "trifans" ||
                   currentName == "tristrips") {
            ReadIndexData(currentNode, pMesh);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a source element
void ColladaParser::ReadSource(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    std::string sourceID;
    XmlParser::getStdStrAttribute(node, "id", sourceID);
    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "float_array" || currentName == "IDREF_array" || currentName == "Name_array") {
            ReadDataArray(currentNode);
        } else if (currentName == "technique_common") {
            XmlNode technique = currentNode.child("accessor");
            if (!technique.empty()) {
                ReadAccessor(technique, sourceID);
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a data array holding a number of floats, and stores it in the global library
void ColladaParser::ReadDataArray(XmlNode &node) {
    std::string name = node.name();
    bool isStringArray = (name == "IDREF_array" || name == "Name_array");

    // read attributes
    std::string id;
    XmlParser::getStdStrAttribute(node, "id", id);
    unsigned int count = 0;
    XmlParser::getUIntAttribute(node, "count", count);
    std::string v;
    XmlParser::getValueAsString(node, v);
    v = ai_trim(v);
    const char *content = v.c_str();
    const char *end = content + v.size();

    // read values and store inside an array in the data library
    mDataLibrary[id] = Data();
    Data &data = mDataLibrary[id];
    data.mIsStringArray = isStringArray;

    // some exporters write empty data arrays, but we need to conserve them anyways because others might reference them
    if (content) {
        if (isStringArray) {
            data.mStrings.reserve(count);
            std::string s;

            for (unsigned int a = 0; a < count; a++) {
                if (*content == 0) {
                    throw DeadlyImportError("Expected more values while reading IDREF_array contents.");
                }

                s.clear();
                while (!IsSpaceOrNewLine(*content)) {
                    s += *content;
                    content++;
                }
                data.mStrings.push_back(s);

                SkipSpacesAndLineEnd(&content, end);
            }
        } else {
            data.mValues.reserve(count);

            for (unsigned int a = 0; a < count; a++) {
                if (*content == 0) {
                    throw DeadlyImportError("Expected more values while reading float_array contents.");
                }

                // read a number
                ai_real value;
                content = fast_atoreal_move<ai_real>(content, value);
                data.mValues.push_back(value);
                // skip whitespace after it
                SkipSpacesAndLineEnd(&content, end);
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an accessor and stores it in the global library
void ColladaParser::ReadAccessor(XmlNode &node, const std::string &pID) {
    // read accessor attributes
    std::string source;
    XmlParser::getStdStrAttribute(node, "source", source);
    if (source[0] != '#') {
        throw DeadlyImportError("Unknown reference format in url \"", source, "\" in source attribute of <accessor> element.");
    }
    int count = 0;
    XmlParser::getIntAttribute(node, "count", count);

    unsigned int offset = 0;
    if (XmlParser::hasAttribute(node, "offset")) {
        XmlParser::getUIntAttribute(node, "offset", offset);
    }
    unsigned int stride = 1;
    if (XmlParser::hasAttribute(node, "stride")) {
        XmlParser::getUIntAttribute(node, "stride", stride);
    }
    // store in the library under the given ID
    mAccessorLibrary[pID] = Accessor();
    Accessor &acc = mAccessorLibrary[pID];
    acc.mCount = count;
    acc.mOffset = offset;
    acc.mStride = stride;
    acc.mSource = source.c_str() + 1; // ignore the leading '#'
    acc.mSize = 0; // gets incremented with every param

    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "param") {
            // read data param
            std::string name;
            if (XmlParser::hasAttribute(currentNode, "name")) {
                XmlParser::getStdStrAttribute(currentNode, "name", name);

                // analyse for common type components and store it's sub-offset in the corresponding field

                // Cartesian coordinates
                if (name == "X")
                    acc.mSubOffset[0] = acc.mParams.size();
                else if (name == "Y")
                    acc.mSubOffset[1] = acc.mParams.size();
                else if (name == "Z")
                    acc.mSubOffset[2] = acc.mParams.size();

                /* RGBA colors */
                else if (name == "R")
                    acc.mSubOffset[0] = acc.mParams.size();
                else if (name == "G")
                    acc.mSubOffset[1] = acc.mParams.size();
                else if (name == "B")
                    acc.mSubOffset[2] = acc.mParams.size();
                else if (name == "A")
                    acc.mSubOffset[3] = acc.mParams.size();

                /* UVWQ (STPQ) texture coordinates */
                else if (name == "S")
                    acc.mSubOffset[0] = acc.mParams.size();
                else if (name == "T")
                    acc.mSubOffset[1] = acc.mParams.size();
                else if (name == "P")
                    acc.mSubOffset[2] = acc.mParams.size();
                /* Generic extra data, interpreted as UV data, too*/
                else if (name == "U")
                    acc.mSubOffset[0] = acc.mParams.size();
                else if (name == "V")
                    acc.mSubOffset[1] = acc.mParams.size();
            }
            if (XmlParser::hasAttribute(currentNode, "type")) {
                // read data type
                // TODO: (thom) I don't have a spec here at work. Check if there are other multi-value types
                // which should be tested for here.
                std::string type;

