#ifndef __JFIT__JSHOWERBRIGHTPOINTREGRESSOR__
#define __JFIT__JSHOWERBRIGHTPOINTREGRESSOR__

#include "JPhysics/JPDFTypes.hh"
#include "JPhysics/JPDFTable.hh"
#include "JPhysics/JPDFToolkit.hh"
#include "JPhysics/JNPETable.hh"
#include "JPhysics/JConstants.hh"

#include "JTools/JResult.hh"

#include "JMath/JZero.hh"

#include "JFit/JGandalf.hh"
#include "JFit/JPoint4E.hh"
#include "JFit/JMEstimator.hh"
#include "JFit/JRegressor.hh"
#include "JFit/JFitToolkit.hh"
#include "JFit/JTimeRange.hh"

#include "Jeep/JMessage.hh"

/**
 * \file
 * Data regression method for JFIT::JPoint4E from a bright point isoptropic emission PDF.
 *
 * \author adomi, vcarretero
 */

namespace JFIT {}
namespace JPP { using namespace JFIT; }

namespace JFIT {

  using JPHYSICS::JPDFType_t;
  using JPHYSICS::DIRECT_LIGHT_FROM_BRIGHT_POINT;                                   
  using JPHYSICS::SCATTERED_LIGHT_FROM_BRIGHT_POINT;
  using JTOOLS::get_value;

  /**
   * Regressor function object for JPoint4E fit using JGandalf minimiser.
   */
  template<>
  struct JRegressor<JPoint4E, JGandalf> :
    public JAbstractRegressor<JPoint4E, JGandalf>
  {
    using JAbstractRegressor<JPoint4E, JGandalf>::operator();

    typedef JTOOLS::JSplineFunction1S_t                                      JFunction1D_t;
    typedef JTOOLS::JMAPLIST<JTOOLS::JPolint2FunctionalMap,
			     JTOOLS::JPolint1FunctionalGridMap>::maplist     JPDFMapList_t;
    typedef JPHYSICS::JPDFTable<JFunction1D_t, JPDFMapList_t>                JPDF_t;


    /**
     * Parameterized constructor
     *
     * The PDF file descriptor should contain the wild card character JPHYSICS::WILDCARD which
     * will be replaced by the corresponding PDF types.
     *
     * \param  fileDescriptor     PDF file descriptor
     * \param  TTS                TTS [ns]
     * \param  numberOfPoints     number of points for Gauss-Hermite integration of TTS
     * \param  epsilon            precision        for Gauss-Hermite integration of TTS
     */
    JRegressor(const std::string& fileDescriptor,
	       const double       TTS,
	       const int          numberOfPoints = 25,
	       const double       epsilon        = 1.0e-10)
    {
      using namespace std;
      using namespace JPP;
      
      const JPDF_t::JSupervisor supervisor(new JPDF_t::JDefaultResult(JMATH::zero));
      
      for (int i = 0; i != NUMBER_OF_PDFS; ++i) {
	
	try {

	  const string file_name = getFilename(fileDescriptor, pdf_t[i]);
	  
	  NOTICE("loading PDF from file " << file_name << "... " << flush);

	  pdf[i].load(file_name.c_str());

	  NOTICE("OK" << endl);

	  pdf[i].setExceptionHandler(supervisor);
	}
	catch(const JException& error) {
	  FATAL(error.what() << endl);
	}
      }

      // Add PDFs
      for (int i = 1; i < NUMBER_OF_PDFS; i += 2) {
  
	pdf[ i ].add(pdf[i-1]); 

	JPDF_t buffer;

	pdf[i-1].swap(buffer);
	
	if        (TTS > 0.0) {
	  pdf[i].blur(TTS, numberOfPoints, epsilon);
	} else if (TTS < 0.0) {
	  ERROR("Illegal value of TTS [ns]: " << TTS << endl);
	}
      }    
    }

    /**
     * Fit function.
     * This method is used to determine the chi2 and gradient of given hit with respect a bright point emitting isotropically
     *
     * JHit_t refers to a data structure which should have the following member methods:
     *   - double getX();       // [m]
     *   - double getY();       // [m]
     *   - double getZ();       // [m]
     *   - double getDX();      // [u]
     *   - double getDY();      // [u]
     *   - double getDZ();      // [u]
     *   - double getT();       // [ns]
     *
     * \param  vx                 shower vertex
     * \param  hit                hit
     * \return                    chi2 and gradient
     */
    template<class JHit_t>
    result_type operator()(const JPoint4E& vx, const JHit_t& hit) const
    {      
      using namespace JPP;

      JPosition3D  D(hit.getPosition());
      JDirection3D U(hit.getDirection());

      D.sub(vx.getPosition());
      double length = D.getLength();
      double ct = U.getDot(D) / length;

      if (ct > +1.0) { ct = +1.0; }
      if (ct < -1.0) { ct = -1.0; }

      const double t  = vx.getT() + (length * getIndexOfRefraction() * getInverseSpeedOfLight());

      const double dt = T_ns.constrain(hit.getT() - t);

