/*
 * $Header:$
 * $Revision: $
 * $Date: $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
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 * $Id:$
 */
package org.apache.commons.jelly.tags.core;

import org.apache.commons.jelly.JellyException;
import org.apache.commons.jelly.TagSupport;
import org.apache.commons.jelly.XMLOutput;


/** 
 * A tag which conditionally evaluates its body if
 * none of its preceeding sibling {@link CaseTag &lt;case&gt;} 
 * tags have been evaluated.
 * 
 * This tag must be contained within the body of some 
 * {@link SwitchTag &lt;switch&gt;} tag.
 * 
 * @see SwitchTag
 * 
 * @author Rodney Waldhoff
 * @version $Revision:$ $Date:$
 */
public class DefaultTag extends TagSupport {

    public DefaultTag() {
    }
    
    // Tag interface
    //------------------------------------------------------------------------- 
    
    public void setFallThru(boolean fallThru) {
        this.fallThru = fallThru;
    }
    
    public void doTag(XMLOutput output) throws Exception {
        SwitchTag tag = (SwitchTag)findAncestorWithClass(SwitchTag.class);
        if(null == tag) {
            throw new JellyException("This tag must be enclosed inside a <switch> tag" );
        }
        if(tag.hasDefaultBeenEncountered()) {
            throw new JellyException("Only one <default> tag is allowed per <switch>.");
        }
        if(tag.isFallingThru() || (!tag.hasSomeCaseMatched())) {
            tag.caseMatched();
            tag.setFallingThru(fallThru);
            invokeBody(output);
        }
    }

    // Attributes
    //------------------------------------------------------------------------- 
    private boolean fallThru = false;
    
}