#ifdef USE_CDFEDM2
//////////////////////////////////////////////////////////////////////////
//
// Component: FourVecSummer.cc
// Purpose: Implementation of FourVecSummer class
//          
// Created: 20/09/99  Pierre Savard (based on Jodi Lamoureux's class)
// History: 
//
//////////////////////////////////////////////////////////////////////////

#include "Calor/FourVectorSummer.hh"
const float EPSILON = 1.E-10;

Centroid FourVectorSummer::sumTowers(const PhysicsTowerView& view) const{

  HepLorentzVector initSum = sumFourVector(view);
  
  // calculate e,et,phi,eta,sinTheta  from  px, py, pz, e
  
  float p,pt,theta,phi,eta,et;
  
  pt = sqrt(initSum.px()*initSum.px() + initSum.py()*initSum.py());
  float pz =initSum.pz();
  p  = sqrt(pz*pz + pt*pt);
  
  theta = atan2(pt,pz); 
  phi   = atan2(initSum.py(),initSum.px()); 
  if (phi<0)   phi = 2*PI + phi;
  et  = initSum.e()*sin(theta);
  eta = 0.5*log(  (p+pz+EPSILON)/(p-pz+EPSILON) );
  
  return Centroid(eta,phi,et);
  
}

HepLorentzVector FourVectorSummer::sumFourVector(const PhysicsTowerView& view) const{
  float px =0.;
  float py =0.;
  float pz =0.;
  float e =0.;
  Towers::const_iterator  iterEnd = view.end();
  
  for(Towers::const_iterator iter = view.begin(); iter != iterEnd; ++iter){ 
    px +=(* iter)->fourMomentum().px(); 
    py += (*iter)->fourMomentum().py(); 
    pz += (*iter)->fourMomentum().pz(); 
    e += (*iter)->fourMomentum().e(); 
  }
  return HepLorentzVector(px,py,pz,e);
}

float FourVectorSummer::dRsquared(const PhysicsTower* tower, float eta, float phi){
  float p = sqrt(tower->px()*tower->px() + 
		 tower->py()*tower->py() +
		 tower->pz()*tower->pz());
  float towerEta = 0.5*log( (p+tower->pz()+EPSILON)/(p-tower->pz()+EPSILON) );
  float towerPhi = atan2(tower->py(), tower->px());
  if (towerPhi<0) towerPhi = 2*PI + towerPhi;
  float phiDiff = towerPhi - phi;
  if (fabs(phiDiff)>PI) { 
    if (phiDiff>0) { phiDiff = -(2*PI - fabs(phiDiff)); }
    else if (phiDiff<=0) { phiDiff = (2*PI - fabs(phiDiff)); }
  }
  return phiDiff*phiDiff + (towerEta-eta)*(towerEta-eta);
}
#endif  // USE_CDFEDM2