/* This file is part of the Joshua Machine Translation System.
 * 
 * Joshua is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */
package joshua.prefix_tree;

import java.util.Collections;
import java.util.List;

import joshua.corpus.MatchedHierarchicalPhrases;
import joshua.corpus.suffix_array.HierarchicalPhrases;
import joshua.corpus.vocab.SymbolTable;
import joshua.decoder.ff.tm.Rule;

/**
 * Special node representing an X nonterminal;
 * this node must be a direct child of the root node.
 *
 * @author Lane Schwartz
 */
public class XNode extends Node {

	private final HierarchicalPhrases matchedPhrases;
	
	XNode(RootNode parent) {
		super(parent);
		
		SymbolTable vocab = (parent.parallelCorpus==null || parent.parallelCorpus.getSourceCorpus()==null) ? null : parent.parallelCorpus.getSourceCorpus().getVocabulary();
		
		this.matchedPhrases = 
			HierarchicalPhrases.emptyList(
					vocab, 
					SymbolTable.X);
		
		this.sourcePattern = this.matchedPhrases.getPattern();
	}
	
	protected List<Rule> getResults() {
		return Collections.emptyList();
	}
	
	protected MatchedHierarchicalPhrases getMatchedPhrases()  {
		return matchedPhrases;
	}

}