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// P. Arce, June-2014 Conversion neutron_hp to particle_hp
//
#ifndef G4ParticleHPMadlandNixSpectrum_h
#define G4ParticleHPMadlandNixSpectrum_h 1

#include "G4Exp.hh"
#include "G4Log.hh"
#include "G4ParticleHPVector.hh"
#include "G4Pow.hh"
#include "G4VParticleHPEDis.hh"
#include "G4ios.hh"
#include "Randomize.hh"
#include "globals.hh"

#include <CLHEP/Units/PhysicalConstants.h>

#include <cmath>
#include <fstream>

//     #include <nag.h> @
//     #include <nags.h> @

// we will need a List of these .... one per term.

class G4ParticleHPMadlandNixSpectrum : public G4VParticleHPEDis
{
  public:
    G4ParticleHPMadlandNixSpectrum()
    {
      expm1 = G4Exp(-1.);
      theAvarageKineticPerNucleonForLightFragments = 0.0;
      theAvarageKineticPerNucleonForHeavyFragments = 0.0;
    }
    ~G4ParticleHPMadlandNixSpectrum() override = default;

    inline void Init(std::istream& aDataFile) override
    {
      theFractionalProb.Init(aDataFile);
      aDataFile >> theAvarageKineticPerNucleonForLightFragments;
      theAvarageKineticPerNucleonForLightFragments *= CLHEP::eV;
      aDataFile >> theAvarageKineticPerNucleonForHeavyFragments;
      theAvarageKineticPerNucleonForHeavyFragments *= CLHEP::eV;
      theMaxTemp.Init(aDataFile);
    }

    inline G4double GetFractionalProbability(G4double anEnergy) override
    {
      return theFractionalProb.GetY(anEnergy);
    }

    G4double Sample(G4double anEnergy) override;

  private:
    G4double Madland(G4double aSecEnergy, G4double tm);

    inline G4double FissionIntegral(G4double tm, G4double anEnergy)
    {
      return 0.5
             * (GIntegral(tm, anEnergy, theAvarageKineticPerNucleonForLightFragments)
                + GIntegral(tm, anEnergy, theAvarageKineticPerNucleonForHeavyFragments));
    }

    G4double GIntegral(G4double tm, G4double anEnergy, G4double aMean);

    inline G4double Gamma05(G4double aValue)
    {
      G4double result;
      // gamma(1.2,x*X) = std::sqrt(CLHEP::pi)*Erf(x)
      G4double x = std::sqrt(aValue);
      G4double t = 1. / (1 + 0.47047 * x);
      result =
        1
        - (0.3480242 * t - 0.0958798 * t * t + 0.7478556 * t * t * t) * G4Exp(-aValue);  // @ check
      result *= std::sqrt(CLHEP::pi);
      return result;
    }

    inline G4double Gamma15(G4double aValue)
    {
      G4double result;
      // gamma(a+1, x) = a*gamma(a,x)-x**a*std::exp(-x)
      result = 0.5 * Gamma05(aValue) - std::sqrt(aValue) * G4Exp(-aValue);  // @ check
      return result;
    }

    inline G4double Gamma25(G4double aValue)
    {
      G4double result;
      result =
        1.5 * Gamma15(aValue) - G4Pow::GetInstance()->powA(aValue, 1.5) * G4Exp(aValue);  // @ check
      return result;
    }

    inline G4double E1(G4double aValue)
    {
      // good only for rather low aValue @@@ replace by the corresponding NAG function for the
      // exponential integral. (<5 seems ok.
      G4double gamma = 0.577216;
      G4double precision = 0.000001;
      G4double result = -gamma - G4Log(aValue);
      G4double term = -aValue;
      // 110527TKDB  Unnessary codes, Detected by gcc4.6 compiler
      // G4double last;
      G4int count = 1;
      result -= term;
      for (;;) {
        count++;
        // 110527TKDB  Unnessary codes, Detected by gcc4.6 compiler
        // last = result;
        term = -term * aValue * (count - 1) / (count * count);
        result -= term;
        if (std::fabs(term) / std::fabs(result) < precision) break;
      }
      //    NagError *fail; @
      //    result = nag_exp_integral(aValue, fail); @
      return result;
    }

  private:
    G4double expm1;

  private:
    G4ParticleHPVector theFractionalProb;

    G4double theAvarageKineticPerNucleonForLightFragments;
    G4double theAvarageKineticPerNucleonForHeavyFragments;

    G4ParticleHPVector theMaxTemp;
};

#endif