////////////////////////////////////////////////////////////////////
/// \class RAT::DU::EffectiveVelocity
///
/// \brief  Return the total transit time given the effective group velocities
///
/// \author Phil G Jones <p.g.jones@qmul.ac.uk>
/// \author Rob Stainforth <R.Stainforth@liverpool.ac.uk> -- contact person
///
/// REVISION HISTORY:
///  - 21 July 2011 : New File.
///  - 2014-03-01 : P G Jones - refactor as part of ds review, moved from ds.
///  - 2014-07-14   J.R.Wilson - change name of scint volume to inner_av
///  - 2014-04-02 : M Mottram - updated to work with partial fill.
///
///
/// \details This class loads effective velocity information from
/// the database and will calculate the transit time taken given
/// the loaded velocities.
/// It can be used in RAT, ROOT or external programs that link to
/// the libRATEvent library.
///
////////////////////////////////////////////////////////////////////
#ifndef __RAT_DU_EffectiveVelocity__
#define __RAT_DU_EffectiveVelocity__

#include <TObject.h>

namespace RAT
{
namespace DU
{

class EffectiveVelocity : public TObject
{
public:
  /// Called at the start of a run, loads from the database
  void BeginOfRun();

  /// Calculate the transit time by distance in the standard 3 SNO+ volumes
  ///
  /// @param[in] distInInnerAV the distance in the scintillator (inner AV) volume
  /// @param[in] distInAV the distance in the AV
  /// @param[in] distInWater the distance in the water (cavity)
  /// @return the transit time
  inline double CalcByDistance( const double distInInnerAV, const double distInAV, const double distInWater ) const;

  /// Get the inner_av volume effective velocity
  ///
  /// @return the inner_av volume effective velocity
  double GetInnerAVVelocity() const { return fInnerAVVelocity; }

  /// Get the av volume effective velocity
  ///
  /// @return the av volume effective velocity
  double GetAVVelocity() const { return fAVVelocity; }

  /// Get the water volume effective velocity
  ///
  /// @return the water volume effective velocity
  double GetWaterVelocity() const { return fWaterVelocity; }

  /// Get the offset time, represents transit time in PMTs
  ///
  /// @return the offset time
  double GetOffset() const { return fOffset; }

  // This ROOT macro adds dictionary methods to this class.
  // The number is 0 as this class is never, and should never be written to disc.
  // It assumes this class has no virtual methods, use ClassDef if change this.
  ClassDefNV( EffectiveVelocity, 0 );
private:
  double fInnerAVVelocity; ///< Effective target (inner_av) effective velocity
  double fAVVelocity; ///< Effective av effective velocity
  double fWaterVelocity; ///< Effective water effective velocity
  double fOffset; ///< Offset required from fit, time taken on average in PMT.
};

double
EffectiveVelocity::CalcByDistance( const double distInInnerAV,
                                   const double distInAV,
                                   const double distInWater ) const
{
  return distInInnerAV / fInnerAVVelocity + distInAV / fAVVelocity + distInWater / fWaterVelocity + fOffset;
}

} // namespace DU

} // namespace RAT

#endif