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//
// Helper namespace field_utils
//
// Description:
//
// Simple methods to extract vectors from arrays in conventions of
// the magnetic field integration.

// Author: Dmitry Sorokin (CERN, Google Summer of Code 2017), 13.10.2017
// Supervision: John Apostolakis (CERN)
// --------------------------------------------------------------------
#ifndef G4FIELD_UTILS_HH
#define G4FIELD_UTILS_HH

#include "G4FieldTrack.hh"
#include "G4Types.hh"
#include "G4ThreeVector.hh"

/**
 * @brief field_utils is a helper namespace, including simple methods to extract
 * vectors from arrays in conventions of the magnetic field integration.
 */

namespace field_utils
{
  using State = G4double[G4FieldTrack::ncompSVEC];

  template <unsigned int N>
  using ShortState = G4double[N];
   
  enum class Value3D
  {
    Position = 0,
    Momentum = 3,
    Spin = 9
  };

  enum class Value1D
  {
    KineticEnergy = 6,
    LabTime = 7,
    ProperTime = 8
  };

  template <typename ArrayType>
  G4double getValue(const ArrayType& array, Value1D value);

  template <typename ArrayType>
  G4double getValue2(const ArrayType& array, Value1D value);

  template <typename ArrayType>
  G4double getValue(const ArrayType& array, Value3D value);

  template <typename ArrayType>
  G4double getValue2(const ArrayType& array, Value3D value);

  template <typename ArrayType>
  G4ThreeVector makeVector(const ArrayType& array, Value3D value);

  G4double absoluteError(
    const G4double y[],
    const G4double yerr[],
    G4double hstep);

  G4double relativeError2(
    const G4double y[],
    const G4double yerr[],
    G4double hstep,
    G4double errorTolerance);

  G4double relativeError(
    const G4double y[],
    const G4double yerr[],
    G4double hstep,
    G4double errorTolerance);

  template <typename SourceArray, typename TargetArray>
  void setValue(const SourceArray& src, Value1D value, TargetArray& trg);

  template <typename SourceArray, typename TargetArray, typename ...TargetArrays>
  void setValue(const SourceArray& src, Value1D value,
                TargetArray& trg, TargetArrays&... trgs);

  void copy(G4double dst[], const G4double src[],
            std::size_t size = G4FieldTrack::ncompSVEC);

  G4double inverseCurvatureRadius(G4double particleCharge,
                                  G4double momentum, G4double BField);

  template <typename T>
  T clamp(T value, T lo, T hi);
}

#include "G4FieldUtils.icc"

#endif
