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#include "G4ErrorEnergyLoss.hh"
#include "G4ErrorPropagatorData.hh"
#include "G4EnergyLossForExtrapolator.hh"

//-------------------------------------------------------------------
G4ErrorEnergyLoss::G4ErrorEnergyLoss(const G4String& processName, 
				     G4ProcessType type)
           : G4VContinuousProcess(processName, type)
{
  if (verboseLevel>2) {
    G4cout << GetProcessName() << " is created " << G4endl;
  }

  InstantiateEforExtrapolator();

  theStepLimit = 1.;
}

//-------------------------------------------------------------------
void G4ErrorEnergyLoss::InstantiateEforExtrapolator()
{
  if( theELossForExtrapolator == 0 ) {
    theELossForExtrapolator = new G4EnergyLossForExtrapolator;
  }
}


//-------------------------------------------------------------------
G4ErrorEnergyLoss::~G4ErrorEnergyLoss() 
{
  if( theELossForExtrapolator != 0 ) {
    delete theELossForExtrapolator;
  }
}

//-------------------------------------------------------------------
G4VParticleChange*
G4ErrorEnergyLoss::AlongStepDoIt(const G4Track& aTrack, const G4Step& aStep)
{
  aParticleChange.Initialize(aTrack);

  G4ErrorPropagatorData* g4edata =  G4ErrorPropagatorData::GetErrorPropagatorData();

  G4double kinEnergyStart = aTrack.GetKineticEnergy();
  G4double step_length  = aStep.GetStepLength();

  const G4Material* aMaterial = aTrack.GetMaterial();
  const G4ParticleDefinition* aParticleDef = aTrack.GetDynamicParticle()->GetDefinition();
  G4double kinEnergyEnd = kinEnergyStart;

  if( g4edata->GetMode() == G4ErrorMode(G4ErrorMode_PropBackwards) ) {
    kinEnergyEnd = theELossForExtrapolator->EnergyBeforeStep( kinEnergyStart, 
							      step_length, 
							      aMaterial, 
							      aParticleDef );
    G4double kinEnergyHalfStep = kinEnergyStart - (kinEnergyStart-kinEnergyEnd)/2.;

#ifdef G4VERBOSE
  if(G4ErrorPropagatorData::verbose() >= 3 ) 
    G4cout << " G4ErrorEnergyLoss FWD  end " << kinEnergyEnd 
	   << " halfstep " << kinEnergyHalfStep << G4endl;
#endif

    //--- rescale to energy lost at 1/2 step
    kinEnergyEnd = theELossForExtrapolator->EnergyBeforeStep( kinEnergyHalfStep, 
							      step_length, 
							      aMaterial, 
							      aParticleDef );
    kinEnergyEnd = kinEnergyStart - (kinEnergyHalfStep - kinEnergyEnd );
  }else if( g4edata->GetMode() == G4ErrorMode(G4ErrorMode_PropForwards) ) {
    kinEnergyEnd = theELossForExtrapolator->EnergyAfterStep( kinEnergyStart, 
							     step_length, 
							     aMaterial, 
							     aParticleDef );
    G4double kinEnergyHalfStep = kinEnergyStart - (kinEnergyStart-kinEnergyEnd)/2.;
#ifdef G4VERBOSE
  if(G4ErrorPropagatorData::verbose() >= 3 ) 
    G4cout << " G4ErrorEnergyLoss BCKD  end " << kinEnergyEnd 
	   << " halfstep " << kinEnergyHalfStep << G4endl;
#endif

    //--- rescale to energy lost at 1/2 step
    kinEnergyEnd = theELossForExtrapolator->EnergyAfterStep( kinEnergyHalfStep, 
							     step_length, 
							     aMaterial, 
							     aParticleDef );
    kinEnergyEnd = kinEnergyStart - (kinEnergyHalfStep - kinEnergyEnd );
  }

  G4double edepo = kinEnergyEnd - kinEnergyStart;

#ifdef G4VERBOSE
  if( G4ErrorPropagatorData::verbose() >= 2 ) 
    G4cout << "AlongStepDoIt Estart= " << kinEnergyStart << " Eend " << kinEnergyEnd 
	   << " Ediff " << kinEnergyStart-kinEnergyEnd << " step= " << step_length 
	   << " mate= " << aMaterial->GetName() 
	   << " particle= " << aParticleDef->GetParticleName() << G4endl;
#endif

  aParticleChange.ClearDebugFlag();
  aParticleChange.ProposeLocalEnergyDeposit( edepo );
  aParticleChange.SetNumberOfSecondaries(0);
 
  aParticleChange.ProposeEnergy( kinEnergyEnd );
  
  return &aParticleChange;
}


//-------------------------------------------------------------------
G4double G4ErrorEnergyLoss::GetContinuousStepLimit(const G4Track& aTrack,
				    G4double ,
				    G4double currentMinimumStep,
                                    G4double& )
{
  G4double Step = DBL_MAX;
  if( theStepLimit != 1. ) { 
    G4double kinEnergyStart = aTrack.GetKineticEnergy();
    G4double kinEnergyLoss = kinEnergyStart;
    const G4Material* aMaterial = aTrack.GetMaterial();
    const G4ParticleDefinition* aParticleDef = aTrack.GetDynamicParticle()->GetDefinition();
    G4ErrorPropagatorData* g4edata =  G4ErrorPropagatorData::GetErrorPropagatorData();
    if( g4edata->GetMode() == G4ErrorMode(G4ErrorMode_PropBackwards) ) {
      kinEnergyLoss = - kinEnergyStart + 
	theELossForExtrapolator->EnergyBeforeStep( kinEnergyStart, currentMinimumStep, 
						   aMaterial, aParticleDef );
    }else if( g4edata->GetMode() == G4ErrorMode(G4ErrorMode_PropForwards) ) {
      kinEnergyLoss = kinEnergyStart - 
	theELossForExtrapolator->EnergyAfterStep( kinEnergyStart, currentMinimumStep, 
						  aMaterial, aParticleDef );
    }
#ifdef G4VERBOSE
  if(G4ErrorPropagatorData::verbose() >= 3 ) 
    G4cout << " G4ErrorEnergyLoss: currentMinimumStep " <<currentMinimumStep 
	   << "  kinEnergyLoss " << kinEnergyLoss 
	   << " kinEnergyStart " << kinEnergyStart << G4endl;
#endif
    if( kinEnergyLoss / kinEnergyStart > theStepLimit ) {
      Step = theStepLimit / (kinEnergyLoss / kinEnergyStart)  * currentMinimumStep;
#ifdef G4VERBOSE
  if(G4ErrorPropagatorData::verbose() >= 2 ) 
    G4cout << " G4ErrorEnergyLoss: limiting Step " << Step 
	   << " energy loss fraction " << kinEnergyLoss / kinEnergyStart 
	   << " > " << theStepLimit << G4endl;
#endif
    }
  }
  
  return Step;

}