/*
 * @(#)$Id: NameClassSimplifier.java,v 1.3 2001/10/11 19:25:37 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.grammar.util;

import com.sun.msv.grammar.*;
import com.sun.msv.util.StringPair;
import java.util.Set;
import java.util.Iterator;

/**
 * Minimizes a name class.
 * 
 * Sometimes, a name class could become unnecessarily big. For example,
 * 
 * <PRE><XMP>
 * <choice>
 *   <anyName/>
 *   <anyName/>
 *   <anyName/>
 * </choice>
 * </XMP></PRE>
 * 
 * This procedure converts those name classes to the equivalent small name class.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public class NameClassSimplifier {
	
	public static NameClass simplify( NameClass nc ) {
		final Set possibleNames = PossibleNamesCollector.calc(nc);
		final String MAGIC = PossibleNamesCollector.MAGIC;
		
		Set uris = new java.util.HashSet();
		
		Iterator itr = possibleNames.iterator();
		while( itr.hasNext() ) {
			StringPair name = (StringPair)itr.next();
			if( name.localName!=MAGIC ) {
				// a simple name.
				if( nc.accepts(name)==nc.accepts( name.namespaceURI, MAGIC ) ) {
					itr.remove();
					continue;
				}
			} else
			if( name.namespaceURI!=MAGIC ) {
				// a ns name
				if( nc.accepts(name)==nc.accepts(MAGIC,MAGIC) ) {
					itr.remove();
					continue;
				}
			}
			
			// collect the remainig namespace URIs.
			if( name.namespaceURI!=MAGIC )
				uris.add(name.namespaceURI);
		}
		
		if( !nc.accepts(MAGIC,MAGIC) )
			possibleNames.remove( new StringPair(MAGIC,MAGIC) );
		
		NameClass result = null;
		Iterator jtr = uris.iterator();
		while( jtr.hasNext() ) {
			final String uri = (String)jtr.next();
			
			NameClass local = null;
			itr = possibleNames.iterator();
			while( itr.hasNext() ) {
				final StringPair name = (StringPair)itr.next();
				
				if(!name.namespaceURI.equals(uri))		continue;
				if(name.localName==MAGIC)				continue;
				
				if(local==null)	local = new SimpleNameClass(name);
				else			local = new ChoiceNameClass(local,new SimpleNameClass(name));
			}
			if(possibleNames.contains(new StringPair(uri,MAGIC))) {
				if(local==null)
					local = new NamespaceNameClass(uri);
				else
					local = new DifferenceNameClass(new NamespaceNameClass(uri),local);
			}
			
			if(local!=null) {
				if(result==null)	result = local;
				else				result = new ChoiceNameClass(result,local);
			}
		}
		
		if( nc.accepts(MAGIC,MAGIC) ) {
			if(result==null)		result = AnyNameClass.theInstance;
			else					result = new NotNameClass(result);
		}
		
		if( result==null )
			result = new NotNameClass( AnyNameClass.theInstance );
		
		return result;
	}
}