// ----------------------------------------------------
// This file belongs to the ray tracing framework
// for the use with Cherenkov detectors
//
// created 2007
//-----------------------------------------------------
#include "PndDrcPhoton.h"

#include "PndDrcOptMatAbs.h"
#include "PndDrcOptDev.h"

#include <iostream>
#include <iomanip>
using std::cout;
//using std::cerr;
//using std::cin;
using std::endl;

#include <TMath.h>
using namespace TMath;
#include <TComplex.h>
// #include <cstdlib>

#include <stdlib.h> // system
#include <TString.h>


static TRandom grandi; // not a fine solution ?


//----------------------------------------------------------------------
PndDrcPhoton::PndDrcPhoton()
{
  fLambda      = 0;
  fPosition    = XYZPoint(0,0,0);
  fPositionOld = XYZPoint(0,0,0);
  fDirection   = XYZPoint(0,0,0);
  fFate        = Drc::kPhotFlying;
  fReflections = 0;
  fVerbosity   = 0;
  fTime        = 0;
  fDev         = 0;
  fReflectionLimit = 1000;
  fPrintFlag   = true;
}
//----------------------------------------------------------------------
void PndDrcPhoton::Copy(const PndDrcPhoton& ph)
{
  fLambda      = ph.fLambda;
  fPosition    = ph.fPosition;
  fPositionOld = ph.fPositionOld;
  fDirection   = ph.fDirection;
  fFate        = ph.fFate;
  fReflections = ph.fReflections;
  fVerbosity   = ph.fVerbosity;
  fTime        = ph.fTime;
  fDev         = ph.fDev;
  fReflectionLimit = ph.fReflectionLimit;
  fPrintFlag   = ph.fPrintFlag;
}
//----------------------------------------------------------------------
PndDrcPhoton::PndDrcPhoton(const PndDrcPhoton& ph)
{
  if (ph.fVerbosity>=1) cout<<"  PndDrcPhoton::PndDrcPhoton"
        <<"(const PndDrcPhoton&)"<<endl;
  Copy(ph);
}
//----------------------------------------------------------------------
PndDrcPhoton& PndDrcPhoton::operator=(const PndDrcPhoton& ph)
{
  if (ph.fVerbosity>=1) cout<<"  PndDrcPhoton::operator="
        <<"(const PndDrcPhoton&) "<<endl;
  if (&ph != this) Copy(ph);
  return *this;

}
//----------------------------------------------------------------------
void PndDrcPhoton::SetPosition(const XYZPoint& pos)
{
  if (fDev && fDev->Radiator()) // no flat device
  {
    double n = (fDev->OptMaterial()).RefIndex(fLambda);
    double dndl = (fDev->OptMaterial()).RefIndexDeriv(fLambda);
    double len = sqrt((pos-fPosition).Mag2()); // mm
    double v_phase = 299.792/n;
    double v_group =  v_phase * ( 1.0 - fLambda/n*dndl);
    double time = len/v_group;
    fTime += time;          // pos in mm time in ns
  }

  fPositionOld = fPosition;
  fPosition    = pos;
};
//----------------------------------------------------------------------
bool PndDrcPhoton::Refract(XYZVector normal, double n1, double ex1, double n2, double ex2, bool fresnelFlag, double diffuseProb, bool test)
{

//   cout << "VOLCHECK2: " << n1 << " " << ex1 << " " << n2 << " " << ex2 << "  flag: " << fresnelFlag << " " << "diffuseProb: " << diffuseProb << endl;
//     fVerbosity =4;
//     cout << "******************** REFRACT ******************" << endl;
  static const double kEps = 1.0e-9;

  bool refract_flag;
  XYZVector dir1   = Direction();

  // norm points outside.
  XYZVector norm = (dir1.Dot(normal)>0) ? normal : -normal;

  //
  // sin(alpha1)   n2
  // ----------- = --  (Snellius)
  // sin(alpha2)   n1
  //

