package causation.lab;

import exercise.*;
import tetrad.graph.TetradGraph;

/**
 * This class does the evaluation of the student's submission for any
 * Causality Lab exercise.  As of right now, all it tests is whether
 * the submitted graph is the same as the correct one, or else has the 
 * same D-separation facts.
 *
 * @version	0.9	June 20, 1999
 * @author	David Danks
 */

public class CLEvaluator implements Evaluator {

/**
 * Null constructor.  Doesn't do anything
 */
	public CLEvaluator() { ; }

/**
 * @param	ex		The CLExercise for this CausalityLab
 * @param	sol	The student's submission 
 * @return	A CLResults object encoded the outcome
 */
	public Evaluation evaluate(Exercise ex, Submission sub) {
		TetradGraph exTG = null;
		TetradGraph subTG = null;
		
		if (ex instanceof CLExercise) 
			exTG = ((CLExercise)ex).getTetradGraph();
		else return null;
		if (sub instanceof CLSubmission) 
			subTG = ((CLSubmission)sub).getTetradGraph();
		else return null;
		
		if (exTG.isEquivalentTo(subTG))
			return new CLEvaluation(CLEvaluation.CORRECT_DIGRAPH);
		else {
			DSeparationFacts exDSF = new DSeparationFacts(exTG);
			DSeparationFacts subDSF = new DSeparationFacts(subTG);
			
			if (exDSF.equals(subDSF)) 
				return new CLEvaluation(CLEvaluation.EQUIVALENT_DIGRAPH);
			else return new CLEvaluation(CLEvaluation.INCORRECT_DIGRAPH);
		}
	}
}