//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************

//---------------------------------------------------------------------------
// ClassName:   G4UCNMicroRoughnessHelper
//
// Class description:
//
// This file contains the headers of various functions all related to the
// calculation of microroughness.
// see A. Steyerl, Z. Physik 254 (1972) 169.
//
// Angular cut: for angles which are closer to the specular direction than a
// certain value (0.01°), the probability is set to 0 in order to avoid a
// hang-up at the generation of the polar angle due to a very sharp angular
// distribution
//
// 12-05-14, adopted from Stefan Heule (PSI) Thesis by P.Gumplinger
//           reported in F. Atchison et al., Eur. Phys. J. A 44, 23–29 (2010)
//                       DOI:  10.1140/epja/i2010-10926-x
//           Thanks to Geza Zsigmond
//
// 02-11-19  Stefan Heule's thesis is available from PSI UCN group pages at
//           https://www.psi.ch/en/ltp-ucn-physics/papers-and-theses
//           or directly at https://opac.nebis.ch/ediss/20080426_002127549.pdf

#ifndef G4MICROROUGHNESSHELPER_HH
#define G4MICROROUGHNESSHELPER_HH 1

#include "G4Types.hh"

class G4UCNMicroRoughnessHelper
{
 public:  // with description
  static G4UCNMicroRoughnessHelper* GetInstance();

 public:  // with description
  // Transmitted intensity with k-vector in vacuum
  // arguments:
  //         1) cos(theta)^2,
  //         2) (k_l/k)^2
  G4double S2(G4double, G4double) const;

  // Transmitted intensity with k-vector within the medium
  // arguments:
  //         1) cos(theta')^2,
  //         2) (k_l/k')^2
  G4double SS2(G4double, G4double) const;

  // Fourier-tranform of the autocorrelation function with k-vector in vacuum
  // arguments:
  //         1) k^2,
  //         2) theta_i,
  //         3) theta_o,
  //         4) phi_o,
  //         5) b^2,
  //         6) w^2,
  //         7) angular cut
  G4double Fmu(G4double, G4double, G4double, G4double, G4double, G4double, G4double) const;

  // Fourier-tranform of the autocorrelation function with k-vector within
  // the medium
  // arguments:
  //         1) k,
  //         2) k',
  //         3) theta_i,
  //         4) theta'_o,
  //         5) phi'_o,
  //         6) b^2,
  //         7) w^2,
  //         8) angular cut
  //         9) theta_refract
  G4double FmuS(
    G4double, G4double, G4double, G4double, G4double, G4double, G4double, G4double, G4double) const;

  // Integral probability for non-specular reflection
  // arguments:
  //         1) E,
  //         2) V_F,
  //         3) theta_i,
  //         4) number of angles theta_o for which the probability is calculated,
  //         5) number of angles phi_o for which the probability is calculated,
  //         6) b^2,
  //         7) w^2,
  //         8) pointer to G4double array with max values of the probability,
  //         9) angular cut
  G4double IntIplus(
    G4double, G4double, G4double, G4int, G4int, G4double, G4double, G4double*, G4double) const;

  // Probability of non-specular reflection with the microroughness model
  // arguments:
  //         1) E,
  //         2) V_F,
  //         3) theta_i,
  //         4) theta_o,
  //         5) phi_o,
  //         6) b,
  //         7) w,
  //         8) angular cut
  G4double ProbIplus(
    G4double, G4double, G4double, G4double, G4double, G4double, G4double, G4double) const;

  // Integral probability for non-specular transmission
  // arguments:
  //         1) E,
  //         2) V_F,
  //         3) theta_i,
  //         4) number of angles theta_o for which the probability is calculated,
  //         5) number of angles phi_o for which the probability is calculated,
  //         6) b^2,
  //         7) w^2,
  //         8) pointer to G4double array with max values of the probability,
  //         9) angular cut
  G4double IntIminus(
    G4double, G4double, G4double, G4int, G4int, G4double, G4double, G4double*, G4double) const;

  // Probability of non-specular transmission with the microroughness model
  // arguments:
  //         1) E,
  //         2) V_F,
  //         3) theta_i,
  //         4) theta'_o,
  //         5) phi'_o,
  //         6) b,
  //         7) w,
  //         8) angular cut
  G4double ProbIminus(
    G4double, G4double, G4double, G4double, G4double, G4double, G4double, G4double) const;

 protected:
  G4UCNMicroRoughnessHelper() = default;
  ~G4UCNMicroRoughnessHelper();

 private:
  static G4UCNMicroRoughnessHelper* fpInstance;
};

#endif  // G4MICROROUGHNESSHELPER_HH