// 30 Oct 2002
// AC3D loader for models generated by the AC3D modeller (www.ac3d.org)
// part of this source code were supplied by the AC3D project (Andy Colebourne)
// eg the basic parsing of an AC3D file.
// Conversion from AC3D scenegraph to OSG by GW Michel.

#include <vector>
#include <iostream>

#include <osg/GL>
#include <osg/GLU>

#include <osg/Math>
#include <osg/BlendFunc>
#include <osg/CullFace>
#include <osg/Geode>
#include <osg/Group>
#include <osg/Geometry>
#include <osg/Light>
#include <osg/LightSource>
#include <osg/Material>
#include <osg/Math>
#include <osg/Texture2D>
#include <osg/TexEnv>
#include <osg/StateSet>
#include <osg/ShadeModel>
#include <osg/Math>
#include <osg/Notify>

#include <osgUtil/Tessellator>

#include <osgDB/FileNameUtils>
#include <osgDB/Registry>
#include <osgDB/ReadFile>
#include <osgDB/FileUtils>

#include "Exception.h"
#include "Geode.h"

namespace ac3d {

osg::Node*
readFile(std::istream& stream, const osgDB::ReaderWriter::Options* options);

}

class geodeVisitor : public osg::NodeVisitor { // collects geodes from scene sub-graph attached to 'this'
        public:
            geodeVisitor():
                osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN) {}

            ~geodeVisitor() { _geodelist.clear();}

            // one apply for each type of Node that might be a user transform
            virtual void apply(osg::Geode& geode) {
                _geodelist.push_back(&geode);
            }
            virtual void apply(osg::Group& gp){
                traverse(gp);    // must continue subgraph traversal.
            }
            std::vector<const osg::Geode *> getGeodes() {return _geodelist;}
        protected:

            typedef std::vector<const osg::Geode *>    Geodelist;
            Geodelist  _geodelist;
};

class ReaderWriterAC : public osgDB::ReaderWriter
{
    public:
        virtual const char* className() const { return "AC3D Database Reader"; }

        virtual bool acceptsExtension(const std::string& extension) const
        {
            return osgDB::equalCaseInsensitive(extension,"ac");
        }
        virtual ReadResult readNode(const std::string& file,const Options* options) const
        {
            std::string ext = osgDB::getFileExtension(file);
            if (!acceptsExtension(ext)) return ReadResult::FILE_NOT_HANDLED;

            // GWM added Dec 2003 - get full path name (change in osgDB handling of files).
            std::string fileName = osgDB::findDataFile( file, options );
            osg::notify(osg::INFO) << "osgDB ac3d reader: starting reading \"" << fileName << "\"" << std::endl;
            
            // Anders Backmann - correct return if path not found
            if (fileName.empty()) return ReadResult::FILE_NOT_FOUND;

            // allocate per file data and start reading
            std::ifstream fin;
            fin.open(fileName.c_str(), std::ios::in);
            if (!fin.is_open()) return ReadResult::FILE_NOT_FOUND;

            // code for setting up the database path so that internally referenced file are
            // searched for on relative paths. 
            osg::ref_ptr<Options> local_opt;
            if (options)
                local_opt = static_cast<Options*>(options->clone(osg::CopyOp::DEEP_COPY_ALL));
            else
                local_opt = new Options;
            local_opt->setDatabasePath(osgDB::getFilePath(fileName));

            ReadResult result = readNode(fin, local_opt.get());
            if (result.validNode())
                result.getNode()->setName(fileName);
            return result;
        }
        virtual ReadResult readNode(std::istream& fin, const Options* options) const
        {
            std::string header;
            fin >> header;
            if (header.substr(0, 4) != "AC3D")
                return osgDB::ReaderWriter::ReadResult::FILE_NOT_HANDLED;

            return ac3d::readFile(fin, options);
        }
        virtual WriteResult writeNode(const osg::Node& node,const std::string& fileName, const Options* /*options*/) const
        {
            std::string ext = osgDB::getFileExtension(fileName);
            if (!acceptsExtension(ext)) return WriteResult::FILE_NOT_HANDLED;
            geodeVisitor vs; // this collects geodes.
            std::vector<unsigned int>iNumMaterials;
            const_cast<osg::Node&>(node).accept(vs); // this parses the tree to streamd Geodes
            std::vector<const osg::Geode *> glist=vs.getGeodes();
            std::ofstream fout(fileName.c_str(), std::ios::out | std::ios::binary);
            // Write out the file header
            std::vector<const osg::Geode *>::iterator itr;
            fout << "AC3Db" << std::endl;
            // output the Materials
            int iNumGeodesWithGeometry = 0;
            for (itr=glist.begin();itr!= glist.end();itr++)
            {
                iNumMaterials.push_back(const_cast<ac3d::Geode*>(static_cast<const ac3d::Geode*>(*itr))->ProcessMaterial(fout,itr-glist.begin()));
                unsigned int iNumDrawables = (*itr)->getNumDrawables();
                int iNumGeometries = 0;
                for (unsigned int i = 0; i < iNumDrawables; i++)
                {
                    const osg::Drawable* pDrawable = (*itr)->getDrawable(i);
                    if (NULL != pDrawable)
                    {
                        const osg::Geometry *pGeometry = pDrawable->asGeometry();
                        if (NULL != pGeometry)
                            iNumGeometries++;
                    }
                    if (iNumGeometries > 0)
                        iNumGeodesWithGeometry++;
                }
            }
            // output the Geometry
            unsigned int nfirstmat=0;
            fout << "OBJECT world" << std::endl;

