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// $Id: G4ParticleGun.cc,v 1.14 2007/11/07 17:13:19 asaim Exp $
// GEANT4 tag $Name:  $
//

// G4ParticleGun
#include "G4ParticleGun.hh"
#include "G4PrimaryParticle.hh"
#include "G4ParticleGunMessenger.hh"
#include "G4Event.hh"
#include "G4ios.hh"

G4ParticleGun::G4ParticleGun()
{
  SetInitialValues();
}

G4ParticleGun::G4ParticleGun(G4int numberofparticles)
{
  SetInitialValues();
  NumberOfParticlesToBeGenerated = numberofparticles;
}

G4ParticleGun::G4ParticleGun
    (G4ParticleDefinition * particleDef, G4int numberofparticles)
{
  SetInitialValues();
  NumberOfParticlesToBeGenerated = numberofparticles;
  SetParticleDefinition( particleDef );
}

void G4ParticleGun::SetInitialValues()
{
  NumberOfParticlesToBeGenerated = 1;
  particle_definition = 0;
  G4ThreeVector zero;
  particle_momentum_direction = (G4ParticleMomentum)zero;
  particle_energy = 0.0;
  particle_momentum = 0.0;
  particle_position = zero;
  particle_time = 0.0;
  particle_polarization = zero;
  particle_charge = 0.0;
  theMessenger = new G4ParticleGunMessenger(this);
}

G4ParticleGun::~G4ParticleGun()
{
  delete theMessenger;
}

G4ParticleGun::G4ParticleGun(const G4ParticleGun& /*right*/)
:G4VPrimaryGenerator()
{ G4Exception("G4ParticleGun : Copy constructor should not be used."); }

const G4ParticleGun& G4ParticleGun::operator=(const G4ParticleGun& right)
{ G4Exception("G4ParticleGun : Equal operator should not be used."); return right; }

G4int G4ParticleGun::operator==(const G4ParticleGun& /*right*/) const
{ G4Exception("G4ParticleGun : == operator should not be used."); return true; }

G4int G4ParticleGun::operator!=(const G4ParticleGun& /*right*/) const
{ G4Exception("G4ParticleGun : == operator should not be used."); return false; }

void G4ParticleGun::SetParticleDefinition
                 (G4ParticleDefinition * aParticleDefinition)
{ 
  if(!aParticleDefinition)
  {
    G4Exception("G4ParticleGun::SetParticleDefinition()","Event00003",FatalException,
     "Null pointer is given.");
  }
  if(aParticleDefinition->IsShortLived())
  {
    if(!(aParticleDefinition->GetDecayTable()))
    {
      G4cerr << "G4ParticleGun does not support shooting a short-lived particle without a valid decay table." << G4endl;
      G4cerr << "G4ParticleGun::SetParticleDefinition for "
             << aParticleDefinition->GetParticleName() << " is ignored." << G4endl;
      return;
    }
  }
  particle_definition = aParticleDefinition; 
  particle_charge = particle_definition->GetPDGCharge();
  if(particle_momentum>0.0)
  {
    G4double mass =  particle_definition->GetPDGMass();
    particle_energy =
                 std::sqrt(particle_momentum*particle_momentum+mass*mass)-mass;
  }
}

void G4ParticleGun::SetParticleEnergy(G4double aKineticEnergy)
{
  particle_energy = aKineticEnergy;
  if(particle_momentum>0.0){
    if(particle_definition){
      G4cout << "G4ParticleGun::" << particle_definition->GetParticleName()
             << G4endl;
    }else{
      G4cout << "G4ParticleGun::" << " " << G4endl;
    }
    G4cout << " was defined in terms of Momentum: " 
           << particle_momentum/GeV << "GeV/c" << G4endl;
    G4cout << " is now defined in terms of KineticEnergy: " 
           << particle_energy/GeV   << "GeV"   << G4endl;
    particle_momentum = 0.0;
  }
}

void G4ParticleGun::SetParticleMomentum(G4double aMomentum)
{
  if(particle_energy>0.0){
    if(particle_definition){
      G4cout << "G4ParticleGun::" << particle_definition->GetParticleName()
             << G4endl;
    }else{
      G4cout << "G4ParticleGun::" << " " << G4endl;
    }
    G4cout << " was defined in terms of KineticEnergy: "
           << particle_energy/GeV << "GeV"   << G4endl;
    G4cout << " is now defined in terms Momentum: "
           << aMomentum/GeV       << "GeV/c" << G4endl;
  }
  if(particle_definition==0)
  {
    G4cout <<"Particle Definition not defined yet for G4ParticleGun"<< G4endl;
    G4cout <<"Zero Mass is assumed"<<G4endl;
    particle_momentum = aMomentum;
    particle_energy = aMomentum;
  }
  else
  {
    G4double mass =  particle_definition->GetPDGMass();
    particle_momentum = aMomentum;
    particle_energy =
                 std::sqrt(particle_momentum*particle_momentum+mass*mass)-mass;
  }
}
 
void G4ParticleGun::SetParticleMomentum(G4ParticleMomentum aMomentum)
{
  if(particle_energy>0.0){
    if(particle_definition){
      G4cout << "G4ParticleGun::" << particle_definition->GetParticleName()
             << G4endl;
    }else{
      G4cout << "G4ParticleGun::" << " " << G4endl;
    }
    G4cout << " was defined in terms of KineticEnergy: "
           << particle_energy/GeV << "GeV"   << G4endl;
    G4cout << " is now defined in terms Momentum: "
           << aMomentum.mag()/GeV << "GeV/c" << G4endl;
  }
  if(particle_definition==0)
  {
    G4cout <<"Particle Definition not defined yet for G4ParticleGun"<< G4endl;
    G4cout <<"Zero Mass is assumed"<<G4endl;
    particle_momentum_direction =  aMomentum.unit();
    particle_momentum = aMomentum.mag();
    particle_energy = aMomentum.mag();
  } 
  else 
  {
    G4double mass =  particle_definition->GetPDGMass();
    particle_momentum = aMomentum.mag();
    particle_momentum_direction =  aMomentum.unit();
    particle_energy = 
                 std::sqrt(particle_momentum*particle_momentum+mass*mass)-mass;
  }
}

void G4ParticleGun::GeneratePrimaryVertex(G4Event* evt)
{
  if(particle_definition==0) return;

  // create a new vertex
  G4PrimaryVertex* vertex = 
    new G4PrimaryVertex(particle_position,particle_time);

  // create new primaries and set them to the vertex
  G4double mass =  particle_definition->GetPDGMass();
  G4double energy = particle_energy + mass;
  G4double pmom = std::sqrt(energy*energy-mass*mass);
  G4double px = pmom*particle_momentum_direction.x();
  G4double py = pmom*particle_momentum_direction.y();
  G4double pz = pmom*particle_momentum_direction.z();
  for( G4int i=0; i<NumberOfParticlesToBeGenerated; i++ )
  {
    G4PrimaryParticle* particle =
      new G4PrimaryParticle(particle_definition,px,py,pz);
    particle->SetMass( mass );
    particle->SetCharge( particle_charge );
    particle->SetPolarization(particle_polarization.x(),
                               particle_polarization.y(),
                               particle_polarization.z());
    vertex->SetPrimary( particle );
  }

  evt->AddPrimaryVertex( vertex );
}