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// $Id: G4QGSDiffractiveExcitation.cc,v 1.1 2007/05/25 07:30:47 gunter Exp $
// ------------------------------------------------------------
//      GEANT 4 class implemetation file
//
//      ---------------- G4QGSDiffractiveExcitation --------------
//             by Gunter Folger, October 1998.
//         diffractive Excitation used by strings models
//	   Take a projectile and a target
//	   excite the projectile and target
//  Essential changed by V. Uzhinsky in November - December 2006
//  in order to put it in a correspondence with original FRITIOF
//  model. Variant of FRITIOF with nucleon de-excitation is implemented.  
// ---------------------------------------------------------------------

// Modified:
//  25-05-07 : G.Folger
//       move from management/G4DiffractiveExcitation to to qgsm/G4QGSDiffractiveExcitation
//                  

#include "globals.hh"
#include "Randomize.hh"

#include "G4QGSDiffractiveExcitation.hh"
#include "G4LorentzRotation.hh"
#include "G4ThreeVector.hh"
#include "G4ParticleDefinition.hh"
#include "G4VSplitableHadron.hh"
#include "G4ExcitedString.hh"
//#include "G4ios.hh"

G4QGSDiffractiveExcitation::G4QGSDiffractiveExcitation()                                     // Uzhi
{
}

G4bool G4QGSDiffractiveExcitation::
  ExciteParticipants(G4VSplitableHadron *projectile, G4VSplitableHadron *target) const
{

	   G4LorentzVector Pprojectile=projectile->Get4Momentum();

// -------------------- Projectile parameters -----------------------------------
           G4bool PutOnMassShell=0;

//	   G4double M0projectile=projectile->GetDefinition()->GetPDGMass();  // With de-excitation
	   G4double M0projectile = Pprojectile.mag();                        // Without de-excitation

           if(M0projectile < projectile->GetDefinition()->GetPDGMass()) 
             {
              PutOnMassShell=1;
              M0projectile=projectile->GetDefinition()->GetPDGMass();
             }

	   G4double Mprojectile2 = M0projectile * M0projectile;

           G4int    PDGcode=projectile->GetDefinition()->GetPDGEncoding();
           G4int    absPDGcode=std::abs(PDGcode);
           G4double ProjectileDiffCut;
           G4double AveragePt2;

           if( absPDGcode > 1000 )                        //------Projectile is baryon --------
             {
              ProjectileDiffCut = 1.1;                    // GeV
              AveragePt2 = 0.3;                           // GeV^2
             }
           else if( absPDGcode == 211 || PDGcode ==  111) //------Projectile is Pion -----------
             {
              ProjectileDiffCut = 1.0;                   // GeV
              AveragePt2 = 0.3;                          // GeV^2
             }
           else if( absPDGcode == 321 || PDGcode == -311) //------Projectile is Kaon -----------
             {
              ProjectileDiffCut = 1.1;                    // GeV
              AveragePt2 = 0.3;                           // GeV^2
             }
           else                                           //------Projectile is undefined, Nucleon assumed
             {
              ProjectileDiffCut = 1.1;                    // GeV
              AveragePt2 = 0.3;                           // GeV^2
             };

           ProjectileDiffCut = ProjectileDiffCut * GeV;
           AveragePt2 = AveragePt2 * GeV*GeV;

// -------------------- Target parameters ----------------------------------------------
  	   G4LorentzVector Ptarget=target->Get4Momentum();

	   G4double M0target = Ptarget.mag();

           if(M0target < target->GetDefinition()->GetPDGMass()) 
             {
              PutOnMassShell=1;
              M0target=target->GetDefinition()->GetPDGMass();
             }
     
   	   G4double Mtarget2 = M0target * M0target;                      //Ptarget.mag2(); // for AA-inter.

