/*
 * @(#)$Id: RefState.java,v 1.11 2001/10/12 23:37:53 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.trex;

import com.sun.msv.reader.ExpressionWithoutChildState;
import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ReferenceExp;
import com.sun.msv.grammar.trex.TREXGrammar;
														   
/**
 * parses <ref> pattern.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public class RefState extends ExpressionWithoutChildState {
	
	public RefState( boolean parentRef ) {
		this.parentRef = parentRef;
	}
	
	protected boolean parentRef;
	
	protected Expression makeExpression() {
		final String name = startTag.getCollapsedAttribute("name");
		
		if(name==null) {
			// name attribute is required.
			reader.reportError( TREXBaseReader.ERR_MISSING_ATTRIBUTE,
				"ref","name");
			// recover by returning something that can be interpreted as Pattern
			return Expression.nullSet;
		}
		
		TREXGrammar grammar = ((TREXBaseReader)this.reader).grammar;
		
		if( parentRef ) {
			grammar = grammar.getParentGrammar();
			
			if( grammar==null ) {
				reader.reportError( TREXBaseReader.ERR_NONEXISTENT_PARENT_GRAMMAR );
				return Expression.nullSet;
				// recover by returning something that can be interpreted as Pattern
			}
		}
		
		ReferenceExp r = grammar.namedPatterns.getOrCreate(name);
		wrapUp(r);
		return r;
	}
	
	/**
	 * Performs the final wrap-up.
	 */
	protected void wrapUp( ReferenceExp r ) {
		reader.backwardReference.memorizeLink(r);
	}

}