            fout << "kids " << iNumGeodesWithGeometry << std::endl;
            for (itr=glist.begin();itr!= glist.end();itr++) {
                const_cast<ac3d::Geode*>(static_cast<const ac3d::Geode*>(*itr))->ProcessGeometry(fout,nfirstmat);
                nfirstmat+=iNumMaterials[itr-glist.begin()];
            }
            fout.close();
            return WriteResult::FILE_SAVED;
        }
        
        virtual WriteResult writeNode(const osg::Node& node,std::ostream& fout, const Options* opts) const
        {
            try
            {
                // write ac file.
                if(dynamic_cast<const osg::Group*>(&node)) {
                    const osg::Group *gp=dynamic_cast<const osg::Group*>(&node);
                    const unsigned int nch=gp->getNumChildren();
                    for (unsigned int i=0; i<nch; i++) {
                        writeNode(*(gp->getChild(i)), fout, opts);
                    }
                }
                else
                    osg::notify(osg::WARN)<<"File must start with a geode "<<std::endl;
                fout.flush();
                return WriteResult::FILE_SAVED;
            }
            catch(ac3d::Exception e)
            {
                osg::notify(osg::WARN)<<"Error parsing OSG tree: "<< e.getError() << std::endl;            
            }
            return WriteResult::FILE_NOT_HANDLED;

        }
private:
};

// now register with osg::Registry to instantiate the above
// reader/writer.
osgDB::RegisterReaderWriterProxy<ReaderWriterAC> g_readerWriter_AC_Proxy;


namespace ac3d {

enum {
  ObjectTypeNormal = 0,
  ObjectTypeGroup = 1,
  ObjectTypeLight = 2,

  SurfaceTypePolygon = 0,
  SurfaceTypeLineLoop = 1,
  SurfaceTypeLineStrip = 2,

  SurfaceShaded = 1<<4,
  SurfaceTwoSided = 1<<5
};

/// Returns a possibly quoted string given in the end of the current line in the stream
static
std::string
readString(std::istream& stream)
{
    std::string s;
    stream >> std::ws;

    if (stream.peek() != '\"')
    {
        // Not quoted, just read the string
        stream >> s;
    }
    else
    {
        // look for quoted strings
    
        // throw away the quote
        stream.get();
    
        // extract characters until either an error happens or a quote is found
        while (stream.good())
        {
            std::istream::char_type c;
            stream.get(c);
            if (c == '\"')
                break;
            s += c;
        }
    }
 
    return s;
}

static void
setTranslucent(osg::StateSet* stateSet)
{
    osg::BlendFunc* blendFunc = new osg::BlendFunc;
    blendFunc->setSource(osg::BlendFunc::SRC_ALPHA);
    blendFunc->setDestination(osg::BlendFunc::ONE_MINUS_SRC_ALPHA);
    stateSet->setAttribute(blendFunc);
    stateSet->setMode(GL_BLEND, osg::StateAttribute::ON);
    stateSet->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);
}

// Just a container to store an ac3d material
class MaterialData
{
  public:
    MaterialData() :
        mMaterial(new osg::Material),
        mColorArray(new osg::Vec4Array(1))
    { }

    void readMaterial(std::istream& stream)
    {
        // note that this might be quoted
        std::string name = readString(stream);
        mMaterial->setName(name);
        std::string tmp;
        stream >> tmp;
        osg::Vec4 diffuse;
        stream >> diffuse[0] >> diffuse[1] >> diffuse[2];
        mMaterial->setDiffuse(osg::Material::FRONT_AND_BACK, diffuse);
        stream >> tmp;
        osg::Vec4 ambient;
        stream >> ambient[0] >> ambient[1] >> ambient[2];
        mMaterial->setAmbient(osg::Material::FRONT_AND_BACK, ambient);
        stream >> tmp;
        osg::Vec4 emmissive;
        stream >> emmissive[0] >> emmissive[1] >> emmissive[2];
        mMaterial->setEmission(osg::Material::FRONT_AND_BACK, emmissive);
        stream >> tmp;
        osg::Vec4 specular;
        stream >> specular[0] >> specular[1] >> specular[2];
        mMaterial->setSpecular(osg::Material::FRONT_AND_BACK, specular);
        stream >> tmp;
        float shininess;
        stream >> shininess;
        mMaterial->setShininess(osg::Material::FRONT_AND_BACK, shininess);
        stream >> tmp;
        float transparency;
        stream >> transparency;
        mMaterial->setTransparency(osg::Material::FRONT_AND_BACK, transparency);
        mTranslucent = 0 < transparency;

        // must correspond to the material we use for the color array below
        mMaterial->setColorMode(osg::Material::DIFFUSE);
        // this must be done past the transparency setting ...
        (*mColorArray)[0] = mMaterial->getDiffuse(osg::Material::FRONT_AND_BACK);
    }

    void toStateSet(osg::StateSet* stateSet) const
    {
        stateSet->setAttribute(mMaterial.get());
        if (mTranslucent)
            setTranslucent(stateSet);
    }

    osg::Vec4Array* getColorArray() const
    {
        return mColorArray.get();
    }

private:
    osg::ref_ptr<osg::Material> mMaterial;
    osg::ref_ptr<osg::Vec4Array> mColorArray;
    bool mTranslucent;
};

class TextureData
{
  public:
    TextureData() :
        mTranslucent(false)
    {
    }

    bool setTexture(const std::string& name, const osgDB::ReaderWriter::Options* options)
    {
        mTexture2D = new osg::Texture2D;
        mTexture2D->setWrap(osg::Texture2D::WRAP_S, osg::Texture2D::REPEAT);
        mTexture2D->setWrap(osg::Texture2D::WRAP_T, osg::Texture2D::REPEAT);

