/*

  * $Source: /usr/cvsroot/melati/melati/src/main/java/org/melati/template/webmacro/PassbackEvaluationExceptionHandler.java,v $

  * $Revision: 1.8 $

  *

  * 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 java.io.IOException;

 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 {

   /**

    * {@inheritDoc}

    * @see org.webmacro.engine.EvaluationExceptionHandler#

    *      init(org.webmacro.Broker, org.webmacro.util.Settings)

    */

   public void init(Broker b, Settings config) {}

   /**

    * {@inheritDoc}

    * @see org.webmacro.engine.EvaluationExceptionHandler#

    * evaluate(org.webmacro.engine.Variable, org.webmacro.Context, java.lang.Exception)

    */

   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);

    }

   /**

    * {@inheritDoc}

    * @see org.webmacro.engine.EvaluationExceptionHandler#

    * expand(org.webmacro.engine.Variable, 

    *        org.webmacro.Context, java.lang.Exception)

    */

   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();

        }

      }

      try {

        return ml.rendered(underlying);

      } catch (IOException e) {

        throw new PropertyException(

          "The exception failed to render " + 

          variable.getVariableName() + ": " + e, e);

      }

    }

    /**

    * {@inheritDoc}

    * @see org.webmacro.engine.EvaluationExceptionHandler#warningString(java.lang.String)

    */

   public String warningString(String warningText) throws PropertyException {

       throw new PropertyException("Evaluation warning: " + warningText);

    }

    /**

    * {@inheritDoc}

    * @see org.webmacro.engine.EvaluationExceptionHandler#errorString(java.lang.String)

    */

   public String errorString(String errorText) throws PropertyException {

       throw new PropertyException("Evaluation error: " + errorText);

    }

 }