  // alpaha1, alpha2 > 0

  if (Verbosity()>=4)
  {
    cout<<"     norm="<<norm.X()<<" "<<norm.Y()<<" "<<norm.Z()<<endl;
    cout<<"     dir1="<<dir1.X()<<" "<<dir1.Y()<<" "<<dir1.Z()<<endl;
    cout<<"     norm*dir="<<norm.Dot(dir1)<<endl;
  }


  double alpha1 = acos(norm.Dot(dir1));
  double alpha2;


  if(test)
  {
    double angle = alpha1 / TMath::Pi() * 180;
//     cout << angle << endl;

    TString angleString;
    angleString += angle;
    angleString.Remove( TString::kLeading , ' ' );

    TString shellString = "echo " + angleString + " >> angle.tmp";
    system( shellString );
  }


  bool reflect;
  if( fresnelFlag )
    reflect = Fresnel( normal, n1, ex1, n2, ex2 );
  else
  {
    if (sin(alpha1) * n1/n2 > 1) // only reflected for total internal reflection
      reflect = true;
    else
      reflect = false;
  }


  if( reflect ) // reflect photon
  {
    double random = grandi.Uniform(0.0,1.0);

    refract_flag = false;

    if( random <= diffuseProb && diffuseProb > 0 )
      Diffuse( normal );
    else
      Reflect( norm );

      //ph.setDirection(dir1 - 2*(norm.Dot(dir1)*norm)); // new direction ???
    if (Verbosity()>=4) cout<<"     reflection"<<endl;
  }
  else                         // refract photon
  {
    refract_flag = true;

    if (Verbosity()>=4) cout<<"     alpha1,n1,n2 = "<<alpha1<<" "<<n1<<" "<<n2<<endl;

    TComplex nIn    = TComplex( n1, ex1 );
    TComplex nOut   = TComplex( n2, ex2 );

    TComplex refr = TComplex::ASin( nIn / nOut * TMath::Sin( alpha1 ) );
    alpha2 = refr.Re();

    if( alpha2 != alpha2 ) // NaN check
      cout << "PndDrcPhoton::Refract :  alpha2 = " << alpha2 << "   Is fDirection (here: dir1) really an unit vector?" << endl;


    XYZVector rhelp = norm.Cross(dir1);
    XYZVector diff  = rhelp.Cross(norm);
    diff = diff.Unit();

    // diff perp to norm points in direction to the tip of vel.
    //
    // dir2 = norm + x*diff such that L(x*diff)/L(n) = tan(alpha2)
    //
    double x = tan(alpha2);
    if (Verbosity()>=4) cout<<"     x,alpha2 = "<<x<<" "<<alpha2<<endl;
    XYZVector dir2 = norm + x*diff;

    if (Verbosity()>=4)
    {
      cout<<"     dir2 before unit = "<<dir2.X()<<" "<<dir2.Y()<<" "<<dir2.Z()<<endl;
    }
    dir2 = dir2.Unit();
    SetDirection(dir2);
    SetPosition(Position() + 2*kEps*dir2); // bring it in new volume or outside.
    if (Verbosity()>=4)
    {
      cout<<"     refraction, brought it inside to "
          <<Position().X()<<" "
          <<Position().Y()<<" "
          <<Position().Z()<<endl;
      cout<<"     refraction, brought in direction "
          <<Direction().X()<<" "
          <<Direction().Y()<<" "
          <<Direction().Z()<<endl;
    }
  }

  return refract_flag;

}

//----------------------------------------------------------------------
void PndDrcPhoton::Reflect(const XYZVector& normal)
{
  XYZVector normal1(normal);

  if (fDirection.Dot(normal) < 0) normal1 *= -1;
  fDirection = fDirection-2*(fDirection.Dot(normal1))*normal1;

  fReflections++;

}
//----------------------------------------------------------------------
void PndDrcPhoton::Diffuse(const XYZVector& normal)
{
    XYZVector normal1(normal);

    if (fDirection.Dot(normal) < 0) normal1 *= -1;

