#ifndef ABSGEOMETRYMESSENGER_HH
#define ABSGEOMETRYMESSENGER_HH
//
// $Id: absGeometryMessenger.hpp,v 1.7 2003/01/23 17:36:20 melanson Exp $
//
// Global definitions
// ----------------------------------------------------------------------------
// ----------------------------------------------------------------------------
//
// File: absGeometryMessenger.hpp
// Purpose: 
// Created: 29-OCT-1997   John Hobbs
//
// $Revision: 1.7 $
//
//

// Include files
#include "d0_geometry/base/BaseGeometry.hpp"
#include "d0om/d0_Ref.hpp"
#include "geometry_db/dbidSet.hpp"
#include "identifiers/EnvID.hpp"

#include <iostream>

/** Abstract Geometry Messenger.

    Rather than include the specific headers for each sub-detector
    {\bf Geometer}, we use a {\em messenger} to enhance physical
    separation.  The messenger is a trivial class for each subdetector
    which implements only a method {\em refresh()}.  If the
    subdetector is X, {\bf XGeometryMessenger} is typically defined as
    follows:

    \begin{verbatim}
    class XGeometryMessenger {
       XGeometryMessenger();
       void refresh(d0_Ref<XGeometry>subdet_geometry);
    };
    \end{verbatim}

 and the typical implementation of {\em refresh()} is:

    \begin{verbatim}
    void XGeometryMessenger::refresh(d0_Ref<XGeometry>subdet_geometry) {
       XGeometer* g=XGeometer::get_instance();
       g->refresh(subdet_geometry);
    }
    \end{verbatim}

    To achieve the desired decoupling, {\em refresh()} cannot be
    implemented in the messenger header file.

 For an example, see silicon\_geometry/base/SiGeometerDecoupler.*


  */
class absGeometryMessenger {
public:

  ///  Constructor
  absGeometryMessenger(absGeometryMessenger* chain=0): _next(chain) {}

  ///  Destructor
  virtual ~absGeometryMessenger() { if( _next) delete _next; }
  
  ///  Notify subdetectors of new BaseGeometry
  void notify_subdetectors(d0_Ref<BaseGeometry>bg, 
			   const bool passnull=false) const;

  /// Implement this to tell specific subdetectors there is a new geometry
  virtual void refresh(d0_Ref<BaseGeometry>bg, 
		       const bool pass_null=false) const =0;

  friend std::ostream& operator<<(std::ostream& os, 
				  const absGeometryMessenger& me);

protected:

  edm::EnvID build_envid(dbidSet::DETDB reco, dbidSet::DETDB user, int serial)
    const;

private:

  /// Allow a chain of messengers
  const absGeometryMessenger* _next;

  ///  Private constructor
  absGeometryMessenger(const absGeometryMessenger& org) {}

  ///  Overload = operator
  absGeometryMessenger& operator=(const absGeometryMessenger& org) 
    { return *this; }

};

// Constructors/Destructors

// Accessors

#endif //ABSGEOMETRYMESSENGER_HH