Players.java

package nextstep.ladder.domain;

import java.util.List;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toList;

public class Players {
    private final List<Player> players;

    private Players(List<Player> players) {
        validate(players);
        this.players = players;
    }

    private void validate(List<Player> players) {
        if (players == null || players.isEmpty()) {
            throw new IllegalArgumentException("참가자가 없습니다.");
        }
    }

    public static Players of(List<String> playerNames) {
        return IntStream.range(0, playerNames.size())
                .mapToObj(index -> new Player(index, playerNames.get(index)))
                .collect(collectingAndThen(toList(), Players::new));
    }

    public int count() {
        return players.size();
    }

    public Player getPlayer(int index) {
        return players.stream()
                .filter(player -> player.sameIndex(index))
                .findFirst()
                .orElseThrow(() -> new IllegalArgumentException("참가자가 없습니다. index: " + index));
    }
}