    // 1. generate any vector (uniformly distributed) around the z-Axis (hemisphere)
    // 2. rotate this vector back in the angle (normal,z-Axis)
//     fDirection.SetXYZ(0,-1,-1.1);
    XYZVector zUnit(0,0,1);

    // safety first
//         cout << "PndDrcPhoton::Diffuse :  fDirection or normal is not an unit vector (should not happen) !!!" << endl;
    normal1 = normal1.Unit();
    fDirection = fDirection.Unit();


    double angle = ACos( normal1.Dot(zUnit) / ( Sqrt(normal1.Mag2()) * Sqrt(zUnit.Mag2()) ) );
    XYZVector rotAxis = zUnit.Cross(normal1).Unit(); // usually Unit() is not necessary

    double costheta = grandi.Uniform(0.0,1.0);
    double phi = grandi.Uniform(0.0,2*Pi());

    XYZVector newf( Cos(phi) * Sqrt(1 - costheta*costheta), Sin(phi) * Sqrt(1 - costheta*costheta), costheta);
//     newf *= Sqrt(fDirection.Mag2());

    // rotation matrix
    double xx = Cos(angle) + rotAxis.X()*rotAxis.X() * (1-Cos(angle));
    double xy = rotAxis.X()*rotAxis.Y() * (1-Cos(angle)) - rotAxis.Z() * Sin(angle);
    double xz = rotAxis.X()*rotAxis.Z() * (1-Cos(angle)) + rotAxis.Y() * Sin(angle);
    double yx = rotAxis.Y()*rotAxis.X() * (1-Cos(angle)) + rotAxis.Z() * Sin(angle);
    double yy = Cos(angle) + rotAxis.Y()*rotAxis.Y() * (1-Cos(angle));
    double yz = rotAxis.Y()*rotAxis.Z() * (1-Cos(angle)) - rotAxis.X() * Sin(angle);
    double zx = rotAxis.Z()*rotAxis.X() * (1-Cos(angle)) - rotAxis.Y() * Sin(angle);
    double zy = rotAxis.Z()*rotAxis.Y() * (1-Cos(angle)) + rotAxis.X() * Sin(angle);
    double zz = Cos(angle) + rotAxis.Z()*rotAxis.Z() * (1-Cos(angle));

    double newfX = xx * newf.X() + xy * newf.Y() +xz * newf.Z();
    double newfY = yx * newf.X() + yy * newf.Y() +yz * newf.Z();
    double newfZ = zx * newf.X() + zy * newf.Y() +zz * newf.Z();

    fDirection.SetXYZ( newfX, newfY, newfZ );

    //safety first
//     cout << "PndDrcPhoton::Diffuse :  fDirection is not an unit vector (should not happen) !!!" << endl;
    fDirection = fDirection.Unit();

    fReflections++;

}
//----------------------------------------------------------------------
bool PndDrcPhoton::Fresnel(XYZVector normal, double n1, double ex1, double n2, double ex2)
{
  XYZVector dir1   = Direction();

 // norm points outside.
  XYZVector norm = (dir1.Dot(normal)>0) ? normal : -normal;

  if (Verbosity()>=4)
  {
    cout<<"     norm="<<norm.X()<<" "<<norm.Y()<<" "<<norm.Z()<<endl;
    cout<<"     dir1="<<dir1.X()<<" "<<dir1.Y()<<" "<<dir1.Z()<<endl;
    cout<<"     norm*dir="<<norm.Dot(dir1)<<endl;
  }


  double inci = acos(norm.Dot(dir1));

  TComplex nIn    = TComplex( n1, ex1 );
  TComplex nOut   = TComplex( n2, ex2 );


  TComplex refr = TComplex::ASin( nIn / nOut * TMath::Sin( inci ) );

  TComplex fresnel_s = ( nIn * TComplex::Cos( refr ) - nOut * TMath::Cos( inci )) /
      ( nOut * TMath::Cos( inci ) + nIn * TComplex::Cos( refr ) );
  double refl_s = TMath::Power( TComplex::Abs( fresnel_s ), 2 );

