#ifndef MPDMOTHERFITTERPART_H
#define MPDMOTHERFITTERPART_H

/// \ingroup rec
/// \class MpdMotherFitterPart
/// \brief Kalman filter mother particle fitter for the MPD detector
/// \brief (using MpdParticle)
///
/// \author Alexander Zinchenko, LHEP JINR Dubna

class MpdKalmanTrack;
class MpdVertex;
class TVector3;
#include "MpdParticle.h"
#include "FairTask.h"
#include <TMatrixD.h>
#include <vector>
using std::vector;

class TClonesArray;

class MpdMotherFitterPart : public FairTask
{

 public:
  static MpdMotherFitterPart* Instance(); ///< get singleton instance
  static MpdMotherFitterPart* Instance(const char *name, const char *title="FAIR Task"); ///< get singleton instance

  virtual void Exec(Option_t * option);

  void Reset();
  void Register();

  //virtual InitStatus ReInit();
  //void WeightAtDca(MpdParticle *part, MpdKalmanTrack &track, Double_t *vert); // obtain MpdParticle weight at DCA
  Double_t BuildMother(MpdParticle *mother, vector<MpdParticle*> &vDaught); // build mother from daughters
  Double_t BuildMother(MpdParticle *mother, vector<MpdKalmanTrack*> &vTracks, vector<MpdParticle*> &vDaught); 
  Double_t FindVertex(vector<MpdParticle*> vDaught, TVector3 &vtx); // find vertex from daughter tracks
  void ComputeAandB(const TMatrixD &xk0, const MpdParticle &part,
                    TMatrixD &a, TMatrixD &b, TMatrixD &ck0, Bool_t flag = kTRUE); // compute matrices of derivatives
  Double_t FieldConst() const { return fieldConst; }
  TMatrixD ComputeQmatr(vector<MpdParticle*> vDaught);
  void ParamsAtDca(MpdParticle* part);
  TMatrixD& GetCovariance() { return fCovar; } //access to covariance matrix
  Double_t Chi2Vertex(MpdParticle *part, const MpdVertex *vtx); ///< compute Chi2 w.r.t. vertex

 protected:
  virtual InitStatus Init();
  virtual InitStatus ReInit();
  virtual void Finish();
  virtual ~MpdMotherFitterPart(); ///< Destructor

 private:
  MpdMotherFitterPart(); ///< Default ctor
  MpdMotherFitterPart(const char *name, const char *title="FAIR Task"); ///< Ctor
  static void DestroyInstance () { if (fgMF) delete fgMF; } // automatic deleting
  void EvalVertex(vector<MpdParticle*> vDaught); // evaluate vertex from daughter tracks
  void Smooth(vector<MpdParticle*> vDaught); // smooth (update track momenta and track lengths)
  void ComputeAB0(const TMatrixD &xk0, const MpdParticle &part, TMatrixD &a, 
		  TMatrixD &b, TMatrixD &ck0, Bool_t flag); // compute matrices of derivatives for neutrals
  void Proxim(const MpdKalmanTrack &track0, MpdKalmanTrack &track); // adjust track params

 private:
  static MpdMotherFitterPart* fgMF;
  Double_t fieldConst; ///< mag. field constant
  Double_t fVtx[3]; ///< decay vertex position
  TMatrixD fCovar; ///< covariance matrix

  ClassDef(MpdMotherFitterPart,1);
};
#endif