/*
 * This file is part of the L2J Mobius project.
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package com.l2jmobius.gameserver.model;

import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledFuture;
import java.util.function.Predicate;

import com.l2jmobius.gameserver.ThreadPoolManager;
import com.l2jmobius.gameserver.model.actor.L2Character;
import com.l2jmobius.gameserver.model.events.EventDispatcher;
import com.l2jmobius.gameserver.model.events.impl.character.OnCreatureSee;

/**
 * @author UnAfraid
 */
public class CreatureContainer
{
	private final Set<Integer> _seen = ConcurrentHashMap.newKeySet();
	private final L2Character _owner;
	private final int _range;
	private ScheduledFuture<?> _task;
	private Predicate<L2Character> _condition = null;
	
	public CreatureContainer(L2Character owner, int range, Predicate<L2Character> condition)
	{
		_owner = owner;
		_range = range;
		_condition = condition;
		start();
	}
	
	public L2Character getOwner()
	{
		return _owner;
	}
	
	public int getRange()
	{
		return _range;
	}
	
	/**
	 * Starts the task that scans for new creatures
	 */
	public void start()
	{
		if ((_task == null) || _task.isDone())
		{
			_task = ThreadPoolManager.getInstance().scheduleAiAtFixedRate(this::update, 1000L, 1000L);
		}
	}
	
	/**
	 * @return {@code false} if the task could not be cancelled, typically because it has already completed normally; {@code true} otherwise
	 */
	public boolean stop()
	{
		return (_task != null) && !_task.isDone() && _task.cancel(false);
	}
	
	/**
	 * Resets the creatures container, all previously seen creature will be discarded and next time update method is called will notify for each creature that owner sees!
	 */
	public void reset()
	{
		_seen.clear();
	}
	
	/**
	 * Scans around the npc and notifies about new creature owner seen
	 */
	private void update()
	{
		final Set<Integer> verified = new HashSet<>();
		L2World.getInstance().forEachVisibleObjectInRange(_owner, L2Character.class, _range, creature ->
		{
			if ((_condition == null) || _condition.test(creature))
			{
				if (_seen.add(creature.getObjectId()))
				{
					EventDispatcher.getInstance().notifyEventAsync(new OnCreatureSee(_owner, creature), _owner);
				}
				verified.add(creature.getObjectId());
			}
		});
		
		_seen.retainAll(verified);
	}
}