                XmlParser::getStdStrAttribute(currentNode, "type", type);
                if (type == "float4x4")
                    acc.mSize += 16;
                else
                    acc.mSize += 1;
            }

            acc.mParams.push_back(name);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads input declarations of per-vertex mesh data into the given mesh
void ColladaParser::ReadVertexData(XmlNode &node, Mesh &pMesh) {
    // extract the ID of the <vertices> element. Not that we care, but to catch strange referencing schemes we should warn about
    XmlParser::getStdStrAttribute(node, "id", pMesh.mVertexID);
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "input") {
            ReadInputChannel(currentNode, pMesh.mPerVertexData);
        } else {
            throw DeadlyImportError("Unexpected sub element <", currentName, "> in tag <vertices>");
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads input declarations of per-index mesh data into the given mesh
void ColladaParser::ReadIndexData(XmlNode &node, Mesh &pMesh) {
    std::vector<size_t> vcount;
    std::vector<InputChannel> perIndexData;

    unsigned int numPrimitives = 0;
    XmlParser::getUIntAttribute(node, "count", numPrimitives);
    // read primitive count from the attribute
    //int attrCount = GetAttribute("count");
    //size_t numPrimitives = (size_t)mReader->getAttributeValueAsInt(attrCount);
    // some mesh types (e.g. tristrips) don't specify primitive count upfront,
    // so we need to sum up the actual number of primitives while we read the <p>-tags
    size_t actualPrimitives = 0;
    SubMesh subgroup;
    if (XmlParser::hasAttribute(node, "material")) {
        XmlParser::getStdStrAttribute(node, "material", subgroup.mMaterial);
    }

    // distinguish between polys and triangles
    std::string elementName = node.name();
    PrimitiveType primType = Prim_Invalid;
    if (elementName == "lines")
        primType = Prim_Lines;
    else if (elementName == "linestrips")
        primType = Prim_LineStrip;
    else if (elementName == "polygons")
        primType = Prim_Polygon;
    else if (elementName == "polylist")
        primType = Prim_Polylist;
    else if (elementName == "triangles")
        primType = Prim_Triangles;
    else if (elementName == "trifans")
        primType = Prim_TriFans;
    else if (elementName == "tristrips")
        primType = Prim_TriStrips;

    ai_assert(primType != Prim_Invalid);

    // also a number of <input> elements, but in addition a <p> primitive collection and probably index counts for all primitives
    XmlNodeIterator xmlIt(node, XmlNodeIterator::PreOrderMode);
    XmlNode currentNode;
    while (xmlIt.getNext(currentNode)) {
        const std::string &currentName = currentNode.name();
        if (currentName == "input") {
            ReadInputChannel(currentNode, perIndexData);
        } else if (currentName == "vcount") {
            if (!currentNode.empty()) {
                if (numPrimitives) // It is possible to define a mesh without any primitives
                {
                    // case <polylist> - specifies the number of indices for each polygon
                    std::string v;
                    XmlParser::getValueAsString(currentNode, v);
                    const char *content = v.c_str();
                    const char *end = content + v.size();

                    vcount.reserve(numPrimitives);
                    SkipSpacesAndLineEnd(&content, end);
                    for (unsigned int a = 0; a < numPrimitives; a++) {
                        if (*content == 0) {
                            throw DeadlyImportError("Expected more values while reading <vcount> contents.");
                        }
                        // read a number
                        vcount.push_back((size_t)strtoul10(content, &content));
                        // skip whitespace after it
                        SkipSpacesAndLineEnd(&content, end);
                    }
                }
            }
        } else if (currentName == "p") {
            if (!currentNode.empty()) {
                // now here the actual fun starts - these are the indices to construct the mesh data from
                actualPrimitives += ReadPrimitives(currentNode, pMesh, perIndexData, numPrimitives, vcount, primType);
            }
        } else if (currentName == "extra") {
            // skip
        } else if (currentName == "ph") {
            // skip
        } else {
            throw DeadlyImportError("Unexpected sub element <", currentName, "> in tag <", elementName, ">");
        }
    }

#ifdef ASSIMP_BUILD_DEBUG
    if (primType != Prim_TriFans && primType != Prim_TriStrips && primType != Prim_LineStrip &&
            primType != Prim_Lines) { // this is ONLY to workaround a bug in SketchUp 15.3.331 where it writes the wrong 'count' when it writes out the 'lines'.
        ai_assert(actualPrimitives == numPrimitives);
    }
#endif

    // only when we're done reading all <p> tags (and thus know the final vertex count) can we commit the submesh
    subgroup.mNumFaces = actualPrimitives;
    pMesh.mSubMeshes.push_back(subgroup);
}

// ------------------------------------------------------------------------------------------------
// Reads a single input channel element and stores it in the given array, if valid
void ColladaParser::ReadInputChannel(XmlNode &node, std::vector<InputChannel> &poChannels) {
    InputChannel channel;

