////////////////////////////////////////////////////////////////////////
/// \class RAT::MultiPathWaterDirection
///
/// \brief PMT-likelihood function for water direction fit using MultiPath fitter.
///
/// \author Jeff Tseng <jeff.tseng@physics.ox.ac.uk> (contact)
///
/// REVISION HISTORY:\n
///     2018-02-06 : J Tseng - new file
///
////////////////////////////////////////////////////////////////////////

#ifndef __RAT_MultiPathWaterDirection__
#define __RAT_MultiPathWaterDirection__

#include <string>
#include <vector>
#include <RAT/VertexFunction.hh>

//#define MULTIPATH_FIXED_SEED

namespace RAT {

class MultiPathWaterDirection : public VertexFunction {

public:

  /// constuctor
  MultiPathWaterDirection();

  /// return the name
  virtual std::string GetName() const { return MultiPathWaterDirection::Name(); }

  /// fitter structure name
  static std::string Name() { return std::string("multiPathWaterDirection"); }

  /// called at beginning of run
  virtual void BeginOfRun( DS::Run& );

  /// called at end of run
  virtual void EndOfRun( DS::Run& ) { }

  /// initialise the function (when instantiated by MultiPath method)
  virtual void Initialise( const std::string& param );

  /// set seed from a previous result
  virtual void SetSeed(const DS::FitResult& result);

  /// set a result from the parameters
  virtual DS::FitResult MakeResult(const std::vector<double>& pars);

  /// set the position, which is fixed in this fit
  void SetVertex(const std::vector<double>& vtx);

  /// set a starting set of parameters for one iteration
  virtual std::vector<double> GetStart();

  /// calculates the figure of merit for a given PMT and vertex.
  virtual double Calculate( const std::vector<double>& pmt,
                            const std::vector<double>& par,
                            std::vector<double>& diff );

  /// check whether the parameters yield a valid result
  virtual bool ValidResult(const std::vector<double>& pars);

private:

  /// look up likelihood profile
  void LAnddLdCosTheta_Ch(double cosTheta, double& L_Ch, double& dLdCosTheta_Ch);

  /// database table FIT_Ch_Angle
  std::vector<double> fPDFChAngle; // sPDFAngle_ChFit
  std::vector<double> fPDFxChAngle; // bin edges
  std::vector<double> fDerivativeChAngle; // derivative histogram
  int fEntriesAngle; // number of histogram bins

  /// drive correction parameters
  bool fDriveCorEnable;
  double fDrivePositionScale;
  double fDriveDirectionScale;

  /// vertex position (set by SetVertex)
  std::vector<double> fVertex;

#ifdef MULTIPATH_FIXED_SEED
  double stepd;
#endif

};

} //::RAT

#endif