/**
    * Copyright 2005-2012 The Kuali Foundation
    *
    * Licensed under the Educational Community License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.opensource.org/licenses/ecl2.php
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.kuali.rice.krms.framework.engine;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import org.kuali.rice.krms.api.engine.ExecutionEnvironment;
  import org.kuali.rice.krms.api.engine.ResultEvent;
  import org.kuali.rice.krms.api.engine.ExecutionFlag;
  import org.kuali.rice.krms.api.repository.LogicalOperator;
  import org.kuali.rice.krms.framework.engine.result.BasicResult;
  
  /**
   *
   * An implementation of {@link Proposition} which holds other Propositions and a {@link LogicalOperator}.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public final class CompoundProposition implements Proposition {
  	
      private static final ResultLogger LOG = ResultLogger.getInstance();
      
  	private final LogicalOperator logicalOperator;
  	private final List<Proposition> propositions;
  
      /**
       * Create a CompoundProposition with the given values
       * @param logicalOperator {@link LogicalOperator} to set logicalOperator to
       * @param propositions to set the propositions to
       */
  	public CompoundProposition(LogicalOperator logicalOperator, List<Proposition> propositions) {
  				
  		if (propositions == null || propositions.isEmpty()) {
  			throw new IllegalArgumentException("Propositions must be non-null and non-empty.");
  		}
  		if (logicalOperator == null) {
  			throw new IllegalArgumentException("Logical operator must be non-null.");
  		}
  		this.logicalOperator = logicalOperator;
  		this.propositions = new ArrayList<Proposition>(propositions);
  	}
  	
  	@Override
  	public PropositionResult evaluate(ExecutionEnvironment environment) {
  		
  		PropositionResult result = evaluateInner(environment);
  		
  		// handle compound proposition result logging
  		if (LOG.isEnabled(environment)) { 
              LOG.logResult(new BasicResult(ResultEvent.PROPOSITION_EVALUATED, this, environment, result.getResult()));
          }
  		
  		return result;
  	}
  
      /**
       * Evaluates then {@link ExecutionEnvironment}
       *
       * @param environment {@link ExecutionEnvironment} to use for evaluation
       * @return PropositionResult {@link PropositionResult} the results of the evaluation
       * @throws IllegalStateException if the logicalOperator is invalid.
       */
  	
      private PropositionResult evaluateInner(ExecutionEnvironment environment) {
      	
      	boolean collatedResult;
      	boolean evaluateAll = environment.getExecutionOptions().getFlag(ExecutionFlag.EVALUATE_ALL_PROPOSITIONS);
      	
          if (logicalOperator == LogicalOperator.AND) {
  
              collatedResult = true;
  
  			for (Proposition proposition : propositions) {
  				
  				PropositionResult singleResult = proposition.evaluate(environment);
  				logPropositionResult(proposition, singleResult, environment);
  								
  				if (!singleResult.getResult()) {
  					collatedResult = false;
  					if(!evaluateAll) break;
  				}
  			}
  			
  			return new PropositionResult(collatedResult);
 			
 		} else if (logicalOperator == LogicalOperator.OR) {
 			
 		    collatedResult = false;
 			
 			for (Proposition proposition : propositions) {
 				
 			    PropositionResult singleResult = proposition.evaluate(environment);
 				logPropositionResult(proposition, singleResult, environment);
 				
 				if (singleResult.getResult()) {
 					collatedResult = true;
 					if(!evaluateAll) break;
 				}
 			}
 			
 			return new PropositionResult(collatedResult);
 		}
 		throw new IllegalStateException("Invalid logical operator: " + logicalOperator);
     }
     
     /*
      * Logs only if the proposition is not compound
      * and have the compound proposition log its own result
      * @param proposition {@link Proposition} to log.  Compound Propositions will not log.
      * @param propositionResult {@link PropositionResult} to log the result and execution details of
      * @param environment {@link ExecutionEnvironment} to log
      */
     
     public void logPropositionResult(Proposition proposition, PropositionResult propositionResult, ExecutionEnvironment environment) {
     	    	
     	if(!proposition.isCompound()) {
             LOG.logResult(new BasicResult(propositionResult.getExecutionDetails(), ResultEvent.PROPOSITION_EVALUATED, proposition, environment, propositionResult.getResult()));
     	}
     	
     }
 
     /**
      * Returns an unmodifiableList of {@link Proposition}s.
      * @return an unmodifiableList of {@link Proposition}s
      */
     @Override
     public List<Proposition> getChildren() {
         return Collections.unmodifiableList(propositions);
     }
     
     @Override
     public boolean isCompound() {
         return true;
     }
 
 }