CoronaSafety.java

package uk.tethys.coronasafety;

import org.bukkit.Bukkit;
import org.bukkit.Sound;
import org.bukkit.entity.Player;
import org.bukkit.event.Listener;
import org.bukkit.plugin.java.JavaPlugin;
import org.bukkit.scheduler.BukkitRunnable;

import java.util.HashMap;
import java.util.List;
import java.util.UUID;
import java.util.stream.Collectors;

public class CoronaSafety extends JavaPlugin implements Listener {

    @Override
    public void onEnable() {
        plugin = this;
        new CoronaCheck().runTaskTimer(this, 0, 10);
        super.onEnable();
    }

    @Override
    public void onDisable() {
        super.onDisable();
    }

    private static CoronaSafety plugin;

    static class CoronaCheck extends BukkitRunnable {
        private final HashMap<UUID, Integer> coronaRingTaskIdMap;

        CoronaCheck() {
            coronaRingTaskIdMap = new HashMap<>();
        }

        @SuppressWarnings("unchecked")
        @Override
        public void run() {
            for (Player player : Bukkit.getOnlinePlayers()) {
                List<Player> nearby = (List<Player>) (List<?>) player.getNearbyEntities(2, 1.5d, 2).stream()
                        .filter(ent -> ent instanceof Player).collect(Collectors.toList());
                nearby.sort((o1, o2) -> (int) (player.getLocation().distance(o1.getLocation())
                        - player.getLocation().distance(o2.getLocation())));
                if (nearby.isEmpty()) {
                    if (coronaRingTaskIdMap.containsKey(player.getUniqueId()))
                        Bukkit.getServer().getScheduler().cancelTask(coronaRingTaskIdMap.get(player.getUniqueId()));
                    continue;
                }
                double distance = player.getLocation().distance(nearby.get(0).getLocation());
                if (distance <= 3) {
                    if (coronaRingTaskIdMap.containsKey(player.getUniqueId())) {
                        Bukkit.getServer().getScheduler().cancelTask(coronaRingTaskIdMap.get(player.getUniqueId()));
                    }
                    coronaRingTaskIdMap.put(player.getUniqueId(), new CoronaRing(player, distance).runTaskTimer(plugin, 0,
                            (int) (distance * 6d)).getTaskId());
                }
            }
        }
    }

    static class CoronaRing extends BukkitRunnable {
        private final Player player;
        private final double distance;

        CoronaRing(Player player, double distance) {
            this.player = player;
            this.distance = distance;
        }

        @Override
        public void run() {
            player.playSound(player.getLocation(), Sound.BLOCK_NOTE_BLOCK_BIT,
                    (float) (2f - distance / 1.3f), (float)(2f - distance / 4f));
        }
    }


}