/*************************************************************************
* Copyright(c) 1998-2009, ALICE Experiment at CERN, All rights reserved. *
*                                                                        *
* Author: The ALICE Off-line Project.                                    *
* Contributors are mentioned in the code where appropriate.              *
*                                                                        *
* Permission to use, copy, modify and distribute this software and its   *
* documentation strictly for non-commercial purposes is hereby granted   *
* without fee, provided that the above copyright notice appears in all   *
* copies and that both the copyright notice and this permission notice   *
* appear in the supporting documentation. The authors make no claims     *
* about the suitability of this software for any purpose. It is          *
* provided "as is" without express or implied warranty.                  *
**************************************************************************/

///////////////////////////////////////////////////////////////////////////
//                                                                       //
//  Dielectron Pair class. Internally it makes use of AliKFParticle.     //
//                                                                       //
///////////////////////////////////////////////////////////////////////////


#include <TDatabasePDG.h>
#include <AliVTrack.h>
#include <AliVVertex.h>
#include <AliPID.h>
#include <AliExternalTrackParam.h>

#include "AliDielectronPair.h"

ClassImp(AliDielectronPair)

AliDielectronPair::AliDielectronPair() :
  fType(-1),
  fLabel(-1),
  fPdgCode(0),
  fPair(),
  fD1(),
  fD2(),
  fRefD1(),
  fRefD2(),
  fKFUsage(kTRUE)
{
  //
  // Default Constructor
  //
  
}

//______________________________________________
AliDielectronPair::AliDielectronPair(AliVTrack * const particle1, Int_t pid1,
                                     AliVTrack * const particle2, Int_t pid2, Char_t type) :
  fType(type),
  fLabel(-1),
  fPdgCode(0),
  fPair(),
  fD1(),
  fD2(),
  fRefD1(),
  fRefD2(),
  fKFUsage(kTRUE)
{
  //
  // Constructor with tracks
  //
  SetTracks(particle1, pid1, particle2, pid2);
}

//______________________________________________
AliDielectronPair::AliDielectronPair(const AliKFParticle * const particle1,
                                     const AliKFParticle * const particle2,
                                     AliVTrack * const refParticle1,
                                     AliVTrack * const refParticle2, Char_t type) :
  fType(type),
  fLabel(-1),
  fPdgCode(0),
  fPair(),
  fD1(),
  fD2(),
  fRefD1(),
  fRefD2(),
  fKFUsage(kTRUE)
{
  //
  // Constructor with tracks
  //
  SetTracks(particle1, particle2,refParticle1,refParticle2);
}

//______________________________________________
AliDielectronPair::~AliDielectronPair()
{
  //
  // Default Destructor
  //
  
}

//______________________________________________
void AliDielectronPair::SetTracks(AliVTrack * const particle1, Int_t pid1,
                                  AliVTrack * const particle2, Int_t pid2)
{
  //
  // Sort particles by pt, first particle larget Pt
  // set AliKF daughters and pair
  // refParticle1 and 2 are the original tracks. In the case of track rotation
  // they are needed in the framework
  //
  fPair.Initialize();
  fD1.Initialize();
  fD2.Initialize();

  AliKFParticle kf1(*particle1,pid1);
  AliKFParticle kf2(*particle2,pid2);

  fPair.AddDaughter(kf1);
  fPair.AddDaughter(kf2);

  if (particle1->Pt()>particle2->Pt()){
    fRefD1 = particle1;
    fRefD2 = particle2;
    fD1+=kf1;
    fD2+=kf2;
  } else {
    fRefD1 = particle2;
    fRefD2 = particle1;
    fD1+=kf2;
    fD2+=kf1;
  }
}

//______________________________________________
void AliDielectronPair::SetTracks(const AliKFParticle * const particle1,
                                  const AliKFParticle * const particle2,
                                  AliVTrack * const refParticle1,
                                  AliVTrack * const refParticle2)
{
  //
  // Sort particles by pt, first particle larget Pt
  // set AliKF daughters and pair
  // refParticle1 and 2 are the original tracks. In the case of track rotation
  // they are needed in the framework
  //
  fPair.Initialize();
  fD1.Initialize();
  fD2.Initialize();
  
