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// $Id: G4DNADingfelderChargeChangeTotalCrossSectionPolicy.icc,v 1.3 2006/06/29 19:33:52 gunter Exp $
// GEANT4 tag $Name: geant4-08-01 $
//

#ifdef   G4DNADINGFELDERCHARGECHANGETOTALCROSSSECTIONPOLICY_HH
 #include "Randomize.hh"

 template <typename IncomingParticlePolicy, typename EnergyLimitsPolicy>
 G4double                               G4DNADingfelderChargeChangeTotalCrossSectionPolicy<IncomingParticlePolicy, EnergyLimitsPolicy> :: TotalCrossSection(G4double k, G4int z)
 {
  if (k < EnergyLimitsPolicy::lowEnergyLimit)
  {
   if (EnergyLimitsPolicy::zeroBelowLowEnergyLimit)
    return 0;
  
   k=EnergyLimitsPolicy::lowEnergyLimit;
  }
  else if (k > EnergyLimitsPolicy::highEnergyLimit)
  {
   if (EnergyLimitsPolicy::zeroAboveHighEnergyLimit)
    return 0;
    
   k=EnergyLimitsPolicy::highEnergyLimit;
  }

  G4int i(IncomingParticlePolicy::NumberOfPartialCrossSections());
  G4double totalCrossSection(0.);
  
  while (i>0)
  {
   i--;
   totalCrossSection+=PartialCrossSection(k, z, i);
  }

  return totalCrossSection;
 }
 
 template <typename IncomingParticlePolicy, typename EnergyLimitsPolicy>
 G4int                                  G4DNADingfelderChargeChangeTotalCrossSectionPolicy<IncomingParticlePolicy, EnergyLimitsPolicy> :: RandomizePartialCrossSection(G4double k, G4int z)
 {
  const G4int n(IncomingParticlePolicy::NumberOfPartialCrossSections());
  G4double * values(new G4double[n]);
  G4double value(0);
  G4int i(n);
  
  while (i>0)
  {
   i--;
   values[i]=PartialCrossSection(k, z, i);
   value+=values[i];
  }
  
  value*=G4UniformRand();
  
  i=n;
  while (i>0)
  {
   i--;
   
   if (values[i]>value)
    break;
  
   value-=values[i];
  }
  
  delete[] values;
  
  return i;
 }

 template <typename IncomingParticlePolicy, typename EnergyLimitsPolicy>
 G4double                             	G4DNADingfelderChargeChangeTotalCrossSectionPolicy<IncomingParticlePolicy, EnergyLimitsPolicy> :: PartialCrossSection(G4double k, G4int /* z */, G4int index)
 {
  //
  // sigma(T) = f0 10 ^ y(std::log10(T/eV))
  //
  //         /  a0 x + b0                    x < x0
  //         |
  // y(x) = <   a0 x + b0 - c0 (x - x0)^d0   x0 <= x < x1
  //         |
  //         \  a1 x + b1                    x >= x1
  //
  //
  // f0, a0, a1, b0, b1, c0, d0, x0, x1 are parameters that change for protons and helium (0, +, ++)
  //
  // f0 has been added to the code in order to manage partial (shell-dependent) cross sections (if no shell dependence is present. f0=1. Sum of f0 over the considered shells should give 1)
  //
  // From Rad. Phys. and Chem. 59 (2000) 255-275, M. Dingfelder et al.
  // Inelastic-collision cross sections of liquid water for interactions of energetic proton
  //
  
  if (IncomingParticlePolicy::x1[index]<IncomingParticlePolicy::x0[index])
  {
   //
   // if x1 < x0 means that x1 and b1 will be calculated with the following formula (this piece of code is run on all alphas and not on protons)
   //
   // x1 = x0 + ((a0 - a1)/(c0 * d0)) ^ (1 / (d0 - 1))
   //
   // b1 = (a0 - a1) * x1 + b0 - c0 * (x1 - x0) ^ d0
   //
 
   IncomingParticlePolicy::x1[index]=IncomingParticlePolicy::x0[index] + std::pow((IncomingParticlePolicy::a0[index] - IncomingParticlePolicy::a1[index]) / (IncomingParticlePolicy::c0[index] * IncomingParticlePolicy::d0[index]), 1. / (IncomingParticlePolicy::d0[index] - 1.));
   IncomingParticlePolicy::b1[index]=(IncomingParticlePolicy::a0[index] - IncomingParticlePolicy::a1[index]) * IncomingParticlePolicy::x1[index] + IncomingParticlePolicy::b0[index] - IncomingParticlePolicy::c0[index] * std::pow(IncomingParticlePolicy::x1[index] - IncomingParticlePolicy::x0[index], IncomingParticlePolicy::d0[index]);
  }

  G4double x(std::log10(k/eV));
  G4double y;
  
  if (x<IncomingParticlePolicy::x0[index])
   y=IncomingParticlePolicy::a0[index] * x + IncomingParticlePolicy::b0[index];
  else if (x<IncomingParticlePolicy::x1[index])
   y=IncomingParticlePolicy::a0[index] * x + IncomingParticlePolicy::b0[index] - IncomingParticlePolicy::c0[index] * std::pow(x - IncomingParticlePolicy::x0[index], IncomingParticlePolicy::d0[index]);
  else
   y=IncomingParticlePolicy::a1[index] * x + IncomingParticlePolicy::b1[index];

  return IncomingParticlePolicy::f0[index] * std::pow(10., y)*m*m;
 }
#endif /* G4DNADINGFELDERCHARGECHANGETOTALCROSSSECTIONPOLICY_HH */