#ifndef TDriftManager_hxx_seen
#define TDriftManager_hxx_seen

#include "IElectronCloud.hxx"
//#include "TVector3.h"
#include <utility>  //For pair
#include <vector>


///    \brief TPC drift electrons
///    \author Christian Hansen, hansen@ific.uv.es

namespace COMET {
  class IDriftManager;
};



class COMET::IDriftManager {
  
public:
  
  IDriftManager();
  virtual ~IDriftManager();


  /// *** DRIFT
  /// The drift is a forth order Runge-Kutta, with adaptive step size and using the 
  /// nominal B-field and a macroscopic theory for the transportation (equation 12):
  /// http://www.pd.infn.it/gruppi/g1/2002Vavra_student_lecture.pdf
  /// Drifts the electron cloud as long as abs(x) < abs(xLim)
  /// If it returns true the cloud hit the readout board (i.e. the +-x wall) 
  /// If it returns false the cloud took too many steps 
  bool DriftUntilXLim(IElectronCloud& cloud, double xLim);

  /// Drifts the electron cloud as long as the dt < tLim
  /// If it return true the cloint main(int argc, char *argv[]) {ud drifted until the time limit 
  /// If it return false the cloud took too many steps 
  bool DriftUntilTLim(IElectronCloud& cloud, double tLim);

  /// This function does the actual drift
  bool Drift(double xLim, bool driftUntilXLim, IElectronCloud& cloud, int& nbrSteps, int& nbrStepCalls, int& nbrVCalls, double& hMin);


  void InitializeFromDB(bool UseAdaptiveStepSize, double MaxDriftStepTime, double MinDriftStepTime, 
			int MaxNbrDriftSteps, double ErrorTol, double InitialDriftStepTime, double OmegaTau, double Mu,double DriftVelocity=0.0785);
   
  void InitializeFromDB(double InitialDriftStepTime, double OmegaTau, double Mu,double DriftVelocity=0.0785);

  TLorentzVector Step(const TLorentzVector& x, double charge, double driftTime, bool useFirstKs);
private:

  //TLorentzVector Step(const TLorentzVector& x, double charge, double driftTime, bool useFirstKs);

  //The velocity   www.pd.infn.it/gruppi/g1/2002Vavra_student_lecture.pdf
  double vx(double charge, TVector3 E, TVector3 B);
  double vy(double charge, TVector3 E, TVector3 B);
  double vz(double charge, TVector3 E, TVector3 B);


  //COMET::IOAMagneticField* fMag;
  //For the RK4 step function
  double fOmegaTau;
  double fMu;
  double fK1x;
  double fK1y;
  double fK1z;
  double fDriftVelocity;
  //For the adaptive step size drifting
  int fUseAdaptiveStepSize;
  double fInitialDriftStepTime;
  double fMaxDriftStepTime;
  double fMinDriftStepTime;
  double fErrorTol;
  int fMaxNbrDriftSteps;

  /// Counters
  int fNbrStepCalls;
  int fNbrVxCalls;
  int fNbrSteps;
  double fMinUsedH;


  bool fInitialized;

  double fCathode;


};

#endif