/* -*-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 <math.h>

//certain math functions were not defined until 10.2
//so this code checks the version so it can add in workarounds for older versions.
#ifdef __APPLE__
// Using std::isnan will work for OS X, but use of <cmath> 
// and std:: are not necessarily portible with other systems so 
// the include of <cmath> is isolated here.
#include <cmath>
#include <AvailabilityMacros.h>
#if !defined(MAC_OS_X_VERSION_10_2) || (MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_2)
    // One extra check to verify the gcc version.
    // The assumption is that there is no possible way to use gcc 4+
    // on anything less than 10.3.9. So if gcc 4 is in use, this means
    // pre-10.2 support is not intended and we need not define APPLE_PRE_10_2.
    // The reason for this extra check is that if the user relies on default
    // settings, MAC_OS_X_VERSION_MIN_REQUIRED will be set to 1010 and hit
    // this code path, but this is probably not what they want if using gcc 4+. 
    #if (__GNUC__ < 4)
        #define APPLE_PRE_10_2
    #endif
#endif
#endif

#if defined(_MSC_VER)
    #include <float.h>
#endif

#if defined (sun) || defined (__APPLE__)

    #include <float.h>

    #ifndef acosf
    inline float acosf(float value) { return static_cast<float>(acos(value)); }
    #endif

    #ifndef asinf
    inline float asinf(float value) { return static_cast<float>(asin(value)); }
    #endif

    #ifndef cosf
    inline float cosf(float value) { return static_cast<float>(cos(value)); }
    #endif

    #ifndef sinf
    inline float sinf(float value) { return static_cast<float>(sin(value)); }
    #endif

    #ifndef logf
    inline float logf(float value) { return static_cast<float>(log(value)); }
    #endif

    #ifndef powf
    inline float powf(float value1,float value2) { return static_cast<float>(pow(value1,value2)); }
    #endif

    #ifndef sqrtf
    inline float sqrtf(float value) { return static_cast<float>(sqrt(value)); }
    #endif
    
    #ifndef fabsf
    inline float fabsf(float value) { return static_cast<float>(fabs(value)); }
    #endif

    #ifndef atan2f
    inline float atan2f(float value1, float value2) { return static_cast<float>(atan2(value1,value2)); }
    #endif

    #ifndef tanf
    inline float tanf(float value) { return static_cast<float>(tan(value)); }
    #endif

#endif


#if defined (sun) || \
    defined (__hpux) || \
    defined (APPLE_PRE_10_2)

    #ifndef floorf
    inline float floorf(float value) { return static_cast<float>(floor(value)); }
    #endif

    #ifndef ceilf
    inline float ceilf(float value) { return static_cast<float>(ceil(value)); }
    #endif

#endif

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;


/** 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 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(WIN32) && !defined(__CYGWIN__) && !defined(__MWERKS__)
    inline bool isNaN(float v) { return _isnan(v)!=0; }
    inline bool isNaN(double v) { return _isnan(v)!=0; }
#else
    #if defined(__APPLE__)
        inline bool isNaN(float v) { return std::isnan(v); }
        inline bool isNaN(double v) { return std::isnan(v); }
    #else
        // Need to use to std::isnan to avoid undef problem from <cmath>
        inline bool isNaN(float v) { return isnan(v); }
        inline bool isNaN(double v) { return isnan(v); }
    #endif
#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);
}

}

#endif  // __OSG_MATH