        std::string absFileName = osgDB::findDataFile(name, options);
        if (absFileName.empty())
        {
            osg::notify(osg::FATAL) << "osgDB ac3d reader: could not find texture \"" << name << "\"" << std::endl;
            return false;
        }
        mImage = osgDB::readImageFile(absFileName, options);
        if (!mImage.valid())
        {
            osg::notify(osg::FATAL) << "osgDB ac3d reader: could not read texture \"" << name << "\"" << std::endl;
            return false;
        }
        mTexture2D->setImage(mImage.get());
        mTranslucent = mImage->isImageTranslucent();
        return true;
    }
    bool valid() const
    {
        return mImage.valid();
    }
    std::string getFileName() const
    {
        if (!mImage.valid())
            return std::string();
        return mImage->getFileName();
    }
    void toTextureStateSet(osg::StateSet* stateSet) const
    {
        if (!valid())
            return;
        osg::TexEnv* texEnv = new osg::TexEnv;
        texEnv->setMode(osg::TexEnv::MODULATE);
        stateSet->setTextureAttribute(0, texEnv);
        stateSet->setTextureAttribute(0, mTexture2D.get());
        stateSet->setTextureMode(0, GL_TEXTURE_2D, osg::StateAttribute::ON);
        if (mTranslucent)
            setTranslucent(stateSet);
    }
private:
    osg::ref_ptr<osg::Texture2D> mTexture2D;
    osg::ref_ptr<osg::Image> mImage;
    bool mTranslucent;
};

class FileData
{
  public:
    FileData(const osgDB::ReaderWriter::Options* options) :
        mOptions(options),
        mLightIndex(1)
    { }

    TextureData toTextureData(const std::string& texName)
    {
        TextureDataMap::iterator i = mTextureStates.find(texName);
        if (i == mTextureStates.end())
            mTextureStates[texName].setTexture(texName, mOptions.get());
        return mTextureStates[texName];
    }

    osg::Light* getNextLight()
    {
        osg::Light* light = new osg::Light;
        light->setLightNum(mLightIndex++);
        return light;
    }

    void addMaterial(const MaterialData& material)
    {
        mMaterials.push_back(material);
    }
    unsigned getNumMaterials() const
    {
        return mMaterials.size();
    }
    const MaterialData& getMaterial(unsigned idx) const
    {
        return mMaterials[idx];
    }

private:
    /// Stores the ac3d file reader options, only used for reading texture files
    osg::ref_ptr<osgDB::ReaderWriter::Options const> mOptions;

    /// The list of ac3d MATERIALS
    std::vector<MaterialData> mMaterials;

    /// Local per model texture attribute cache.
    /// ... images are usualy cached in the registries object cache
    typedef std::map<std::string, TextureData> TextureDataMap;
    TextureDataMap mTextureStates;

    /// Hack to include light nodes from ac3d into the scenegraph
    unsigned mLightIndex;
};

struct RefData {
    RefData(const osg::Vec3& _weightedNormal, const osg::Vec2& _texCoord, bool _smooth) :
        weightedFlatNormal(_weightedNormal),
        weightedFlatNormalLength(_weightedNormal.length()),
        texCoord(_texCoord),
        smooth(_smooth)
    { }
    // weighted flat surface normal
    osg::Vec3 weightedFlatNormal;
    float weightedFlatNormalLength;
    osg::Vec2 texCoord;
    // resulting vertex normal
    osg::Vec3 finalNormal;
    // if zero no need to smooth
    unsigned smooth;
};

struct VertexData {
    VertexData(const osg::Vec3& vertex) : _vertex(vertex) {}
    unsigned addRefData(const RefData& refData)
    {
        unsigned index = _refs.size();
        _refs.push_back(refData);
        return index;
    }

    void collect(float cosCreaseAngle, const RefData& ref)
    {
        unsigned size = _refs.size();
        for (unsigned i = 0; i < size; ++i)
        {
            if (_refs[i].smooth == ~0u)
            {
                float dot = _refs[i].weightedFlatNormal*ref.weightedFlatNormal;
                float lengths = _refs[i].weightedFlatNormalLength*ref.weightedFlatNormalLength;
                if (cosCreaseAngle*lengths <= dot)
                {
                    // Ok put that into the current set
                    _refs[i].smooth = ref.smooth;
                    collect(cosCreaseAngle, _refs[i]);
                }
            }
        }
    }

    void smoothNormals(float cosCreaseAngle)
    {
        // compute sets of vertices smoothed to the same normal
        // if smooth is zero we do not need to smooth
        // in a first pass mark all refs not yet in a set to ~0u
        unsigned size = _refs.size();
        for (unsigned i = 0; i < size; ++i)
        {
            if (_refs[i].smooth)
            {
                _refs[i].smooth = ~0u;
            }
        }
        // Now collect the sets
        unsigned currentSet = 1;
        for (unsigned i = 0; i < size; ++i)
        {
            if (_refs[i].smooth == ~0u)
            {
                _refs[i].smooth = currentSet++;
                collect(cosCreaseAngle, _refs[i]);
            }
        }
        // smooth and normalize the sets
        for (--currentSet; 0 < currentSet; --currentSet)
        {
            osg::Vec3 normal(0, 0, 0);
            for (unsigned i = 0; i < size; ++i)
            {
                if (_refs[i].smooth == currentSet)
                {
                    normal += _refs[i].weightedFlatNormal;
                }
            }
            normal.normalize();
            for (unsigned i = 0; i < size; ++i)
            {
                if (_refs[i].smooth == currentSet)
                {
                  _refs[i].finalNormal = normal;
                }
            }
        }

