#ifndef __JCONSTANTS__
#define __JCONSTANTS__

#include <math.h>

namespace JTOOLS {

  /**
   * Constants.
   */
  static const double INDEX_OF_REFRACTION_WATER = 1.3800851282;    //!< average index of refraction of water

  // derived quantities

  static const double TAN_THETA_C_WATER         = sqrt((INDEX_OF_REFRACTION_WATER - 1.0) * (INDEX_OF_REFRACTION_WATER + 1.0));
  static const double COS_THETA_C_WATER         = 1.0 / INDEX_OF_REFRACTION_WATER;
  static const double SIN_THETA_C_WATER         = TAN_THETA_C_WATER * COS_THETA_C_WATER;

  static const double PI                     = 3.1415927;            //!< pi
  static const double EULER                  = 0.577215664901533;    //!< Euler number
  static const double C                      = 0.299792458;          //!< Speed of light in vacuum [m/ns]
  static const double C_INVERSE              = 1.0/C;                //!< Inverse speed of light in vacuum [ns/m]
  static const double AVOGADRO               = 6.0221415e23;         //!< Avogadro's number [gr^-1]
  static const double H                      = 4.13566733e-15;       //!< Planck constant [eV s]
  static const double HBAR                   = H/(2*PI);             //!< Planck constant [eV s]
  static const double HBARC                  = HBAR*C*1.0e9;         //!< Planck constant [eV m]
  static const double ALPHA_ELECTRO_MAGNETIC = 1.0/137.036;          //!< Electro-Magnetic coupling constant
  static const double DENSITY_SEA_WATER      = 1.027;                //!< Density  of sea water [g/cm^3]
  static const double DENSITY_ROCK           = 2.65;                 //!< Density  of rock      [g/cm^3]
  static const double SALINITY_SEA_WATER     = 0.035;                //!< Salinity of sea water

  static const double MASS_ELECTRON          = 0.511e-3;             //!< electron mass [GeV]
  static const double MASS_MUON              = 0.10566;              //!< muon     mass [GeV]
  static const double MASS_PROTON            = 0.938;                //!< proton   mass [GeV]

 
  /** 
   * Get speed of light.
   * 
   * return           speed of light [m/ns]
   */
  inline const double getSpeedOfLight()
  {
    return C;
  }


  /**
   * Get inverse speed of light.
   *
   * return           inverse speed of light [ns/m]
   */
  inline const double getInverseSpeedOfLight()
  { 
    return C_INVERSE; 
  }


  /**
   * Average index of refraction of water.
   *
   * \return          index of refraction
   */
  inline double getIndexOfRefraction() 
  {
    return INDEX_OF_REFRACTION_WATER;
  }


  /**
   * Average tangent of Cherenkov angle of water
   *
   * \return          tan(theta_C)
   */
  inline double getTanThetaC() 
  {
    return TAN_THETA_C_WATER;
  }


  /**
   * Average cosine of Cherenkov angle of water
   *
   * \return          cos(theta_C)
   */
  inline double getCosThetaC() 
  {
    return COS_THETA_C_WATER;
  }


  /**
   * Average sine of Cherenkov angle of water
   *
   * \return          sin(theta_C)
   */
  inline double getSinThetaC() 
  {
    return SIN_THETA_C_WATER;
  }
}

#endif