/**
   \file
    Declaration of AnalyticalCherenkovModel

   \author Luis Prado Jr.
   \version $Id: AnalyticalCherenkovModel.h 20705 2012-03-28 16:20:59Z javierg $
   \date 27 Jan 2004
*/

#ifndef _atm_AnalyticalCherenkovModel_h_
#define _atm_AnalyticalCherenkovModel_h_

static const char CVSId_atm_AnalyticalCherenkovModel[] =
  "$Id: AnalyticalCherenkovModel.h 20705 2012-03-28 16:20:59Z javierg $";

#include <atm/VCherenkovModel.h>
#include <utl/TabulatedFunction.h>
#include <utl/Point.h>


namespace utl {
  class TabulatedFunction;
}

namespace atm {

  /**
     \class AnalyticalCherenkovModel AnalyticalCherenkovModel.h
     "atm/AnalyticalCherenkovModel.h"

     \brief Model with analytical calculation of the Cherenkov light

     \author Luis Prado Jr
     \date 27 Jan 2004
     \ingroup atm_models
  */

  class AnalyticalCherenkovModel : public atm::VCherenkovModel {

  public:
    /// Model Constructor
    AnalyticalCherenkovModel();
    /// Model Destructor
    virtual ~AnalyticalCherenkovModel() { }
    /// Init method of the model
    void Init();

    // Possible parametrizations for the Energy Electron Spectrum.
    enum Parametrization { eHillas, eGiller, eNerling };

    // Possible parametrizations for the Angular Electron Distribution.
    enum ParametrizationAngular { eAngHillas, eAngNerling, eAngGiller };

    /// Calculation of Cherenkov photons produced between two points
    utl::TabulatedFunction&
    EvaluateCherenkovPhotons(const utl::Point& xA,
                             const utl::Point& xB,
                             const double showerAge) const;

    /// Calculation of probability of Cherenkov emission
    utl::TabulatedFunction&
    EvaluateCherenkovDirect(const utl::Point& xA,
                            const utl::Point& xB,
                            const utl::Point& xEye,
                            const double showerAge) const;
    double
    EvaluateDirectCherenkovProbability(const utl::Point& xA, const utl::Point& xB,
                                       const utl::Point& xEye, const double showerAge) const;

    double AngularCDF(const double theta, const double verticalDepth,
                      const double showerAge) const;
    double AngularPDF(const double theta, const double verticalDepth,
                      const double showerAge) const;

    bool HasData() const {return true;};

    void SetEnergyCutoff(double ecut) const;

  private:
    static const double fdE;
    static const double fjMax;
    /// Limits for the shower age in the use of the Nerling parameterizations
    static const double fNerlingMinValidShowerAge;
    static const double fNerlingMaxValidShowerAge;

    /// Number of photons as function of the wavelength
    mutable utl::TabulatedFunction fCherenkovPhotons;
    mutable utl::TabulatedFunction fDirectCherenkovPhotons;

    /// Wavelengths to calculate the light production
    std::vector<double> fWavelength;

    /// Parametrization to be used in the Cherenkov light calculation
    Parametrization fParam;
    ParametrizationAngular fParamAngular;

    /// Calculation of a special track length to be used in the Cherenkov light evaluation
    double CherenkovTrackLength(double energy, double showerAge) const;

    /// Calculation of Cherenkov Photons between two wavelengths
    double DeltaPhotons(double nIndex, double eelec,
                        double dSlant, double wl1, double wl2) const;

    /// Calculation of the Cherenkov angle integral int(df/dtheta*sin(theta))
    double CherenkovIntegral(double lowAngle, double highAngle,
                             double meanShowerAge, double eThreshold) const;

    const std::vector<double>& GetWavelengths() const
    { return fWavelength; }

    /// Keep reference to previous calculation, to prevent re-calculation
    mutable utl::Point fxAprevious;
    mutable utl::Point fxBprevious;
    mutable double fShowerAgePrevious;
    mutable std::vector<double> fNerlingFactor;

    REGISTER_MODEL(atm::VCherenkovModel, "Analytical",AnalyticalCherenkovModel);
  };

}


#endif

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