        // normalize the ones which do not need smoothing
        for (unsigned i = 0; i < size; ++i)
        {
            if (_refs[i].smooth == 0)
            {
                _refs[i].finalNormal = _refs[i].weightedFlatNormal;
                _refs[i].finalNormal.normalize();
            }
        }
    }
    osg::Vec3 _vertex;
    std::vector<RefData> _refs;
};
struct VertexIndex {
    VertexIndex(unsigned _vertexIndex = 0, unsigned _refIndex = 0) :
        vertexIndex(_vertexIndex), refIndex(_refIndex)
    { }
    unsigned vertexIndex;
    unsigned refIndex;
};

class VertexSet : public osg::Referenced {
public:
    VertexSet() : _dirty(true)
    { }
    void reserve(unsigned n)
    {
        _vertices.reserve(n);
    }
    unsigned size() const
    {
        return _vertices.size();
    }
    void setCreaseAngle(float crease)
    {
        _dirty = true;
        if (crease <= 0)
            _cosCreaseAngle = 1;
        else if (180 <= crease)
            _cosCreaseAngle = -1;
        else
            _cosCreaseAngle = cosf(osg::DegreesToRadians(crease));
    }
    void addVertex(const osg::Vec3& vertex)
    {
        _dirty = true;
        _vertices.push_back(vertex);
    }
    const osg::Vec3& getVertex(unsigned index)
    {
        return _vertices[index]._vertex;
    }
    const osg::Vec3& getVertex(const VertexIndex& vertexIndex)
    {
        return _vertices[vertexIndex.vertexIndex]._vertex;
    }
    const osg::Vec3& getNormal(const VertexIndex& vertexIndex)
    {
        if (_dirty)
            smoothNormals();
        return _vertices[vertexIndex.vertexIndex]._refs[vertexIndex.refIndex].finalNormal;
    }
    const osg::Vec2& getTexCoord(const VertexIndex& vertexIndex)
    {
        return _vertices[vertexIndex.vertexIndex]._refs[vertexIndex.refIndex].texCoord;
    }

    VertexIndex addRefData(unsigned i, const RefData& refData)
    {
         if (_vertices.size() <= i)
         {
             osg::notify(osg::FATAL) << "osgDB ac3d reader: internal error, got invalid vertex index!" << std::endl;
             return VertexIndex(0, 0);
         }
        _dirty = true;
        return VertexIndex(i, _vertices[i].addRefData(refData));
    }

private:
    void smoothNormals()
    {
        std::vector<VertexData>::iterator i;
        for (i = _vertices.begin(); i != _vertices.end(); ++i)
        {
            i->smoothNormals(_cosCreaseAngle);
        }
        _dirty = false;
    }

    std::vector<VertexData> _vertices;
    float _cosCreaseAngle;
    bool _dirty;
};


class PrimitiveBin : public osg::Referenced
{
  public:
    PrimitiveBin(unsigned flags, VertexSet* vertexSet) :
        _geode(new osg::Geode),
        _vertexSet(vertexSet),
        _flags(flags)
    { }

    virtual bool beginPrimitive(unsigned nRefs) = 0;
    virtual bool vertex(unsigned vertexIndex, const osg::Vec2& texCoord) = 0;
    virtual bool endPrimitive() = 0;

    virtual osg::Geode* finalize(const MaterialData& material, const TextureData& textureData) = 0;

  protected:
    bool isLineLoop() const
    {
        return (_flags & SurfaceTypeLineLoop)!=0;
    }
    bool isLineStrip() const
    {
        return (_flags & SurfaceTypeLineStrip)!=0;
    }
    bool isTwoSided() const
    {
        return (_flags & SurfaceTwoSided)!=0;
    }
    bool isSmooth() const
    {
        return (_flags & SurfaceShaded)!=0;
    }

    osg::ref_ptr<osg::Geode> _geode;
    osg::ref_ptr<VertexSet> _vertexSet;

  private:
    unsigned _flags;
};

class LineBin : public PrimitiveBin
{
  private:
    osg::ref_ptr<osg::Geometry> _geometry;
    osg::ref_ptr<osg::Vec3Array> _vertices;
    osg::ref_ptr<osg::Vec2Array> _texCoords;
    struct Ref {
      osg::Vec2 texCoord;
      unsigned index;
    };
    std::vector<Ref> _refs;

  public:
    LineBin(unsigned flags, VertexSet* vertexSet) :
        PrimitiveBin(flags, vertexSet),
        _geometry(new osg::Geometry),
        _vertices(new osg::Vec3Array),
        _texCoords(new osg::Vec2Array)
    {
        _geometry->setVertexArray(_vertices.get());
        _geometry->setTexCoordArray(0, _texCoords.get());
        osg::StateSet* stateSet = _geode->getOrCreateStateSet();
        stateSet->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
    }

    virtual bool beginPrimitive(unsigned nRefs)
    {
        // Check if we have enough for a line or someting broken ...
        if (nRefs < 2) {
            osg::notify(osg::WARN) << "osgDB ac3d reader: detected line with less than 2 vertices!" << std::endl;
            return false;
        }

