package  org.lcsim.recon.tracking.trfzp;
   
   import org.lcsim.recon.tracking.trfutil.Assert;
   
   import org.lcsim.recon.tracking.trfbase.Hit;
   import org.lcsim.recon.tracking.trfbase.HitVector;
   import org.lcsim.recon.tracking.trfbase.HitError;
   import org.lcsim.recon.tracking.trfbase.HitDerivative;
   import org.lcsim.recon.tracking.trfbase.ETrack;
  
  /**
   * Describes a one dimensional xy measurement on a ZPlane.
   * axy = wx*x + wy*y
   *<p>
   * This is a very simple hit.  It produces one prediction with fixed
   * measurement which is simply the axy of the track.
   *
   *@author Norman A. Graf
   *@version 1.0
   *
   */
  //cng changed to public for component tests
  public class HitZPlane1 extends Hit
  {
      
      // Only ClusZPlane1 is allowed to construct HitZPlane1 objects.
      // therefore package protection
      
      
      //
      /**
       *Return a String representation of the class' type name.
       *Included for completeness with the C++ version.
       *
       * @return   A String representation of the class' type name.
       */
      public static String typeName()
      { return "HitZPlane1";
      }
      
      //
      
      /**
       *Return a String representation of the class' type name.
       *Included for completeness with the C++ version.
       *
       * @return   A String representation of the class' type name.
       */
      public static String staticType()
      { return typeName();
      }
      
      
      // prediction for axy
      private double _axy_pre;
      
      // error matrix for axy
      private double _eaxy_pre;
      
      
      /**
       * Test equality.
       * Hits are equal if they have the same parent cluster.
       *
       * @param   hit The Hit to test against.
       * @return true if the Hits are the same.
       */
      protected boolean equal( Hit hit)
      {
          Assert.assertTrue( type().equals(hit.type()) );
          return cluster().equals(hit.cluster());
      }
      
      // constructor (package access for ClusZPlane1)
      HitZPlane1(double axy, double eaxy)
      {
          _axy_pre = axy;
          _eaxy_pre = eaxy;
      }
      
      //
      
      /**
       *Construct an instance replicating the HitZPlane1 ( copy constructor ).
       *
       * @param   hit The Hit to replicate.
       */
      public HitZPlane1( HitZPlane1 hit)
      {
          super(hit);
          _axy_pre = hit._axy_pre;
          _eaxy_pre = hit._eaxy_pre;
      }
      
      //
      
      /**
       *Return a String representation of the class' type name.
       *Included for completeness with the C++ version.
      *
      * @return   A String representation of the class' type name.
      */
     public String type()
     { return staticType();
     }
     
     //
     
     /**
      *Return the dimension of an xy measurement on a z plane.
      *axy = wx*x + wy*y
      *The value is always one.
      *
      * @return The dimension of this hit (1).
      */
     public int size()
     { return 1;
     }
     
     //
     
     /**
      *Return the measured hit vector.
      *
      * @return The HitVector for this hit.
      */
     public HitVector measuredVector()
     {
         return new HitVector( fullCluster().aXY() );
     }
     
     //
     
     /**
      *Return the measured hit error.
      *
      * @return The HitError for this hit.
      */
     public HitError measuredError()
     {
         double daxy = fullCluster().daXY();
         return new HitError( daxy*daxy );
     }
     
     //
     
     /**
      *Return the predicted hit vector.
      *
      * @return The HitVector for the prediction.
      */
     public HitVector predictedVector()
     {
         return new HitVector( _axy_pre );
     }
     
     //
     
     /**
      *Return the predicted hit error.
      *
      * @return The HitError for the prediction.
      */
     public HitError predictedError()
     {
         return new HitError( _eaxy_pre );
     }
     
     //
     
     /**
      *Return the hit derivative with respect to a track on this surface.
      *
      * @return The HitDerivative for a track on this surface.
      */
     public HitDerivative dHitdTrack()
     {
         double values[] =
         { 0.0, 0.0, 0.0, 0.0, 0.0 };
         values[0] = fullCluster().wX();
         values[1] = fullCluster().wY();
         HitDerivative deriv = new HitDerivative(1,values);
         return deriv;
     }
     
     //
     
     /**
      *Return the difference between prediction and measurement.
      *
      * @return The HitVector for the difference between the hit prediction and measurement.
      */
     public HitVector differenceVector()
     {
         return new HitVector( _axy_pre-fullCluster().aXY() );
     }
     
     //
     
     /**
      *Update the prediction (measurement and derivative do not change).
      *
      * @param   tre The ETrack for which to predict this hit measurement.
      */
     public void update(  ETrack tre)
     {
         
         double x_track = tre.vector().get(SurfZPlane.IX);
         double y_track = tre.vector().get(SurfZPlane.IY);
         double exx_track = tre.error().get(SurfZPlane.IX,SurfZPlane.IX);
         double exy_track = tre.error().get(SurfZPlane.IX,SurfZPlane.IY);
         double eyy_track = tre.error().get(SurfZPlane.IY,SurfZPlane.IY);
         
         double cl_wx = fullCluster().wX();
         double cl_wy = fullCluster().wY();
         
         _axy_pre = cl_wx*x_track + cl_wy*y_track;
         _eaxy_pre =   exx_track*cl_wx*cl_wx +
         2.*exy_track*cl_wx*cl_wy +
         eyy_track*cl_wy*cl_wy;
     }
     
     //
     
     /**
      *Return a ClusZPlane1 reference to the cluster.
      *
      * @return The hit as a ClusZPlane1 object.
      */
     public ClusZPlane1 fullCluster()
     {
         return (ClusZPlane1) _pclus;
     }
     
     
     /**
      *output stream
      *
      * @return  A String representation of this instance.
      */
     public String toString()
     {
         if( _pclus != null )
         {
             return "HitZPlane1 from " + _pclus;
         }
         else
         {
             return "HitZPlane1 with no parent clusters";
         }
     }
 }