    // read semantic
    std::string semantic;
    XmlParser::getStdStrAttribute(node, "semantic", semantic);
    channel.mType = GetTypeForSemantic(semantic);

    // read source
    std::string source;
    XmlParser::getStdStrAttribute(node, "source", source);
    if (source[0] != '#') {
        throw DeadlyImportError("Unknown reference format in url \"", source, "\" in source attribute of <input> element.");
    }
    channel.mAccessor = source.c_str() + 1; // skipping the leading #, hopefully the remaining text is the accessor ID only

    // read index offset, if per-index <input>
    if (XmlParser::hasAttribute(node, "offset")) {
        XmlParser::getUIntAttribute(node, "offset", (unsigned int &)channel.mOffset);
    }

    // read set if texture coordinates
    if (channel.mType == IT_Texcoord || channel.mType == IT_Color) {
        unsigned int attrSet = 0;
        if (XmlParser::getUIntAttribute(node, "set", attrSet))
            channel.mIndex = attrSet;
    }

    // store, if valid type
    if (channel.mType != IT_Invalid)
        poChannels.push_back(channel);
}

// ------------------------------------------------------------------------------------------------
// Reads a <p> primitive index list and assembles the mesh data into the given mesh
size_t ColladaParser::ReadPrimitives(XmlNode &node, Mesh &pMesh, std::vector<InputChannel> &pPerIndexChannels,
        size_t pNumPrimitives, const std::vector<size_t> &pVCount, PrimitiveType pPrimType) {
    // determine number of indices coming per vertex
    // find the offset index for all per-vertex channels
    size_t numOffsets = 1;
    size_t perVertexOffset = SIZE_MAX; // invalid value
    for (const InputChannel &channel : pPerIndexChannels) {
        numOffsets = std::max(numOffsets, channel.mOffset + 1);
        if (channel.mType == IT_Vertex)
            perVertexOffset = channel.mOffset;
    }

    // determine the expected number of indices
    size_t expectedPointCount = 0;
    switch (pPrimType) {
    case Prim_Polylist: {
        for (size_t i : pVCount)
            expectedPointCount += i;
        break;
    }
    case Prim_Lines:
        expectedPointCount = 2 * pNumPrimitives;
        break;
    case Prim_Triangles:
        expectedPointCount = 3 * pNumPrimitives;
        break;
    default:
        break;
    }

    // and read all indices into a temporary array
    std::vector<size_t> indices;
    if (expectedPointCount > 0) {
        indices.reserve(expectedPointCount * numOffsets);
    }

    // It is possible to not contain any indices
    if (pNumPrimitives > 0) {
        std::string v;
        XmlParser::getValueAsString(node, v);
        const char *content = v.c_str();
        const char *end = content + v.size();

        SkipSpacesAndLineEnd(&content, end);
        while (*content != 0) {
            // read a value.
            // Hack: (thom) Some exporters put negative indices sometimes. We just try to carry on anyways.
            int value = std::max(0, strtol10(content, &content));
            indices.push_back(size_t(value));
            // skip whitespace after it
            SkipSpacesAndLineEnd(&content, end);
        }
    }

    // complain if the index count doesn't fit
    if (expectedPointCount > 0 && indices.size() != expectedPointCount * numOffsets) {
        if (pPrimType == Prim_Lines) {
            // HACK: We just fix this number since SketchUp 15.3.331 writes the wrong 'count' for 'lines'
            ReportWarning("Expected different index count in <p> element, %zu instead of %zu.", indices.size(), expectedPointCount * numOffsets);
            pNumPrimitives = (indices.size() / numOffsets) / 2;
        } else {
            throw DeadlyImportError("Expected different index count in <p> element.");
        }
    } else if (expectedPointCount == 0 && (indices.size() % numOffsets) != 0) {
        throw DeadlyImportError("Expected different index count in <p> element.");
    }

    // find the data for all sources
    for (auto it = pMesh.mPerVertexData.begin(); it != pMesh.mPerVertexData.end(); ++it) {
        InputChannel &input = *it;
        if (input.mResolved) {
            continue;
        }

        // find accessor
        input.mResolved = &ResolveLibraryReference(mAccessorLibrary, input.mAccessor);
        // resolve accessor's data pointer as well, if necessary
        const Accessor *acc = input.mResolved;
        if (!acc->mData) {
            acc->mData = &ResolveLibraryReference(mDataLibrary, acc->mSource);
            const size_t dataSize = acc->mOffset + acc->mCount * acc->mStride;
            if (dataSize > acc->mData->mValues.size()) {
                throw DeadlyImportError("Not enough data for accessor");
            }
        }
    }
    // and the same for the per-index channels
    for (auto it = pPerIndexChannels.begin(); it != pPerIndexChannels.end(); ++it) {
        InputChannel &input = *it;
        if (input.mResolved) {
            continue;
        }

