/*
 * @(#)$Id: ElementRefState.java,v 1.4 2001/05/01 18:13:19 Bear Exp $
 *
 * Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */
package com.sun.msv.reader.xmlschema;

import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ReferenceContainer;
import com.sun.msv.grammar.xmlschema.XMLSchemaSchema;
import com.sun.msv.reader.ExpressionWithoutChildState;

/**
 * used to parse <element > element with ref attribute.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public class ElementRefState extends ExpressionWithoutChildState {

	protected Expression makeExpression() {
		final XMLSchemaReader reader = (XMLSchemaReader)this.reader;
		
		// TODO: what attributes can be used with @ref?
		
		if( !startTag.containsAttribute("ref") )
			// existance of @ref must be checked before instanciation of this object.
			throw new Error();
		
		// this this tag has @ref.
		Expression exp = reader.resolveQNameRef(
			startTag, "ref",
			new XMLSchemaReader.RefResolver() {
				public ReferenceContainer get( XMLSchemaSchema g ) {
					return g.elementDecls;
				}
			} );
		if( exp==null )		return Expression.epsilon;	// couldn't resolve QName.
		
		// minOccurs/maxOccurs is processed through interception
		return exp;
	}
}