  AliKFParticle kf1(*particle1);
  AliKFParticle kf2(*particle2);
  
  fPair.AddDaughter(kf1);
  fPair.AddDaughter(kf2);
  
  if (kf1.GetPt()>kf2.GetPt()){
    fRefD1 = refParticle1;
    fRefD2 = refParticle2;
    fD1+=kf1;
    fD2+=kf2;
  } else {
    fRefD1 = refParticle2;
    fRefD2 = refParticle1;
    fD1+=kf2;
    fD2+=kf1;
  }
}

//______________________________________________
void AliDielectronPair::GetThetaPhiCM(Double_t &thetaHE, Double_t &phiHE, Double_t &thetaCS, Double_t &phiCS) const
{
  //
  // Calculate theta and phi in helicity and Collins-Soper coordinate frame
  //
  const Double_t kBeamEnergy   = 3500.;
  Double_t pxyz1[3]={fD1.GetPx(),fD1.GetPy(),fD1.GetPz()};
  Double_t pxyz2[3]={fD2.GetPx(),fD2.GetPy(),fD2.GetPz()};
  Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
  Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
  
//   AliVParticle *d1 = static_cast<AliVParticle*>(fRefD1.GetObject());
//   AliVParticle *d2 = static_cast<AliVParticle*>(fRefD2.GetObject());

//   d1->PxPyPz(pxyz1);
//   d2->PxPyPz(pxyz2);
  
  TLorentzVector projMom(0.,0.,-kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  TLorentzVector targMom(0.,0., kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  
  // first & second daughter 4-mom
  TLorentzVector p1Mom(pxyz1[0],pxyz1[1],pxyz1[2],
                       TMath::Sqrt(pxyz1[0]*pxyz1[0]+pxyz1[1]*pxyz1[1]+pxyz1[2]*pxyz1[2]+eleMass*eleMass));
  TLorentzVector p2Mom(pxyz2[0],pxyz2[1],pxyz2[2],
                       TMath::Sqrt(pxyz2[0]*pxyz2[0]+pxyz2[1]*pxyz2[1]+pxyz2[2]*pxyz2[2]+eleMass*eleMass));
  // J/Psi 4-momentum vector
  TLorentzVector motherMom=p1Mom+p2Mom;
  
  // boost all the 4-mom vectors to the mother rest frame
  TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
  p1Mom.Boost(beta);
  p2Mom.Boost(beta);
  projMom.Boost(beta);
  targMom.Boost(beta);

    // x,y,z axes
  TVector3 zAxisHE = (motherMom.Vect()).Unit();
  TVector3 zAxisCS = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
  TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
  TVector3 xAxisHE = (yAxis.Cross(zAxisHE)).Unit();
  TVector3 xAxisCS = (yAxis.Cross(zAxisCS)).Unit();
  
  // fill theta and phi
  if(fD1.GetQ()>0){
    thetaHE = zAxisHE.Dot((p1Mom.Vect()).Unit());
    thetaCS = zAxisCS.Dot((p1Mom.Vect()).Unit());
    phiHE   = TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisHE));
    phiCS   = TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisCS));
  } else {
    thetaHE = zAxisHE.Dot((p2Mom.Vect()).Unit());
    thetaCS = zAxisCS.Dot((p2Mom.Vect()).Unit());
    phiHE   = TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisHE));
    phiCS   = TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisCS));
  }
}

//______________________________________________
Double_t AliDielectronPair::PsiPair(Double_t MagField) const
{
  //Following idea to use opening of colinear pairs in magnetic field from e.g. PHENIX
  //to ID conversions. Adapted from AliTRDv0Info class
  Double_t x, y, z;
  x = fPair.GetX();
  y = fPair.GetY();
  z = fPair.GetZ();

  Double_t m1[3] = {0,0,0};
  Double_t m2[3] = {0,0,0};

  m1[0] = fD1.GetPx();
  m1[1] = fD1.GetPy();
  m1[2] = fD1.GetPz();  

  m2[0] = fD2.GetPx();
  m2[1] = fD2.GetPy();
  m2[2] = fD2.GetPz();

  Double_t deltat = 1.;
  deltat = TMath::ATan(m2[2]/(TMath::Sqrt(m2[0]*m2[0] + m2[1]*m2[1])+1.e-13))-
	TMath::ATan(m1[2]/(TMath::Sqrt(m1[0]*m1[0] + m1[1]*m1[1])+1.e-13));//difference of angles of the two daughter tracks with z-axis

  Double_t radiussum = TMath::Sqrt(x*x + y*y) + 50;//radius to which tracks shall be propagated