        _refs.reserve(nRefs);
        _refs.resize(0);
        return true;
    }
    virtual bool vertex(unsigned vertexIndex, const osg::Vec2& texCoord)
    {
        Ref ref;
        ref.index = vertexIndex;
        ref.texCoord = texCoord;
        _refs.push_back(ref);
        return true;
    }
    virtual bool endPrimitive()
    {
        GLint type;
        if (isLineLoop())
            type = osg::PrimitiveSet::LINE_LOOP;
        else if (isLineStrip())
            type = osg::PrimitiveSet::LINE_STRIP;
        else {
            osg::notify(osg::FATAL) << "osgDB ac3d reader: non surface flags in surface bin!" << std::endl;
            return false;
        }
        unsigned nRefs = _refs.size();
        unsigned start = _vertices->size();
        for (unsigned i = 0; i < nRefs; ++i) {
            osg::Vec3 vertex = _vertexSet->getVertex(_refs[i].index);
            _vertices->push_back(vertex);
            _texCoords->push_back(_refs[i].texCoord);
        }
        _geometry->addPrimitiveSet(new osg::DrawArrays(type, start, nRefs));

        return true;
    }

    virtual osg::Geode* finalize(const MaterialData& material, const TextureData& textureData)
    {
        _geode->addDrawable(_geometry.get());
        material.toStateSet(_geode->getOrCreateStateSet());
        _geometry->setColorArray(material.getColorArray());
        _geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
        _geometry->setNormalBinding(osg::Geometry::BIND_OFF);
        return _geode.get();
    }
};



class SurfaceBin : public PrimitiveBin {
  private:
    struct Ref {
        osg::Vec2 texCoord;
        unsigned index;
    };
    std::vector<Ref> _refs;
  
    struct TriangleData {
        VertexIndex index[3];
    };
    std::vector<TriangleData> _triangles;
  
    struct QuadData {
        VertexIndex index[4];
    };
    std::vector<QuadData> _quads;

    struct PolygonData {
        std::vector<VertexIndex> index;
    };
    std::vector<PolygonData> _polygons;
    std::vector<PolygonData> _toTessellatePolygons;

  public:
    SurfaceBin(unsigned flags, VertexSet *vertexSet) :
        PrimitiveBin(flags, vertexSet)
    { }

    virtual bool beginPrimitive(unsigned nRefs)
    {
        _refs.reserve(nRefs);
        _refs.clear();

        // Check if we have enough for a line or someting broken ...
        if (nRefs < 3) {
            osg::notify(osg::WARN) << "osgDB ac3d reader: detected surface with less than 3 vertices!" << std::endl;
            return false;
        }
        return true;
    }
    virtual bool vertex(unsigned vertexIndex, const osg::Vec2& texCoord)
    {
        Ref ref;
        ref.index = vertexIndex;
        ref.texCoord = texCoord;
        _refs.push_back(ref);
        return true;
    }
    virtual bool endPrimitive()
    {
        unsigned nRefs = _refs.size();

        // Compute the normal times the enclosed area.
        // During that check if the surface is convex. If so, put in the surface as such.
        bool needTessellation = false;
        osg::Vec3 prevEdgeNormal;
        osg::Vec3 weightedNormal(0, 0, 0);
        osg::Vec3 v0 = _vertexSet->getVertex(_refs[0].index);
        for (unsigned i = 2; i < nRefs; ++i) {
            osg::Vec3 side1 = _vertexSet->getVertex(_refs[i-1].index) - v0;
            osg::Vec3 side2 = _vertexSet->getVertex(_refs[i].index) - v0;
            osg::Vec3 newNormal = side1^side2;
            if (!needTessellation)
            {
                if (3 < nRefs && newNormal*weightedNormal < 0)
                {
                    needTessellation = true;
                }
                if (i < 3)
                {
                    prevEdgeNormal = newNormal;
                }
                else // if (3 <= i) // due to the for loop
                {
                    osg::Vec3 sideim1 = _vertexSet->getVertex(_refs[i-1].index) - _vertexSet->getVertex(_refs[i-2].index);
                    osg::Vec3 sidei = _vertexSet->getVertex(_refs[i].index) - _vertexSet->getVertex(_refs[i-2].index);
                    osg::Vec3 edgeNormal = sideim1^sidei;
                    if (edgeNormal*prevEdgeNormal < 0)
                    {
                        needTessellation = true;
                    }
                    prevEdgeNormal = edgeNormal;
                }
            }

            weightedNormal += newNormal;
        }
        
        if (needTessellation)
        {
            unsigned polygonIndex = _toTessellatePolygons.size();
            _toTessellatePolygons.resize(polygonIndex + 1);
            for (unsigned i = 0; i < nRefs; ++i) {
                RefData refData(weightedNormal, _refs[i].texCoord, isSmooth());
                VertexIndex vertexIndex = _vertexSet->addRefData(_refs[i].index, refData);
                _toTessellatePolygons[polygonIndex].index.push_back(vertexIndex);
            }
        }
        else if (nRefs == 3)
        {
            unsigned triangleIndex = _triangles.size();
            _triangles.resize(triangleIndex + 1);
            for (unsigned i = 0; i < 3; ++i) {
                RefData refData(weightedNormal, _refs[i].texCoord, isSmooth());
                VertexIndex vertexIndex = _vertexSet->addRefData(_refs[i].index, refData);
                _triangles[triangleIndex].index[i] = vertexIndex;
            }
        }
        else if (nRefs == 4)
        {
            unsigned quadIndex = _quads.size();
            _quads.resize(quadIndex + 1);
            for (unsigned i = 0; i < 4; ++i) {
                RefData refData(weightedNormal, _refs[i].texCoord, isSmooth());
                VertexIndex vertexIndex = _vertexSet->addRefData(_refs[i].index, refData);
                _quads[quadIndex].index[i] = vertexIndex;
            }
        }
        else
        {
            unsigned polygonIndex = _polygons.size();
            _polygons.resize(polygonIndex + 1);
            for (unsigned i = 0; i < nRefs; ++i) {
                RefData refData(weightedNormal, _refs[i].texCoord, isSmooth());
                VertexIndex vertexIndex = _vertexSet->addRefData(_refs[i].index, refData);
                _polygons[polygonIndex].index.push_back(vertexIndex);
            }
        }
        return true;
    }

