/*
 * @(#)$Id: DefineState.java,v 1.1 2001/05/30 20:56:04 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.classic;

import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ReferenceExp;
import com.sun.msv.reader.SequenceState;
import org.xml.sax.Locator;

/**
 * parses <define> declaration.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public class DefineState extends com.sun.msv.reader.trex.DefineState {
	
	/**
	 * combines two expressions into one as specified by the combine parameter,
	 * and returns a new expression.
	 * 
	 * If the combine parameter is invalid, then return null.
	 */
	protected Expression doCombine( ReferenceExp baseExp, Expression newExp, String combine ) {
		
		final TREXGrammarReader reader = (TREXGrammarReader)this.reader;
		
		if( baseExp.exp==null ) {
			// this is the first time definition
			if( combine!=null )
				// "combine" attribute will be ignored
				reader.reportWarning( reader.WRN_COMBINE_IGNORED, baseExp.name );
			return newExp;
		}

		// some pattern is already defined under this name.
		
		// make sure that the previous definition was in a different file.
		if( reader.getDeclaredLocationOf(baseExp).getSystemId().equals(
				reader.locator.getSystemId() ) ) {
			reader.reportError( reader.ERR_DUPLICATE_DEFINITION, baseExp.name );
			// recovery by ignoring this definition
			return baseExp.exp;
		}
			
		if( combine==null ) {
			// second definition without @combine.
			reader.reportError( new Locator[]{location, reader.getDeclaredLocationOf(baseExp)},
								reader.ERR_COMBINE_MISSING, new Object[]{baseExp.name} );
			// recover by ignoring this definition
			return baseExp.exp;
		}

		
		
		if( combine.equals("group") )
			return reader.pool.createSequence( baseExp.exp, newExp );
		else
		if( combine.equals("choice") )
			return reader.pool.createChoice( baseExp.exp, newExp );
		else
		if( combine.equals("replace") )
			return exp;
		else
		if( combine.equals("interleave") )
			return reader.pool.createInterleave( baseExp.exp, newExp );
		else
		if( combine.equals("concur") )
			return reader.pool.createConcur( baseExp.exp, newExp );
		else
			return null;
	}
}