        // ignore vertex pointer, it doesn't refer to an accessor
        if (input.mType == IT_Vertex) {
            // warn if the vertex channel does not refer to the <vertices> element in the same mesh
            if (input.mAccessor != pMesh.mVertexID) {
                throw DeadlyImportError("Unsupported vertex referencing scheme.");
            }
            continue;
        }

        // find accessor
        input.mResolved = &ResolveLibraryReference(mAccessorLibrary, input.mAccessor);
        // resolve accessor's data pointer as well, if necessary
        const Accessor *acc = input.mResolved;
        if (!acc->mData) {
            acc->mData = &ResolveLibraryReference(mDataLibrary, acc->mSource);
            const size_t dataSize = acc->mOffset + acc->mCount * acc->mStride;
            if (dataSize > acc->mData->mValues.size()) {
                throw DeadlyImportError("Not enough data for accessor");
            }
        }
    }

    // For continued primitives, the given count does not come all in one <p>, but only one primitive per <p>
    size_t numPrimitives = pNumPrimitives;
    if (pPrimType == Prim_TriFans || pPrimType == Prim_Polygon) {
        numPrimitives = 1;
    }

    // For continued primitives, the given count is actually the number of <p>'s inside the parent tag
    if (pPrimType == Prim_TriStrips) {
        size_t numberOfVertices = indices.size() / numOffsets;
        numPrimitives = numberOfVertices - 2;
    }
    if (pPrimType == Prim_LineStrip) {
        size_t numberOfVertices = indices.size() / numOffsets;
        numPrimitives = numberOfVertices - 1;
    }

    pMesh.mFaceSize.reserve(numPrimitives);
    pMesh.mFacePosIndices.reserve(indices.size() / numOffsets);

    size_t polylistStartVertex = 0;
    for (size_t currentPrimitive = 0; currentPrimitive < numPrimitives; currentPrimitive++) {
        // determine number of points for this primitive
        size_t numPoints = 0;
        switch (pPrimType) {
        case Prim_Lines:
            numPoints = 2;
            for (size_t currentVertex = 0; currentVertex < numPoints; currentVertex++)
                CopyVertex(currentVertex, numOffsets, numPoints, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
            break;
        case Prim_LineStrip:
            numPoints = 2;
            for (size_t currentVertex = 0; currentVertex < numPoints; currentVertex++)
                CopyVertex(currentVertex, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
            break;
        case Prim_Triangles:
            numPoints = 3;
            for (size_t currentVertex = 0; currentVertex < numPoints; currentVertex++)
                CopyVertex(currentVertex, numOffsets, numPoints, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
            break;
        case Prim_TriStrips:
            numPoints = 3;
            ReadPrimTriStrips(numOffsets, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
            break;
        case Prim_Polylist:
            numPoints = pVCount[currentPrimitive];
            for (size_t currentVertex = 0; currentVertex < numPoints; currentVertex++)
                CopyVertex(polylistStartVertex + currentVertex, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, 0, indices);
            polylistStartVertex += numPoints;
            break;
        case Prim_TriFans:
        case Prim_Polygon:
            numPoints = indices.size() / numOffsets;
            for (size_t currentVertex = 0; currentVertex < numPoints; currentVertex++)
                CopyVertex(currentVertex, numOffsets, numPoints, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
            break;
        default:
            // LineStrip is not supported due to expected index unmangling
            throw DeadlyImportError("Unsupported primitive type.");
        }

        // store the face size to later reconstruct the face from
        pMesh.mFaceSize.push_back(numPoints);
    }

    // if I ever get my hands on that guy who invented this steaming pile of indirection...
    return numPrimitives;
}

///@note This function won't work correctly if both PerIndex and PerVertex channels have same channels.
///For example if TEXCOORD present in both <vertices> and <polylist> tags this function will create wrong uv coordinates.
///It's not clear from COLLADA documentation whether this is allowed or not. For now only exporter fixed to avoid such behavior
void ColladaParser::CopyVertex(size_t currentVertex, size_t numOffsets, size_t numPoints, size_t perVertexOffset, Mesh &pMesh,
        std::vector<InputChannel> &pPerIndexChannels, size_t currentPrimitive, const std::vector<size_t> &indices) {
    // calculate the base offset of the vertex whose attributes we ant to copy
    size_t baseOffset = currentPrimitive * numOffsets * numPoints + currentVertex * numOffsets;

    // don't overrun the boundaries of the index list
    ai_assert((baseOffset + numOffsets - 1) < indices.size());

    // extract per-vertex channels using the global per-vertex offset
    for (auto it = pMesh.mPerVertexData.begin(); it != pMesh.mPerVertexData.end(); ++it) {
        ExtractDataObjectFromChannel(*it, indices[baseOffset + perVertexOffset], pMesh);
    }
    // and extract per-index channels using there specified offset
    for (auto it = pPerIndexChannels.begin(); it != pPerIndexChannels.end(); ++it) {
        ExtractDataObjectFromChannel(*it, indices[baseOffset + it->mOffset], pMesh);
    }

