/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2004 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_MATH
#define __OSG_MATH

#include <cmath>
#include <cfloat>

#include <osg/Export>

namespace osg {

// define the standard trig values
#ifdef PI
#undef PI
#undef PI_2
#undef PI_4
#endif
const double PI   = 3.14159265358979323846;
const double PI_2 = 1.57079632679489661923;
const double PI_4 = 0.78539816339744830962;
const double LN_2 = 0.69314718055994530942;
const double INVLN_2 = 1.0 / LN_2;


template<typename T>
inline T absolute(T v) { return v<(T)0?-v:v; }

/** return true if float lhs and rhs are equivalent,
  * meaning that the difference between them is less than an epsilon value
  * which defaults to 1e-6.
*/
inline bool equivalent(float lhs,float rhs,float epsilon=1e-6)
  { float delta = rhs-lhs; return delta<0.0f?delta>=-epsilon:delta<=epsilon; }

/** return true if double lhs and rhs are equivalent,
  * meaning that the difference between them is less than an epsilon value
  * which defaults to 1e-6.
*/
inline bool equivalent(double lhs,double rhs,double epsilon=1e-6)
  { double delta = rhs-lhs; return delta<0.0?delta>=-epsilon:delta<=epsilon; }

/** return the minimum of two values, equivalent to std::min.
  * std::min not used because of STL implementation under IRIX not containing
  * std::min.
*/
template<typename T>
inline T minimum(T lhs,T rhs) { return lhs<rhs?lhs:rhs; }

/** return the maximum of two values, equivalent to std::max.
  * std::max not used because of STL implementation under IRIX not containing
  * std::max.
*/
template<typename T>
inline T maximum(T lhs,T rhs) { return lhs>rhs?lhs:rhs; }

template<typename T>
inline T clampTo(T v,T minimum,T maximum) { return v<minimum?minimum:v>maximum?maximum:v; }

template<typename T>
inline T clampAbove(T v,T minimum) { return v<minimum?minimum:v; }

template<typename T>
inline T clampBelow(T v,T maximum) { return v>maximum?maximum:v; }

template<typename T>
inline T clampBetween(T v,T minimum, T maximum)
  { return clampBelow(clampAbove(v,minimum),maximum); }

template<typename T>
inline T sign(T v) { return v<(T)0?(T)-1:(T)1; }

template<typename T>
inline T signOrZero(T v) { return v<(T)0 ? (T)-1 : ( v>(T)0 ? (T)1 : 0 ); }

template<typename T>
inline T square(T v) { return v*v; }

template<typename T>
inline T signedSquare(T v) { return v<(T)0?-v*v:v*v;; }

inline float inDegrees(float angle) { return angle*(float)PI/180.0f; }
inline double inDegrees(double angle) { return angle*PI/180.0; }

template<typename T>
inline T inRadians(T angle) { return angle; }

inline float DegreesToRadians(float angle) { return angle*(float)PI/180.0f; }
inline double DegreesToRadians(double angle) { return angle*PI/180.0; }

inline float RadiansToDegrees(float angle) { return angle*180.0f/(float)PI; }
inline double RadiansToDegrees(double angle) { return angle*180.0/PI; }

inline float round(float v) { return v>=0.0f?floorf(v+0.5f):ceilf(v-0.5f); }
inline double round(double v) { return v>=0.0?floor(v+0.5):ceil(v-0.5); }

#if defined(_MSC_VER)
    inline bool isNaN(double v) { return _isnan(v)!=0; }
#elif defined(__ANDROID__)
    inline bool isNaN(float v) { return isnan(v); }
    inline bool isNaN(double v) { return isnan(v); }
#else
    inline bool isNaN(float v) { return std::isnan(v); }
    inline bool isNaN(double v) { return std::isnan(v); }
#endif


/** compute the volume of a tetrahedron. */
template<typename T>
inline float computeVolume(const T& a,const T& b,const T& c,const T& d)
{
    return fabsf(((b-c)^(a-b))*(d-b));
}

/** compute the volume of a prism. */
template<typename T>
inline float computeVolume(const T& f1,const T& f2,const T& f3,
                           const T& b1,const T& b2,const T& b3)
{
    return computeVolume(f1,f2,f3,b1)+
           computeVolume(b1,b2,b3,f2)+
           computeVolume(b1,b3,f2,f3);
}

/** Convert a ascii number to a double, ignoring locale settings.*/
extern OSG_EXPORT double asciiToDouble(const char* str);

/** Convert a ascii number to a float, ignoring locale settings.*/
inline float asciiToFloat(const char* str) { return static_cast<float>(asciiToDouble(str)); }

/** Detect first ascii POSITIVE number in string and convert to double.*/
extern OSG_EXPORT double findAsciiToDouble(const char* str);

/** Detect first ascii POSITIVE number in string and convert to double.*/
inline float findAsciiToFloat(const char* str) { return static_cast<float>(findAsciiToDouble(str)); }

}


#endif  // __OSG_MATH

