source: anac2020/TheDiceHaggler/src/main/java/geniusweb/bagga/dicehaggler/SimpleLinearOrdering.java@ 43

package geniusweb.bagga.dicehaggler;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.List;

import geniusweb.issuevalue.Bid;
import geniusweb.issuevalue.Domain;
import geniusweb.profile.DefaultPartialOrdering;
import geniusweb.profile.Profile;
import geniusweb.profile.utilityspace.UtilitySpace;

/**
 * A simple list of bids, but all bids are fully ordered (better or worse than
 * other bids in the list).
 */
public class SimpleLinearOrdering implements UtilitySpace {

        private final Domain domain;
        private final List<Bid> bids; // worst bid first, best bid last.

        SimpleLinearOrdering(Profile profile) {
                this(profile.getDomain(), getSortedBids(profile));
        }

        /**
         * 
         * @param domain
         * @param bids   a list of bids, ordered from lowest to highest util. The
         *               first bid will have utility 0, the last utility 1. If only
         *               0 or 1 bid in the list, or if the bid is not known, it will
         *               have utility 0.
         */
        SimpleLinearOrdering(Domain domain, List<Bid> bids) {
                this.domain = domain;
                this.bids = bids;
        }

        @Override
        public String getName() {
                throw new UnsupportedOperationException();
        }

        @Override
        public Domain getDomain() {
                return domain;
        }

        @Override
        public Bid getReservationBid() {
                throw new UnsupportedOperationException();
        }

        @Override
        public BigDecimal getUtility(Bid bid) {
                if (bids.size() < 2 || !bids.contains(bid)) {
                        return BigDecimal.ZERO;
                }
                // using 8 decimals, we have to pick something here
                return new BigDecimal(bids.indexOf(bid)).divide(
                                new BigDecimal((bids.size() - 1)), 8, RoundingMode.HALF_UP);
        }

        /**
         * 
         * @param bid
         * @return true iff bid is contained in this ordering
         */
        public boolean contains(Bid bid) {
                return bids.contains(bid);
        }

        /**
         * 
         * @return list of all bids in the current ordering.
         */
        public List<Bid> getBids() {
                return Collections.unmodifiableList(bids);
        }

        /**
         * 
         * @param profile
         * @return a list of bids in the profile sorted from low to high utility.
         */
        private static List<Bid> getSortedBids(Profile profile) {
                if (!(profile instanceof DefaultPartialOrdering)) {
                        throw new UnsupportedOperationException(
                                        "Only DefaultPartialOrdering supported");
                }
                DefaultPartialOrdering prof = (DefaultPartialOrdering) profile;
                List<Bid> bidslist = prof.getBids();
                // NOTE sort defaults to ascending order, this is missing in docs.
                Collections.sort(bidslist, new Comparator<Bid>() {

                        @Override
                        public int compare(Bid b1, Bid b2) {
                                return prof.isPreferredOrEqual(b1, b2) ? 1 : -1;
                        }

                });

                return bidslist;
        }

        /**
         * @param bid       a new bid to be inserted
         * @param worseBids all bids that are worse than this bid.
         * @return a SimpleLinearOrdering, updated with the given comparison. Thee
         *         bid will be inserted after the first bid that is not worse than
         *         bid.
         */
        public SimpleLinearOrdering with(Bid bid, List<Bid> worseBids) {
                int n = 0;
                while (n < bids.size() && worseBids.contains(bids.get(n)))
                        n++;
                LinkedList<Bid> newbids = new LinkedList<Bid>(bids);
                newbids.add(n, bid);
                return new SimpleLinearOrdering(domain, newbids);
        }

}