// PropCyl.h

#ifndef PropCyl_H
#define PropCyl_H

// Propagates tracks from one cylinder to another in a constant field.
//
// Propagation will fail if either the origin or destination is 
// not a cylinder.
//
// Propagation more than halfway around one loop is not allowed and
// will result in failure if attempted.
//
// ObjStream example:
//
// [ myprop PropCyl bfield=2.0 ]
//
// To use the global bfield:
//
// [ myprop PropCyl bfield=@bfield ]
//
// The optional parameter dir may be used to specify the default
// direction for propagation.  It must have one of the following
// values: "forward", "backward" or "nearest".  E.g.
// [ myprop PropCyl bfield=2.0 dir="forward" ]
// or
// [ bmap PropCylFieldConst bfield=2.0 ]
// [ myprop PropCyl bfield_map=*bmap dir="forward" ]
//

#include "trfbase/PropDirected.h"
#include "ptr/Ptr.h"
#include "PropCylField.h"
#include "trfbase/ObjDoublePtr.h"

namespace trf {

class PropCylField;

class PropCyl : public PropDirected {

public:  // typedefs

  typedef Ptr<const PropCylField, LocalSharedDeletePolicy> PropCylFieldPtr;

public:  // static methods

  // Return the type name.
  static TypeName get_type_name() { return "PropCyl"; }

  // Return the creator.
  static ObjCreator get_creator();

  // Return the type.
  static Type get_static_type() { return get_creator(); }

private:  // attributes

  // Constant magnet field.
  ObjDoublePtr _bfield;

  // B-field map.
  // Null means to use constant value.
  PropCylFieldPtr _pmap;

private:

  // output stream
  void ostr(std::ostream& stream) const;

public:

  // constructors from magnetic field in Tesla.
  PropCyl(ObjDoublePtr bfield);

  // constructor from magnetic field mapper
  PropCyl(PropCylFieldPtr pmap);

  // destructor
  ~PropCyl();

  // Clone.
  Propagator* new_propagator( ) const;

  // Return the type.
  Type get_type() const { return get_static_type(); }

  // Write the object data.
  ObjData write_data() const;

  // propagate a track without error in the specified direction
  PropStat
  vec_dir_prop(VTrack& trv, const Surface& srf, PropDir dir,
               TrackDerivative* pder =0) const;

  // return the magnetic field
  double get_bfield() const;

  // Return the field mapper.
  PropCylFieldPtr get_map() const { return _pmap; }

};

}  // end namespace trf

#endif