/*
 * WorldEdit, a Minecraft world manipulation toolkit
 * Copyright (C) sk89q <http://www.sk89q.com>
 * Copyright (C) WorldEdit team and contributors
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.sk89q.worldedit.sponge;

import org.spongepowered.api.Sponge;
import org.spongepowered.api.entity.living.player.Player;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * Caches data that cannot be accessed from another thread safely.
 */
public class ThreadSafeCache implements Runnable {

    private static final ThreadSafeCache INSTANCE = new ThreadSafeCache();
    private Set<UUID> onlineIds = new CopyOnWriteArraySet<>();

    /**
     * Get an concurrent-safe set of UUIDs of online players.
     *
     * @return a set of UUIDs
     */
    public Set<UUID> getOnlineIds() {
        return onlineIds;
    }

    @Override
    public void run() {
        List<UUID> onlineIds = new ArrayList<>();

        for (Player player : Sponge.getServer().getOnlinePlayers()) {
            onlineIds.add(player.getUniqueId());
        }

        this.onlineIds = new CopyOnWriteArraySet<>(onlineIds);
    }

    public static ThreadSafeCache getInstance() {
        return INSTANCE;
    }

}