           G4double NuclearNucleonDiffCut = 1.1*GeV;        

           G4double ProjectileDiffCut2 = ProjectileDiffCut * ProjectileDiffCut;
           G4double NuclearNucleonDiffCut2 = NuclearNucleonDiffCut * NuclearNucleonDiffCut;

// Transform momenta to cms and then rotate parallel to z axis;

	   G4LorentzVector Psum;
	   Psum=Pprojectile+Ptarget;

	   G4LorentzRotation toCms(-1*Psum.boostVector());

	   G4LorentzVector Ptmp=toCms*Pprojectile;

	   if ( Ptmp.pz() <= 0. )
	   {
	   // "String" moving backwards in  CMS, abort collision !!
           //G4cout << " abort Collision!! " << G4endl;
		   return false; 
	   }
	   		   
	   toCms.rotateZ(-1*Ptmp.phi());
	   toCms.rotateY(-1*Ptmp.theta());
	
	   G4LorentzRotation toLab(toCms.inverse());

	   Pprojectile.transform(toCms);
	   Ptarget.transform(toCms);

	   G4double Pt2;                                                    
           G4double ProjMassT2, ProjMassT;                                  
           G4double TargMassT2, TargMassT;                                  
           G4double PZcms2, PZcms;                                          
           G4double PMinusNew, TPlusNew;                                    

           G4double S=Psum.mag2();                                          
           G4double SqrtS=std::sqrt(S);                                     

           if(SqrtS < 2200*MeV) {return false;}   // The model cannot work for pp-interactions
                                                  // at Plab < 1.3 GeV/c. Uzhi   

	   PZcms2=(S*S+Mprojectile2*Mprojectile2+Mtarget2*Mtarget2-
                                 2*S*Mprojectile2-2*S*Mtarget2-2*Mprojectile2*Mtarget2)/4./S;
           if(PZcms2 < 0) 
             {return false;}   // It can be in an interaction with off-shell nuclear nucleon

           PZcms = std::sqrt(PZcms2);

           if(PutOnMassShell)
             {
              if(Pprojectile.z() > 0.)
                {
                 Pprojectile.setPz( PZcms);
                 Ptarget.setPz(    -PZcms);
                }
              else
                 {
                 Pprojectile.setPz(-PZcms);
                 Ptarget.setPz(     PZcms);
                };

               Pprojectile.setE(std::sqrt(Mprojectile2+
                                                       Pprojectile.x()*Pprojectile.x()+
                                                       Pprojectile.y()*Pprojectile.y()+
                                                       PZcms2));
               Ptarget.setE(std::sqrt(    Mtarget2    +
                                                       Ptarget.x()*Ptarget.x()+
                                                       Ptarget.y()*Ptarget.y()+
                                                       PZcms2));
             }

           G4double maxPtSquare = PZcms2;

//G4cout << "Pprojectile aft boost : " << Pprojectile << G4endl;
//G4cout << "Ptarget aft boost : " << Ptarget << G4endl;
//	   G4cout << "cms aft boost : " << (Pprojectile+ Ptarget) << G4endl;

//	   G4cout << " Projectile Xplus / Xminus : " << 
//	   	Pprojectile.plus() << " / " << Pprojectile.minus() << G4endl;
//	   G4cout << " Target Xplus / Xminus : " << 
//	   	Ptarget.plus() << " / " << Ptarget.minus() << G4endl;

	   G4LorentzVector Qmomentum;
           G4double Qminus, Qplus;                                          

// /* Vova
	   G4int whilecount=0;
	   do {
//  Generate pt		

	       if (whilecount++ >= 500 && (whilecount%100)==0) 
//	   	 G4cout << "G4QGSDiffractiveExcitation::ExciteParticipants possibly looping"
//	   	 << ", loop count/ maxPtSquare : " 
//           	 << whilecount << " / " << maxPtSquare << G4endl;
               if (whilecount > 1000 ) 
               {
           	 Qmomentum=G4LorentzVector(0.,0.,0.,0.);
	   	 return false; 	  //  Ignore this interaction 
               }

	       Qmomentum=G4LorentzVector(GaussianPt(AveragePt2,maxPtSquare),0);

