//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//

#ifndef TCACHED_MAGNETIC_FIELD_DEF
#define TCACHED_MAGNETIC_FIELD_DEF

#include "G4Types.hh"
#include "G4ThreeVector.hh"
#include "G4MagneticField.hh"

template <class T_Field>
class G4TCachedMagneticField : public G4MagneticField
{
 public:  // with description
  G4TCachedMagneticField(T_Field* pTField, G4double distance)
    : G4MagneticField()
    , fLastLocation(DBL_MAX, DBL_MAX, DBL_MAX)
    , fLastValue(DBL_MAX, DBL_MAX, DBL_MAX)
    , fCountCalls(0)
    , fCountEvaluations(0)
  {
    fpMagneticField = pTField;
    fDistanceConst  = distance;

    // G4cout << " Cached-B-Field constructor> Distance = " << distance <<
    // G4endl;
    this->ClearCounts();
  }

  G4TCachedMagneticField(const G4TCachedMagneticField<T_Field>& rightCMF)
  {
    fpMagneticField = rightCMF.fpMagneticField;
    fDistanceConst  = rightCMF.fDistanceConst;
    fLastLocation   = rightCMF.fLastLocation;
    fLastValue      = rightCMF.fLastValue;
    this->ClearCounts();
  }

  G4TCachedMagneticField* Clone() const
  {
    G4cout << "Clone is called" << G4endl;
    // Cannot use copy constructor: I need to clone the associated magnetif
    // field
    T_Field* aF = this->fpMagneticField->T_Field::Clone();
    G4TCachedMagneticField* cloned =
      new G4TCachedMagneticField(aF, this->fDistanceConst);
    cloned->fLastLocation = this->fLastLocation;
    cloned->fLastValue    = this->fLastValue;
    return cloned;
  }

  virtual ~G4TCachedMagneticField() { ; }
  // Constructor and destructor. No actions.

  void ReportStatistics()
  {
    G4cout << " Cached field: " << G4endl
           << "   Number of calls:        " << fCountCalls << G4endl
           << "   Number of evaluations : " << fCountEvaluations << G4endl;
  }

  virtual void GetFieldValue(const G4double Point[4], G4double* Bfield) const
  {
    G4ThreeVector newLocation(Point[0], Point[1], Point[2]);

    G4double distSq = (newLocation - fLastLocation).mag2();
    fCountCalls++;
    if(distSq < fDistanceConst * fDistanceConst)
    {
      Bfield[0] = fLastValue.x();
      Bfield[1] = fLastValue.y();
      Bfield[2] = fLastValue.z();
    }
    else
    {
      // G4CachedMagneticField* thisNonC=
      // const_cast<G4CachedMagneticField*>(this);
      fpMagneticField->T_Field::GetFieldValue(Point, Bfield);
      // G4cout << " Evaluating. " << G4endl;
      fCountEvaluations++;
      // thisNonC->
      fLastLocation = G4ThreeVector(Point[0], Point[1], Point[2]);
      // thisNonC->
      fLastValue = G4ThreeVector(Bfield[0], Bfield[1], Bfield[2]);
    }
  }

  G4double GetConstDistance() const { return fDistanceConst; }
  void SetConstDistance(G4double dist) { fDistanceConst = dist; }

  G4int GetCountCalls() const { return fCountCalls; }
  G4int GetCountEvaluations() const { return fCountEvaluations; }
  void ClearCounts()
  {
    fCountCalls       = 0;
    fCountEvaluations = 0;
  }

  G4TCachedMagneticField& operator=(const G4TCachedMagneticField& right)
  {
    if(&right == this)
      return *this;

    fpMagneticField = right.fpMagneticField;

    fDistanceConst= right.fDistanceConst;
    fLastLocation = right.fLastLocation;
    fLastValue = right.fLastValue;

    fCountCalls = 0;
    fCountEvaluations = 0;
    
    return *this;
 }

 private:
  T_Field* fpMagneticField;
  // When the field is evaluated within this distance it will not change
  G4double fDistanceConst;
  // Caching state
  mutable G4ThreeVector fLastLocation;
  mutable G4ThreeVector fLastValue;

 protected:
  mutable G4int fCountCalls, fCountEvaluations;
};

#endif /* TCACHED_MAGNETIC_FIELD_DEF */