#ifndef __JAANET__JEVTWEIGHTFACTORMUPAGE__
#define __JAANET__JEVTWEIGHTFACTORMUPAGE__

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

#include "JLang/JException.hh"
#include "JLang/JPredicate.hh"

#include "JGeometry2D/JCircle2D.hh"
#include "JGeometry3D/JVector3D.hh"
#include "JGeometry3D/JRotation3D.hh"

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wall"
#include "TFormula.h"
#pragma GCC diagnostic pop


/**
 * \author bjung
 */

namespace JAANET {}
namespace JPP { using namespace JAANET; }

namespace JAANET {

  /**
   * 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;
      
      for (vector<Trk>::const_iterator i = evt.mc_trks.cbegin(); i != evt.mc_trks.cend(); ++i) {
	if (is_muon(*i) && is_finalstate(*i)) {
	  muons.push_back(getTrack(*i));
	}
      }

      if (!muons.empty()) {

	Double_t  vars[NUMBER_OF_VARIABLES] = { 0.0 };

	double    Etot = 0.0;
	JVector3D dir;

	for (vector<JTrack3E>::const_iterator i = muons.begin(); i != muons.end(); ++i) {
	  Etot += i->getE();
	  dir  += i->getDirection();
	}
	
	const JDirection3D D(dir);
	const JRotation3D  R(D);

	for (vector<JTrack3E>::iterator i = muons.begin(); i != muons.end(); ++i) {
	  i->rotate(R);
	}

	vector<Trk>::const_iterator iBundle = find_if(evt.mc_trks.cbegin(), evt.mc_trks.cend(),
						      make_predicate(&Trk::status, TRK_ST_MUONBUNDLE));

	vars[MUON_MULTIPLICITY] = (iBundle != evt.mc_trks.cend() && iBundle->len > 0 ? iBundle->len : (double) muons.size());
	vars[TOTAL_MUON_ENERGY] = (iBundle != evt.mc_trks.cend() ? iBundle->E : Etot);
	vars[MEAN_ZENITH_ANGLE] = D.getDZ();

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

	  const JCircle2D circle = JCircle2D(muons.cbegin(), muons.cend()); // smallest enclosing circle

	  vars[LATERAL_SPREAD] = circle.getRadius();
	}
	  
	return this->DoEval(&vars[0]);

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

#endif