/*
---------------------------------------------------------------------------
Open Asset Import Library (assimp)
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Copyright (c) 2006-2019, assimp team



All rights reserved.

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* Redistributions of source code must retain the above
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*/

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

#ifndef ASSIMP_BUILD_NO_COLLADA_IMPORTER

#include <sstream>
#include <stdarg.h>
#include "ColladaParser.h"
#include <assimp/fast_atof.h>
#include <assimp/ParsingUtils.h>
#include <assimp/StringUtils.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>
#include <assimp/light.h>
#include <assimp/TinyFormatter.h>
#include <assimp/ZipArchiveIOSystem.h>

#include <memory>

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

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
ColladaParser::ColladaParser(IOSystem* pIOHandler, const std::string& pFile)
    : mFileName(pFile)
    , mReader(nullptr)
    , mDataLibrary()
    , mAccessorLibrary()
    , mMeshLibrary()
    , mNodeLibrary()
    , mImageLibrary()
    , mEffectLibrary()
    , mMaterialLibrary()
    , mLightLibrary()
    , mCameraLibrary()
    , mControllerLibrary()
    , mRootNode(nullptr)
    , mAnims()
    , mUnitSize(1.0f)
    , mUpDirection(UP_Y)
    , mFormat(FV_1_5_n)    // We assume the newest file format by default
{
    // validate io-handler instance
    if (nullptr == pIOHandler) {
        throw DeadlyImportError("IOSystem is NULL.");
    }

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

    // Determine type
    std::string extension = BaseImporter::GetExtension(pFile);
    if (extension != "dae") {
        zip_archive.reset(new ZipArchiveIOSystem(pIOHandler, pFile));
    }

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

        if (dae_filename.empty()) {
            ThrowException(std::string("Invalid ZAE"));
        }

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

    // generate a XML reader for it
    std::unique_ptr<CIrrXML_IOStreamReader> mIOWrapper(new CIrrXML_IOStreamReader(daefile.get()));
    mReader = irr::io::createIrrXMLReader(mIOWrapper.get());
    if (!mReader) {
        ThrowException("Unable to read file, malformed XML");
    }

    // start reading
    ReadContents();

    // read embedded textures
    if (zip_archive && zip_archive->isOpen()) {
        ReadEmbeddedTextures(*zip_archive);
    }
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
ColladaParser::~ColladaParser()
{
    delete mReader;
    for (NodeLibrary::iterator it = mNodeLibrary.begin(); it != mNodeLibrary.end(); ++it)
        delete it->second;
    for (MeshLibrary::iterator it = mMeshLibrary.begin(); it != mMeshLibrary.end(); ++it)
        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 std::string();

        return file_list.front();
    }

    std::unique_ptr<CIrrXML_IOStreamReader> mIOWrapper(new CIrrXML_IOStreamReader(manifestfile.get()));
    std::unique_ptr<irr::io::IrrXMLReader> manifest_reader(irr::io::createIrrXMLReader(mIOWrapper.get()));

    while (manifest_reader->read())
    {
        // find the manifest "dae_root" element
        if (manifest_reader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (::strcmp(manifest_reader->getNodeName(), "dae_root") == 0)
            {
                if (!manifest_reader->read())
                    return std::string();
                if (manifest_reader->getNodeType() != irr::io::EXN_TEXT && manifest_reader->getNodeType() != irr::io::EXN_CDATA)
                    return std::string();

                const char* filepath = manifest_reader->getNodeData();
                if (filepath == nullptr)
                    return std::string();

                return std::string(filepath);
            }
        }
    }
    return std::string();
}

// ------------------------------------------------------------------------------------------------
// Read bool from text contents of current element
bool ColladaParser::ReadBoolFromTextContent()
{
    const char* cur = GetTextContent();
    return (!ASSIMP_strincmp(cur, "true", 4) || '0' != *cur);
}

// ------------------------------------------------------------------------------------------------
// Read float from text contents of current element
ai_real ColladaParser::ReadFloatFromTextContent()
{
    const char* cur = GetTextContent();
    return fast_atof(cur);
}

// ------------------------------------------------------------------------------------------------
// Reads the contents of the file
void ColladaParser::ReadContents()
{
    while (mReader->read())
    {
        // handle the root element "COLLADA"
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("COLLADA"))
            {
                // check for 'version' attribute
                const int attrib = TestAttribute("version");
                if (attrib != -1) {
                    const char* version = mReader->getAttributeValue(attrib);

                    if (!::strncmp(version, "1.5", 3)) {
                        mFormat = FV_1_5_n;
                        ASSIMP_LOG_DEBUG("Collada schema version is 1.5.n");
                    }
                    else if (!::strncmp(version, "1.4", 3)) {
                        mFormat = FV_1_4_n;
                        ASSIMP_LOG_DEBUG("Collada schema version is 1.4.n");
                    }
                    else if (!::strncmp(version, "1.3", 3)) {
                        mFormat = FV_1_3_n;
                        ASSIMP_LOG_DEBUG("Collada schema version is 1.3.n");
                    }
                }

                ReadStructure();
            }
            else
            {
                ASSIMP_LOG_DEBUG_F("Ignoring global element <", mReader->getNodeName(), ">.");
                SkipElement();
            }
        }
        else
        {
            // skip everything else silently
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the structure of the file
void ColladaParser::ReadStructure()
{
    while (mReader->read())
    {
        // beginning of elements
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("asset"))
                ReadAssetInfo();
            else if (IsElement("library_animations"))
                ReadAnimationLibrary();
            else if (IsElement("library_animation_clips"))
                ReadAnimationClipLibrary();
            else if (IsElement("library_controllers"))
                ReadControllerLibrary();
            else if (IsElement("library_images"))
                ReadImageLibrary();
            else if (IsElement("library_materials"))
                ReadMaterialLibrary();
            else if (IsElement("library_effects"))
                ReadEffectLibrary();
            else if (IsElement("library_geometries"))
                ReadGeometryLibrary();
            else if (IsElement("library_visual_scenes"))
                ReadSceneLibrary();
            else if (IsElement("library_lights"))
                ReadLightLibrary();
            else if (IsElement("library_cameras"))
                ReadCameraLibrary();
            else if (IsElement("library_nodes"))
                ReadSceneNode(NULL); /* some hacking to reuse this piece of code */
            else if (IsElement("scene"))
                ReadScene();
            else
                SkipElement();
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            break;
        }
    }

    PostProcessRootAnimations();
    PostProcessControllers();
}

// ------------------------------------------------------------------------------------------------
// Reads asset information such as coordinate system information and legal blah
void ColladaParser::ReadAssetInfo()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("unit"))
            {
                // read unit data from the element's attributes
                const int attrIndex = TestAttribute("meter");
                if (attrIndex == -1) {
                    mUnitSize = 1.f;
                }
                else {
                    mUnitSize = mReader->getAttributeValueAsFloat(attrIndex);
                }

                // consume the trailing stuff
                if (!mReader->isEmptyElement())
                    SkipElement();
            }
            else if (IsElement("up_axis"))
            {
                // read content, strip whitespace, compare
                const char* content = GetTextContent();
                if (strncmp(content, "X_UP", 4) == 0)
                    mUpDirection = UP_X;
                else if (strncmp(content, "Z_UP", 4) == 0)
                    mUpDirection = UP_Z;
                else
                    mUpDirection = UP_Y;

                // check element end
                TestClosing("up_axis");
            }
            else if (IsElement("contributor"))
            {
                ReadContributorInfo();
            }
            else
            {
                ReadMetaDataItem(mAssetMetaData);
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "asset") != 0)
                ThrowException("Expected end of <asset> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the contributor info
void ColladaParser::ReadContributorInfo()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            ReadMetaDataItem(mAssetMetaData);
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "contributor") != 0)
                ThrowException("Expected end of <contributor> element.");
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a single string metadata item
void ColladaParser::ReadMetaDataItem(StringMetaData &metadata)
{
    // Metadata such as created, keywords, subject etc
    const char* key_char = mReader->getNodeName();
    if (key_char != nullptr)
    {
        const std::string key_str(key_char);
        const char* value_char = TestTextContent();
        if (value_char != nullptr)
        {
            std::string camel_key_str = key_str;
            ToCamelCase(camel_key_str);
            aiString aistr;
            aistr.Set(value_char);
            metadata.emplace(camel_key_str, aistr);
        }
        TestClosing(key_str.c_str());
    }
    else
        SkipElement();
}