//G4cout << "generated Pt " << Qmomentum << G4endl;
//G4cout << "Pprojectile with pt : " << Pprojectile+Qmomentum << G4endl;
//G4cout << "Ptarget with pt : " << Ptarget-Qmomentum << G4endl;

//  Momentum transfer
/*                                                                          // Uzhi
	       G4double Xmin = minmass / ( Pprojectile.e() + Ptarget.e() );
	       G4double Xmax=1.;
	       G4double Xplus =ChooseX(Xmin,Xmax);
	       G4double Xminus=ChooseX(Xmin,Xmax);

//	       G4cout << " X-plus  " << Xplus << G4endl;
//	       G4cout << " X-minus " << Xminus << G4endl;
	       
	       G4double pt2=G4ThreeVector(Qmomentum.vect()).mag2();
	       G4double Qplus =-1 * pt2 / Xminus/Ptarget.minus();
	       G4double Qminus=     pt2 / Xplus /Pprojectile.plus();
*/                                                                          // Uzhi    *

	       Pt2=G4ThreeVector(Qmomentum.vect()).mag2();                  
               ProjMassT2=Mprojectile2+Pt2;                           
               ProjMassT =std::sqrt(ProjMassT2);                            

               TargMassT2=Mtarget2+Pt2;                               
               TargMassT =std::sqrt(TargMassT2);                            

               PZcms2=(S*S+ProjMassT2*ProjMassT2+                           
                           TargMassT2*TargMassT2-                           
                           2.*S*ProjMassT2-2.*S*TargMassT2-                 
                           2.*ProjMassT2*TargMassT2)/4./S;                  
               if(PZcms2 < 0 ) {PZcms2=0;};                                 
               PZcms =std::sqrt(PZcms2);                                    

               G4double PMinusMin=std::sqrt(ProjMassT2+PZcms2)-PZcms;       
               G4double PMinusMax=SqrtS-TargMassT;                          

               PMinusNew=ChooseP(PMinusMin,PMinusMax);                      
               Qminus=PMinusNew-Pprojectile.minus();                        

               G4double TPlusMin=std::sqrt(TargMassT2+PZcms2)-PZcms;        
               G4double TPlusMax=SqrtS-ProjMassT;                           

               TPlusNew=ChooseP(TPlusMin, TPlusMax);                        
               Qplus=-(TPlusNew-Ptarget.plus());                            

	       Qmomentum.setPz( (Qplus-Qminus)/2 );
	       Qmomentum.setE(  (Qplus+Qminus)/2 );

//G4cout << "Qplus / Qminus " << Qplus << " / " << Qminus<<G4endl;
//	     G4cout << "pt2" << pt2 << G4endl;
//	     G4cout << "Qmomentum " << Qmomentum << G4endl;
//	     G4cout << " Masses (P/T) : " << (Pprojectile+Qmomentum).mag() <<
//	   		       " / " << (Ptarget-Qmomentum).mag() << G4endl;
/*                                                                                 // Uzhi
	   } while ( (Pprojectile+Qmomentum).mag2() <= Mprojectile2 ||
	   	     (Ptarget-Qmomentum).mag2()     <= Mtarget2 );
*/                                                                                 // Uzhi     *


	   } while (( (Pprojectile+Qmomentum).mag2() <  Mprojectile2       ||      // Uzhi No without excitation
	   	      (Ptarget    -Qmomentum).mag2() <  Mtarget2             ) ||  // Uzhi   
                    ( (Pprojectile+Qmomentum).mag2()  <  ProjectileDiffCut2 &&     // Uzhi No double Diffraction
                      (Ptarget    -Qmomentum).mag2()  <  NuclearNucleonDiffCut2) );// Uzhi

           if((Ptarget-Qmomentum).mag2() < NuclearNucleonDiffCut2)                 // Uzhi Projectile diffraction
             {
              G4double TMinusNew=SqrtS-PMinusNew;
              Qminus=Ptarget.minus()-TMinusNew;
              TPlusNew=TargMassT2/TMinusNew;
              Qplus=Ptarget.plus()-TPlusNew;