    void pushVertex(const VertexIndex& vertexIndex, osg::Vec3Array* vertexArray,
                    osg::Vec3Array* normalArray, osg::Vec2Array* texcoordArray)
    {
        vertexArray->push_back(_vertexSet->getVertex(vertexIndex));
        normalArray->push_back(_vertexSet->getNormal(vertexIndex));
        if (texcoordArray)
            texcoordArray->push_back(_vertexSet->getTexCoord(vertexIndex));
    }

    virtual osg::Geode* finalize(const MaterialData& material, const TextureData& textureData)
    {
        osg::StateSet* stateSet = _geode->getOrCreateStateSet();
        material.toStateSet(stateSet);
        textureData.toTextureStateSet(stateSet);
        stateSet->setMode(GL_LIGHTING, osg::StateAttribute::ON);

        // Single- or doublesided culling
        if (isTwoSided()) {
            stateSet->setMode(GL_CULL_FACE, osg::StateAttribute::OFF);
        } else {
            osg::CullFace* cullFace = new osg::CullFace;
            cullFace->setMode(osg::CullFace::BACK);
            stateSet->setAttribute(cullFace);
            stateSet->setMode(GL_CULL_FACE, osg::StateAttribute::ON);
        }

        // Flat or smooth shading
        osg::ShadeModel* shadeModel = new osg::ShadeModel;
        if (isSmooth())
            shadeModel->setMode(osg::ShadeModel::SMOOTH);
        else
            shadeModel->setMode(osg::ShadeModel::FLAT);
        stateSet->setAttribute(shadeModel);
        
        // Set up the arrays, allways store texture coords, may be we need them later ...
        osg::Geometry* geometry = new osg::Geometry;
        _geode->addDrawable(geometry);
        geometry->setColorArray(material.getColorArray());
        geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
        geometry->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
        osg::Vec3Array* normalArray = new osg::Vec3Array;
        geometry->setNormalArray(normalArray);
        osg::Vec3Array* vertexArray = new osg::Vec3Array;
        geometry->setVertexArray(vertexArray);
        osg::Vec2Array* texcoordArray = 0;
        if (textureData.valid())
        {
            texcoordArray = new osg::Vec2Array;
            geometry->setTexCoordArray(0, texcoordArray);
        }

        // At first handle the the polygons to tessellate, fix them and append the other polygons later
        if (!_toTessellatePolygons.empty())
        {
            unsigned start = vertexArray->size();
            osg::DrawArrayLengths* drawArrayLengths = new osg::DrawArrayLengths(osg::PrimitiveSet::POLYGON, start);
            drawArrayLengths->reserve(_toTessellatePolygons.size());
            for (unsigned i = 0; i < _toTessellatePolygons.size(); ++i)
            {
                for (unsigned j = 0; j < _toTessellatePolygons[i].index.size(); ++j)
                {
                    pushVertex(_toTessellatePolygons[i].index[j], vertexArray, normalArray, texcoordArray);
                }
                drawArrayLengths->push_back(_toTessellatePolygons[i].index.size());
            }
            geometry->addPrimitiveSet(drawArrayLengths);

            osgUtil::Tessellator Tessellator;
            Tessellator.retessellatePolygons(*geometry);
        }

        // handle triangles
        if (!_triangles.empty())
        {
            unsigned start = vertexArray->size();
            for (unsigned i = 0; i < _triangles.size(); ++i)
            {
                for (unsigned j = 0; j < 3; ++j)
                {
                    pushVertex(_triangles[i].index[j], vertexArray, normalArray, texcoordArray);
                }
            }
            osg::DrawArrays* drawArray = new osg::DrawArrays(osg::PrimitiveSet::TRIANGLES, start, 3*_triangles.size());
            geometry->addPrimitiveSet(drawArray);
        }

        // handle quads
        if (!_quads.empty())
        {
            unsigned start = vertexArray->size();
            for (unsigned i = 0; i < _quads.size(); ++i)
            {
                for (unsigned j = 0; j < 4; ++j)
                {
                    pushVertex(_quads[i].index[j], vertexArray, normalArray, texcoordArray);
                }
            }
            osg::DrawArrays* drawArray = new osg::DrawArrays(osg::PrimitiveSet::QUADS, start, 4*_quads.size());
            geometry->addPrimitiveSet(drawArray);
        }

        // handle polygons
        if (!_polygons.empty())
        {
            unsigned start = vertexArray->size();
            osg::DrawArrayLengths* drawArrayLengths = new osg::DrawArrayLengths(osg::PrimitiveSet::POLYGON, start);
            drawArrayLengths->reserve(_polygons.size());
            for (unsigned i = 0; i < _polygons.size(); ++i)
            {
                for (unsigned j = 0; j < _polygons[i].index.size(); ++j)
                {
                    pushVertex(_polygons[i].index[j], vertexArray, normalArray, texcoordArray);
                }
                drawArrayLengths->push_back(_polygons[i].index.size());
            }
            geometry->addPrimitiveSet(drawArrayLengths);
        }

        return _geode.get();
    }
};

