source: bidspace/src/main/java/geniusweb/bidspace/IssueInfo.java@ 41

package geniusweb.bidspace;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import geniusweb.issuevalue.Value;
import geniusweb.issuevalue.ValueSet;
import geniusweb.profile.utilityspace.ValueSetUtilities;

/**
 * Tool class to collect all relevant info about one issue (from LinearAdditive)
 * in one class. Used for internally grouping data for more efficient
 * processing. This class may change in the future, not recommended for direct
 * use.
 * <p>
 * immutable
 */
public class IssueInfo {
        private final String name;
        private final ValueSet values;
        private final Interval interval;
        private final Map<Value, BigDecimal> weightedUtils;

        /**
         * 
         * @param name      the issue name
         * @param values    the {@link ValueSet} of the issue
         * @param utils     the {@link ValueSetUtilities} of the issue profile
         * @param weight    the weight of the {@link ValueSetUtilities}
         * @param precision the precision to compute with. Basically the number of
         *                  decimal places used for the computations.
         * 
         */
        public IssueInfo(String name, ValueSet values, ValueSetUtilities utils,
                        BigDecimal weight, int precision) {
                this.name = name;
                this.values = values;
                this.weightedUtils = computeWeightedUtils(utils, weight, precision);
                this.interval = getRange();
        }

        public ValueSet getValues() {
                return values;
        }

        public String getName() {
                return name;
        }

        /**
         * 
         * @return weighted minimum and maximum utility achievable with this issue,
         *         rounded to the requested precision.
         */
        public Interval getInterval() {
                return interval;
        }

        /**
         * 
         * @param isMax if true the max {@link Value} is returned, else the min is
         *              returned.
         * @return the extreme value, either the minimum if isMax=false or maximum
         *         if isMax=true
         */
        public Value getExtreme(boolean isMax) {
                BigDecimal extremeutil = null;
                Value extremeval = null;
                for (Value val : values) {
                        BigDecimal util = weightedUtils.get(val);
                        if (extremeval == null) {
                                extremeutil = weightedUtils.get(val);
                                extremeval = val;
                        } else {
                                if (isMax) {
                                        if (util.compareTo(extremeutil) > 0) {
                                                extremeutil = util;
                                                extremeval = val;
                                        }
                                } else {
                                        if (util.compareTo(extremeutil) < 0) {
                                                extremeutil = util;
                                                extremeval = val;
                                        }

                                }
                        }
                }
                return extremeval;
        }

        /**
         * @param val the issue value to be evaluated
         * @return weighted utility of given value, rounded to nearest value with
         *         the requested precision number of digits.
         */
        public BigDecimal getWeightedUtil(Value val) {
                return weightedUtils.get(val);
        }

        /**
         * 
         * @param interval an {@link Interval} of utility values.
         * @return all values that are inside the interval.
         */
        protected List<Value> subset(Interval interval) {

                List<Value> selection = new ArrayList<>();
                for (Value value : values) {
                        if (interval.contains(getWeightedUtil(value)))
                                selection.add(value);
                }
                return selection;
        }

        /**
         * Faster way to determine subset size, it does not create a list
         * 
         * @param interval an {@link Interval} of utility values.
         * @return size of the subset that you will get from calling subset
         */
        protected int subsetSize(Interval interval) {
                int n = 0;
                for (Value value : values)
                        if (interval.contains(getWeightedUtil(value)))
                                n++;
                return n;
        }

        /**
         * @return the {@link Interval} (minimum and maximum) of the utility of the
         *         weighted utility of this issue, properly rounded to the
         *         {@link #precision}/
         * 
         */
        private Interval getRange() {
                BigDecimal min = BigDecimal.ONE;
                BigDecimal max = BigDecimal.ZERO;
                for (Value value : values) {
                        BigDecimal util = getWeightedUtil(value);
                        if (util.compareTo(min) < 0)
                                min = util;
                        if (util.compareTo(max) > 0)
                                max = util;
                }
                return new Interval(min, max);

        }

        private Map<Value, BigDecimal> computeWeightedUtils(
                        ValueSetUtilities utilities, BigDecimal w, int prec) {
                Map<Value, BigDecimal> map = new HashMap<>();

                for (Value val : values) {
                        map.put(val, utilities.getUtility(val).multiply(w).setScale(prec,
                                        RoundingMode.HALF_UP));
                }
                return map;
        }

}