/*
 * @(#)$Id: TREXSequencedStringChecker.java,v 1.14 2001/10/31 19:54:28 kk122374 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.RunAwayExpressionChecker;
import com.sun.msv.grammar.*;
import com.sun.msv.grammar.trex.*;
import java.util.Set;
import java.util.Map;

/**
 * makes sure that there is no sequenced string.
 * 
 * "sequenced string" is something like this.
 * <XMP>
 * <oneOrMore>
 *   <string> abc </string>
 * </oneOrMore>
 * </XMP>
 * 
 * Also, TREX prohibits sequence of typed strings and elements.
 * 
 * <p>
 * In this checker, we introduce a function "f" that takes
 * a string and computes the string-sensitivity of the pattern.
 * 
 * <p>
 * "f" returns 3 bits of information. One is whether it contains
 * elements. Another is whehter it contains text. And the last is
 * whether it contains DataExp/ValueExp.
 * 
 * <p>
 * "f" is computed recursively through the pattern.
 * 
 * @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
 */
public class TREXSequencedStringChecker implements ExpressionVisitor
{
	/**
	 * If this flag is set to true, this class raises an error for
	 * anyStrings in two branches of interleave.
	 */
	private final boolean rejectTextInInterleave;
	
	/** integer pool implementation. */
	private static final Integer[] intPool = new Integer[]{
			new Integer(0),new Integer(1),new Integer(2),new Integer(3),
			new Integer(4),new Integer(5),new Integer(6),new Integer(7) };
	
	// 3 bit of information
	private static final int HAS_ELEMENT = 4;
	private static final int HAS_ANYSTRING = 2;
	private static final int HAS_DATA = 1; // data or value.
	
	
	private final TREXBaseReader reader;
	
	public TREXSequencedStringChecker( TREXBaseReader reader, boolean _rejectTextInInterleave ) {
		this.reader = reader;
		this.rejectTextInInterleave = _rejectTextInInterleave;
	}

	/**
	 * set of checked Expressions.
	 * 
	 * once an ElementExp/AttributeExp is checked, it will be added to this set.
	 * this set is used to prevent infinite recursion.
	 */
	private final Set checkedExps = new java.util.HashSet();
	
	/**
	 * set of checked ReferenceExps.
	 * 
	 * Once a ReferenceExp is checked, it will be added (with its result)
	 * to this map. This is useful to speed up the check.
	 */
	private final Map checkedRefExps = new java.util.HashMap();
	
	public Object onRef( ReferenceExp exp ) {
		Object r = checkedRefExps.get(exp);
		if(r!=null)	return r;
		checkedRefExps.put(exp, r=exp.exp.visit(this) );
		return r;
	}
	public Object onOther( OtherExp exp ) {
		return exp.exp.visit(this);
	}
	
	public Object onInterleave( InterleaveExp exp ) {
		Object l = exp.exp1.visit(this);
		Object r = exp.exp2.visit(this);
		
		if(isError(l,r)) {
			// where is the source of error?
			reader.reportError( reader.ERR_INTERLEAVED_STRING );
			return intPool[0];
		}
		if( rejectTextInInterleave
		&&  (toInt(l)&HAS_ANYSTRING)!=0
		&&  (toInt(r)&HAS_ANYSTRING)!=0 ) {
			reader.reportError( reader.ERR_INTERLEAVED_ANYSTRING );
			return intPool[0];
		}
		
		return merge(l,r);
	}
	
	public Object onSequence( SequenceExp exp ) {
		Object l = exp.exp1.visit(this);
		Object r = exp.exp2.visit(this);
		
		if(isError(l,r)) {
			// where is the source of error?
			reader.reportError( reader.ERR_SEQUENCED_STRING );
			return intPool[0];
		}
		
		return merge(l,r);
	}
	
	public Object onEpsilon() { return intPool[0]; }
	public Object onNullSet() { return intPool[0]; }
	public Object onData( DataExp exp )		{ return intPool[HAS_DATA]; }
	public Object onValue( ValueExp exp )	{ return intPool[HAS_DATA]; }
	// do not traverse contents of list.
	public Object onList( ListExp exp )		{ return intPool[HAS_DATA]; }
	public Object onAnyString()				{ return intPool[HAS_ANYSTRING]; }
	
	public Object onAttribute( AttributeExp exp ) {
		if( checkedExps.add(exp) )
			exp.exp.visit(this);
		return intPool[0];
	}
	
	public Object onElement( ElementExp exp ) {
		if( checkedExps.add(exp) )
			// if this is the first visit
			// this has to be done before checking content model
			// otherwise it leads to the infinite recursion.
			exp.contentModel.visit(this);
		return intPool[HAS_ELEMENT];
	}
	
	private static final int toInt( Object o ) { return ((Integer)o).intValue(); }
	
	private static Object merge( Object o1, Object o2 ) {
		return intPool[toInt(o1)|toInt(o2)];
	}
	/**
	 * It is an error if a pattern with data is combined to other patterns.
	 */
	private static boolean isError( Object o1, Object o2 ) {
		return (toInt(o1)&HAS_DATA)!=0 && toInt(o2)!=0
			|| (toInt(o2)&HAS_DATA)!=0 && toInt(o1)!=0;
	}
	
	public Object onChoice( ChoiceExp exp ) {
		return merge( exp.exp1.visit(this), exp.exp2.visit(this) );
	}
	
	public Object onConcur( ConcurExp exp ) {
		return merge( exp.exp1.visit(this), exp.exp2.visit(this) );
	}
	
	public Object onOneOrMore( OneOrMoreExp exp ) {
		Object o = exp.exp.visit(this);
		if( (toInt(o)&HAS_DATA) !=0 ) {
			reader.reportError(reader.ERR_REPEATED_STRING);
			return intPool[0];
		}
		return o;
	}
	
	public Object onMixed( MixedExp exp ) {
		Object o = exp.exp.visit(this);
		
		if( rejectTextInInterleave
		&&  (toInt(o)&HAS_ANYSTRING)!=0 ) {
			reader.reportError( reader.ERR_INTERLEAVED_ANYSTRING );
			return intPool[0];
		}
		
		return merge(o,intPool[HAS_ANYSTRING]);
	}

}