struct Bins
{
    PrimitiveBin* getOrCreatePrimitiveBin(unsigned flags, VertexSet* vertexSet)
    {
        if ((flags & SurfaceTypeLineLoop) || (flags & SurfaceTypeLineStrip))
        {
            if (!lineBin.valid())
            {
                lineBin = new LineBin(flags, vertexSet);
            }
            return lineBin.get();
        }
        else if (flags & SurfaceShaded)
        {
            if (flags & SurfaceTwoSided)
            {
                if (!smoothDoubleSurfaceBin.valid())
                {
                    smoothDoubleSurfaceBin = new SurfaceBin(flags, vertexSet);
                }
                return smoothDoubleSurfaceBin.get();
            }
            else
            {
                if (!smoothSingleSurfaceBin.valid())
                {
                    smoothSingleSurfaceBin = new SurfaceBin(flags, vertexSet);
                }
                return smoothSingleSurfaceBin.get();
            }
        }
        else
        {
            if (flags & SurfaceTwoSided)
            {
                if (!flatDoubleSurfaceBin.valid())
                {
                    flatDoubleSurfaceBin = new SurfaceBin(flags, vertexSet);
                }
                return flatDoubleSurfaceBin.get();
            }
            else
            {
                if (!flatSingleSurfaceBin.valid())
                {
                    flatSingleSurfaceBin = new SurfaceBin(flags, vertexSet);
                }
                return flatSingleSurfaceBin.get();
            }
        }
    }
    void finalize(osg::Group* group, const MaterialData& material, const TextureData& textureData)
    {
        if (lineBin.valid())
        {
            group->addChild(lineBin->finalize(material, textureData));
        }
        if (smoothDoubleSurfaceBin.valid())
        {
            group->addChild(smoothDoubleSurfaceBin->finalize(material, textureData));
        }
        if (smoothSingleSurfaceBin.valid())
        {
            group->addChild(smoothSingleSurfaceBin->finalize(material, textureData));
        }
        if (flatDoubleSurfaceBin.valid())
        {
            group->addChild(flatDoubleSurfaceBin->finalize(material, textureData));
        }
        if (flatSingleSurfaceBin.valid())
        {
            group->addChild(flatSingleSurfaceBin->finalize(material, textureData));
        }
    }

private:
    osg::ref_ptr<LineBin> lineBin;
    osg::ref_ptr<SurfaceBin> flatDoubleSurfaceBin;
    osg::ref_ptr<SurfaceBin> flatSingleSurfaceBin;
    osg::ref_ptr<SurfaceBin> smoothDoubleSurfaceBin;
    osg::ref_ptr<SurfaceBin> smoothSingleSurfaceBin;
};

osg::Node*
readObject(std::istream& stream, FileData& fileData, const osg::Matrix& parentTransform, TextureData textureData)
{
    // most of this logic came from Andy Colebourne (developer of the AC3D editor) so it had better be right!

    // The transform configured in this current object level
    osg::Matrix transform;
    // The vertex pool in this object
    osg::ref_ptr<VertexSet> vertexSet = new VertexSet;
    osg::ref_ptr<osg::Group> group = new osg::Group;
    osg::Vec2 textureOffset(0, 0);
    osg::Vec2 textureRepeat(1, 1);
    float creaseAngle = 61;
    unsigned objectType = ObjectTypeGroup;
    
    while (!stream.eof() && stream.good()) {
        std::string token;
        stream >> token;
      
        if (token == "MATERIAL") {
            MaterialData mat;
            mat.readMaterial(stream);
            fileData.addMaterial(mat);
        }
        else if (token == "OBJECT") {
            std::string type;
            stream >> type;
            
            if (type == "group")
                objectType = ObjectTypeGroup;
            else if (type == "light")
                objectType = ObjectTypeLight;
            else if (type == "world")
                objectType = ObjectTypeGroup;
            else
                objectType = ObjectTypeNormal;
        }
        else if (token == "crease") {
            stream >> creaseAngle;
        }
        else if (token == "data") {
            int len;
            stream >> len;
            std::vector<char> tmp(len);
            stream.read(&(tmp[0]), len);
        }
        else if (token == "name") {
            group->setName(readString(stream));
        }
        else if (token == "texture") {
            // read the texture name
            std::string texname = readString(stream);
            
            // strip the path to the texture, just look in the directory we read the ac file
            std::string::size_type p = texname.rfind('\\');
            if (p != std::string::npos)
                texname = texname.substr(p+1, std::string::npos);
            p = texname.rfind('/');
            if (p != std::string::npos)
                texname = texname.substr(p+1, std::string::npos);
        
            textureData  = fileData.toTextureData(texname);
        }
        else if (token == "texrep") {
            stream >> textureRepeat[0] >> textureRepeat[1];
        }
        else if (token == "texoff") {
            stream >> textureOffset[0] >> textureOffset[1];
        }
        else if (token == "rot") {
            for (unsigned n = 0; n < 3; ++n)
                for (unsigned m = 0; m < 3; ++m)
                    stream >> transform(m, n);
        }
        else if (token == "loc") {
            for (unsigned n = 0; n < 3; ++n)
                stream >> transform(3, n);
        }
        else if (token == "url") {
            std::string url;
            stream >> url;
            group->addDescription(url);
        }
        else if (token == "numvert") {
            osg::Matrix currentTransform = transform*parentTransform;
            
            unsigned num;
            stream >> num;
            if (num != 0) {
                vertexSet->reserve(num);
              
                for (unsigned n = 0; n < num; ++n) {
                    osg::Vec3 p;
                    stream >> p[0] >> p[1] >> p[2];
                    vertexSet->addVertex(currentTransform.preMult(p));
                }
            }
        }
        else if (token == "numsurf") {
            unsigned num;
            stream >> num;
            if (0 < num) {
                // list of materials required- generate one geode per material
                std::vector<Bins> primitiveBins(fileData.getNumMaterials());
                vertexSet->setCreaseAngle(creaseAngle);
                
                for (unsigned n = 0; n < num; ++n) {
                    std::string token;
                    stream >> token;
                    
                    if (token != "SURF") {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: expected SURF line while reading object \""
                                                << group->getName() << "\"!" << std::endl;
                        return group.release();
                    }
                    
                    stream >> token;
                    unsigned flags = strtol(token.c_str(), NULL, 0);
                    
                    stream >> token;
                    if (token != "mat") {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: expected mat line while reading object \""
                                                << group->getName() << "\"!" << std::endl;
                        return group.release();
                    }
                    
