//-----------------------------------------------------------
// File and Version Information:
// $Id$
//
// Description:
//      Implementation of class PndTpcRiemannHit
//      see PndTpcRiemannHit.hh for details
//
// Environment:
//      Software developed for the PANDA Detector at FAIR.
//
// Author List:
//      Sebastian Neubert    TUM            (original author)
//
//
//-----------------------------------------------------------

// Panda Headers ----------------------

// This Class' Header ------------------
#include "PndTpcRiemannHit.h"
#include "TMath.h"
// C/C++ Headers ----------------------
#include "PndTpcCluster.h"
#include <assert.h>

// Collaborating Class Headers --------
#include "PndTpcRiemannTrack.h"

// Class Member definitions -----------


// scale factor! r=1 => z'=0.5 !!!
// to normalize cm-range 
#define RIEMANNSCALE 100.

ClassImp(PndTpcRiemannHit)


PndTpcRiemannHit::PndTpcRiemannHit(double r, double phi)
  : _cluster(NULL)
{
  double r2=r*r;
  double d=1+r2;
  _x.SetX(r*TMath::Cos(phi)/d);
  _x.SetY(r*TMath::Sin(phi)/d);
  _x.SetZ(r2/d);
}

PndTpcRiemannHit::PndTpcRiemannHit(PndTpcCluster* cl)
  : _cluster(cl)
{
  TVector2 a(cl->pos().X(),cl->pos().Y());
  double r=a.Mod()/RIEMANNSCALE; 
  double phi=a.Phi();
  double r2=r*r;
  double d=1+r2;
  _x.SetX(r*TMath::Cos(phi)/d);
  _x.SetY(r*TMath::Sin(phi)/d);
  _x.SetZ(r2/d);
}


PndTpcRiemannHit::~PndTpcRiemannHit(){}

double
PndTpcRiemannHit::z()const {
  if(_cluster==NULL)return 0;
  else return _cluster->pos().Z();
}

void 
PndTpcRiemannHit::calcPosOnTrk(PndTpcRiemannTrack* trk){
  assert(trk!=NULL);
  TVectorD o=trk->orig(); 
  o*=RIEMANNSCALE;// convert back to cm;
  double r=trk->r();
  r*=RIEMANNSCALE;
  const PndTpcCluster* firstCl=trk->getHit(0)->cluster();
  assert(firstCl!=NULL);
  TVector2 k(firstCl->pos().X()-o[0],firstCl->pos().Y()-o[1]);
  TVector2 l(_cluster->pos().X()-o[0],_cluster->pos().Y()-o[1]);
  _alpha=l.DeltaPhi(k);
  _s=_alpha*r;
}