  Double_t mom1Prop[3];
  Double_t mom2Prop[3];

  AliExternalTrackParam *d1 = static_cast<AliExternalTrackParam*>(fRefD1.GetObject());
  AliExternalTrackParam *d2 = static_cast<AliExternalTrackParam*>(fRefD2.GetObject());

  AliExternalTrackParam nt(*d1), pt(*d2);

  Double_t fPsiPair = 4.;
  if(nt.PropagateTo(radiussum,MagField) == 0)//propagate tracks to the outside
	fPsiPair =  -5.;
  if(pt.PropagateTo(radiussum,MagField) == 0)
	fPsiPair = -5.;
  pt.GetPxPyPz(mom1Prop);//Get momentum vectors of tracks after propagation
  nt.GetPxPyPz(mom2Prop);



  Double_t pEle =
	TMath::Sqrt(mom2Prop[0]*mom2Prop[0]+mom2Prop[1]*mom2Prop[1]+mom2Prop[2]*mom2Prop[2]);//absolute momentum val
  Double_t pPos =
	TMath::Sqrt(mom1Prop[0]*mom1Prop[0]+mom1Prop[1]*mom1Prop[1]+mom1Prop[2]*mom1Prop[2]);//absolute momentum val

  Double_t scalarproduct =
	mom1Prop[0]*mom2Prop[0]+mom1Prop[1]*mom2Prop[1]+mom1Prop[2]*mom2Prop[2];//scalar product of propagated posit

  Double_t chipair = TMath::ACos(scalarproduct/(pEle*pPos));//Angle between propagated daughter tracks

  fPsiPair =  TMath::Abs(TMath::ASin(deltat/chipair));

  return fPsiPair;

}

//______________________________________________
Double_t AliDielectronPair::ThetaPhiCM(const AliVParticle* d1, const AliVParticle* d2, 
                                       const Bool_t isHE, const Bool_t isTheta)
{
  // The function calculates theta and phi in the mother rest frame with
  // respect to the helicity coordinate system and Collins-Soper coordinate system
  // TO DO: generalize for different decays (only J/Psi->e+e- now)

  // Laboratory frame 4-vectors:
  // projectile beam & target beam 4-mom
  // TODO: need to retrieve the beam energy from somewhere
  const Double_t kBeamEnergy   = 3500.;
  Double_t px1=d1->Px();
  Double_t py1=d1->Py();
  Double_t pz1=d1->Pz();
  Double_t px2=d2->Px();
  Double_t py2=d2->Py();
  Double_t pz2=d2->Pz();
  Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
  Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
  
  TLorentzVector projMom(0.,0.,-kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  TLorentzVector targMom(0.,0., kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  
  // first & second daughter 4-mom
  TLorentzVector p1Mom(px1,py1,pz1,TMath::Sqrt(px1*px1+py1*py1+pz1*pz1+eleMass*eleMass));
  TLorentzVector p2Mom(px2,py2,pz2,TMath::Sqrt(px2*px2+py2*py2+pz2*pz2+eleMass*eleMass));
  // J/Psi 4-momentum vector
  TLorentzVector motherMom=p1Mom+p2Mom;
  
  // boost all the 4-mom vectors to the mother rest frame
  TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
  p1Mom.Boost(beta);
  p2Mom.Boost(beta);
  projMom.Boost(beta);
  targMom.Boost(beta);
  
  // x,y,z axes 
  TVector3 zAxis;
  if(isHE) zAxis = (motherMom.Vect()).Unit();
  else zAxis = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
  TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
  TVector3 xAxis = (yAxis.Cross(zAxis)).Unit();
  
  // return either theta or phi
  if(isTheta) {
    if(d1->Charge()>0)
      return zAxis.Dot((p1Mom.Vect()).Unit());
    else 
      return zAxis.Dot((p2Mom.Vect()).Unit());

  }
  else {
    if(d1->Charge()>0)
      return TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxis));
    else
      return TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxis));
  }
}

//______________________________________________
Double_t AliDielectronPair::ThetaPhiCM(const Bool_t isHE, const Bool_t isTheta) const {
  // The function calculates theta and phi in the mother rest frame with 
  // respect to the helicity coordinate system and Collins-Soper coordinate system
  // TO DO: generalize for different decays (only J/Psi->e+e- now)

