common/src/main/java/org/saturnclient/client/player/SaturnPlayer.java

package org.saturnclient.client.player;

import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.saturnclient.client.ServiceClient;
import org.saturnclient.common.provider.Providers;

public class SaturnPlayer {
    /** Players known to be using Saturn. */
    private static final Map<UUID, SaturnPlayer> PLAYERS = new ConcurrentHashMap<>();

    /**
     * Earliest time (ms) a player without a Saturn entry may be looked up again,
     * so non-Saturn players aren't re-requested every frame.
     */
    private static final Map<UUID, Long> NEXT_LOOKUP = new ConcurrentHashMap<>();

    /** Players queued or being looked up. */
    private static final Set<UUID> PENDING = ConcurrentHashMap.newKeySet();

    private static final long NOT_SATURN_RECHECK_MS = 60_000;
    private static final long FAILED_LOOKUP_RETRY_MS = 5_000;

    private static final ExecutorService LOOKUPS = Executors.newSingleThreadExecutor(runnable -> {
        Thread thread = new Thread(runnable, "SaturnPlayer-Worker");
        thread.setDaemon(true);
        return thread;
    });

    public volatile String cloak = "";
    public volatile String hat = "";
    public final UUID uuid;
    public final String name;

    public SaturnPlayer(UUID uuid, String name, String cloak, String hat) {
        this.cloak = cloak;
        this.hat = hat;
        this.uuid = uuid;
        this.name = name;
    }

    public static SaturnPlayer get() {
        UUID self = ServiceClient.uuid;
        if (self == null) {
            return null;
        }
        return PLAYERS.get(self);
    }

    /**
     * Returns the player if they are known to use Saturn, otherwise null. An
     * unknown player is looked up in the background, at most once at a time and
     * no more often than {@link #NEXT_LOOKUP} allows. Safe to call every frame.
     */
    public static SaturnPlayer get(String name, UUID uuid) {
        if (uuid == null)
            return null;

        SaturnPlayer player = PLAYERS.get(uuid);

        if (player == null) {
            requestLookup(name, uuid);
        }

        return player;
    }

    public static SaturnPlayer get(UUID uuid) {
        return get(Providers.saturn.getClient().getPlayerListEntry(uuid), uuid);
    }

    public static SaturnPlayer get(String name) {
        return get(name, Providers.saturn.getClient().getPlayerListEntryUUID(name));
    }

    /** Forgets every cached player, e.g. after reconnecting to the server. */
    public static void clear() {
        PLAYERS.clear();
        NEXT_LOOKUP.clear();
    }

    public static void set(SaturnPlayer player) {
        PLAYERS.put(player.uuid, player);
        NEXT_LOOKUP.remove(player.uuid);
    }

    public static String[] getExternalUUIDAsString() {
        UUID self = ServiceClient.uuid;

        return PLAYERS.keySet().stream().filter(id -> self == null || !id.equals(self))
                .map(UUID::toString)
                .toArray(String[]::new);
    }

    private static void requestLookup(String name, UUID uuid) {
        if (!ServiceClient.isConnected()) {
            return;
        }

        Long next = NEXT_LOOKUP.get(uuid);
        if (next != null && System.currentTimeMillis() < next) {
            return;
        }

        if (!PENDING.add(uuid)) {
            return;
        }

        LOOKUPS.execute(() -> {
            try {
                SaturnPlayer player = ServiceClient.getPlayer(uuid, name);

                if (player != null) {
                    set(player);
                } else {
                    NEXT_LOOKUP.put(uuid, System.currentTimeMillis() + NOT_SATURN_RECHECK_MS);
                }
            } catch (Exception e) {
                Providers.saturn.logError("Failed to fetch player " + uuid, e);
                NEXT_LOOKUP.put(uuid, System.currentTimeMillis() + FAILED_LOOKUP_RETRY_MS);
            } finally {
                PENDING.remove(uuid);
            }
        });
    }
}