HungerGames/src/main/java/com/alttd/hunger_games/services/RoundService.java

package com.alttd.hunger_games.services;

import com.alttd.hunger_games.data_objects.PLAYER_STATE;
import com.alttd.hunger_games.data_objects.ROUND_STATE;
import lombok.Getter;

import java.util.*;
import java.util.stream.Collectors;

public class RoundService implements RoundListener {

    private static RoundService instance = null;

    @Getter
    private ROUND_STATE roundState;
    private final HashMap<UUID, PLAYER_STATE> players = new HashMap<>();

    public static RoundService createSingletonInstance(Round round) {
        if (instance != null) {
            throw new IllegalStateException("RoundService is already initialized.");
        }
        instance = new RoundService(round);
        return instance;
    }

    private RoundService(Round round) {
        this.roundState = round.register(this);
    }

    public Set<UUID> getPlayers(PLAYER_STATE playerState) {
        return players.entrySet().stream()
                .filter(entry -> entry.getValue().equals(playerState))
                .map(Map.Entry::getKey)
                .collect(Collectors.toSet());
    }

    protected void setPlayerState(UUID uuid, PLAYER_STATE playerState) {
        players.put(uuid, playerState);
    }

    protected void clear() {
        players.clear();
    }

    public Optional<PLAYER_STATE> getPlayerState(UUID uuid) {
        return Optional.ofNullable(players.get(uuid));
    }

    @Override
    public void stateChange(ROUND_STATE roundState) {
        this.roundState = roundState;
        if (roundState.equals(ROUND_STATE.PLAYER_REGISTRATION)) {
            clear();
        }
    }
}