    // store the vertex-data index for later assignment of bone vertex weights
    pMesh.mFacePosIndices.push_back(indices[baseOffset + perVertexOffset]);
}

void ColladaParser::ReadPrimTriStrips(size_t numOffsets, size_t perVertexOffset, Mesh &pMesh, std::vector<InputChannel> &pPerIndexChannels,
        size_t currentPrimitive, const std::vector<size_t> &indices) {
    if (currentPrimitive % 2 != 0) {
        //odd tristrip triangles need their indices mangled, to preserve winding direction
        CopyVertex(1, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
        CopyVertex(0, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
        CopyVertex(2, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
    } else { //for non tristrips or even tristrip triangles
        CopyVertex(0, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
        CopyVertex(1, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
        CopyVertex(2, numOffsets, 1, perVertexOffset, pMesh, pPerIndexChannels, currentPrimitive, indices);
    }
}

// ------------------------------------------------------------------------------------------------
// Extracts a single object from an input channel and stores it in the appropriate mesh data array
void ColladaParser::ExtractDataObjectFromChannel(const InputChannel &pInput, size_t pLocalIndex, Mesh &pMesh) {
    // ignore vertex referrer - we handle them that separate
    if (pInput.mType == IT_Vertex) {
        return;
    }

    const Accessor &acc = *pInput.mResolved;
    if (pLocalIndex >= acc.mCount) {
        throw DeadlyImportError("Invalid data index (", pLocalIndex, "/", acc.mCount, ") in primitive specification");
    }

    // get a pointer to the start of the data object referred to by the accessor and the local index
    const ai_real *dataObject = &(acc.mData->mValues[0]) + acc.mOffset + pLocalIndex * acc.mStride;

    // assemble according to the accessors component sub-offset list. We don't care, yet,
    // what kind of object exactly we're extracting here
    ai_real obj[4];
    for (size_t c = 0; c < 4; ++c) {
        obj[c] = dataObject[acc.mSubOffset[c]];
    }

    // now we reinterpret it according to the type we're reading here
    switch (pInput.mType) {
    case IT_Position: // ignore all position streams except 0 - there can be only one position
        if (pInput.mIndex == 0) {
            pMesh.mPositions.emplace_back(obj[0], obj[1], obj[2]);
        } else {
            ASSIMP_LOG_ERROR("Collada: just one vertex position stream supported");
        }
        break;
    case IT_Normal:
        // pad to current vertex count if necessary
        if (pMesh.mNormals.size() < pMesh.mPositions.size() - 1)
            pMesh.mNormals.insert(pMesh.mNormals.end(), pMesh.mPositions.size() - pMesh.mNormals.size() - 1, aiVector3D(0, 1, 0));

        // ignore all normal streams except 0 - there can be only one normal
        if (pInput.mIndex == 0) {
            pMesh.mNormals.emplace_back(obj[0], obj[1], obj[2]);
        } else {
            ASSIMP_LOG_ERROR("Collada: just one vertex normal stream supported");
        }
        break;
    case IT_Tangent:
        // pad to current vertex count if necessary
        if (pMesh.mTangents.size() < pMesh.mPositions.size() - 1)
            pMesh.mTangents.insert(pMesh.mTangents.end(), pMesh.mPositions.size() - pMesh.mTangents.size() - 1, aiVector3D(1, 0, 0));

        // ignore all tangent streams except 0 - there can be only one tangent
        if (pInput.mIndex == 0) {
            pMesh.mTangents.emplace_back(obj[0], obj[1], obj[2]);
        } else {
            ASSIMP_LOG_ERROR("Collada: just one vertex tangent stream supported");
        }
        break;
    case IT_Bitangent:
        // pad to current vertex count if necessary
        if (pMesh.mBitangents.size() < pMesh.mPositions.size() - 1) {
            pMesh.mBitangents.insert(pMesh.mBitangents.end(), pMesh.mPositions.size() - pMesh.mBitangents.size() - 1, aiVector3D(0, 0, 1));
        }

        // ignore all bitangent streams except 0 - there can be only one bitangent
        if (pInput.mIndex == 0) {
            pMesh.mBitangents.emplace_back(obj[0], obj[1], obj[2]);
        } else {
            ASSIMP_LOG_ERROR("Collada: just one vertex bitangent stream supported");
        }
        break;
    case IT_Texcoord:
        // up to 4 texture coord sets are fine, ignore the others
        if (pInput.mIndex < AI_MAX_NUMBER_OF_TEXTURECOORDS) {
            // pad to current vertex count if necessary
            if (pMesh.mTexCoords[pInput.mIndex].size() < pMesh.mPositions.size() - 1)
                pMesh.mTexCoords[pInput.mIndex].insert(pMesh.mTexCoords[pInput.mIndex].end(),
                        pMesh.mPositions.size() - pMesh.mTexCoords[pInput.mIndex].size() - 1, aiVector3D(0, 0, 0));