  TComplex fresnel_p = ( nIn * TMath::Cos( inci ) - nOut * TComplex::Cos( refr )) /
      ( nIn * TMath::Cos( inci ) + nOut * TComplex::Cos( refr ) );
  double refl_p = TMath::Power( TComplex::Abs( fresnel_p ), 2 );


  double random = grandi.Uniform(0.0,1.0);
//     cout << "random: " << random << endl;
  double reflProb = refl_s * random + refl_p * (1-random);


//     system("echo $RANDOM > random.dat");
//     ifstream in;
//     in.open( "random.dat" );
//     double random;
//     if( !in )
//     {
//         cout << "Error opening input stream" << endl;
//         return;
//     }
//     while ( true )
//     {
//         in >> random;
//         if( !in.good() )
//             break;
//     }
//     random = random/32767;


  random = grandi.Uniform(0.0,1.0);

//     cout << "refl. probability: " << reflProb << "  random: " << random << "  inci: " << (inci/TMath::Pi()*180) //<< endl;
//             << "  refr: " << refr << "  refl_s: " << refl_s << "  refl_p: " << refl_p << endl;

  if (random <= reflProb )
  {
//         cout << "fresnel reflected:  " //<< endl;
//         << "refl. probability: " << reflProb << "  random: " << random << "  inci: " << (inci/TMath::Pi()*180) << endl;
    return true;
  }
  else
    return false;
}
//----------------------------------------------------------------------
int PndDrcPhoton::ColorNumber(double lambda) const
{

  // the colors were taken from wikipedia entry about colors.

  if      (lambda< 0.1) return 17; // grey
  if      (lambda> 740) return 50; // dark red
  else if (lambda> 625) return 2;  // red
  else if (lambda> 590) return 42; // orange
  else if (lambda> 565) return 5;  // yellow
  else if (lambda> 520) return 3;  // green
  else if (lambda> 500) return 7;  // cyan
  else if (lambda> 450) return 4;  // blue
  else if (lambda> 430) return 9;  // indigo
  else if (lambda> 380) return 39; // violet

  return 33; // blue grey
}
//----------------------------------------------------------------------
void PndDrcPhoton::Print(fstream& stream) const
{

  if (fPrintFlag)
  {
    stream<<" TPolyLine3D *l = new TPolyLine3D(2);"<<endl;

    stream<<" l->SetPoint("<<0<<","
        <<fPositionOld.X()<<","
        <<fPositionOld.Y()<<","
        <<fPositionOld.Z()<<");"<<endl;
    stream<<" l->SetPoint("<<1<<","
        <<fPosition.X()<<","
        <<fPosition.Y()<<","
        <<fPosition.Z()<<");"<<endl;
    stream<<" l->SetLineColor("<<ColorNumber(fLambda)<<");"<<endl;
    stream<<" l->Draw();"<<endl;
  }

}
//----------------------------------------------------------------------
void PndDrcPhoton::Print() const
{
  cout<<" --- photon ---"<<endl;
  cout<<"     pos    = "<<fPosition<<endl;
  cout<<"     dir    = "<<fDirection<<endl;
  cout<<"     time   = "<<fTime<<endl;
  cout<<"     lambda = "<<fLambda<<endl;
  cout<<"     refl   = "<<fReflections<<endl;
  string str="unknown";
  if (fFate==Drc::kPhotFlying)   str="flying";
  if (fFate==Drc::kPhotMeasured) str="measured";
  if (fFate==Drc::kPhotLost)     str="lost";
  if (fFate==Drc::kPhotAbsorbed) str="absorbed";
  cout<<"     fate   = "<<str<<endl;
  if (fDev)
  {
    cout<<"     dev    = "<<fDev->Name()<<endl;
  }
  else
  {
    cout<<"     dev    = "<<"zero pointer"<<endl;
  }
  cout<<" --------------"<<endl;
}