	      Qmomentum.setPz( (Qplus-Qminus)/2 );                          
	      Qmomentum.setE(  (Qplus+Qminus)/2 );                          
             }
           else if((Pprojectile+Qmomentum).mag2() <  ProjectileDiffCut2)    // Uzhi Target diffraction
             {
              G4double PPlusNew=SqrtS-TPlusNew;
              Qplus=PPlusNew-Pprojectile.plus();
              PMinusNew=ProjMassT2/PPlusNew;
              Qminus=PMinusNew-Pprojectile.minus();

	      Qmomentum.setPz( (Qplus-Qminus)/2 );                          
	      Qmomentum.setE(  (Qplus+Qminus)/2 );                          
             };

	   Pprojectile += Qmomentum;
	   Ptarget     -= Qmomentum;

   // Vova

/*
Pprojectile.setPz(0.);
Pprojectile.setE(SqrtS-M0target);

Ptarget.setPz(0.);
Ptarget.setE(M0target);
*/

//G4cout << "Pprojectile with Q : " << Pprojectile << G4endl;
//G4cout << "Ptarget with Q : " << Ptarget << G4endl;
	
//	   G4cout << "Projectile back: " << toLab * Pprojectile << G4endl;
//	   G4cout << "Target back: " << toLab * Ptarget << G4endl;

// Transform back and update SplitableHadron Participant.
	   Pprojectile.transform(toLab);
	   Ptarget.transform(toLab);

//G4cout << "Pprojectile with Q M: " << Pprojectile<<" "<<  Pprojectile.mag() << G4endl;
//G4cout << "Ptarget     with Q M: " << Ptarget    <<" "<<  Ptarget.mag()     << G4endl;

//G4cout << "Target	 mass  " <<  Ptarget.mag() << G4endl;     
	   		   
	   target->Set4Momentum(Ptarget);

//G4cout << "Projectile mass  " <<  Pprojectile.mag() << G4endl; 

	   projectile->Set4Momentum(Pprojectile);

	   return true;
}


G4ExcitedString * G4QGSDiffractiveExcitation::
           String(G4VSplitableHadron * hadron, G4bool isProjectile) const
{
	hadron->SplitUp();
	G4Parton *start= hadron->GetNextParton();
	if ( start==NULL) 
	{ G4cout << " G4FTFModel::String() Error:No start parton found"<< G4endl;
	  return NULL;
	}
	G4Parton *end  = hadron->GetNextParton();
	if ( end==NULL) 
	{ G4cout << " G4FTFModel::String() Error:No end parton found"<< G4endl;
	  return NULL;
	}
	
	G4ExcitedString * string;
	if ( isProjectile ) 
	{
		string= new G4ExcitedString(end,start, +1);
	} else {
		string= new G4ExcitedString(start,end, -1);
	}
	
	string->SetPosition(hadron->GetPosition());

// momenta of string ends
	G4double ptSquared= hadron->Get4Momentum().perp2();
	G4double transverseMassSquared= hadron->Get4Momentum().plus()
				    *	hadron->Get4Momentum().minus();


	G4double maxAvailMomentumSquared=
		 sqr( std::sqrt(transverseMassSquared) - std::sqrt(ptSquared) );

        G4double widthOfPtSquare = 0.25;          // Uzhi <Pt^2>=0.25 ??????????????????
	G4ThreeVector pt=GaussianPt(widthOfPtSquare,maxAvailMomentumSquared);

	G4LorentzVector Pstart(G4LorentzVector(pt,0.));
	G4LorentzVector Pend;
	Pend.setPx(hadron->Get4Momentum().px() - pt.x());
	Pend.setPy(hadron->Get4Momentum().py() - pt.y());

	G4double tm1=hadron->Get4Momentum().minus() +
	  ( Pend.perp2()-Pstart.perp2() ) / hadron->Get4Momentum().plus();

	G4double tm2= std::sqrt( std::max(0., sqr(tm1) -
	     4. * Pend.perp2() * hadron->Get4Momentum().minus()
	      /  hadron->Get4Momentum().plus() ));

