/** @file CbmBeam.cxx
 ** @author Volker Friese <v.friese@gsi.de>
 ** @since 1 August 2019
 **/

#include "CbmBeam.h"

#include <cassert>
#include <sstream>



// -----   Default constructor   --------------------------------------------
CbmBeam::CbmBeam(Double_t x, Double_t y, Double_t z,
								 Double_t thetaX, Double_t thetaY) :
								 fPosition(x, y, z),
								 fDirection(TMath::Tan(thetaX), TMath::Tan(thetaY), 1.)
{
}
// --------------------------------------------------------------------------



// -----   Extrapolation to a plane   ---------------------------------------
TVector3 CbmBeam::ExtrapolateToPlane(const TVector3& point,
																		 const TVector3& norm) const {

	// The beam should not be parallel to the plane
	assert( norm * fDirection );

	// Calculate intersection point. Just some analytic geometry.
	Double_t numer = norm * ( point - fPosition );
	Double_t denom = norm * fDirection;
	return fPosition + ( numer / denom ) * fDirection;

}
// --------------------------------------------------------------------------



// -----   Info   -----------------------------------------------------------
std::string CbmBeam::ToString() const {

	std::stringstream ss;
	ss << "Current beam: position (" << fPosition.X() << ", " << fPosition.Y()
				 << ", " << fPosition.Z() << ") cm, angle (" << fDirection.X() << ", "
				 << fDirection.Y() << ") rad";

	return ss.str();
}
// --------------------------------------------------------------------------