  // Laboratory frame 4-vectors:
  // projectile beam & target beam 4-mom
  AliVParticle *d1 = static_cast<AliVParticle*>(fRefD1.GetObject());
  AliVParticle *d2 = static_cast<AliVParticle*>(fRefD2.GetObject());
  
  const Double_t kBeamEnergy   = 3500.;
  Double_t px1=d1->Px();
  Double_t py1=d1->Py();
  Double_t pz1=d1->Pz();
  Double_t px2=d2->Px();
  Double_t py2=d2->Py();
  Double_t pz2=d2->Pz();
  Double_t eleMass=AliPID::ParticleMass(AliPID::kElectron);
  Double_t proMass=AliPID::ParticleMass(AliPID::kProton);
  
  TLorentzVector projMom(0.,0.,-kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  TLorentzVector targMom(0.,0., kBeamEnergy,TMath::Sqrt(kBeamEnergy*kBeamEnergy+proMass*proMass));
  
  // first & second daughter 4-mom
  // first & second daughter 4-mom
  TLorentzVector p1Mom(px1,py1,pz1,TMath::Sqrt(px1*px1+py1*py1+pz1*pz1+eleMass*eleMass));
  TLorentzVector p2Mom(px2,py2,pz2,TMath::Sqrt(px2*px2+py2*py2+pz2*pz2+eleMass*eleMass));
  // J/Psi 4-momentum vector
  TLorentzVector motherMom=p1Mom+p2Mom;

  // boost all the 4-mom vectors to the mother rest frame
  TVector3 beta = (-1.0/motherMom.E())*motherMom.Vect();
  p1Mom.Boost(beta);
  p2Mom.Boost(beta);
  projMom.Boost(beta);
  targMom.Boost(beta);

  // x,y,z axes 
  TVector3 zAxis;
  if(isHE) zAxis = (motherMom.Vect()).Unit();
  else zAxis = ((projMom.Vect()).Unit()-(targMom.Vect()).Unit()).Unit();
  TVector3 yAxis = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
  TVector3 xAxis = (yAxis.Cross(zAxis)).Unit();

  // return either theta or phi
  if(isTheta) {
    if(fD1.GetQ()>0) 
      return zAxis.Dot((p1Mom.Vect()).Unit());
    else
      return zAxis.Dot((p2Mom.Vect()).Unit());
  }
  else {
    if(fD1.GetQ()>0)
      return TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxis));
    else
      return TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxis));
  }
}
//______________________________________________
Double_t AliDielectronPair::GetCosPointingAngle(const AliVVertex *primVtx) const
{
  //
  // Calculate the poiting angle of the pair to the primary vertex and take the cosine
  //
  if(!primVtx) return -1.;

  Double_t deltaPos[3]; //vector between the reference point and the V0 vertex
  deltaPos[0] = fPair.GetX() - primVtx->GetX();
  deltaPos[1] = fPair.GetY() - primVtx->GetY();
  deltaPos[2] = fPair.GetZ() - primVtx->GetZ();

  Double_t momV02    = fPair.GetPx()*fPair.GetPx() + fPair.GetPy()*fPair.GetPy() + fPair.GetPz()*fPair.GetPz();
  Double_t deltaPos2 = deltaPos[0]*deltaPos[0] + deltaPos[1]*deltaPos[1] + deltaPos[2]*deltaPos[2];

  Double_t cosinePointingAngle = (deltaPos[0]*fPair.GetPx() + deltaPos[1]*fPair.GetPy() + deltaPos[2]*fPair.GetPz()) / TMath::Sqrt(momV02 * deltaPos2);
  
  return TMath::Abs(cosinePointingAngle);

}

// //______________________________________________
// Double_t AliDielectronPair::GetLXY(const AliVVertex * const vtx) const
// {
//   //
//   // Calculate the decay length in XY taking into account the primary vertex position
//   //
//   if(!vtx) return 0;
//   return ( (Xv()-vtx->GetX()) * Px() + (Yv()-vtx->GetY()) * Py() )/Pt()  ;
// }

// //______________________________________________
// Double_t AliDielectronPair::GetPseudoProperTime(const AliVVertex * const vtx) const
// {
//   //
//   // Calculate the pseudo proper time
//   //
//   Double_t lxy=GetLXY(vtx);
//   Double_t psProperDecayLength = lxy*(TDatabasePDG::Instance()->GetParticle(443)->Mass())/Pt();
//   return psProperDecayLength;
// }