/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSG_COORDINATESYSTEMNODE
#define OSG_COORDINATESYSTEMNODE 1

#include <osg/Group>
#include <osg/Matrixd>

namespace osg
{

const double WGS_84_RADIUS_EQUATOR = 6378137.0;
const double WGS_84_RADIUS_POLAR = 6356752.3142;

/** EllipsoidModel encapsulates the ellipsoid used to model astronomical bodies,
 * such as sun, planets, moon etc. 
 * All distance quantities (i.e. heights + radius) are in meters,
 * and latitude and longitude are in radians.*/
class EllipsoidModel : public Object
{
    public:

        /** WGS_84 is a common representation of the earth's spheroid */
        EllipsoidModel(double radiusEquator = WGS_84_RADIUS_EQUATOR,
                       double radiusPolar = WGS_84_RADIUS_POLAR):
            _radiusEquator(radiusEquator),
            _radiusPolar(radiusPolar) { computeCoefficients(); }

        EllipsoidModel(const EllipsoidModel& et,const CopyOp& copyop=CopyOp::SHALLOW_COPY):
            Object(et,copyop),
            _radiusEquator(et._radiusEquator),
            _radiusPolar(et._radiusPolar) { computeCoefficients(); }

        META_Object(osg,EllipsoidModel);

        void setRadiusEquator(double radius) { _radiusEquator = radius; computeCoefficients(); }
        double getRadiusEquator() const { return _radiusEquator; }

        void setRadiusPolar(double radius) { _radiusPolar = radius; computeCoefficients(); }
        double getRadiusPolar() const { return _radiusPolar; }

        inline void convertLatLongHeightToXYZ(double latitude, double longitude, double height,
                                              double& X, double& Y, double& Z) const;

        inline void convertXYZToLatLongHeight(double X, double Y, double Z,
                                              double& latitude, double& longitude, double& height) const;

        inline void computeLocalToWorldTransformFromLatLongHeight(double latitude, double longitude, double height, osg::Matrixd& localToWorld) const;

        inline void computeLocalToWorldTransformFromXYZ(double X, double Y, double Z, osg::Matrixd& localToWorld) const;

        inline osg::Vec3d computeLocalUpVector(double X, double Y, double Z) const;

    protected:

        void computeCoefficients()
        {
            double flattening = (_radiusEquator-_radiusPolar)/_radiusEquator;
            _eccentricitySquared = 2*flattening - flattening*flattening;
        }

        double _radiusEquator;
        double _radiusPolar;
        double _eccentricitySquared;

};

/** CoordinateFrame encapsulates the orientation of east, north and up.*/ 
typedef Matrixd CoordinateFrame;

/** CoordinateSystem encapsulate the coordinate system that is associated with objects in a scene.
    For an overview of common earth bases coordinate systems see http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html */
class OSG_EXPORT CoordinateSystemNode : public Group
{
    public:

        CoordinateSystemNode();

        CoordinateSystemNode(const std::string& format, const std::string& cs);

        /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
        CoordinateSystemNode(const CoordinateSystemNode&,const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);
        
        META_Node(osg,CoordinateSystemNode);
        
        
        /** Set the coordinate system node up by copy the format, coordinate system string, and ellipsoid model of another coordinate system node.*/
        void set(const CoordinateSystemNode& csn);
                
        /** Set the coordinate system format string. Typical values would be WKT, PROJ4, USGS etc.*/
        void setFormat(const std::string& format) { _format = format; }
        
        /** Get the coordinate system format string.*/
        const std::string& getFormat() const { return _format; }

        /** Set the CoordinateSystem reference string, should be stored in a form consistent with the Format.*/
        void setCoordinateSystem(const std::string& cs) { _cs = cs; }
        
        /** Get the CoordinateSystem reference string.*/
        const std::string& getCoordinateSystem() const { return _cs; }
        
        
        /** Set EllipsoidModel to describe the model used to map lat, long and height into geocentric XYZ and back. */
        void setEllipsoidModel(EllipsoidModel* ellipsode) { _ellipsoidModel = ellipsode; }
        
        /** Get the EllipsoidModel.*/
        EllipsoidModel* getEllipsoidModel() { return _ellipsoidModel.get(); }
        
        /** Get the const EllipsoidModel.*/
        const EllipsoidModel* getEllipsoidModel() const { return _ellipsoidModel.get(); }
        
