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/*
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.xwiki.velocity.internal.directive;

import java.io.Writer;

import org.apache.velocity.context.InternalContextAdapter;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.directive.Directive;
import org.apache.velocity.runtime.parser.node.ASTBlock;
import org.apache.velocity.runtime.parser.node.Node;

/**
 * Allows catching exception from Velocity. Example usage:
 *  * {@code #try()
 *   ...
 *   #end
 *
 *   ## At this stage $exception contains the exception if any has been thrown.
 *   ## It can be tested like this:
 *   #if ("$!exception" != '')
 *     ## An exception has been thrown
 *   #end}
 * 
 *
 * @version $Id: a677e4a4653bd66468f891256d319ea0444ca10d $
 * @since 6.3M1
 */
public class TryCatchDirective extends Directive
{
    private static final String EXCEPTION_KEY_NAME = "exception";

    @Override
    public String getName()
    {
        return "try";
    }

    @Override
    public int getType()
    {
        return BLOCK;
    }

    @Override
    public boolean render(InternalContextAdapter context, Writer writer, Node node)
        throws ResourceNotFoundException, ParseErrorException, MethodInvocationException
    {
        boolean result = true;

        String exceptionVariableName = EXCEPTION_KEY_NAME;
        for (int i = 0; i < node.jjtGetNumChildren(); i++) {
            if (node.jjtGetChild(i) != null) {
                if (!(node.jjtGetChild(i) instanceof ASTBlock)) {
                    // Reading and casting inline parameters. We handle one parameter which is the name of the Velocity
                    // variable in which we'll save the exception. If not specified we'll use EXCEPTION_KEY_NAME
                    if (i == 0) {
                        exceptionVariableName = (String) node.jjtGetChild(i).value(context);
                    } else {
                        break;
                    }
                } else {
                    try {
                        // Make sure to clear any previous exception
                        context.remove(exceptionVariableName);
                        result = node.jjtGetChild(i).render(context, writer);
                    } catch (Exception e) {
                        // Save the exception in the $exception velocity context variable
                        context.put(exceptionVariableName, e);
                        result = true;
                    }
                    break;
                }
            }
        }

        return result;
    }
}