            pMesh.mTexCoords[pInput.mIndex].emplace_back(obj[0], obj[1], obj[2]);
            if (0 != acc.mSubOffset[2] || 0 != acc.mSubOffset[3]) {
                pMesh.mNumUVComponents[pInput.mIndex] = 3;
            }
        } else {
            ASSIMP_LOG_ERROR("Collada: too many texture coordinate sets. Skipping.");
        }
        break;
    case IT_Color:
        // up to 4 color sets are fine, ignore the others
        if (pInput.mIndex < AI_MAX_NUMBER_OF_COLOR_SETS) {
            // pad to current vertex count if necessary
            if (pMesh.mColors[pInput.mIndex].size() < pMesh.mPositions.size() - 1)
                pMesh.mColors[pInput.mIndex].insert(pMesh.mColors[pInput.mIndex].end(),
                        pMesh.mPositions.size() - pMesh.mColors[pInput.mIndex].size() - 1, aiColor4D(0, 0, 0, 1));

            aiColor4D result(0, 0, 0, 1);
            for (size_t i = 0; i < pInput.mResolved->mSize; ++i) {
                result[static_cast<unsigned int>(i)] = obj[pInput.mResolved->mSubOffset[i]];
            }
            pMesh.mColors[pInput.mIndex].push_back(result);
        } else {
            ASSIMP_LOG_ERROR("Collada: too many vertex color sets. Skipping.");
        }

        break;
    default:
        // IT_Invalid and IT_Vertex
        ai_assert(false && "shouldn't ever get here");
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the library of node hierarchies and scene parts
void ColladaParser::ReadSceneLibrary(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "visual_scene") {
            // read ID. Is optional according to the spec, but how on earth should a scene_instance refer to it then?
            std::string id;
            XmlParser::getStdStrAttribute(currentNode, "id", id);

            // read name if given.
            std::string attrName = "Scene";
            if (XmlParser::hasAttribute(currentNode, "name")) {
                XmlParser::getStdStrAttribute(currentNode, "name", attrName);
            }

            // create a node and store it in the library under its ID
            Node *sceneNode = new Node;
            sceneNode->mID = id;
            sceneNode->mName = attrName;
            mNodeLibrary[sceneNode->mID] = sceneNode;

            ReadSceneNode(currentNode, sceneNode);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a scene node's contents including children and stores it in the given node
void ColladaParser::ReadSceneNode(XmlNode &node, Node *pNode) {
    // quit immediately on <bla/> elements
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "node") {
            Node *child = new Node;
            if (XmlParser::hasAttribute(currentNode, "id")) {
                XmlParser::getStdStrAttribute(currentNode, "id", child->mID);
            }
            if (XmlParser::hasAttribute(currentNode, "sid")) {
                XmlParser::getStdStrAttribute(currentNode, "sid", child->mSID);
            }
            if (XmlParser::hasAttribute(currentNode, "name")) {
                XmlParser::getStdStrAttribute(currentNode, "name", child->mName);
            }
            if (pNode) {
                pNode->mChildren.push_back(child);
                child->mParent = pNode;
            } else {
                // no parent node given, probably called from <library_nodes> element.
                // create new node in node library
                mNodeLibrary[child->mID] = child;
            }

            // read on recursively from there
            ReadSceneNode(currentNode, child);
            continue;
        } else if (!pNode) {
            // For any further stuff we need a valid node to work on
            continue;
        }
        if (currentName == "lookat") {
            ReadNodeTransformation(currentNode, pNode, TF_LOOKAT);
        } else if (currentName == "matrix") {
            ReadNodeTransformation(currentNode, pNode, TF_MATRIX);
        } else if (currentName == "rotate") {
            ReadNodeTransformation(currentNode, pNode, TF_ROTATE);
        } else if (currentName == "scale") {
            ReadNodeTransformation(currentNode, pNode, TF_SCALE);
        } else if (currentName == "skew") {
            ReadNodeTransformation(currentNode, pNode, TF_SKEW);
        } else if (currentName == "translate") {
            ReadNodeTransformation(currentNode, pNode, TF_TRANSLATE);
        } else if (currentName == "render" && pNode->mParent == nullptr && 0 == pNode->mPrimaryCamera.length()) {
            // ... scene evaluation or, in other words, postprocessing pipeline,
            // or, again in other words, a turing-complete description how to
            // render a Collada scene. The only thing that is interesting for
            // us is the primary camera.
            if (XmlParser::hasAttribute(currentNode, "camera_node")) {
                std::string s;
                XmlParser::getStdStrAttribute(currentNode, "camera_node", s);
                if (s[0] != '#') {
                    ASSIMP_LOG_ERROR("Collada: Unresolved reference format of camera");
                } else {
                    pNode->mPrimaryCamera = s.c_str() + 1;
                }
            }
        } else if (currentName == "instance_node") {
            // find the node in the library
            if (XmlParser::hasAttribute(currentNode, "url")) {
                std::string s;
                XmlParser::getStdStrAttribute(currentNode, "url", s);
                if (s[0] != '#') {
                    ASSIMP_LOG_ERROR("Collada: Unresolved reference format of node");
                } else {
                    pNode->mNodeInstances.emplace_back();
                    pNode->mNodeInstances.back().mNode = s.c_str() + 1;
                }
            }
        } else if (currentName == "instance_geometry" || currentName == "instance_controller") {
            // Reference to a mesh or controller, with possible material associations
            ReadNodeGeometry(currentNode, pNode);
        } else if (currentName == "instance_light") {
            // Reference to a light, name given in 'url' attribute
            if (XmlParser::hasAttribute(currentNode, "url")) {
                std::string url;
                XmlParser::getStdStrAttribute(currentNode, "url", url);
                if (url[0] != '#') {
                    throw DeadlyImportError("Unknown reference format in <instance_light> element");
                }