// ------------------------------------------------------------------------------------------------
// Convert underscore_seperated to CamelCase: "authoring_tool" becomes "AuthoringTool"
void ColladaParser::ToCamelCase(std::string &text)
{
    if (text.empty())
        return;
    // Capitalise first character
    text[0] = ToUpper(text[0]);
    for (auto it = text.begin(); it != text.end(); /*iterated below*/)
    {
        if ((*it) == '_')
        {
            it = text.erase(it);
            if (it != text.end())
                (*it) = ToUpper(*it);
        }
        else
            ++it;
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the animation clips
void ColladaParser::ReadAnimationClipLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("animation_clip"))
            {
                // optional name given as an attribute
                std::string animName;
                int indexName = TestAttribute("name");
                int indexID = TestAttribute("id");
                if (indexName >= 0)
                    animName = mReader->getAttributeValue(indexName);
                else if (indexID >= 0)
                    animName = mReader->getAttributeValue(indexID);
                else
                    animName = std::string("animation_") + to_string(mAnimationClipLibrary.size());

                std::pair<std::string, std::vector<std::string> > clip;

                clip.first = animName;

                while (mReader->read())
                {
                    if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
                    {
                        if (IsElement("instance_animation"))
                        {
                            int indexUrl = TestAttribute("url");
                            if (indexUrl >= 0)
                            {
                                const char* url = mReader->getAttributeValue(indexUrl);
                                if (url[0] != '#')
                                    ThrowException("Unknown reference format");

                                url++;

                                clip.second.push_back(url);
                            }
                        }
                        else
                        {
                            // ignore the rest
                            SkipElement();
                        }
                    }
                    else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
                    {
                        if (strcmp(mReader->getNodeName(), "animation_clip") != 0)
                            ThrowException("Expected end of <animation_clip> element.");

                        break;
                    }
                }

                if (clip.second.size() > 0)
                {
                    mAnimationClipLibrary.push_back(clip);
                }
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_animation_clips") != 0)
                ThrowException("Expected end of <library_animation_clips> element.");

            break;
        }
    }
}

void ColladaParser::PostProcessControllers()
{
    std::string meshId;
    for (ControllerLibrary::iterator it = mControllerLibrary.begin(); it != mControllerLibrary.end(); ++it) {
        meshId = it->second.mMeshId;
        ControllerLibrary::iterator 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.size() > 0)
    {
        Animation temp;

        for (AnimationClipLibrary::iterator it = mAnimationClipLibrary.begin(); it != mAnimationClipLibrary.end(); ++it)
        {
            std::string clipName = it->first;

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

            temp.mSubAnims.push_back(clip);

            for (std::vector<std::string>::iterator a = it->second.begin(); a != it->second.end(); ++a)
            {
                std::string animationID = *a;

                AnimationLibrary::iterator 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();
    }
    else
    {
        mAnims.CombineSingleChannelAnimations();
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the animation library
void ColladaParser::ReadAnimationLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("animation"))
            {
                // delegate the reading. Depending on the inner elements it will be a container or a anim channel
                ReadAnimation(&mAnims);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_animations") != 0)
                ThrowException("Expected end of <library_animations> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an animation into the given parent structure
void ColladaParser::ReadAnimation(Collada::Animation* pParent)
{
    if (mReader->isEmptyElement())
        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
    typedef std::map<std::string, AnimationChannel> ChannelMap;
    ChannelMap channels;
    // this is the anim container in case we're a container
    Animation* anim = NULL;

    // optional name given as an attribute
    std::string animName;
    std::string animID;
    int indexName = TestAttribute("name");
    int indexID = TestAttribute("id");

    if (indexID >= 0)
        animID = mReader->getAttributeValue(indexID);

    if (indexName >= 0)
        animName = mReader->getAttributeValue(indexName);
    else if (indexID >= 0)
        animName = animID;
    else
        animName = "animation";

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            // we have subanimations
            if (IsElement("animation"))
            {
                // create container from our element
                if (!anim)
                {
                    anim = new Animation;
                    anim->mName = animName;
                    pParent->mSubAnims.push_back(anim);
                }

                // recurse into the subelement
                ReadAnimation(anim);
            }
            else if (IsElement("source"))
            {
                // possible animation data - we'll never know. Better store it
                ReadSource();
            }
            else if (IsElement("sampler"))
            {
                // read the ID to assign the corresponding collada channel afterwards.
                int indexID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(indexID);
                ChannelMap::iterator newChannel = channels.insert(std::make_pair(id, AnimationChannel())).first;

                // have it read into a channel
                ReadAnimationSampler(newChannel->second);
            }
            else if (IsElement("channel"))
            {
                // the binding element whose whole purpose is to provide the target to animate
                // Thanks, Collada! A directly posted information would have been too simple, I guess.
                // Better add another indirection to that! Can't have enough of those.
                int indexTarget = GetAttribute("target");
                int indexSource = GetAttribute("source");
                const char* sourceId = mReader->getAttributeValue(indexSource);
                if (sourceId[0] == '#')
                    sourceId++;
                ChannelMap::iterator cit = channels.find(sourceId);
                if (cit != channels.end())
                    cit->second.mTarget = mReader->getAttributeValue(indexTarget);

                if (!mReader->isEmptyElement())
                    SkipElement();
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "animation") != 0)
                ThrowException("Expected end of <animation> element.");

            break;
        }
    }

    // it turned out to have channels - add them
    if (!channels.empty())
    {
        // FIXME: Is this essentially doing the same as "single-anim-node" codepath in
        //        ColladaLoader::StoreAnimations? For now, this has been deferred to after
        //        all animations and all clips have been read. Due to handling of
        //        <library_animation_clips> this cannot be done here, as the channel owner
        //        is lost, and some exporters make up animations by referring to multiple
        //        single-channel animations from an <instance_animation>.
/*
        // special filtering for stupid exporters packing each channel into a separate animation
        if( channels.size() == 1)
        {
            pParent->mChannels.push_back( channels.begin()->second);
        } else
*/
        {
            // else create the animation, if not done yet, and store the channels
            if (!anim)
            {
                anim = new Animation;
                anim->mName = animName;
                pParent->mSubAnims.push_back(anim);
            }
            for (ChannelMap::const_iterator it = channels.begin(); it != channels.end(); ++it)
                anim->mChannels.push_back(it->second);

            if (indexID >= 0)
            {
                mAnimationLibrary[animID] = anim;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an animation sampler into the given anim channel
void ColladaParser::ReadAnimationSampler(Collada::AnimationChannel& pChannel)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("input"))
            {
                int indexSemantic = GetAttribute("semantic");
                const char* semantic = mReader->getAttributeValue(indexSemantic);
                int indexSource = GetAttribute("source");
                const char* source = mReader->getAttributeValue(indexSource);
                if (source[0] != '#')
                    ThrowException("Unsupported URL format");
                source++;

                if (strcmp(semantic, "INPUT") == 0)
                    pChannel.mSourceTimes = source;
                else if (strcmp(semantic, "OUTPUT") == 0)
                    pChannel.mSourceValues = source;
                else if (strcmp(semantic, "IN_TANGENT") == 0)
                    pChannel.mInTanValues = source;
                else if (strcmp(semantic, "OUT_TANGENT") == 0)
                    pChannel.mOutTanValues = source;
                else if (strcmp(semantic, "INTERPOLATION") == 0)
                    pChannel.mInterpolationValues = source;

                if (!mReader->isEmptyElement())
                    SkipElement();
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "sampler") != 0)
                ThrowException("Expected end of <sampler> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the skeleton controller library
void ColladaParser::ReadControllerLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("controller"))
            {
                // read ID. Ask the spec if it's necessary or optional... you might be surprised.
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

