////////////////////////////////////////////////////////////////////////
///
/// \class  MultiPath
///
/// \brief  Fitter method for different media with the possibility of
///         multiple path calculations of LLH.
///
/// \author Jeff Tseng     jeff.tseng@physics.ox.ac.uk
///         Aksel Hallin   aksel.hallin@ualberta.ca
///         Jie Hu         jhu9@ualberta.ca
///         David Auty     auty@ualberta.ca
///         Kalpana Singh  kalpana.singh@ualberta.ca
///
/// REVISION HISTORY:
/// Dec 29, 2014 :  Aksel Hallin  First itteration as part of
///                               Particle water fitter
/// Jul 29, 2015 :  Kalpana Singh Split the fitter out to make a
///                               generic fitter that can run other
///                               detector states
/// Apr 30, 2016 :  David Auty    Integrated partial air water
///                               fitter in this structure
/// Feb  6, 2018 :  Jeff Tseng    Restructured
///
/// May  1, 2018 :  Jie Hu        Add partial-fitter and scint-fitter
///
/// This method can be invoked from the FitterProcessor.
///
/// The position fitter is invoked with
///   /rat/proc fitter
///   /rat/procset method "multipath-waterposition"
///   /rat/procset name "multipath"
///
/// The direction fitter requires a seed, from which it copies the
/// vertex position, which it leaves fixed.  In the following,
/// the multipath position fit is used.
///   /rat/proc fitter
///   /rat/procset/method "multipath-waterdirection"
///   /rat/procset/seed "multipath"
///
/// The partial fitter is invoked with
///   /rat/proc fitter
///   /rat/procset method "multipath-scintwater"
///   /rat/procset name "multipath"
///
/// The scint fitter is invoked with
///   /rat/proc fitter
///   /rat/procset method "multipath-scint"
///   /rat/procset name "multipath"
///
////////////////////////////////////////////////////////////////////////

#ifndef __RAT_MultiPath__
#define __RAT_MultiPath__

#include <string>
#include <RAT/SeededMethod.hh>
#include <RAT/SelectorMethod.hh>
#include <RAT/VertexFunction.hh>
#include "TVectorD.h"
#include "TMatrixT.h"

namespace RAT {

namespace Methods {

class MultiPath : public SeededMethod, SelectorMethod {

public:

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

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

  /// constructor
  MultiPath();

  /// destructor
  ~MultiPath();

  /// initialise the method (by factory)
  ///   "waterposition" :  MultiPathWaterPosition
  ///   "waterdirection":  MultiPathWaterDirection
  virtual void Initialise( const std::string& param );

  /// set the default seed (origin, t=230ns, big errors)
  virtual void DefaultSeed();

  /// Reads constants from the database
  ///   FIT_MULTIPATH.ratdb
  virtual void BeginOfRun( DS::Run& run );

  /// forwards EndOfRun to VertexFunction
  virtual void EndOfRun( DS::Run& run );

  /// runs the algorithm and returns the answer
  virtual DS::FitResult GetBestFit();

  /// dump likelihood contours to a TFile
  void DumpLikelihood(int index, int gtid, std::string dumpVariable);

protected:

  std::string fInitString; // initialization parameter (waterposition or waterdirection)
  /// set the VertexFunction to use
  void SetFunction(VertexFunction* func);
  /// this index is used to select the fit parameters of a specific geo in FIT_MULTIPATH.ratdb
  std::string materialIndex;

  // sum likelihoods from PMTs' Calculate() functions.
  // Returns log(L), and fBeta and fCov.
  double SumLikelihoods(const std::vector<double>& par);

  VertexFunction* fFunction; // the PMT-vertex likelihood function
  int fStepsBelowTolerance; // number of steps to do after reaching tolerance
  int fMaximumIterations; // convergence parameter
  int fMaxGoodFits; // how many good fits to define a valid fit
  double fTolerance; // chisquare tolerance
  double fMax_nStart; // for boundaryCut; for boundary events, set a limit for start position
  double fBoundaryTolerance; // for boundaryCut; boundary tolerance
  double fFitterPar; // save extra parameters required by special fitter, eg. fWaterLevel for scintwater fitter

  bool fBoundaryCut; // set to true to reduce iterations for boundary events
  /// geometry parameters used by partial and scint fitter, to set seeding boundary
  double fZoff; // z offset of AV to the PSUP
  double fAVRadius;
  double fAVRadiusOuter;
  double fNeckRadius;
  double fNeckRadiusOuter;
  double fZneckLo; // bottom of the neck

  bool fDumpValid; // set to true to dump likelihood contours
  std::vector<int> fGTID; // GTID's for which to dump likelihood contours
  int fNEvents; // counter of fits

  /// reduced PMT data:
  ///   positions and times only for the selected PMTs
  std::vector< std::vector<double> > fPMTReduced;

  /// calculated by SumLikelihoods
  TVectorD fBeta; // derivatives
  TMatrixT<double> fCov; // covariance matrix

  /// calculated by GetBestFit
  std::vector<double> fParsBest; // best fit
  double fLBest; // best fit likelihood
};

} //::Methods

} //::RAT

#endif