      JPDF_t::result_type H0 = getH0(hit.getR(), dt);                    // getH0 = Get background hypothesis value 
      JPDF_t::result_type H1 = getH1(length, ct, dt);  // getH1 = Get signal hypothesis value / 1 GeV

      if (get_value(H1) >= Vmax_npe) {
        H1 *= Vmax_npe / get_value(H1);
      }

      double H1_value = get_value(H1);
      double v_H1 = H1.v; //Integral from tmin to t of just H1
      double V_H1 = H1.V; //Integral from tmin to tmax of just H1
      H1 *= vx.getE();
      
      JPDF_t::result_type HT = H1+H0; //now H1 is signal + background
      double HT_value = get_value(HT);
      result_type result;
      result.chi2 = HT.getChi2() - H0.getChi2();  // Likelihood ratio
      
      double exp_V_HT = exp(-HT.V); //V is the integral from tmin to tmax of EH1+H0

      double energy_gradient = -1 / HT_value; //dPdE
      energy_gradient *= (H1_value -  HT_value * v_H1) * (1-exp_V_HT)  -  HT_value * exp_V_HT * V_H1; //Numerator
      energy_gradient /= (1-exp_V_HT); // Denominator

      /*
       * Here it is evaluated: d(chi2)/d(ct) * d(ct)/d(x0,y0,z0,t0)  + d(chi2)/dE
       */
      result.gradient = JPoint4E(JPoint4D(JVector3D(-getIndexOfRefraction() * D.getX() / length,    // d(ct)/d(x0) 
						    -getIndexOfRefraction() * D.getY() / length,    // d(ct)/d(y0) 
						    -getIndexOfRefraction() * D.getZ() / length),   // d(ct)/d(z0) 
					  getSpeedOfLight()),                                               // d(ct)/d(t0)
				 energy_gradient);                                                              // d(chi2)/d(E)
      
      static_cast<JPoint4D&>(result.gradient).mul(getInverseSpeedOfLight() * (HT.getDerivativeOfChi2() -
									      H0.getDerivativeOfChi2()));                 // x d(chi2)/d(ct1)

      return result;

    }

    /**
     * Get background hypothesis value for time differentiated PDF.
     *
     * \param  R_Hz               rate [Hz]
     * \param  t1                 time [ns]
     * \return                    hypothesis value
     */
    JPDF_t::result_type getH0(const double R_Hz,
			      const double t1) const
    {
      using namespace JPP;

      return JPDF_t::result_type(R_Hz * 1e-9, t1, T_ns);
    }
    
    /**
     * Get signal hypothesis value per 1 GeV for bright point emission PDF.
     *
     * \param  D                hit distance from shower vertex [m]
     * \param  ct               cosine of the HIT angle
     * \param  t                arrival time of the light
     * \return                  hypothesis value / GeV
     */
    JPDF_t::result_type getH1(const double D,
			      const double ct,
			      const double t) const
    {
      using namespace JPP;

      JPDF_t::result_type h1 = JMATH::zero;
	
      for (int i = 0; i != NUMBER_OF_PDFS; ++i) {

	if (!pdf[i].empty() && D <= pdf[i].getXmax()) {

	  try {

	    JPDF_t::result_type y1 = pdf[i](std::max(D, pdf[i].getXmin()), ct, t);
	    
	    // safety measures
	    
	    if (y1.f <= 0.0) {
	      y1.f  = 0.0;
	      y1.fp = 0.0;
	    }
	    
	    if (y1.v <= 0.0) {
	      y1.v  = 0.0;
	    }
	    
	    h1 += y1;
	  
	  }
	  catch(JLANG::JException& error) {
	    ERROR(error << std::endl);
	  }
	}
      }

      return h1;
    }

    /**
     * Get maximal road width of PDF.
     *
     * \return                    road width [m]
     */
    inline double getRmax() const
    {
      using namespace JPP;

      double xmax = 0.0;

      for (int i = 0; i != NUMBER_OF_PDFS; ++i) {

	if (!pdf[i].empty() && pdf[i].getXmax() > xmax) {
	  xmax = pdf[i].getXmax();
	}
	
      }

      return xmax;
    }

    static JTimeRange   T_ns;                      //!< Time window with respect to Cherenkov hypothesis [ns]
    static double       Vmax_npe;                  //!< Maximal integral of PDF [npe]

    static const int    NUMBER_OF_PDFS = 2;

    static const JPDFType_t pdf_t[NUMBER_OF_PDFS];

    JPDF_t              pdf[NUMBER_OF_PDFS];       //!< PDF
  };  


  /**
   * PDF types.
   */
  const JPDFType_t JRegressor<JPoint4E, JGandalf>::pdf_t[] = { DIRECT_LIGHT_FROM_BRIGHT_POINT, 
							       SCATTERED_LIGHT_FROM_BRIGHT_POINT };

  /**
   * Default values.
   */
  JTimeRange JRegressor<JPoint4E, JGandalf>::T_ns;
  double     JRegressor<JPoint4E, JGandalf>::Vmax_npe = std::numeric_limits<double>::max();

}

#endif