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

                // read on from there
                ReadController(mControllerLibrary[id]);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_controllers") != 0)
                ThrowException("Expected end of <library_controllers> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a controller into the given mesh structure
void ColladaParser::ReadController(Collada::Controller& pController)
{
    // initial values
    pController.mType = Skin;
    pController.mMethod = Normalized;
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            // two types of controllers: "skin" and "morph". Only the first one is relevant, we skip the other
            if (IsElement("morph"))
            {
                pController.mType = Morph;
                int baseIndex = GetAttribute("source");
                pController.mMeshId = mReader->getAttributeValue(baseIndex) + 1;
                int methodIndex = GetAttribute("method");
                if (methodIndex > 0) {
                    const char *method = mReader->getAttributeValue(methodIndex);
                    if (strcmp(method, "RELATIVE") == 0)
                        pController.mMethod = Relative;
                }
            }
            else if (IsElement("skin"))
            {
                // read the mesh it refers to. According to the spec this could also be another
                // controller, but I refuse to implement every single idea they've come up with
                int sourceIndex = GetAttribute("source");
                pController.mMeshId = mReader->getAttributeValue(sourceIndex) + 1;
            }
            else if (IsElement("bind_shape_matrix"))
            {
                // content is 16 floats to define a matrix... it seems to be important for some models
                const char* content = GetTextContent();

                // read the 16 floats
                for (unsigned int a = 0; a < 16; a++)
                {
                    // read a number
                    content = fast_atoreal_move<ai_real>(content, pController.mBindShapeMatrix[a]);
                    // skip whitespace after it
                    SkipSpacesAndLineEnd(&content);
                }

                TestClosing("bind_shape_matrix");
            }
            else if (IsElement("source"))
            {
                // data array - we have specialists to handle this
                ReadSource();
            }
            else if (IsElement("joints"))
            {
                ReadControllerJoints(pController);
            }
            else if (IsElement("vertex_weights"))
            {
                ReadControllerWeights(pController);
            }
            else if (IsElement("targets"))
            {
                while (mReader->read()) {
                    if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
                        if (IsElement("input")) {
                            int semanticsIndex = GetAttribute("semantic");
                            int sourceIndex = GetAttribute("source");

                            const char *semantics = mReader->getAttributeValue(semanticsIndex);
                            const char *source = mReader->getAttributeValue(sourceIndex);
                            if (strcmp(semantics, "MORPH_TARGET") == 0) {
                                pController.mMorphTarget = source + 1;
                            }
                            else if (strcmp(semantics, "MORPH_WEIGHT") == 0)
                            {
                                pController.mMorphWeight = source + 1;
                            }
                        }
                    }
                    else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
                        if (strcmp(mReader->getNodeName(), "targets") == 0)
                            break;
                        else
                            ThrowException("Expected end of <targets> element.");
                    }
                }
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "controller") == 0)
                break;
            else if (strcmp(mReader->getNodeName(), "skin") != 0 && strcmp(mReader->getNodeName(), "morph") != 0)
                ThrowException("Expected end of <controller> element.");
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the joint definitions for the given controller
void ColladaParser::ReadControllerJoints(Collada::Controller& pController)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            // Input channels for joint data. Two possible semantics: "JOINT" and "INV_BIND_MATRIX"
            if (IsElement("input"))
            {
                int indexSemantic = GetAttribute("semantic");
                const char* attrSemantic = mReader->getAttributeValue(indexSemantic);
                int indexSource = GetAttribute("source");
                const char* attrSource = mReader->getAttributeValue(indexSource);

                // local URLS always start with a '#'. We don't support global URLs
                if (attrSource[0] != '#')
                    ThrowException(format() << "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
                    ThrowException(format() << "Unknown semantic \"" << attrSemantic << "\" in <joints> data <input> element");

                // skip inner data, if present
                if (!mReader->isEmptyElement())
                    SkipElement();
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "joints") != 0)
                ThrowException("Expected end of <joints> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the joint weights for the given controller
void ColladaParser::ReadControllerWeights(Collada::Controller& pController)
{
    // read vertex count from attributes and resize the array accordingly
    int indexCount = GetAttribute("count");
    size_t vertexCount = (size_t)mReader->getAttributeValueAsInt(indexCount);
    pController.mWeightCounts.resize(vertexCount);

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            // Input channels for weight data. Two possible semantics: "JOINT" and "WEIGHT"
            if (IsElement("input") && vertexCount > 0)
            {
                InputChannel channel;

                int indexSemantic = GetAttribute("semantic");
                const char* attrSemantic = mReader->getAttributeValue(indexSemantic);
                int indexSource = GetAttribute("source");
                const char* attrSource = mReader->getAttributeValue(indexSource);
                int indexOffset = TestAttribute("offset");
                if (indexOffset >= 0)
                    channel.mOffset = mReader->getAttributeValueAsInt(indexOffset);

                // local URLS always start with a '#'. We don't support global URLs
                if (attrSource[0] != '#')
                    ThrowException(format() << "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
                    ThrowException(format() << "Unknown semantic \"" << attrSemantic << "\" in <vertex_weights> data <input> element");

                // skip inner data, if present
                if (!mReader->isEmptyElement())
                    SkipElement();
            }
            else if (IsElement("vcount") && vertexCount > 0)
            {
                // read weight count per vertex
                const char* text = GetTextContent();
                size_t numWeights = 0;
                for (std::vector<size_t>::iterator it = pController.mWeightCounts.begin(); it != pController.mWeightCounts.end(); ++it)
                {
                    if (*text == 0)
                        ThrowException("Out of data while reading <vcount>");

                    *it = strtoul10(text, &text);
                    numWeights += *it;
                    SkipSpacesAndLineEnd(&text);
                }

                TestClosing("vcount");

                // reserve weight count
                pController.mWeights.resize(numWeights);
            }
            else if (IsElement("v") && vertexCount > 0)
            {
                // read JointIndex - WeightIndex pairs
                const char* text = GetTextContent();

                for (std::vector< std::pair<size_t, size_t> >::iterator it = pController.mWeights.begin(); it != pController.mWeights.end(); ++it)
                {
                    if (*text == 0)
                        ThrowException("Out of data while reading <vertex_weights>");
                    it->first = strtoul10(text, &text);
                    SkipSpacesAndLineEnd(&text);
                    if (*text == 0)
                        ThrowException("Out of data while reading <vertex_weights>");
                    it->second = strtoul10(text, &text);
                    SkipSpacesAndLineEnd(&text);
                }

                TestClosing("v");
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "vertex_weights") != 0)
                ThrowException("Expected end of <vertex_weights> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the image library contents
void ColladaParser::ReadImageLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("image"))
            {
                // read ID. Another entry which is "optional" by design but obligatory in reality
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

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

                // read on from there
                ReadImage(mImageLibrary[id]);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "library_images") != 0)
                ThrowException("Expected end of <library_images> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an image entry into the given image
void ColladaParser::ReadImage(Collada::Image& pImage)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            // Need to run different code paths here, depending on the Collada XSD version
            if (IsElement("image")) {
                SkipElement();
            }
            else if (IsElement("init_from"))
            {
                if (mFormat == FV_1_4_n)
                {
                    // FIX: C4D exporter writes empty <init_from/> tags
                    if (!mReader->isEmptyElement()) {
                        // element content is filename - hopefully
                        const char* sz = TestTextContent();
                        if (sz)pImage.mFileName = sz;
                        TestClosing("init_from");
                    }
                    if (!pImage.mFileName.length()) {
                        pImage.mFileName = "unknown_texture";
                    }
                }
                else if (mFormat == FV_1_5_n)
                {
                    // make sure we skip over mip and array initializations, which
                    // we don't support, but which could confuse the loader if
                    // they're not skipped.
                    int attrib = TestAttribute("array_index");
                    if (attrib != -1 && mReader->getAttributeValueAsInt(attrib) > 0) {
                        ASSIMP_LOG_WARN("Collada: Ignoring texture array index");
                        continue;
                    }

                    attrib = TestAttribute("mip_index");
                    if (attrib != -1 && mReader->getAttributeValueAsInt(attrib) > 0) {
                        ASSIMP_LOG_WARN("Collada: Ignoring MIP map layer");
                        continue;
                    }

