#ifdef USE_CDFEDM2
//////////////////////////////////////////////////////////////////////////
//
// Component: SnowMassSummer.cc
// Purpose: This class inherits from TowerSummer.  Physics towers
//          are summed according to the Snowmass convention.  
//          N.B. The four-vector will be massless
//          
// Created: 20/09/99  Pierre Savard (based on Jodi Lamoureux's class)
// History: 
//
//////////////////////////////////////////////////////////////////////////

#include "Calor/SnowMassSummer.hh"

Centroid SnowMassSummer::sumTowers(const PhysicsTowerView& view) const{
    
  // Sum Et, eta, phi weighted by Et.
 
  if(view.size() == 0)
    {
      Centroid ctd(0.,0.,0.); 
      return ctd;
    } 

// something is wrong here...

 Towers::const_iterator firstIter = view.begin();   
  
  float et =0.;
  float eta =0.;
  float phi =0.;
  
  for(Towers::const_iterator iter = view.begin(); iter != view.end(); ++iter)
    {
      et  += (*iter)->totEt();
      eta += (*iter)->totEt() * (*iter)->totEta();
      float dphi = (*iter)->dPhi(*firstIter);
      phi += ((*iter)->totEt())*dphi;
    }
  if(et == 0.) 
    {
      Centroid ctd(0.,0.,0.); 
      return ctd;
    }
  eta = ( eta/et );
  phi = ( (*firstIter)->totPhi() + phi/et );
  if (phi < 0)  phi = ( 2*PI + phi );
  if (phi>2*PI) phi = ( phi - 2*PI );

  return  Centroid(eta,phi,et);;
  
}

HepLorentzVector SnowMassSummer::sumFourVector(const PhysicsTowerView& view) const{


   if (view.size()==0) {
     HepLorentzVector vec(0.,0.,0.,0.);
      return vec;
   }


  // must assume that jets are massless.

   Centroid initSum = sumTowers(view);

// calculate the other variables from Et, eta and phi.

   float theta =  2.*atan(exp(-initSum.eta()));
   float sinTheta = sin(theta);
   float energy;
   if (sinTheta>0) energy = initSum.et()/sinTheta;

   double e = energy;
   double pz = energy*cos( theta );
   double px = initSum.et()*cos( initSum.phi() );
   double py = initSum.et()*sin( initSum.phi() );
   
   return HepLorentzVector(px,py,pz,e);;

}
#endif  // USE_CDFEDM2