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/**
 * Copyright (C) 2016 LibRec
 * 
 * This file is part of LibRec.
 * LibRec is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 

 * LibRec 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with LibRec. If not, see .
 */
package net.librec.eval.rating;

import net.librec.eval.AbstractRecommenderEvaluator;
import net.librec.recommender.item.ContextKeyValueEntry;
import net.librec.recommender.item.RecommendedList;

import java.util.Iterator;

/**
 * MAE: mean absolute error
 *
 * @author Keqiang Wang
 */

public class MAEEvaluator extends AbstractRecommenderEvaluator {

    public double evaluate(RecommendedList groundTruthList, RecommendedList recommendedList) {
        if(groundTruthList.size()==0){
            return 0.0;
        }
        double mae = 0.0;
        int testSize = 0;

        Iterator groundTruthIter = groundTruthList.iterator();
        Iterator recommendedEntryIter = recommendedList.iterator();

        while (groundTruthIter.hasNext()) {

            if (recommendedEntryIter.hasNext()) {

                ContextKeyValueEntry groundEntry = groundTruthIter.next();
                ContextKeyValueEntry recommendedEntry = recommendedEntryIter.next();

                if (groundEntry.getContextIdx() == recommendedEntry.getContextIdx()
                        && groundEntry.getKey() == recommendedEntry.getKey()) {

                    double realRating = groundEntry.getValue();
                    double predictRating = recommendedEntry.getValue();
                    mae += Math.abs(realRating - predictRating);

                    testSize++;

                } else {
                    throw new IndexOutOfBoundsException("index of recommendedList does not equal testMatrix index");
                }

            } else {
                throw new IndexOutOfBoundsException("index cardinality of recommendedList does not equal testMatrix index cardinality");
            }
        }

        return testSize > 0 ? mae / testSize : 0.0d;
    }

}