                    // TODO: correctly jump over cube and volume maps?
                }
            }
            else if (mFormat == FV_1_5_n)
            {
                if (IsElement("ref"))
                {
                    // element content is filename - hopefully
                    const char* sz = TestTextContent();
                    if (sz)pImage.mFileName = sz;
                    TestClosing("ref");
                }
                else if (IsElement("hex") && !pImage.mFileName.length())
                {
                    // embedded image. get format
                    const int attrib = TestAttribute("format");
                    if (-1 == attrib)
                        ASSIMP_LOG_WARN("Collada: Unknown image file format");
                    else pImage.mEmbeddedFormat = mReader->getAttributeValue(attrib);

                    const char* data = GetTextContent();

                    // 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));

                    TestClosing("hex");
                }
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "image") == 0)
                break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the material library
void ColladaParser::ReadMaterialLibrary()
{
    if (mReader->isEmptyElement())
        return;

    std::map<std::string, int> names;
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("material"))
            {
                // read ID. By now you probably know my opinion about this "specification"
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

                std::string name;
                int attrName = TestAttribute("name");
                if (attrName >= 0)
                    name = mReader->getAttributeValue(attrName);

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

                if (!name.empty())
                {
                    std::map<std::string, int>::iterator 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(mMaterialLibrary[id]);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_materials") != 0)
                ThrowException("Expected end of <library_materials> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the light library
void ColladaParser::ReadLightLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("light"))
            {
                // read ID. By now you probably know my opinion about this "specification"
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

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

            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "library_lights") != 0)
                ThrowException("Expected end of <library_lights> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the camera library
void ColladaParser::ReadCameraLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("camera"))
            {
                // read ID. By now you probably know my opinion about this "specification"
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

                // create an entry and store it in the library under its ID
                Camera& cam = mCameraLibrary[id];
                attrID = TestAttribute("name");
                if (attrID != -1)
                    cam.mName = mReader->getAttributeValue(attrID);

                ReadCamera(cam);

            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "library_cameras") != 0)
                ThrowException("Expected end of <library_cameras> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a material entry into the given material
void ColladaParser::ReadMaterial(Collada::Material& pMaterial)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("material")) {
                SkipElement();
            }
            else if (IsElement("instance_effect"))
            {
                // referred effect by URL
                int attrUrl = GetAttribute("url");
                const char* url = mReader->getAttributeValue(attrUrl);
                if (url[0] != '#')
                    ThrowException("Unknown reference format");

                pMaterial.mEffect = url + 1;

                SkipElement();
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "material") != 0)
                ThrowException("Expected end of <material> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a light entry into the given light
void ColladaParser::ReadLight(Collada::Light& pLight)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("light")) {
                SkipElement();
            }
            else if (IsElement("spot")) {
                pLight.mType = aiLightSource_SPOT;
            }
            else if (IsElement("ambient")) {
                pLight.mType = aiLightSource_AMBIENT;
            }
            else if (IsElement("directional")) {
                pLight.mType = aiLightSource_DIRECTIONAL;
            }
            else if (IsElement("point")) {
                pLight.mType = aiLightSource_POINT;
            }
            else if (IsElement("color")) {
                // text content contains 3 floats
                const char* content = GetTextContent();

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

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

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

                TestClosing("color");
            }
            else if (IsElement("constant_attenuation")) {
                pLight.mAttConstant = ReadFloatFromTextContent();
                TestClosing("constant_attenuation");
            }
            else if (IsElement("linear_attenuation")) {
                pLight.mAttLinear = ReadFloatFromTextContent();
                TestClosing("linear_attenuation");
            }
            else if (IsElement("quadratic_attenuation")) {
                pLight.mAttQuadratic = ReadFloatFromTextContent();
                TestClosing("quadratic_attenuation");
            }
            else if (IsElement("falloff_angle")) {
                pLight.mFalloffAngle = ReadFloatFromTextContent();
                TestClosing("falloff_angle");
            }
            else if (IsElement("falloff_exponent")) {
                pLight.mFalloffExponent = ReadFloatFromTextContent();
                TestClosing("falloff_exponent");
            }
            // FCOLLADA extensions
            // -------------------------------------------------------
            else if (IsElement("outer_cone")) {
                pLight.mOuterAngle = ReadFloatFromTextContent();
                TestClosing("outer_cone");
            }
            // ... and this one is even deprecated
            else if (IsElement("penumbra_angle")) {
                pLight.mPenumbraAngle = ReadFloatFromTextContent();
                TestClosing("penumbra_angle");
            }
            else if (IsElement("intensity")) {
                pLight.mIntensity = ReadFloatFromTextContent();
                TestClosing("intensity");
            }
            else if (IsElement("falloff")) {
                pLight.mOuterAngle = ReadFloatFromTextContent();
                TestClosing("falloff");
            }
            else if (IsElement("hotspot_beam")) {
                pLight.mFalloffAngle = ReadFloatFromTextContent();
                TestClosing("hotspot_beam");
            }
            // OpenCOLLADA extensions
            // -------------------------------------------------------
            else if (IsElement("decay_falloff")) {
                pLight.mOuterAngle = ReadFloatFromTextContent();
                TestClosing("decay_falloff");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "light") == 0)
                break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a camera entry into the given light
void ColladaParser::ReadCamera(Collada::Camera& pCamera)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("camera")) {
                SkipElement();
            }
            else if (IsElement("orthographic")) {
                pCamera.mOrtho = true;
            }
            else if (IsElement("xfov") || IsElement("xmag")) {
                pCamera.mHorFov = ReadFloatFromTextContent();
                TestClosing((pCamera.mOrtho ? "xmag" : "xfov"));
            }
            else if (IsElement("yfov") || IsElement("ymag")) {
                pCamera.mVerFov = ReadFloatFromTextContent();
                TestClosing((pCamera.mOrtho ? "ymag" : "yfov"));
            }
            else if (IsElement("aspect_ratio")) {
                pCamera.mAspect = ReadFloatFromTextContent();
                TestClosing("aspect_ratio");
            }
            else if (IsElement("znear")) {
                pCamera.mZNear = ReadFloatFromTextContent();
                TestClosing("znear");
            }
            else if (IsElement("zfar")) {
                pCamera.mZFar = ReadFloatFromTextContent();
                TestClosing("zfar");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "camera") == 0)
                break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the effect library
void ColladaParser::ReadEffectLibrary()
{
    if (mReader->isEmptyElement()) {
        return;
    }

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("effect"))
            {
                // read ID. Do I have to repeat my ranting about "optional" attributes?
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

                // create an entry and store it in the library under its ID
                mEffectLibrary[id] = Effect();
                // read on from there
                ReadEffect(mEffectLibrary[id]);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "library_effects") != 0)
                ThrowException("Expected end of <library_effects> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry into the given effect
void ColladaParser::ReadEffect(Collada::Effect& pEffect)
{
    // for the moment we don't support any other type of effect.
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("profile_COMMON"))
                ReadEffectProfileCommon(pEffect);
            else
                SkipElement();
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "effect") != 0)
                ThrowException("Expected end of <effect> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an COMMON effect profile
void ColladaParser::ReadEffectProfileCommon(Collada::Effect& pEffect)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("newparam")) {
                // save ID
                int attrSID = GetAttribute("sid");
                std::string sid = mReader->getAttributeValue(attrSID);
                pEffect.mParams[sid] = EffectParam();
                ReadEffectParam(pEffect.mParams[sid]);
            }
            else if (IsElement("technique") || IsElement("extra"))
            {
                // just syntactic sugar
            }

            else if (mFormat == FV_1_4_n && IsElement("image"))
            {
                // read ID. Another entry which is "optional" by design but obligatory in reality
                int attrID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(attrID);

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

                // read on from there
                ReadImage(mImageLibrary[id]);
            }

            /* Shading modes */
            else if (IsElement("phong"))
                pEffect.mShadeType = Shade_Phong;
            else if (IsElement("constant"))
                pEffect.mShadeType = Shade_Constant;
            else if (IsElement("lambert"))
                pEffect.mShadeType = Shade_Lambert;
            else if (IsElement("blinn"))
                pEffect.mShadeType = Shade_Blinn;

