/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/RecoPixelVertexing/PixelTriplets/plugins/ThirdHitPredictionFromCircle.h

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#ifndef ThirdHitPredictionFromCircle_H
#define ThirdHitPredictionFromCircle_H

#include "DataFormats/GeometryVector/interface/Basic2DVector.h"
#include "DataFormats/GeometryVector/interface/Basic3DVector.h"

#include "DataFormats/GeometryVector/interface/GlobalPoint.h"
#include "RecoTracker/TkMSParametrization/interface/PixelRecoRange.h"


class ThirdHitPredictionFromCircle {

public:
  using Scalar = double;
  typedef PixelRecoRange<float> Range;
  typedef Basic2DVector<Scalar> Vector2D;
  typedef Basic2DVector<float> VectorF2D;

  ThirdHitPredictionFromCircle(const GlobalPoint & P1, const GlobalPoint & P2,
                               float tolerance);

  float phi(float curvature, float radius) const;
  float angle(float curvature, float radius) const;

  Range operator()(Range curvature, float radius) const;

  Range curvature(double transverseIP) const;
  double curvature(const  Vector2D &thirdPoint) const;
  double transverseIP(const  Vector2D &thirdPoint) const;

  // like PixelRecoLineRZ, but makes use of the bending computation
  // from the circle fit to get an actual Helix propagation
  class HelixRZ {
    public:
    using Vector2D=ThirdHitPredictionFromCircle::Vector2D;
    using Scalar=ThirdHitPredictionFromCircle::Scalar;
    // using Vector2D=ThirdHitPredictionFromCircle::VectorF2D;
    // using Scalar=float;
    
    HelixRZ() : circle(0) {}
    HelixRZ(const ThirdHitPredictionFromCircle *icircle,
            double iz1, double z2, double curv);
    
    Scalar zAtR(Scalar r) const;
    Scalar rAtZ(Scalar z) const;
    
    static double maxCurvature(const ThirdHitPredictionFromCircle *circle,
                               double z1, double z2, double z3);
    
  private:
    const ThirdHitPredictionFromCircle *circle;
    Vector2D center;
    Scalar curvature, radius, z1, seg, dzdu;
  };

private:
  friend class HelixRZ;

  Scalar invCenterOnAxis(const  Vector2D &thirdPoint) const;

  Vector2D p1, center, axis;
  Scalar delta, delta2;
  float theTolerance;
};

#endif