#ifndef __JAANET__JEVTWEIGHTFACTORMUPAGE__
#define __JAANET__JEVTWEIGHTFACTORMUPAGE__

#include "km3net-dataformat/offline/Evt.hh"
#include "km3net-dataformat/offline/Trk.hh"

#include "JLang/JException.hh"

#include "JGeometry2D/JCircle2D.hh"

#include "TFormula.h"


/**
 * \author bjung
 */

namespace JAANET {

  using JLANG::JValueOutOfRange;
  using JLANG::JNullPointerException;


  /**
   * Implementation of reweighting factor for mupage events according to a specifiable ROOT TFormula.
   *
   * Note: The ROOT TFormula may assume any number of parameters, but should be restricted to\n
   *       the physical variables listed among `JEvtWeightFactorMupage::variables`.\n
   *       These variables may be specified within the ROOT TFormula as 'x[\<index\>]',\n
   *       where \<index\> corresponds to the index of the desired physical variable within `JEvtWeightFactorMupage::variables`.
   */
  struct JEvtWeightFactorMupage :
    public TFormula
  {
    /**
     * Indices of reweighting variables for MUPAGE.
     */
    enum variables {
      MUON_MULTIPLICITY,  //!< Muon multiplicity      
      MEAN_ZENITH_ANGLE,  //!< Average cosine of zenith angle
      TOTAL_MUON_ENERGY,  //!< Muon bundle total energy         [GeV]
      LATERAL_SPREAD,     //!< Muon bundle lateral spread       [m]
      
      NUMBER_OF_VARIABLES //!< Number of reweighting variables; \n
                          //!< N.B.\ This enum value needs to be specified last!
    }; 

    
    /**
     * Default constructor.
     */
    JEvtWeightFactorMupage() :
      TFormula()
    {}


    /**
     * Constructor.
     *
     * \param  name            name
     * \param  formula         formula
     */
    JEvtWeightFactorMupage(const char* name,
			   const char* formula) :
      TFormula(name, formula)
    {}

    
    /**
     * Get weighting factor for given event.
     *
     * \param  evt             event
     * \return                 weighting factor
     */
    double operator()(const Evt& evt) const
    {
      using namespace std;
      using namespace JPP;

      vector<JTrack3E> muons;
      
      vector<Double_t> vars(NUMBER_OF_VARIABLES);

      for (vector<Trk>::const_iterator i = evt.mc_trks.cbegin(); i != evt.mc_trks.cend(); ++i) {
	
	if (is_muon(*i)) {

	  vars[MEAN_ZENITH_ANGLE] += i->dir.z / i->dir.len();
	  vars[TOTAL_MUON_ENERGY] += i->E;

	  muons.push_back(getTrack(*i));
	}
      }

      if (muons.size() > 0) {

	vars[MUON_MULTIPLICITY]  = (Double_t) muons.size();
	vars[MEAN_ZENITH_ANGLE] /= vars[MUON_MULTIPLICITY];

	if (this->GetNdim() > (int) LATERAL_SPREAD) {

	  JCircle2D circle     = JCircle2D(muons.cbegin(), muons.cend()); // smallest enclosing circle
	  vars[LATERAL_SPREAD] = (Double_t) circle.getRadius();
	}
	  
	return this->DoEval(&vars[0]);

      } else {
	
	THROW(JNullPointerException, "JEvtWeightFactorMupage::operator(): No muon for event " << evt.id << '.' << endl);	
      }
    }
  };
}

#endif