            /* Color + texture properties */
            else if (IsElement("emission"))
                ReadEffectColor(pEffect.mEmissive, pEffect.mTexEmissive);
            else if (IsElement("ambient"))
                ReadEffectColor(pEffect.mAmbient, pEffect.mTexAmbient);
            else if (IsElement("diffuse"))
                ReadEffectColor(pEffect.mDiffuse, pEffect.mTexDiffuse);
            else if (IsElement("specular"))
                ReadEffectColor(pEffect.mSpecular, pEffect.mTexSpecular);
            else if (IsElement("reflective")) {
                ReadEffectColor(pEffect.mReflective, pEffect.mTexReflective);
            }
            else if (IsElement("transparent")) {
                pEffect.mHasTransparency = true;

                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(pEffect.mTransparent, pEffect.mTexTransparent);
            }
            else if (IsElement("shininess"))
                ReadEffectFloat(pEffect.mShininess);
            else if (IsElement("reflectivity"))
                ReadEffectFloat(pEffect.mReflectivity);

            /* Single scalar properties */
            else if (IsElement("transparency"))
                ReadEffectFloat(pEffect.mTransparency);
            else if (IsElement("index_of_refraction"))
                ReadEffectFloat(pEffect.mRefractIndex);

            // GOOGLEEARTH/OKINO extensions
            // -------------------------------------------------------
            else if (IsElement("double_sided"))
                pEffect.mDoubleSided = ReadBoolFromTextContent();

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

            // MAX3D extensions
            // -------------------------------------------------------
            else if (IsElement("wireframe")) {
                pEffect.mWireframe = ReadBoolFromTextContent();
                TestClosing("wireframe");
            }
            else if (IsElement("faceted")) {
                pEffect.mFaceted = ReadBoolFromTextContent();
                TestClosing("faceted");
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "profile_COMMON") == 0)
            {
                break;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Read texture wrapping + UV transform settings from a profile==Maya chunk
void ColladaParser::ReadSamplerProperties(Sampler& out)
{
    if (mReader->isEmptyElement()) {
        return;
    }

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {

            // MAYA extensions
            // -------------------------------------------------------
            if (IsElement("wrapU")) {
                out.mWrapU = ReadBoolFromTextContent();
                TestClosing("wrapU");
            }
            else if (IsElement("wrapV")) {
                out.mWrapV = ReadBoolFromTextContent();
                TestClosing("wrapV");
            }
            else if (IsElement("mirrorU")) {
                out.mMirrorU = ReadBoolFromTextContent();
                TestClosing("mirrorU");
            }
            else if (IsElement("mirrorV")) {
                out.mMirrorV = ReadBoolFromTextContent();
                TestClosing("mirrorV");
            }
            else if (IsElement("repeatU")) {
                out.mTransform.mScaling.x = ReadFloatFromTextContent();
                TestClosing("repeatU");
            }
            else if (IsElement("repeatV")) {
                out.mTransform.mScaling.y = ReadFloatFromTextContent();
                TestClosing("repeatV");
            }
            else if (IsElement("offsetU")) {
                out.mTransform.mTranslation.x = ReadFloatFromTextContent();
                TestClosing("offsetU");
            }
            else if (IsElement("offsetV")) {
                out.mTransform.mTranslation.y = ReadFloatFromTextContent();
                TestClosing("offsetV");
            }
            else if (IsElement("rotateUV")) {
                out.mTransform.mRotation = ReadFloatFromTextContent();
                TestClosing("rotateUV");
            }
            else if (IsElement("blend_mode")) {

                const char* sz = GetTextContent();
                // 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");
                }
                TestClosing("blend_mode");
            }
            // OKINO extensions
            // -------------------------------------------------------
            else if (IsElement("weighting")) {
                out.mWeighting = ReadFloatFromTextContent();
                TestClosing("weighting");
            }
            else if (IsElement("mix_with_previous_layer")) {
                out.mMixWithPrevious = ReadFloatFromTextContent();
                TestClosing("mix_with_previous_layer");
            }
            // MAX3D extensions
            // -------------------------------------------------------
            else if (IsElement("amount")) {
                out.mWeighting = ReadFloatFromTextContent();
                TestClosing("amount");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "technique") == 0)
                break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry containing a color or a texture defining that color
void ColladaParser::ReadEffectColor(aiColor4D& pColor, Sampler& pSampler)
{
    if (mReader->isEmptyElement())
        return;

    // Save current element name
    const std::string curElem = mReader->getNodeName();

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("color"))
            {
                // text content contains 4 floats
                const char* content = GetTextContent();

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

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

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

                content = fast_atoreal_move<ai_real>(content, (ai_real&)pColor.a);
                SkipSpacesAndLineEnd(&content);
                TestClosing("color");
            }
            else if (IsElement("texture"))
            {
                // get name of source texture/sampler
                int attrTex = GetAttribute("texture");
                pSampler.mName = mReader->getAttributeValue(attrTex);

                // 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.
                attrTex = TestAttribute("texcoord");
                if (attrTex >= 0)
                    pSampler.mUVChannel = mReader->getAttributeValue(attrTex);
                //SkipElement();

                // 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 (IsElement("technique"))
            {
                const int _profile = GetAttribute("profile");
                const char* profile = mReader->getAttributeValue(_profile);

                // Some extensions are quite useful ... ReadSamplerProperties processes
                // several extensions in MAYA, OKINO and MAX3D profiles.
                if (!::strcmp(profile, "MAYA") || !::strcmp(profile, "MAX3D") || !::strcmp(profile, "OKINO"))
                {
                    // get more information on this sampler
                    ReadSamplerProperties(pSampler);
                }
                else SkipElement();
            }
            else if (!IsElement("extra"))
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (mReader->getNodeName() == curElem)
                break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect entry containing a float
void ColladaParser::ReadEffectFloat(ai_real& pFloat)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("float"))
            {
                // text content contains a single floats
                const char* content = GetTextContent();
                content = fast_atoreal_move<ai_real>(content, pFloat);
                SkipSpacesAndLineEnd(&content);

                TestClosing("float");
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads an effect parameter specification of any kind
void ColladaParser::ReadEffectParam(Collada::EffectParam& pParam)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("surface"))
            {
                // image ID given inside <init_from> tags
                TestOpening("init_from");
                const char* content = GetTextContent();
                pParam.mType = Param_Surface;
                pParam.mReference = content;
                TestClosing("init_from");

                // don't care for remaining stuff
                SkipElement("surface");
            }
            else if (IsElement("sampler2D") && (FV_1_4_n == mFormat || FV_1_3_n == mFormat))
            {
                // surface ID is given inside <source> tags
                TestOpening("source");
                const char* content = GetTextContent();
                pParam.mType = Param_Sampler;
                pParam.mReference = content;
                TestClosing("source");

                // don't care for remaining stuff
                SkipElement("sampler2D");
            }
            else if (IsElement("sampler2D"))
            {
                // surface ID is given inside <instance_image> tags
                TestOpening("instance_image");
                int attrURL = GetAttribute("url");
                const char* url = mReader->getAttributeValue(attrURL);
                if (url[0] != '#')
                    ThrowException("Unsupported URL format in instance_image");
                url++;
                pParam.mType = Param_Sampler;
                pParam.mReference = url;
                SkipElement("sampler2D");
            }
            else
            {
                // ignore unknown element
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the geometry library contents
void ColladaParser::ReadGeometryLibrary()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("geometry"))
            {
                // read ID. Another entry which is "optional" by design but obligatory in reality
                int indexID = GetAttribute("id");
                std::string id = mReader->getAttributeValue(indexID);

                // TODO: (thom) support SIDs
                // ai_assert( TestAttribute( "sid") == -1);

                // create a mesh and store it in the library under its ID
                Mesh* mesh = new Mesh;
                mMeshLibrary[id] = mesh;

                // read the mesh name if it exists
                const int nameIndex = TestAttribute("name");
                if (nameIndex != -1)
                {
                    mesh->mName = mReader->getAttributeValue(nameIndex);
                }

                // read on from there
                ReadGeometry(mesh);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_geometries") != 0)
                ThrowException("Expected end of <library_geometries> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a geometry from the geometry library.
void ColladaParser::ReadGeometry(Collada::Mesh* pMesh)
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("mesh"))
            {
                // read on from there
                ReadMesh(pMesh);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "geometry") != 0)
                ThrowException("Expected end of <geometry> element.");

