/*
    * $Source$
    * $Revision$
    *
    * Copyright (C) 2000 Tim Joyce
    *
    * Part of Melati (http://melati.org), a framework for the rapid
    * development of clean, maintainable web applications.
    *
   * Melati is free software; Permission is granted to copy, distribute
   * and/or modify this software under the terms either:
   *
   * a) the GNU General Public License as published by the Free Software
   *    Foundation; either version 2 of the License, or (at your option)
   *    any later version,
   *
   *    or
   *
   * b) any version of the Melati Software License, as published
   *    at http://melati.org
   *
   * You should have received a copy of the GNU General Public License and
   * the Melati Software License along with this program;
   * if not, write to the Free Software Foundation, Inc.,
   * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
   * GNU General Public License and visit http://melati.org to obtain the
   * Melati Software License.
   *
   * Feel free to contact the Developers of Melati (http://melati.org),
   * if you would like to work out a different arrangement than the options
   * outlined here.  It is our intention to allow Melati to be used by as
   * wide an audience as possible.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * Contact details for copyright holder:
   *
   *     Tim Joyce <timj At paneris.org>
   */
  
  package org.melati.template.webmacro;
  
  import org.melati.template.MarkupLanguage;
  
  import org.webmacro.PropertyException;
  import org.webmacro.Context;
  import org.webmacro.Broker;
  import org.webmacro.engine.EvaluationExceptionHandler;
  import org.webmacro.engine.Variable;
  import org.webmacro.util.Settings;
  
  /**
   * An implementation of EvaluationExceptionHandler which attempts to use a 
   * templet to render the exception.
   */
  public class PassbackEvaluationExceptionHandler 
    implements EvaluationExceptionHandler {
  
    @Override
    public void init(Broker b, Settings config) {}
  
    @Override
    public void evaluate(Variable variable, 
                          Context context, 
                          Exception problem) 
     throws PropertyException {
       if (problem instanceof PropertyException.NoSuchVariableException
        || problem instanceof PropertyException.NullValueException
        || problem instanceof PropertyException.NullToStringException) 
         return;
       throw new PropertyException("Failed to evaluate " + 
       variable.getVariableName() + ": " + problem,problem);
     }
  
    @Override
    public String expand(Variable variable, 
                          Context context, 
                          Exception problem) 
     throws PropertyException {
       MarkupLanguage ml = (MarkupLanguage)context.get("ml");
       if (ml == null) throw new PropertyException(
         "Error, to use the Passback Evaluation Exception Handler, you must " +
         "place your MarkupLanguage in the context as $ml" + 
         variable.getVariableName() + ": " + problem, problem);
       Throwable underlying = problem;
       if (problem instanceof PropertyException) {
         PropertyException prob = (PropertyException)problem;
         if (prob.getCause() != null) { 
           if (prob.getCause()  instanceof PropertyException)
             prob = (PropertyException)prob.getCause();
           underlying = prob.getCause();
         }
       }
       return ml.rendered(underlying);
     }
  
   @Override
   public String warningString(String warningText) throws PropertyException {
       throw new PropertyException("Evaluation warning: " + warningText);
    }
 
   @Override
   public String errorString(String errorText) throws PropertyException {
       throw new PropertyException("Evaluation error: " + errorText);
    }
 }