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/*
 *
 *          Copyright (c) 2013,2019  AT&T Knowledge Ventures
 *                     SPDX-License-Identifier: MIT
 */
package com.att.research.xacmlatt.pdp.std.combiners;

import java.util.Iterator;
import java.util.List;

import com.att.research.xacml.api.Decision;
import com.att.research.xacml.api.Identifier;
import com.att.research.xacml.std.StdStatus;
import com.att.research.xacml.std.StdStatusCode;
import com.att.research.xacmlatt.pdp.eval.EvaluationContext;
import com.att.research.xacmlatt.pdp.eval.EvaluationException;
import com.att.research.xacmlatt.pdp.eval.EvaluationResult;
import com.att.research.xacmlatt.pdp.eval.MatchResult;
import com.att.research.xacmlatt.pdp.policy.CombinerParameter;
import com.att.research.xacmlatt.pdp.policy.CombiningElement;
import com.att.research.xacmlatt.pdp.policy.PolicySetChild;

/**
 * OnlyOneApplicable extends {@link com.att.research.xacmlatt.pdp.std.combiners.CombiningAlgorithmBase} to implement the
 * XACML 1.0 "only-one-applicable" combining algorithm for policies and rules.
 * 
 * @author car
 * @version $Revision: 1.1 $
 * 
 */
public class OnlyOneApplicable extends CombiningAlgorithmBase {

	public OnlyOneApplicable(Identifier identifierIn) {
		super(identifierIn);
	}

	@Override
	public EvaluationResult combine(EvaluationContext evaluationContext,
			List> elements,
			List combinerParameters)
			throws EvaluationException {
		Iterator> iterElements	= elements.iterator();
		PolicySetChild policySetChildApplicable					= null;
		while (iterElements.hasNext()) {
			CombiningElement combiningElement		= iterElements.next();
			MatchResult matchResultElement				= combiningElement.getEvaluatable().match(evaluationContext);
			
			switch(matchResultElement.getMatchCode()) {
			case INDETERMINATE:
				return new EvaluationResult(Decision.INDETERMINATE, matchResultElement.getStatus());
			case MATCH:
				if (policySetChildApplicable == null) {
					policySetChildApplicable	= combiningElement.getEvaluatable();
				} else {
					return new EvaluationResult(Decision.INDETERMINATE, new StdStatus(StdStatusCode.STATUS_CODE_PROCESSING_ERROR, "More than one applicable policy"));
				}
				break;
			case NOMATCH:
				break;
			default:
				throw new EvaluationException("Illegal Decision: \"" + matchResultElement.getMatchCode().toString());
			}			
		}
		
		if (policySetChildApplicable != null) {
			return policySetChildApplicable.evaluate(evaluationContext);
		} else {
			return new EvaluationResult(Decision.NOTAPPLICABLE);
		}		
	}

}