            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a mesh from the geometry library
void ColladaParser::ReadMesh(Mesh* pMesh)
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("source"))
            {
                // we have professionals dealing with this
                ReadSource();
            }
            else if (IsElement("vertices"))
            {
                // read per-vertex mesh data
                ReadVertexData(pMesh);
            }
            else if (IsElement("triangles") || IsElement("lines") || IsElement("linestrips")
                || IsElement("polygons") || IsElement("polylist") || IsElement("trifans") || IsElement("tristrips"))
            {
                // read per-index mesh data and faces setup
                ReadIndexData(pMesh);
            }
            else
            {
                // ignore the restf
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "technique_common") == 0)
            {
                // end of another meaningless element - read over it
            }
            else if (strcmp(mReader->getNodeName(), "mesh") == 0)
            {
                // end of <mesh> element - we're done here
                break;
            }
            else
            {
                // everything else should be punished
                ThrowException("Expected end of <mesh> element.");
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a source element
void ColladaParser::ReadSource()
{
    int indexID = GetAttribute("id");
    std::string sourceID = mReader->getAttributeValue(indexID);

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("float_array") || IsElement("IDREF_array") || IsElement("Name_array"))
            {
                ReadDataArray();
            }
            else if (IsElement("technique_common"))
            {
                // I don't care for your profiles
            }
            else if (IsElement("accessor"))
            {
                ReadAccessor(sourceID);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "source") == 0)
            {
                // end of <source> - we're done
                break;
            }
            else if (strcmp(mReader->getNodeName(), "technique_common") == 0)
            {
                // end of another meaningless element - read over it
            }
            else
            {
                // everything else should be punished
                ThrowException("Expected end of <source> element.");
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a data array holding a number of floats, and stores it in the global library
void ColladaParser::ReadDataArray()
{
    std::string elmName = mReader->getNodeName();
    bool isStringArray = (elmName == "IDREF_array" || elmName == "Name_array");
    bool isEmptyElement = mReader->isEmptyElement();

    // read attributes
    int indexID = GetAttribute("id");
    std::string id = mReader->getAttributeValue(indexID);
    int indexCount = GetAttribute("count");
    unsigned int count = (unsigned int)mReader->getAttributeValueAsInt(indexCount);
    const char* content = TestTextContent();

    // 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)
                    ThrowException("Expected more values while reading IDREF_array contents.");

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

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

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

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

    // test for closing tag
    if (!isEmptyElement)
        TestClosing(elmName.c_str());
}

// ------------------------------------------------------------------------------------------------
// Reads an accessor and stores it in the global library
void ColladaParser::ReadAccessor(const std::string& pID)
{
    // read accessor attributes
    int attrSource = GetAttribute("source");
    const char* source = mReader->getAttributeValue(attrSource);
    if (source[0] != '#')
        ThrowException(format() << "Unknown reference format in url \"" << source << "\" in source attribute of <accessor> element.");
    int attrCount = GetAttribute("count");
    unsigned int count = (unsigned int)mReader->getAttributeValueAsInt(attrCount);
    int attrOffset = TestAttribute("offset");
    unsigned int offset = 0;
    if (attrOffset > -1)
        offset = (unsigned int)mReader->getAttributeValueAsInt(attrOffset);
    int attrStride = TestAttribute("stride");
    unsigned int stride = 1;
    if (attrStride > -1)
        stride = (unsigned int)mReader->getAttributeValueAsInt(attrStride);

    // 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 + 1; // ignore the leading '#'
    acc.mSize = 0; // gets incremented with every param

    // and read the components
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("param"))
            {
                // read data param
                int attrName = TestAttribute("name");
                std::string name;
                if (attrName > -1)
                {
                    name = mReader->getAttributeValue(attrName);

                    // 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();
                    //  else if( name == "Q") acc.mSubOffset[3] = acc.mParams.size();
                        /* 4D uv coordinates are not supported in Assimp */

                        /* 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();
                    //else
                    //  DefaultLogger::get()->warn( format() << "Unknown accessor parameter \"" << name << "\". Ignoring data channel." );
                }

                // read data type
                int attrType = TestAttribute("type");
                if (attrType > -1)
                {
                    // for the moment we only distinguish between a 4x4 matrix and anything else.
                    // 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 = mReader->getAttributeValue(attrType);
                    if (type == "float4x4")
                        acc.mSize += 16;
                    else
                        acc.mSize += 1;
                }

                acc.mParams.push_back(name);

                // skip remaining stuff of this element, if any
                SkipElement();
            }
            else
            {
                ThrowException(format() << "Unexpected sub element <" << mReader->getNodeName() << "> in tag <accessor>");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "accessor") != 0)
                ThrowException("Expected end of <accessor> element.");
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads input declarations of per-vertex mesh data into the given mesh
void ColladaParser::ReadVertexData(Mesh* pMesh)
{
    // extract the ID of the <vertices> element. Not that we care, but to catch strange referencing schemes we should warn about
    int attrID = GetAttribute("id");
    pMesh->mVertexID = mReader->getAttributeValue(attrID);

    // a number of <input> elements
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("input"))
            {
                ReadInputChannel(pMesh->mPerVertexData);
            }
            else
            {
                ThrowException(format() << "Unexpected sub element <" << mReader->getNodeName() << "> in tag <vertices>");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "vertices") != 0)
                ThrowException("Expected end of <vertices> element.");

            break;
        }
    }
}

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

    // 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;

    // material subgroup
    int attrMaterial = TestAttribute("material");
    SubMesh subgroup;
    if (attrMaterial > -1)
        subgroup.mMaterial = mReader->getAttributeValue(attrMaterial);

    // distinguish between polys and triangles
    std::string elementName = mReader->getNodeName();
    PrimitiveType primType = Prim_Invalid;
    if (IsElement("lines"))
        primType = Prim_Lines;
    else if (IsElement("linestrips"))
        primType = Prim_LineStrip;
    else if (IsElement("polygons"))
        primType = Prim_Polygon;
    else if (IsElement("polylist"))
        primType = Prim_Polylist;
    else if (IsElement("triangles"))
        primType = Prim_Triangles;
    else if (IsElement("trifans"))
        primType = Prim_TriFans;
    else if (IsElement("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
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("input"))
            {
                ReadInputChannel(perIndexData);
            }
            else if (IsElement("vcount"))
            {
                if (!mReader->isEmptyElement())
                {
                    if (numPrimitives)  // It is possible to define a mesh without any primitives
                    {
                        // case <polylist> - specifies the number of indices for each polygon
                        const char* content = GetTextContent();
                        vcount.reserve(numPrimitives);
                        for (unsigned int a = 0; a < numPrimitives; a++)
                        {
                            if (*content == 0)
                                ThrowException("Expected more values while reading <vcount> contents.");
                            // read a number
                            vcount.push_back((size_t)strtoul10(content, &content));
                            // skip whitespace after it
                            SkipSpacesAndLineEnd(&content);
                        }
                    }

                    TestClosing("vcount");
                }
            }
            else if (IsElement("p"))
            {
                if (!mReader->isEmptyElement())
                {
                    // now here the actual fun starts - these are the indices to construct the mesh data from
                    actualPrimitives += ReadPrimitives(pMesh, perIndexData, numPrimitives, vcount, primType);
                }
            }
            else if (IsElement("extra"))
            {
                SkipElement("extra");
            }
            else if (IsElement("ph")) {
                SkipElement("ph");
            }
            else {
                ThrowException(format() << "Unexpected sub element <" << mReader->getNodeName() << "> in tag <" << elementName << ">");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (mReader->getNodeName() != elementName)
                ThrowException(format() << "Expected end of <" << elementName << "> element.");

            break;
        }
    }

#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(std::vector<InputChannel>& poChannels)
{
    InputChannel channel;

    // read semantic
    int attrSemantic = GetAttribute("semantic");
    std::string semantic = mReader->getAttributeValue(attrSemantic);
    channel.mType = GetTypeForSemantic(semantic);

