/**
   \file
   Declaration of HumidAirRayleighModel, a model to estimate molecular
   scattering and attenuation using the dispersion and height dependence of the
   index of refraction of air and the Rayleigh scattering cross section.

   \author M. Will
   \version $Id: HumidAirRayleighModel.h,v 1.1 2003/09/22 11:56:12 prado 
            Exp $
   \date 25 Mar 2009
*/

#ifndef _atm_HumidAirRayleighModel_h_
#define _atm_HumidAirRayleighModel_h_

#include <atm/VRayleighModel.h>
#include <vector>

namespace atm {

  class ScatteringResult;
  class AttenuationResult;
  
  /**
     \class HumidAirRayleighModel HumidAirRayleighModel.h 
           "atm/HumidAirRayleighModel.h"

     \brief Model for Rayleigh scattering and attenuation in a humid atmosphere

     \date 25 Mar 2009
     \ingroup atm_models
  */
  class HumidAirRayleighModel : public atm::VRayleighModel {

    public:

      HumidAirRayleighModel();

      virtual ~HumidAirRayleighModel() { }

      atm::ScatteringResult EvaluateRayleighScattering(
                                      const utl::Point& xA,
                                      const utl::Point& xB,
                                      const double angle,
                                      const double distance,
                                      const std::vector<double>& wLength) const;

      atm::ScatteringResult EvaluateRayleighScattering(
                                      const utl::Point& xA,
                                      const utl::Point& xB,
                                      const double angle,
                                      const double distance,
                                      const AttenuationResult& raylAtt) const;
      
      atm::AttenuationResult EvaluateRayleighAttenuation(
                                      const utl::Point& xInit, 
                                      const utl::Point& xFinal,  
                                      const std::vector<double>& wLength) const;

      double EvaluateRayleighScattering(const utl::Point& xA,
                                        const utl::Point& xB,
                                        const double angle,
                                        const double distance,
                                        double wLength) const;
      
      double EvaluateRayleighScattering(const utl::Point& xA,
                                        const utl::Point& xB,
                                        const double angle,
                                        const double distance,
                                        const double raylAtt,
                                        double wLength) const;
      
      double EvaluateRayleighAttenuation(const utl::Point& xInit, 
                                         const utl::Point& xFinal,  
                                         double wLength) const;

      /// Attenuation in units of length [1/scattering coefficient]
      double GetAttenuationLength(const utl::Point& p, 
                                  const double wLength) const;
      
      double EvaluateScatteringAngle(const utl::Point& p,
                                     const double angle,
                                     const double wLength) const;
      
      bool HasData() const {
        return true;
      }

      void Init();

    private:

      double fIntegrationStepWidth;

      double KingFactor(const double wl,
                        const double pressure,
                        const double vaporPressure) const;

      double RayleighCrossSection(const double wl, 
                                  const double refIndex,
                                  const double temperature,
                                  const double pressure,
                                  const double vaporPressure) const;

      REGISTER_MODEL(atm::VRayleighModel, "HumidAir", HumidAirRayleighModel);
  };

} // atm


#endif // _atm_HumidAirRayleighModel_h_