                pNode->mLights.emplace_back();
                pNode->mLights.back().mLight = url.c_str() + 1;
            }
        } else if (currentName == "instance_camera") {
            // Reference to a camera, name given in 'url' attribute
            if (XmlParser::hasAttribute(currentNode, "url")) {
                std::string url;
                XmlParser::getStdStrAttribute(currentNode, "url", url);
                if (url[0] != '#') {
                    throw DeadlyImportError("Unknown reference format in <instance_camera> element");
                }
                pNode->mCameras.emplace_back();
                pNode->mCameras.back().mCamera = url.c_str() + 1;
            }
        }
    }
}


// ------------------------------------------------------------------------------------------------
// Processes bind_vertex_input and bind elements
void ColladaParser::ReadMaterialVertexInputBinding(XmlNode &node, Collada::SemanticMappingTable &tbl) {
    std::string name = node.name();
    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "bind_vertex_input") {
            Collada::InputSemanticMapEntry vn;

            // effect semantic
            if (XmlParser::hasAttribute(currentNode, "semantic")) {
                std::string s;
                XmlParser::getStdStrAttribute(currentNode, "semantic", s);
                XmlParser::getUIntAttribute(currentNode, "input_semantic", (unsigned int &)vn.mType);
            }
            std::string s;
            XmlParser::getStdStrAttribute(currentNode, "semantic", s);

            // input semantic
            XmlParser::getUIntAttribute(currentNode, "input_semantic", (unsigned int &)vn.mType);

            // index of input set
            if (XmlParser::hasAttribute(currentNode, "input_set")) {
                XmlParser::getUIntAttribute(currentNode, "input_set", vn.mSet);
            }

            tbl.mMap[s] = vn;
        } else if (currentName == "bind") {
            ASSIMP_LOG_WARN("Collada: Found unsupported <bind> element");
        }
    }
}

void ColladaParser::ReadEmbeddedTextures(ZipArchiveIOSystem &zip_archive) {
    // Attempt to load any undefined Collada::Image in ImageLibrary
    for (auto &it : mImageLibrary) {
        if (Image &image = it.second; image.mImageData.empty()) {
            std::unique_ptr<IOStream> image_file(zip_archive.Open(image.mFileName.c_str()));
            if (image_file) {
                image.mImageData.resize(image_file->FileSize());
                image_file->Read(image.mImageData.data(), image_file->FileSize(), 1);
                image.mEmbeddedFormat = BaseImporter::GetExtension(image.mFileName);
                if (image.mEmbeddedFormat == "jpeg") {
                    image.mEmbeddedFormat = "jpg";
                }
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a mesh reference in a node and adds it to the node's mesh list
void ColladaParser::ReadNodeGeometry(XmlNode &node, Node *pNode) {
    // referred mesh is given as an attribute of the <instance_geometry> element
    std::string url;
    XmlParser::getStdStrAttribute(node, "url", url);
    if (url[0] != '#') {
        throw DeadlyImportError("Unknown reference format");
    }

    Collada::MeshInstance instance;
    instance.mMeshOrController = url.c_str() + 1; // skipping the leading #

    for (XmlNode currentNode = node.first_child(); currentNode; currentNode = currentNode.next_sibling()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "bind_material") {
            XmlNode techNode = currentNode.child("technique_common");
            if (techNode) {
                for (XmlNode instanceMatNode = techNode.child("instance_material"); instanceMatNode; instanceMatNode = instanceMatNode.next_sibling())
                {
                    const std::string &instance_name = instanceMatNode.name();
                    if (instance_name == "instance_material")
                    {
                        // read ID of the geometry subgroup and the target material
                        std::string group;
                        XmlParser::getStdStrAttribute(instanceMatNode, "symbol", group);
                        XmlParser::getStdStrAttribute(instanceMatNode, "target", url);
                        const char *urlMat = url.c_str();
                        Collada::SemanticMappingTable s;
                        if (urlMat[0] == '#')
                            urlMat++;

                        s.mMatName = urlMat;
                        ReadMaterialVertexInputBinding(instanceMatNode, s);
                        // store the association
                        instance.mMaterials[group] = s;
                    }
                }
            }
        }
    }

