DestinyOrderedMatchGeneration.java

package cryodex.modules.destiny;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import javax.swing.JOptionPane;

import cryodex.Main;

/**
 * Generate matches in order of ranking or as close to it as possible. This
 * algorithm finds the best possible match set that holds truest to the original
 * ranking. Every permutation is calculated and given a score based on the
 * distance each player is from their true ranking. The permutation with the
 * lowest score wins.
 * 
 * @author cbrown
 * 
 */
public class DestinyOrderedMatchGeneration {

	private final DestinyTournament tournament;
	private final List<DestinyPlayer> players;

	private Integer lowScore = null;
	private List<DestinyMatch> matchSetAtLowScore = null;

	public DestinyOrderedMatchGeneration(DestinyTournament tournament,
			List<DestinyPlayer> players) {
		this.tournament = tournament;
		this.players = players;

	}

	public List<DestinyMatch> generateMatches() {

		List<DestinyPlayer> tempList = new ArrayList<>();
		tempList.addAll(players);
		Collections.sort(tempList, new DestinyComparator(tournament,
				DestinyComparator.pairingCompare));

		generateMatch(new ArrayList<DestinyMatch>(), tempList);

		// If no valid match set was found then we create the true ranking match
		// set and return it
		if (matchSetAtLowScore == null) {
			matchSetAtLowScore = new ArrayList<>();

			for (int counter = 0; counter < players.size(); counter += 2) {
				DestinyMatch m = new DestinyMatch(players.get(counter),
						players.get(counter + 1));
				m.checkDuplicate(tournament.getAllRounds());
				matchSetAtLowScore.add(m);
			}

		}

		if (lowScore != null && lowScore != 0) {
			JOptionPane.showMessageDialog(Main.getInstance(),
					"Matches were modified to avoid duplicate pairings. Avoidance score = "
							+ lowScore + " (2-10 is a minor change)");
		}

		return matchSetAtLowScore;
	}

	private void generateMatch(List<DestinyMatch> matches, List<DestinyPlayer> player1List) {

		if (player1List.size() == 0) {
			scorePermutation(matches);
			return;
		}

		for (DestinyPlayer xp : player1List) {

			List<DestinyPlayer> player2List = new ArrayList<>();
			player2List.addAll(player1List);
			player2List.remove(xp);

			getPlayer2(xp, matches, player2List);

			if (lowScore != null && lowScore <= 2) {
				return;
			}
		}
	}

	private void getPlayer2(DestinyPlayer player1, List<DestinyMatch> matches,
			List<DestinyPlayer> player2List) {
		for (DestinyPlayer player2 : player2List) {
			DestinyMatch xm = new DestinyMatch(player1, player2);
			xm.checkDuplicate(tournament.getAllRounds());

			if (xm.isDuplicate() == false) {
				matches.add(xm);
				if (shouldContinue(matches)) {
					List<DestinyPlayer> player1List = new ArrayList<>();
					player1List.addAll(player2List);
					player1List.remove(xm.getPlayer2());

					generateMatch(matches, player1List);
				}
			}

			matches.remove(xm);

			if (lowScore != null && lowScore <= 2) {
				return;
			}
		}
	}

	private boolean shouldContinue(List<DestinyMatch> matches) {
		if (lowScore == null) {
			return true;
		}
		return getScore(matches) < lowScore;
	}

	private void scorePermutation(List<DestinyMatch> matches) {
		int score = getScore(matches);

		if (lowScore == null || score < lowScore) {
			matchSetAtLowScore = new ArrayList<>();
			matchSetAtLowScore.addAll(matches);

			lowScore = score;
		}
	}

	private int getScore(List<DestinyMatch> matches) {

		// order players
		Collections.sort(players, new DestinyComparator(tournament,
				DestinyComparator.pairingCompare));

		// get list of players in order of matches
		List<DestinyPlayer> playerByMatchOrder = new ArrayList<DestinyPlayer>();
		for (DestinyMatch xm : matches) {
			playerByMatchOrder.add(xm.getPlayer1());
			playerByMatchOrder.add(xm.getPlayer2());
		}

		int score = 0;

		for (int counter = 0; counter < playerByMatchOrder.size(); counter++) {
			int index = players.indexOf(playerByMatchOrder.get(counter));

			score += Math.abs(counter - index);
		}

		return score;
	}
}