/** @file CbmEventGenerator.h
 ** @author Volker Friese <v.friese@gsi.de>
 ** @since 29 July 2019
 **/


#ifndef CBMEVENTGENERATOR_H
#define CBMEVENTGENERATOR_H 1


#include <memory>
#include "FairPrimaryGenerator.h"
#include "CbmBeamProfile.h"
#include "CbmTarget.h"

class FairGenericStack;



/** @brief CbmEventGenerator
 ** @author Volker Friese <v.friese@gsi.de>
 ** @since 29 July 2019
 ** @date 29 July 2019
 **
 ** The EventGenerator defines the primary particles as input
 ** to the transport simulation. Several event generator objects can be
 ** registered to the EventGenerator, each generating primary particles.
 ** The EventGenerator generates the common event vertex and rotation
 ** according to the user specification.
 **
 ** CbmEventGenerator derives from FairPrimaryGenerator. It re-implements
 ** the methods MakeBeam and MakeVertex such as to ensure that the generated
 ** vertex falls into the target volume.
 **/
class CbmEventGenerator : public FairPrimaryGenerator
{

	public:

		/** @brief Default constructor  **/
		CbmEventGenerator();


		/** @brief Destructor  **/
		virtual ~CbmEventGenerator();


		/** @brief Enable or disable forcing the vertex to be in the target
		 ** @param choice If true, the vertex will be generated in the target
		 **/
		void ForceVertexInTarget(Bool_t choice = kTRUE) {
		  fForceVertexInTarget = choice;
		}


		/** @brief Beam profile
		 ** @return Reference to beam profile object
		 **/
		const CbmBeamProfile& GetBeamProfile() { return fBeamProfile; }


		/** @brief Generate the input event
		 ** @param stack  Pointer to stack object
		 **
		 ** This is the main functionality, invoked from FairRunSim.
		 ** It fills the stack at the beginning of each event with
		 ** the primary particles provided by the generator instances.
		 ** All primary track momenta are rotated according to the
		 ** beam direction (in x-z and y-z) and and by the event plane (in x-y).
		 **
		 ** Re-implemented from base-class FairPrimaryGenerator.
		 **/
	  virtual Bool_t GenerateEvent(FairGenericStack* stack);


		/** @brief Log output **/
		virtual void Print(Option_t* opt = "") const;


		/** @brief Set the beam angle in the focal plane
		 ** @param meanThetaX   Mean angle in x-z [rad]
		 ** @param meanThetaY   Mean angle in y-z [rad]
		 ** @param sigmaThetaX  RMS of beam angle in x-z [rad]
		 ** @param sigmaThetaY  RMS of beam angle in y-z [rad]
		 **
		 ** The beam angles will be sampled from Gaussian distributions
		 ** with the specified mean values and RMS. If the latter are negative,
		 ** the beam angles will be fixed to their mean values.
		 **
		 ** Default is (0., 0.), no sampling.
		 **
		 ** Note: Re-implements the non-virtual method in FairPrimaryGenerator.
		 */
		void SetBeamAngle(Double_t meanThetaX, Double_t meanThetaY,
											Double_t sigmaThetaX = -1., Double_t sigmaThetaY = -1.);


		/** @brief Set the beam position in the focal plane
		 ** @param meanX    Mean x position [cm]
		 ** @param meanY    Mean y position [cm|
		 ** @param sigmaX   RMS of x position [cm]
		 ** @param sigmaY   RMS of y position [cm]
		 ** @param zF       z position of focal plane [cm]
		 **
		 ** If the beam widths in x and/or y are positive, the beam
		 ** position will be sampled randomly for each event from a
		 ** Gauss distribution. Otherwise, it is fixed for all events.
		 **
		 ** Default is (0.,0.,0.) for the position, no sampling.
		 */
		void SetBeamPosition(Double_t meanX, Double_t meanY,
												 Double_t sigmaX = -1., Double_t sigmaY = -1.,
												 Double_t zF = 0.);


		/** @brief Set target properties
		 ** @param target  Pointer to CbmTarget instance
		 **
		 ** When a target is specified, the event vertex will be sampled
		 ** by a constant distribution along the (straight) trajectory
		 ** of the beam inside the target. If SmearVertexZ(kFALSE) is
		 ** set afterwards, the vertex will always be in the target
		 ** centre plane.
		 **/
		void SetTarget(std::shared_ptr<const CbmTarget> target) {
			fTarget = target;
		}


	private:

		CbmBeamProfile fBeamProfile;  ///< Beam properties
		std::shared_ptr<const CbmTarget> fTarget;   ///< Target properties
		Bool_t fForceVertexInTarget;   ///< If set, vertex must be in target


		/** @brief Generate beam angle
		 **
		 ** Will be called from FairPrimaryGenerator::GenerateEvent().
		 ** The method is re-implemented here as empty. The beam angle
		 ** will be generated along with the beam position in the method
		 ** MakeVertex().
		 **/
		virtual void MakeBeamAngle() { };


		/** @brief Generate event vertex position
		 **
		 ** Will be called from FairPrimaryGenerator::GenerateEvent().
		 ** Beam position and angles in the focal plane are sampled
		 ** from the specified distributions. If a target is specified,
		 ** the event vertex is sampled from the beam trajectory within the
		 ** target - flat distributions between entry and exit point, or
		 ** always in the target centre plane, depending on the choice set
		 ** with SetSmearVertexZ(). If no target is specified, the event vertex
		 ** is the beam position in the focal plane.
		 **/
		virtual void MakeVertex();


		/** @brief Generate event vertex position in the beam focal plane
		 **
		 ** Will be called if no target was specified.
		 **/
		virtual void MakeVertexInFocalPlane();


		/** @brief Generate event vertex position in the target
		 **
		 ** Will be called if a target was specified.
		 **/
		virtual void MakeVertexInTarget();



		ClassDef(CbmEventGenerator,1);

};


#endif /* CBMEVENTGENERATOR_H */