    // store it
    pNode->mMeshes.push_back(instance);
}

// ------------------------------------------------------------------------------------------------
// Reads the collada scene
void ColladaParser::ReadScene(XmlNode &node) {
    if (node.empty()) {
        return;
    }

    for (XmlNode &currentNode : node.children()) {
        const std::string &currentName = currentNode.name();
        if (currentName == "instance_visual_scene") {
            // should be the first and only occurrence
            if (mRootNode) {
                throw DeadlyImportError("Invalid scene containing multiple root nodes in <instance_visual_scene> element");
            }

            // read the url of the scene to instance. Should be of format "#some_name"
            std::string url;
            XmlParser::getStdStrAttribute(currentNode, "url", url);
            if (url[0] != '#') {
                throw DeadlyImportError("Unknown reference format in <instance_visual_scene> element");
            }

            // find the referred scene, skip the leading #
            auto sit = mNodeLibrary.find(url.c_str() + 1);
            if (sit == mNodeLibrary.end()) {
                throw DeadlyImportError("Unable to resolve visual_scene reference \"", std::string(std::move(url)), "\" in <instance_visual_scene> element.");
            }
            mRootNode = sit->second;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Calculates the resulting transformation from all the given transform steps
aiMatrix4x4 ColladaParser::CalculateResultTransform(const std::vector<Transform> &pTransforms) const {
    aiMatrix4x4 res;

    for (std::vector<Transform>::const_iterator it = pTransforms.begin(); it != pTransforms.end(); ++it) {
        const Transform &tf = *it;
        switch (tf.mType) {
        case TF_LOOKAT: {
            aiVector3D pos(tf.f[0], tf.f[1], tf.f[2]);
            aiVector3D dstPos(tf.f[3], tf.f[4], tf.f[5]);
            aiVector3D up = aiVector3D(tf.f[6], tf.f[7], tf.f[8]).Normalize();
            aiVector3D dir = aiVector3D(dstPos - pos).Normalize();
            aiVector3D right = (dir ^ up).Normalize();

            res *= aiMatrix4x4(
                    right.x, up.x, -dir.x, pos.x,
                    right.y, up.y, -dir.y, pos.y,
                    right.z, up.z, -dir.z, pos.z,
                    0, 0, 0, 1);
            break;
        }
        case TF_ROTATE: {
            aiMatrix4x4 rot;
            ai_real angle = tf.f[3] * ai_real(AI_MATH_PI) / ai_real(180.0);
            aiVector3D axis(tf.f[0], tf.f[1], tf.f[2]);
            aiMatrix4x4::Rotation(angle, axis, rot);
            res *= rot;
            break;
        }
        case TF_TRANSLATE: {
            aiMatrix4x4 trans;
            aiMatrix4x4::Translation(aiVector3D(tf.f[0], tf.f[1], tf.f[2]), trans);
            res *= trans;
            break;
        }
        case TF_SCALE: {
            aiMatrix4x4 scale(tf.f[0], 0.0f, 0.0f, 0.0f, 0.0f, tf.f[1], 0.0f, 0.0f, 0.0f, 0.0f, tf.f[2], 0.0f,
                    0.0f, 0.0f, 0.0f, 1.0f);
            res *= scale;
            break;
        }
        case TF_SKEW:
            // TODO: (thom)
            ai_assert(false);
            break;
        case TF_MATRIX: {
            aiMatrix4x4 mat(tf.f[0], tf.f[1], tf.f[2], tf.f[3], tf.f[4], tf.f[5], tf.f[6], tf.f[7],
                    tf.f[8], tf.f[9], tf.f[10], tf.f[11], tf.f[12], tf.f[13], tf.f[14], tf.f[15]);
            res *= mat;
            break;
        }
        default:
            ai_assert(false);
            break;
        }
    }

    return res;
}

// ------------------------------------------------------------------------------------------------
// Determines the input data type for the given semantic string
InputType ColladaParser::GetTypeForSemantic(const std::string &semantic) {
    if (semantic.empty()) {
        ASSIMP_LOG_WARN("Vertex input type is empty.");
        return IT_Invalid;
    }

    if (semantic == "POSITION")
        return IT_Position;
    else if (semantic == "TEXCOORD")
        return IT_Texcoord;
    else if (semantic == "NORMAL")
        return IT_Normal;
    else if (semantic == "COLOR")
        return IT_Color;
    else if (semantic == "VERTEX")
        return IT_Vertex;
    else if (semantic == "BINORMAL" || semantic == "TEXBINORMAL")
        return IT_Bitangent;
    else if (semantic == "TANGENT" || semantic == "TEXTANGENT")
        return IT_Tangent;

    ASSIMP_LOG_WARN("Unknown vertex input type \"", semantic, "\". Ignoring.");
    return IT_Invalid;
}

#endif // !! ASSIMP_BUILD_NO_DAE_IMPORTER