                    // read the material index
                    unsigned matIdx;
                    stream >> matIdx;
                    if (primitiveBins.size() <= matIdx) {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: invalid material number while reading object \""
                                                << group->getName() << "\"" << std::endl;
                        return group.release();
                    }
                    
                    // now get the correct PrimitiveBin
                    PrimitiveBin* primitiveBin = 0;
                    primitiveBin = primitiveBins[matIdx].getOrCreatePrimitiveBin(flags, vertexSet.get());
                    if (!primitiveBin) {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: unexpected primitive flags while reading object \""
                                                << group->getName() << "\"" << std::endl;
                        return group.release();
                    }
                    
                    // read the refs
                    stream >> token;
                    if (token != "refs") {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: expected refs line while reading object \""
                                                << group->getName() << "\"" << std::endl;
                        return group.release();
                    }
                    
                    unsigned nRefs = 0;
                    stream >> nRefs;
                    if (!stream) {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: could not read number of refs while reading object \""
                                                << group->getName() << "\"" << std::endl;
                        return group.release();
                    }
                    
                    // in case this is an invalid refs count for this primitive
                    // read further, but do not store that primitive
                    bool acceptPrimitive = primitiveBin->beginPrimitive(nRefs);
                    for (unsigned i = 0; i < nRefs; ++i) {
                        // Read the vertex index
                        unsigned index;
                        stream >> index;
                        if (vertexSet->size() <= index)
                        {
                            osg::notify(osg::FATAL) << "osgDB ac3d reader: invalid ref vertex index while reading object \""
                                                    << group->getName() << "\"" << std::endl;
                            return group.release();
                        }
                        
                        // Read the texture corrdinates
                        osg::Vec2 texCoord;
                        stream >> texCoord[0] >> texCoord[1];
                        if (!stream) {
                            osg::notify(osg::WARN) << "osgDB ac3d reader: could not parse texture coords while reading object \""
                                                   << group->getName() << "\" setting to (0,0)" << std::endl;
                            stream.clear();
                            std::string dummy;
                            std::getline(stream, dummy);
                        }
                        
                        if (acceptPrimitive)
                        {
                            texCoord[0] = textureOffset[0] + texCoord[0]*textureRepeat[0];
                            texCoord[1] = textureOffset[1] + texCoord[1]*textureRepeat[1];
                        
                            if (!primitiveBin->vertex(index, texCoord))
                            {
                                return group.release();
                            }
                        }
                    }
                    if (acceptPrimitive)
                    {
                        if (!primitiveBin->endPrimitive())
                        {
                            return group.release();
                        }
                    }
                }
                
                for (unsigned i = 0; i < primitiveBins.size(); ++i)
                    primitiveBins[i].finalize(group.get(), fileData.getMaterial(i), textureData);
            }
        }
        else if (token == "kids") {
            unsigned num;
            stream >> num;
            if (num != 0) {
                for (unsigned n = 0; n < num; n++) {
                    osg::Node *k = readObject(stream, fileData, transform*parentTransform, textureData);
                    if (k == 0) {
                        osg::notify(osg::FATAL) << "osgDB ac3d reader: error reading child object" << std::endl;
                        return group.release();
                    }
                    else {
                        osg::LightSource *ls = dynamic_cast<osg::LightSource*>(k);
                        if (ls) {
                            osg::StateSet* lightStateSet = group->getOrCreateStateSet();
                            group->setStateSet(lightStateSet);
                            group->setCullingActive(false);
                            ls->setStateSetModes(*lightStateSet, osg::StateAttribute::ON);
                        }
                        
                        group->addChild(k);
                    }
                }
            }
            else if (objectType == ObjectTypeLight) { // add a light source to the scene 1 Nov 2003
                osg::Light* ac3dLight = fileData.getNextLight();
                osg::Matrix tt = transform*parentTransform;
                ac3dLight->setPosition(osg::Vec4(tt(3, 0), tt(3, 1), tt(3, 2), 1));
                ac3dLight->setDirection(osg::Matrix::transform3x3(osg::Vec3(0.0f, 0.0f, -1.0f), tt));
                ac3dLight->setAmbient(osg::Vec4(0.5f,0.5f,0.5f,1.0f));
                ac3dLight->setDiffuse(osg::Vec4(0.5f,0.5f,0.5f,1.0f));
                ac3dLight->setSpecular(osg::Vec4(1.0f,1.0f,0.5f,1.0f));
                
                osg::LightSource* ac3dLightSource = new osg::LightSource;    
                ac3dLightSource->setLight(ac3dLight);
                ac3dLightSource->setLocalStateSetModes(osg::StateAttribute::ON);
                
                // for some mad reason, you need to set this so that the light works.  WHY?
                return ac3dLightSource;
            }
            return group.release();
        }
    }
    
    return group.release();
}

osg::Node*
readFile(std::istream& stream, const osgDB::ReaderWriter::Options* options)
{
    FileData fileData(options);
    osg::Matrix idetityTransform;
    osg::Node* node = readObject(stream, fileData, idetityTransform, TextureData());
    if (node)
      node->setName("World");
    return node;
}

} // namespace ac3d
