/*
 * @(#)$Id: NameClassWithChildState.java,v 1.8 2001/07/13 00:30:14 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.grammar.NameClass;
import com.sun.msv.grammar.AnyNameClass;
import com.sun.msv.reader.State;
import com.sun.msv.util.StartTagInfo;

/**
 * parses name class that has child name classes
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public abstract class NameClassWithChildState extends NameClassState implements NameClassOwner
{
	/**
	 * name class object that is being created.
	 * See {@link castNameClass} and {@link annealNameClass} methods
	 * for how a pattern will be created.
	 */
	protected NameClass nameClass = null;

	/**
	 * if this flag is true, then it is OK not to have any children.
	 */
	protected boolean allowNullChild = false;
	
	/**
	 * receives a Pattern object that is contained in this element.
	 */
	public final void onEndChild( NameClass childNameClass ) {
		nameClass = castNameClass( nameClass, childNameClass );
	}
	
	protected final NameClass makeNameClass() {
		if( nameClass==null && !allowNullChild ) {
			reader.reportError( TREXBaseReader.ERR_MISSING_CHILD_NAMECLASS );
			nameClass = AnyNameClass.theInstance;
			// recover by assuming some name class.
		}
		return annealNameClass(nameClass);
	}
	
	protected State createChildState( StartTagInfo tag ) {
		return ((TREXBaseReader)reader).createNameClassChildState(this,tag);
	}

		
	/**
	 * combines half-made name class and newly found child name class into the name class.
	 * 
	 * <p>
	 * Say this container has three child name class n1,n2, and n3.
	 * Then, the name class of this container will be made by the following method
	 * invocations.
	 * 
	 * <pre>
	 *   annealNameClass( castNameClass( castNameClass( castNameClass(null,p1), p2), p3 ) )
	 * </pre>
	 */
	protected abstract NameClass castNameClass(
		NameClass halfCastedNameClass, NameClass newChildNameClass );
	
	/**
	 * performs final wrap-up and returns a fully created NameClass object
	 * that represents this element.
	 */
	protected NameClass annealNameClass( NameClass nameClass ) {
		// default implementation does nothing.
		return nameClass;
	}
}