    // read source
    int attrSource = GetAttribute("source");
    const char* source = mReader->getAttributeValue(attrSource);
    if (source[0] != '#')
        ThrowException(format() << "Unknown reference format in url \"" << source << "\" in source attribute of <input> element.");
    channel.mAccessor = source + 1; // skipping the leading #, hopefully the remaining text is the accessor ID only

    // read index offset, if per-index <input>
    int attrOffset = TestAttribute("offset");
    if (attrOffset > -1)
        channel.mOffset = mReader->getAttributeValueAsInt(attrOffset);

    // read set if texture coordinates
    if (channel.mType == IT_Texcoord || channel.mType == IT_Color) {
        int attrSet = TestAttribute("set");
        if (attrSet > -1) {
            attrSet = mReader->getAttributeValueAsInt(attrSet);
            if (attrSet < 0)
                ThrowException(format() << "Invalid index \"" << (attrSet) << "\" in set attribute of <input> element");

            channel.mIndex = attrSet;
        }
    }

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

    // skip remaining stuff of this element, if any
    SkipElement();
}

// ------------------------------------------------------------------------------------------------
// Reads a <p> primitive index list and assembles the mesh data into the given mesh
size_t ColladaParser::ReadPrimitives(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:
        // other primitive types don't state the index count upfront... we need to guess
        break;
    }

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

    if (pNumPrimitives > 0) // It is possible to not contain any indices
    {
        const char* content = GetTextContent();
        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);
        }
    }

    // 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
            ThrowException("Expected different index count in <p> element.");

    }
    else if (expectedPointCount == 0 && (indices.size() % numOffsets) != 0)
        ThrowException("Expected different index count in <p> element.");

    // find the data for all sources
    for (std::vector<InputChannel>::iterator 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);
    }
    // and the same for the per-index channels
    for (std::vector<InputChannel>::iterator 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)
                ThrowException("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);
    }

    // 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
            ThrowException("Unsupported primitive type.");
            break;
        }

        // 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...
    TestClosing("p");
    return numPrimitives;
}

///@note This function willn'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 is this 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 (std::vector<InputChannel>::iterator 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 (std::vector<InputChannel>::iterator 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)
        ThrowException(format() << "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.push_back(aiVector3D(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.push_back(aiVector3D(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.push_back(aiVector3D(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.push_back(aiVector3D(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].push_back(aiVector3D(obj[0], obj[1], obj[2]));
            if (0 != acc.mSubOffset[2] || 0 != acc.mSubOffset[3]) /* hack ... consider cleaner solution */
                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()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            // a visual scene - generate root node under its ID and let ReadNode() do the recursive work
            if (IsElement("visual_scene"))
            {
                // read ID. Is optional according to the spec, but how on earth should a scene_instance refer to it then?
                int indexID = GetAttribute("id");
                const char* attrID = mReader->getAttributeValue(indexID);

                // read name if given.
                int indexName = TestAttribute("name");
                const char* attrName = "unnamed";
                if (indexName > -1)
                    attrName = mReader->getAttributeValue(indexName);

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

                ReadSceneNode(node);
            }
            else
            {
                // ignore the rest
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
        {
            if (strcmp(mReader->getNodeName(), "library_visual_scenes") == 0)
                //ThrowException( "Expected end of \"library_visual_scenes\" element.");

                break;
        }
    }
}

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

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
        {
            if (IsElement("node"))
            {
                Node* child = new Node;
                int attrID = TestAttribute("id");
                if (attrID > -1)
                    child->mID = mReader->getAttributeValue(attrID);
                int attrSID = TestAttribute("sid");
                if (attrSID > -1)
                    child->mSID = mReader->getAttributeValue(attrSID);

                int attrName = TestAttribute("name");
                if (attrName > -1)
                    child->mName = mReader->getAttributeValue(attrName);

                // TODO: (thom) support SIDs
                // ai_assert( TestAttribute( "sid") == -1);

                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(child);
                continue;
            }
            // For any further stuff we need a valid node to work on
            else if (!pNode)
                continue;

            if (IsElement("lookat"))
                ReadNodeTransformation(pNode, TF_LOOKAT);
            else if (IsElement("matrix"))
                ReadNodeTransformation(pNode, TF_MATRIX);
            else if (IsElement("rotate"))
                ReadNodeTransformation(pNode, TF_ROTATE);
            else if (IsElement("scale"))
                ReadNodeTransformation(pNode, TF_SCALE);
            else if (IsElement("skew"))
                ReadNodeTransformation(pNode, TF_SKEW);
            else if (IsElement("translate"))
                ReadNodeTransformation(pNode, TF_TRANSLATE);
            else if (IsElement("render") && pNode->mParent == NULL && 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.
                int attrId = TestAttribute("camera_node");
                if (-1 != attrId)
                {
                    const char* s = mReader->getAttributeValue(attrId);
                    if (s[0] != '#')
                        ASSIMP_LOG_ERROR("Collada: Unresolved reference format of camera");
                    else
                        pNode->mPrimaryCamera = s + 1;
                }
            }
            else if (IsElement("instance_node"))
            {
                // find the node in the library
                int attrID = TestAttribute("url");
                if (attrID != -1)
                {
                    const char* s = mReader->getAttributeValue(attrID);
                    if (s[0] != '#')
                        ASSIMP_LOG_ERROR("Collada: Unresolved reference format of node");
                    else
                    {
                        pNode->mNodeInstances.push_back(NodeInstance());
                        pNode->mNodeInstances.back().mNode = s + 1;
                    }
                }
            }
            else if (IsElement("instance_geometry") || IsElement("instance_controller"))
            {
                // Reference to a mesh or controller, with possible material associations
                ReadNodeGeometry(pNode);
            }
            else if (IsElement("instance_light"))
            {
                // Reference to a light, name given in 'url' attribute
                int attrID = TestAttribute("url");
                if (-1 == attrID)
                    ASSIMP_LOG_WARN("Collada: Expected url attribute in <instance_light> element");
                else
                {
                    const char* url = mReader->getAttributeValue(attrID);
                    if (url[0] != '#')
                        ThrowException("Unknown reference format in <instance_light> element");

                    pNode->mLights.push_back(LightInstance());
                    pNode->mLights.back().mLight = url + 1;
                }
            }
            else if (IsElement("instance_camera"))
            {
                // Reference to a camera, name given in 'url' attribute
                int attrID = TestAttribute("url");
                if (-1 == attrID)
                    ASSIMP_LOG_WARN("Collada: Expected url attribute in <instance_camera> element");
                else
                {
                    const char* url = mReader->getAttributeValue(attrID);
                    if (url[0] != '#')
                        ThrowException("Unknown reference format in <instance_camera> element");

                    pNode->mCameras.push_back(CameraInstance());
                    pNode->mCameras.back().mCamera = url + 1;
                }
            }
            else
            {
                // skip everything else for the moment
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Reads a node transformation entry of the given type and adds it to the given node's transformation list.
void ColladaParser::ReadNodeTransformation(Node* pNode, TransformType pType)
{
    if (mReader->isEmptyElement())
        return;

    std::string tagName = mReader->getNodeName();

    Transform tf;
    tf.mType = pType;

    // read SID
    int indexSID = TestAttribute("sid");
    if (indexSID >= 0)
        tf.mID = mReader->getAttributeValue(indexSID);

    // how many parameters to read per transformation type
    static const unsigned int sNumParameters[] = { 9, 4, 3, 3, 7, 16 };
    const char* content = GetTextContent();

    // read as many parameters and store in the transformation
    for (unsigned int a = 0; a < sNumParameters[pType]; a++)
    {
        // read a number
        content = fast_atoreal_move<ai_real>(content, tf.f[a]);
        // skip whitespace after it
        SkipSpacesAndLineEnd(&content);
    }

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

    // and consume the closing tag
    TestClosing(tagName.c_str());
}

// ------------------------------------------------------------------------------------------------
// Processes bind_vertex_input and bind elements
void ColladaParser::ReadMaterialVertexInputBinding(Collada::SemanticMappingTable& tbl)
{
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("bind_vertex_input"))
            {
                Collada::InputSemanticMapEntry vn;

                // effect semantic
                int n = GetAttribute("semantic");
                std::string s = mReader->getAttributeValue(n);