        /** Compute the local coordinate frame for specified point.*/
        CoordinateFrame computeLocalCoordinateFrame(const Vec3d& position) const;
        
        /** Compute the local coordinate frame for specified point.*/
        osg::Vec3d computeLocalUpVector(const Vec3d& position) const;

    protected:

        virtual ~CoordinateSystemNode() {}
                
        std::string             _format;
        std::string             _cs;
        ref_ptr<EllipsoidModel> _ellipsoidModel;

};



////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// implement inline methods.
//
inline void EllipsoidModel::convertLatLongHeightToXYZ(double latitude, double longitude, double height,
                                      double& X, double& Y, double& Z) const
{
    // for details on maths see http://www.colorado.edu/geography/gcraft/notes/datum/gif/llhxyz.gif
    double sin_latitude = sin(latitude);
    double cos_latitude = cos(latitude);
    double N = _radiusEquator / sqrt( 1.0 - _eccentricitySquared*sin_latitude*sin_latitude);
    X = (N+height)*cos_latitude*cos(longitude);
    Y = (N+height)*cos_latitude*sin(longitude);
    Z = (N*(1-_eccentricitySquared)+height)*sin_latitude;
}


inline void EllipsoidModel::convertXYZToLatLongHeight(double X, double Y, double Z,
                                      double& latitude, double& longitude, double& height) const
{
    // http://www.colorado.edu/geography/gcraft/notes/datum/gif/xyzllh.gif
    double p = sqrt(X*X + Y*Y);
    double theta = atan2(Z*_radiusEquator , (p*_radiusPolar));
    double eDashSquared = (_radiusEquator*_radiusEquator - _radiusPolar*_radiusPolar)/
                          (_radiusPolar*_radiusPolar);

    double sin_theta = sin(theta);
    double cos_theta = cos(theta);

    latitude = atan( (Z + eDashSquared*_radiusPolar*sin_theta*sin_theta*sin_theta) /
                     (p - _eccentricitySquared*_radiusEquator*cos_theta*cos_theta*cos_theta) );
    longitude = atan2(Y,X);

    double sin_latitude = sin(latitude);
    double N = _radiusEquator / sqrt( 1.0 - _eccentricitySquared*sin_latitude*sin_latitude);

    height = p/cos(latitude) - N;
}

inline void EllipsoidModel::computeLocalToWorldTransformFromLatLongHeight(double latitude, double longitude, double height, osg::Matrixd& localToWorld) const
{
    double X, Y, Z;
    convertLatLongHeightToXYZ(latitude,longitude,height,X,Y,Z);
    computeLocalToWorldTransformFromXYZ(X,Y,Z,localToWorld);
}

inline void EllipsoidModel::computeLocalToWorldTransformFromXYZ(double X, double Y, double Z, osg::Matrixd& localToWorld) const
{
    localToWorld.makeTranslate(X,Y,Z);


    // normalize X,Y,Z
    double inverse_length = 1.0/sqrt(X*X + Y*Y + Z*Z);
    
    X *= inverse_length;
    Y *= inverse_length;
    Z *= inverse_length;

    double length_XY = sqrt(X*X + Y*Y);
    double inverse_length_XY = 1.0/length_XY;

    // Vx = |(-Y,X,0)|
    localToWorld(0,0) = -Y*inverse_length_XY;
    localToWorld(0,1) = X*inverse_length_XY;
    localToWorld(0,2) = 0.0;

    // Vy = /(-Z*X/(sqrt(X*X+Y*Y), -Z*Y/(sqrt(X*X+Y*Y),sqrt(X*X+Y*Y))| 
    double Vy_x = -Z*X*inverse_length_XY;
    double Vy_y = -Z*Y*inverse_length_XY;
    double Vy_z = length_XY;
    inverse_length = 1.0/sqrt(Vy_x*Vy_x + Vy_y*Vy_y + Vy_z*Vy_z);            
    localToWorld(1,0) = Vy_x*inverse_length;
    localToWorld(1,1) = Vy_y*inverse_length;
    localToWorld(1,2) = Vy_z*inverse_length;

    // Vz = (X,Y,Z)
    localToWorld(2,0) = X;
    localToWorld(2,1) = Y;
    localToWorld(2,2) = Z;
}

inline osg::Vec3d EllipsoidModel::computeLocalUpVector(double X, double Y, double Z) const
{
    osg::Vec3d normal(X,Y,Z);
    normal.normalize();
    return normal;
}

}
#endif