/* 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.decoder.hypergraph;


import java.util.List;

import joshua.decoder.chart_parser.SourcePath;
import joshua.decoder.ff.tm.Rule;

/**
 * this class implement Hyperedge
 * 
 * @author Zhifei Li, <zhifei.work@gmail.com>
 * @version $LastChangedDate: 2010-01-14 19:15:28 -0600 (Thu, 14 Jan 2010) $
 */

public class HyperEdge {
	
	/** the 1-best logP of all possible derivations: 
	 * best logP of ant hgnodes + transitionlogP
	 **/
	public double bestDerivationLogP = Double.NEGATIVE_INFINITY;

	/**this remembers the stateless + non_stateless logP 
	 * assocated with the rule (excluding the best-logP from ant nodes)
	 * */
	private Double transitionLogP=null;
	
	private Rule rule;
	
	private SourcePath srcPath = null;

	/**If antNodes is null, then this edge corresponds to a rule with zero arity.
	 * Aslo, the nodes appear in the list as per the index of the Foreign side non-terminal
	 * */
	private List<HGNode> antNodes = null; 
	
	public HyperEdge(Rule rule, double bestDerivationLogP, Double transitionLogP, List<HGNode> antNodes, SourcePath srcPath){
		this.bestDerivationLogP = bestDerivationLogP;
		this.transitionLogP=transitionLogP;
		this.rule=rule;
		this.antNodes= antNodes;
		this.srcPath = srcPath;
	}
	
	public Rule getRule(){
		return rule;
	}

	public SourcePath getSourcePath() {
		return srcPath;
	}
	
	public List<HGNode> getAntNodes(){
		return antNodes;
	}
	
	
	public double getTransitionLogP(boolean forceCompute){//note: transitionLogP is already linearly interpolated
		if(forceCompute || transitionLogP==null){
			double res = bestDerivationLogP;
			if(antNodes!=null)	
				for(HGNode antNode : antNodes)
					res -= antNode.bestHyperedge.bestDerivationLogP;
			transitionLogP = res;				
		}
		return transitionLogP;
	}
	
	public void setTransitionLogP(double transitionLogP){
		this.transitionLogP = transitionLogP;
	}
	
	
	
	
}