	G4int Sign= isProjectile ? -1 : 1;
	
	G4double endMinus  = 0.5 * (tm1 + Sign*tm2);
	G4double startMinus= hadron->Get4Momentum().minus() - endMinus;

	G4double startPlus= Pstart.perp2() /  startMinus;
	G4double endPlus  = hadron->Get4Momentum().plus() - startPlus;

	Pstart.setPz(0.5*(startPlus - startMinus));
	Pstart.setE(0.5*(startPlus + startMinus));

	Pend.setPz(0.5*(endPlus - endMinus));
	Pend.setE(0.5*(endPlus + endMinus));

	start->Set4Momentum(Pstart);
	end->Set4Momentum(Pend);
	
#ifdef G4_FTFDEBUG
	G4cout << " generated string flavors          " << start->GetPDGcode() << " / " << end->GetPDGcode() << G4endl;
	G4cout << " generated string momenta:   quark " << start->Get4Momentum() << "mass : " <<start->Get4Momentum().mag()<< G4endl;
	G4cout << " generated string momenta: Diquark " << end ->Get4Momentum() << "mass : " <<end->Get4Momentum().mag()<< G4endl;
	G4cout << " sum of ends                       " << Pstart+Pend << G4endl;
	G4cout << " Original                          " << hadron->Get4Momentum() << G4endl;
#endif
	
	return string;	
}


// --------- private methods ----------------------

G4double G4QGSDiffractiveExcitation::ChooseP(G4double Pmin, G4double Pmax) const // Uzhi
{
// choose an x between Xmin and Xmax with P(x) ~ 1/x

//  to be improved...

	G4double range=Pmax-Pmin;                                         // Uzhi
	
	if ( Pmin <= 0. || range <=0. ) 
	{
		G4cout << " Pmin, range : " << Pmin << " , " << range << G4endl;
		throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation::ChooseP : Invalid arguments ");
	}

	G4double P;
/*                                                                          // Uzhi
	do {
	    x=Xmin + G4UniformRand() * range;
	}  while ( Xmin/x < G4UniformRand() );
*/                                                                          // Uzhi

        P=Pmin * std::pow(Pmax/Pmin,G4UniformRand());                       // Uzhi

//debug-hpw	cout << "DiffractiveX "<<x<<G4endl;
	return P;
}

G4ThreeVector G4QGSDiffractiveExcitation::GaussianPt(G4double AveragePt2, G4double maxPtSquare) const // Uzhi
{            //  @@ this method is used in FTFModel as well. Should go somewhere common!
	
	G4double Pt2;
/*                                                                          // Uzhi
	do {
	    pt2=widthSquare * std::log( G4UniformRand() );
	} while ( pt2 > maxPtSquare);
*/                                                                          // Uzhi

        Pt2 = -AveragePt2 * std::log(1. + G4UniformRand() * (std::exp(-maxPtSquare/AveragePt2)-1.));// Uzhi 
	
	G4double Pt=std::sqrt(Pt2);

	G4double phi=G4UniformRand() * twopi;
	
	return G4ThreeVector (Pt*std::cos(phi), Pt*std::sin(phi), 0.);    
}

G4QGSDiffractiveExcitation::G4QGSDiffractiveExcitation(const G4QGSDiffractiveExcitation &)
{
	throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation copy contructor not meant to be called");
}


G4QGSDiffractiveExcitation::~G4QGSDiffractiveExcitation()
{
}


const G4QGSDiffractiveExcitation & G4QGSDiffractiveExcitation::operator=(const G4QGSDiffractiveExcitation &)
{
	throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation = operator meant to be called");
	return *this;
}


int G4QGSDiffractiveExcitation::operator==(const G4QGSDiffractiveExcitation &) const
{
	throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation == operator meant to be called");
	return false;
}

int G4QGSDiffractiveExcitation::operator!=(const G4QGSDiffractiveExcitation &) const
{
	throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation != operator meant to be called");
	return true;
}