                // input semantic
                n = GetAttribute("input_semantic");
                vn.mType = GetTypeForSemantic(mReader->getAttributeValue(n));

                // index of input set
                n = TestAttribute("input_set");
                if (-1 != n)
                    vn.mSet = mReader->getAttributeValueAsInt(n);

                tbl.mMap[s] = vn;
            }
            else if (IsElement("bind")) {
                ASSIMP_LOG_WARN("Collada: Found unsupported <bind> element");
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            if (strcmp(mReader->getNodeName(), "instance_material") == 0)
                break;
        }
    }
}

void Assimp::ColladaParser::ReadEmbeddedTextures(ZipArchiveIOSystem& zip_archive)
{
    // Attempt to load any undefined Collada::Image in ImageLibrary
    for (ImageLibrary::iterator it = mImageLibrary.begin(); it != mImageLibrary.end(); ++it) {
        Collada::Image &image = (*it).second;

        if (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(Node* pNode)
{
    // referred mesh is given as an attribute of the <instance_geometry> element
    int attrUrl = GetAttribute("url");
    const char* url = mReader->getAttributeValue(attrUrl);
    if (url[0] != '#')
        ThrowException("Unknown reference format");

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

    if (!mReader->isEmptyElement())
    {
        // read material associations. Ignore additional elements in between
        while (mReader->read())
        {
            if (mReader->getNodeType() == irr::io::EXN_ELEMENT)
            {
                if (IsElement("instance_material"))
                {
                    // read ID of the geometry subgroup and the target material
                    int attrGroup = GetAttribute("symbol");
                    std::string group = mReader->getAttributeValue(attrGroup);
                    int attrMaterial = GetAttribute("target");
                    const char* urlMat = mReader->getAttributeValue(attrMaterial);
                    Collada::SemanticMappingTable s;
                    if (urlMat[0] == '#')
                        urlMat++;

                    s.mMatName = urlMat;

                    // resolve further material details + THIS UGLY AND NASTY semantic mapping stuff
                    if (!mReader->isEmptyElement())
                        ReadMaterialVertexInputBinding(s);

                    // store the association
                    instance.mMaterials[group] = s;
                }
            }
            else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
            {
                if (strcmp(mReader->getNodeName(), "instance_geometry") == 0
                    || strcmp(mReader->getNodeName(), "instance_controller") == 0)
                    break;
            }
        }
    }

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

// ------------------------------------------------------------------------------------------------
// Reads the collada scene
void ColladaParser::ReadScene()
{
    if (mReader->isEmptyElement())
        return;

    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT) {
            if (IsElement("instance_visual_scene"))
            {
                // should be the first and only occurrence
                if (mRootNode)
                    ThrowException("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"
                int urlIndex = GetAttribute("url");
                const char* url = mReader->getAttributeValue(urlIndex);
                if (url[0] != '#')
                    ThrowException("Unknown reference format in <instance_visual_scene> element");

                // find the referred scene, skip the leading #
                NodeLibrary::const_iterator sit = mNodeLibrary.find(url + 1);
                if (sit == mNodeLibrary.end())
                    ThrowException("Unable to resolve visual_scene reference \"" + std::string(url) + "\" in <instance_visual_scene> element.");
                mRootNode = sit->second;
            }
            else {
                SkipElement();
            }
        }
        else if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END) {
            break;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Aborts the file reading with an exception
AI_WONT_RETURN void ColladaParser::ThrowException(const std::string& pError) const
{
    throw DeadlyImportError(format() << "Collada: " << mFileName << " - " << pError);
}
void ColladaParser::ReportWarning(const char* msg, ...)
{
    ai_assert(NULL != msg);

    va_list args;
    va_start(args, msg);

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

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

// ------------------------------------------------------------------------------------------------
// Skips all data until the end node of the current element
void ColladaParser::SkipElement()
{
    // nothing to skip if it's an <element />
    if (mReader->isEmptyElement())
        return;

    // reroute
    SkipElement(mReader->getNodeName());
}

// ------------------------------------------------------------------------------------------------
// Skips all data until the end node of the given element
void ColladaParser::SkipElement(const char* pElement)
{
    // copy the current node's name because it'a pointer to the reader's internal buffer,
    // which is going to change with the upcoming parsing
    std::string element = pElement;
    while (mReader->read())
    {
        if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END)
            if (mReader->getNodeName() == element)
                break;
    }
}

// ------------------------------------------------------------------------------------------------
// Tests for an opening element of the given name, throws an exception if not found
void ColladaParser::TestOpening(const char* pName)
{
    // read element start
    if (!mReader->read())
        ThrowException(format() << "Unexpected end of file while beginning of <" << pName << "> element.");
    // whitespace in front is ok, just read again if found
    if (mReader->getNodeType() == irr::io::EXN_TEXT)
        if (!mReader->read())
            ThrowException(format() << "Unexpected end of file while reading beginning of <" << pName << "> element.");

    if (mReader->getNodeType() != irr::io::EXN_ELEMENT || strcmp(mReader->getNodeName(), pName) != 0)
        ThrowException(format() << "Expected start of <" << pName << "> element.");
}

// ------------------------------------------------------------------------------------------------
// Tests for the closing tag of the given element, throws an exception if not found
void ColladaParser::TestClosing(const char* pName)
{
    // check if we're already on the closing tag and return right away
    if (mReader->getNodeType() == irr::io::EXN_ELEMENT_END && strcmp(mReader->getNodeName(), pName) == 0)
        return;

    // if not, read some more
    if (!mReader->read())
        ThrowException(format() << "Unexpected end of file while reading end of <" << pName << "> element.");
    // whitespace in front is ok, just read again if found
    if (mReader->getNodeType() == irr::io::EXN_TEXT)
        if (!mReader->read())
            ThrowException(format() << "Unexpected end of file while reading end of <" << pName << "> element.");

    // but this has the be the closing tag, or we're lost
    if (mReader->getNodeType() != irr::io::EXN_ELEMENT_END || strcmp(mReader->getNodeName(), pName) != 0)
        ThrowException(format() << "Expected end of <" << pName << "> element.");
}

// ------------------------------------------------------------------------------------------------
// Returns the index of the named attribute or -1 if not found. Does not throw, therefore useful for optional attributes
int ColladaParser::GetAttribute(const char* pAttr) const
{
    int index = TestAttribute(pAttr);
    if (index != -1)
        return index;

    // attribute not found -> throw an exception
    ThrowException(format() << "Expected attribute \"" << pAttr << "\" for element <" << mReader->getNodeName() << ">.");
    return -1;
}

// ------------------------------------------------------------------------------------------------
// Tests the present element for the presence of one attribute, returns its index or throws an exception if not found
int ColladaParser::TestAttribute(const char* pAttr) const
{
    for (int a = 0; a < mReader->getAttributeCount(); a++)
        if (strcmp(mReader->getAttributeName(a), pAttr) == 0)
            return a;

    return -1;
}

// ------------------------------------------------------------------------------------------------
// Reads the text contents of an element, throws an exception if not given. Skips leading whitespace.
const char* ColladaParser::GetTextContent()
{
    const char* sz = TestTextContent();
    if (!sz) {
        ThrowException("Invalid contents in element \"n\".");
    }
    return sz;
}

// ------------------------------------------------------------------------------------------------
// Reads the text contents of an element, returns NULL if not given. Skips leading whitespace.
const char* ColladaParser::TestTextContent()
{
    // present node should be the beginning of an element
    if (mReader->getNodeType() != irr::io::EXN_ELEMENT || mReader->isEmptyElement())
        return NULL;

    // read contents of the element
    if (!mReader->read())
        return NULL;
    if (mReader->getNodeType() != irr::io::EXN_TEXT && mReader->getNodeType() != irr::io::EXN_CDATA)
        return NULL;

    // skip leading whitespace
    const char* text = mReader->getNodeData();
    SkipSpacesAndLineEnd(&text);

    return text;
}

// ------------------------------------------------------------------------------------------------
// Calculates the resulting transformation fromm 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
Collada::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_F("Unknown vertex input type \"", semantic, "\". Ignoring.");
    return IT_Invalid;
}

#endif // !! ASSIMP_BUILD_NO_DAE_IMPORTER
