#ifndef ALI_TPCGG_VOLT_ERROR_H
#define ALI_TPCGG_VOLT_ERROR_H

/* Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 * See cxx source for full Copyright notice                               */

// _________________________________________________________________
//
// Begin_Html
//   <h2> AliTPCGGVoltError class   </h2>         
//   The class calculates the electric field and the resulting space point distortions 
//   due a Gating Grid (GG) voltage error. It uses the analytical solution for such a problem. 
//   <p>
//   The input is the effective GG voltage residual in respect to the ideal setting. The effective 
//   residual voltage can be set via the functions SetDeltaVGGx. Note that this effective 
//   voltage-residuals are approx. a factor 0.9 lower than the actual difference in the setting 
//   of the GG due to the fact that the voltage on the GG is partially screened by the wire 
//   structure. The calculation has to be performed with the observable effective voltage difference.
//   <p>
//   Unfortunately, the class is not capable of calculation the $dz$ offset due to possible changes 
//   of the drift velocity in dependence of the electric field. The special case of the numerical 
//   approximation (AliTPCBoundaryVoltError), which is capable of calculating the same effect, should 
//   be used for this purpose. 
// End_Html
//
// Begin_Macro(source) 
//   {
//   gROOT->SetStyle("Plain"); gStyle->SetPalette(1);
//   TCanvas *c2 = new TCanvas("c2","c2",500,300); 
//   AliTPCGGVoltError gg;
//   gg.SetDeltaVGGA(-40); gg.SetDeltaVGGC(-40); // 40 Volt offset
//   gg.InitGGVoltErrorDistortion();
//   gg.SetOmegaTauT1T2(0,1,1); // B=0
//   gg.CreateHistoDRinZR(0)->Draw("surf2"); 
//   return c2;
//   } 
// End_Macro
//
// Begin_Html
//   <p>
//   Date: 27/04/2010  <br>
//   Authors: Jim Thomas, Stefan Rossegger, Magnus Mager   
// End_Html 
// _________________________________________________________________


#include "AliTPCCorrection.h"

class AliTPCGGVoltError : public AliTPCCorrection {
public:
  AliTPCGGVoltError();
  virtual ~AliTPCGGVoltError();

  // initialization and update functions
  virtual void Init();
  virtual void Update(const TTimeStamp &timeStamp);

  // common setters and getters for ExB
  virtual void SetOmegaTauT1T2(Float_t omegaTau,Float_t t1,Float_t t2) {
    fT1=t1; fT2=t2;
    const Double_t wt0=t2*omegaTau;     fC0=1./(1.+wt0*wt0);
    const Double_t wt1=t1*omegaTau;     fC1=wt1/(1.+wt1*wt1);
  };

  void SetC0C1(Double_t c0,Double_t c1) {fC0=c0;fC1=c1;} // CAUTION: USE WITH CARE
  Float_t GetC0() const {return fC0;}
  Float_t GetC1() const {return fC1;}

  // setters and getters for GG
  void SetDeltaVGGA(Double_t deltaVGGA) {fDeltaVGGA=deltaVGGA;}
  void SetDeltaVGGC(Double_t deltaVGGC) {fDeltaVGGC=deltaVGGC;}
  Double_t GetDeltaVGGA() const {return fDeltaVGGA;}
  Double_t GetDeltaVGGC() const {return fDeltaVGGC;}

  void InitGGVoltErrorDistortion();

  Float_t GetIntErOverEz(const Float_t x[],const Short_t roc);

  virtual void Print(const Option_t* option="") const;

protected:
  virtual void GetCorrection(const Float_t x[],const Short_t roc, Float_t dx[]);
private:

  Float_t fC0; // coefficient C0                 (compare Jim Thomas's notes for definitions)
  Float_t fC1; // coefficient C1                 (compare Jim Thomas's notes for definitions)

  Double_t fDeltaVGGA;            // Missmatch of gating grid voltage on A-side [V]
  Double_t fDeltaVGGC;            // Missmatch of gating grid voltage on C-side [V]
  Double_t fGGVoltErrorER[kNZ][kNR]; // Array to store electric field for GGVoltError calculation

  Bool_t fInitLookUp;             // flag to check it the Look Up table was created

  ClassDef(AliTPCGGVoltError,1);
};

#endif