#ifndef ALI_TPC_EX_B_TWIST_H
#define ALI_TPC_EX_B_TWIST_H

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

// _________________________________________________________________
//
// Begin_Html
//   <h2> AliTPCExBTwist class    </h2>       
//   The class calculates the space point distortions due to a mismatch     
//   of the E and B field axis (original code from STAR)                    
//   <p>
//   It assumes a homogeneous magnetic and electric field. The calculations performed 
//   within this class can be written in a compact form as well (compare notes of Jim Thomas)
//   <p>
//   The inputs to this class are the twist angles in the x and y plane ($\theta_x,\theta_y$) 
//   in cartesian coordinates. They can be set via the member functions SetXTwist and SetYTwist.
// End_Html
//
// Begin_Macro(source)
//   {
//   gROOT->SetStyle("Plain"); gStyle->SetPalette(1);
//   TCanvas *c2 = new TCanvas("cAliTPCExBTwist","cAliTPCExBTwist",500,300); 
//   AliTPCExBTwist twist;
//   twist.SetXTwist(0.001);  // x angle in [rad]
//   twist.SetXTwist(0.0005); // y angle in [rad]
//   twist.SetOmegaTauT1T2(0.32,1,1);
//   twist.CreateHistoDRPhiinXY(1.)->Draw("surf2"); // A side
//   return c2;
//   } 
// End_Macro
//
// Begin_Html
//   <p>
// Date: 27/04/2010  <br>
// Authors: Jim Thomas, Magnus Mager, Stefan Rossegger 
// Support since 2010: mrain.ivanov@cern.ch
// End_Html 
// _________________________________________________________________

#include "AliTPCCorrection.h"

class AliTPCExBTwist : public AliTPCCorrection {
public:
  AliTPCExBTwist();
  virtual ~AliTPCExBTwist();
  virtual Bool_t AddCorrectionCompact(AliTPCCorrection* corr, Double_t weight);
  // 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 Float_t wt1=t1*omegaTau;     fC1=wt1/(1.+wt1*wt1);
    const Float_t wt2=t2*omegaTau;     fC2=wt2*wt2/(1.+wt2*wt2);
  };
  void SetC1C2(Float_t c1,Float_t c2) {fC1=c1;fC2=c2;} // CAUTION: USE WITH CARE
  Float_t GetC1() const {return fC1;}
  Float_t GetC2() const {return fC2;}

  // setters and getters for twist
  void SetXTwist(Float_t xTwist) {fXTwist=xTwist;}
  void SetYTwist(Float_t yTwist) {fYTwist=yTwist;}
  Float_t GetXTwist() const {return fXTwist;}
  Float_t GetYTwist() const {return fYTwist;}

  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 fC1; // coefficient C1                 (compare Jim Thomas's notes for definitions)
  Float_t fC2; // coefficient C2                 (compare Jim Thomas's notes for definitions)

  Float_t fXTwist;               // Twist of E to B field in X-Z [rad]
  Float_t fYTwist;               // Twist of E to B field in Y-Z [rad]

  ClassDef(AliTPCExBTwist,1);
};

#endif