RandomZone schedule

package net.sf.l2j.gameserver.taskmanager;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;

import net.sf.l2j.commons.pool.ThreadPool;

import net.sf.l2j.Config;
import net.sf.l2j.gameserver.data.manager.ZoneManager;
import net.sf.l2j.gameserver.data.xml.AdminData;
import net.sf.l2j.gameserver.enums.ZoneId;
import net.sf.l2j.gameserver.model.World;
import net.sf.l2j.gameserver.model.actor.Creature;
import net.sf.l2j.gameserver.model.actor.Npc;
import net.sf.l2j.gameserver.model.actor.Player;
import net.sf.l2j.gameserver.network.clientpackets.Say2;
import net.sf.l2j.gameserver.network.serverpackets.CreatureSay;

public final class RandomZoneTaskManager
{
    private int currentZoneId;
    private int timer;

    private List<Npc> zoneMonsters = new ArrayList<>();

    public RandomZoneTaskManager()
    {
        if (getZonesCount() > 1)
            scheduleEvent();
    }

    private void scheduleEvent()
    {
        Calendar currentTime = Calendar.getInstance();
        Calendar nextStartTime = null;

        for (String time : Config.RANDOM_ZONE_SCHEDULE_TIME)
        {
            final String[] splitTime = time.split(":");

            nextStartTime = Calendar.getInstance();
            nextStartTime.setLenient(true);

            nextStartTime.set(Calendar.HOUR_OF_DAY, Integer.parseInt(splitTime[0]));
            nextStartTime.set(Calendar.MINUTE, Integer.parseInt(splitTime[1]));

            if (nextStartTime.getTimeInMillis() > System.currentTimeMillis())
            {
                final long delay = nextStartTime.getTimeInMillis() - System.currentTimeMillis();
                World.announceToOnlinePlayers("Next Random zone will start on: " + new SimpleDateFormat("dd-MM-yyyy HH:mm").format(nextStartTime.getTimeInMillis()) + ".", true);
                ThreadPool.scheduleAtFixedRate(new EventTask(), delay, 1000);
                break;
            }
        }
    }

    private class EventTask implements Runnable
    {
        public EventTask()
        {
            selectZone();
        }

        @Override
        public void run()
        {
            switch (timer)
            {
                case 0:
                    spawnMonsters();
                    scheduleEvent();
                    break;

                case 1:
                case 2:
                case 3:
                case 4:
                case 5:
                case 10:
                case 20:
                case 30:
                    World.announceToOnlinePlayers("Random zone will finish in " + timer + " second(s).", true);
                    break;

                case 60:
                case 120:
                case 180:
                case 240:
                case 300:
                case 600:
                case 1200:
                case 1800:
                    World.announceToOnlinePlayers("Random zone will finish in " + (timer / 60) + " minute(s).", true);
                    break;

                case 3600:
                case 7200:
                    World.announceToOnlinePlayers("Random zone will finish in " + (timer / 60 / 60) + " hour(s).", true);
                    break;
            }
            timer--;
        }
    }

    private void selectZone()
    {
        currentZoneId = currentZoneId == getZonesCount() ? 1 : ++currentZoneId;

        final RandomZone zone = ZoneManager.getInstance().getZoneById(currentZoneId, RandomZone.class);
        if (zone == null)
        {
            AdminData.getInstance().broadcastToGMs(new CreatureSay(0, Say2.PARTYROOM_COMMANDER, "RandomZone", "No zone with id: " + currentZoneId));
            return;
        }

        timer = zone.getTime() * 60;

        World.announceToOnlinePlayers("New Random Zone: " + zone.getName() + ". Duration: " + zone.getTime() + " min(s).", true);
        World.getInstance().getPlayers().stream().filter(p -> p.isInsideZone(ZoneId.RANDOM) && zone.isActive()).forEach(this::teleport);
        despawnMonsters(currentZoneId);
    }

    private final void despawnMonsters(int zoneId)
    {
        final RandomZone zone = ZoneManager.getInstance().getZoneById(zoneId, RandomZone.class);
        if (zone.despawnNpcs())
        {
            for (Creature creature : zone.getCharacters())
            {
                if (creature instanceof Npc)
                {
                    final Npc npc = (Npc) creature;
                    npc.decayMe();

                    zoneMonsters.add(npc);
                }
            }
        }
    }

    private final void spawnMonsters()
    {
        if (zoneMonsters.isEmpty())
            return;

        zoneMonsters.forEach(Npc::spawnMe);
        zoneMonsters.clear();
    }

    private final void teleport(Player player)
    {
        if (player.isDead())
            player.doRevive();

        player.teleToLocation(getCurrentZone().getSpawnLoc(), 0);
    }

    public void onEnter(Player player)
    {
        if (currentZoneId > 0)
            player.sendPacket(new CreatureSay(0, Say2.HERO_VOICE, "RandomZone", "Current zone: " + getCurrentZone().getName()));
    }

    public final int getCurrentZoneId()
    {
        return currentZoneId;
    }

    private static final int getZonesCount()
    {
        return ZoneManager.getInstance().getAllZones(RandomZone.class).size();
    }

    public final RandomZone getCurrentZone()
    {
        return ZoneManager.getInstance().getAllZones(RandomZone.class).stream().filter(t -> t.getId() == currentZoneId).findFirst().orElse(null);
    }

    public static final RandomZoneTaskManager getInstance()
    {
        return SingletonHolder.INSTANCE;
    }

    private static class SingletonHolder
    {
        protected static final RandomZoneTaskManager INSTANCE = new RandomZoneTaskManager();
    }
}