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Fork of Artemis Entity System Framework.
There is a newer version: 2.3.0
package com.artemis;

import com.artemis.utils.Bag;
import com.artemis.utils.ImmutableBag;
import com.artemis.utils.IntBag;


/**
 * Entity system for iterating a entities matching a single Aspect. Likely the
 * most common type of system.
 *
 * @author Arni Arent
 */
public abstract class EntitySystem extends BaseSystem
		implements EntitySubscription.SubscriptionListener {

	private final Aspect.Builder aspectConfiguration;
	protected EntitySubscription subscription;

	/**
	 * Creates an entity system that uses the specified aspect as a matcher
	 * against entities.
	 *
	 * @param aspect
	 *			to match against entities
	 */
	public EntitySystem(Aspect.Builder aspect) {
		super();
		if (aspect == null) {
			String error = "Aspect.Builder was null; to use systems which " +
					"do not subscribe to entities, extend BaseSystem directly.";
			throw new NullPointerException(error);
		}

		aspectConfiguration = aspect;
	}

	protected void setWorld(World world) {
		super.setWorld(world);

		subscription = getSubscription();
		subscription.addSubscriptionListener(this);
	}

	public EntitySubscription getSubscription() {
		AspectSubscriptionManager sm = world.getManager(AspectSubscriptionManager.class);
		return sm.get(aspectConfiguration);
	}

	@Override
	public void inserted(IntBag entities) {
		int[] ids = entities.getData();
		for (int i = 0, s = entities.size(); s > i; i++) {
			inserted(ids[i]);
		}
	}

	/**
	 * Called if the system has received a entity it is interested in, e.g
	 * created or a component was added to it.
	 *
	 * @param entityId
	 *			the entity that was added to this system
	 */
	protected void inserted(int entityId) {}

	@Override
	public void removed(IntBag entities) {
		int[] ids = entities.getData();
		for (int i = 0, s = entities.size(); s > i; i++) {
			removed(ids[i]);
		}
	}

	/**
	 * Called if a entity was removed from this system, e.g deleted or had one
	 * of it's components removed.
	 *
	 * @param entityId
	 *			the entity that was removed from this system
	 */
	protected void removed(int entityId) {}


	/**
	 * Get all entities being processed by this system.
	 *
	 * @return a bag containing all active entities of the system
	 *
	 * @deprecated Retrieve the entities from the {@link com.artemis.EntitySubscription}
	 * directly.
	 */
	@Deprecated
	public Bag getActives(Bag fillBag) {
		IntBag actives = subscription.getEntities();
		int[] array = actives.getData();
		for (int i = 0, s = actives.size(); s > i; i++) {
			fillBag.add(world.getEntity(array[i]));
		}

		return fillBag;
	}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	protected final void check(Entity e) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void added(Entity e) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void added(ImmutableBag entities) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void changed(ImmutableBag entities) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void deleted(ImmutableBag entities) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void changed(Entity e) {}

	/**
	 * This method no longer performs any operations due to entity subscriptions lists
	 * being refactored into {@link com.artemis.AspectSubscriptionManager} and
	 * {@link com.artemis.EntitySubscription}.
	 */
	@Deprecated
	public final void deleted(Entity e) {}

	/**
	 * Call when an entity interesting to the system was disabled.
	 *
	 * 
	 * If the disabled entity is in this system it will be removed
	 * 
	 *
	 * @param e
	 *			the disabled entity
	 */
	@Deprecated
	public final void disabled(Entity e) {}

	/**
	 * Call when an entity interesting to the system was (re)enabled.
	 * 
	 * If the enabled entity is of interest, in will be (re)inserted.
	 * 
	 *
	 * @param e
	 *			the (re)enabled entity
	 */
	@Deprecated
	public final void enabled(Entity e) {}

	/**
	 * Get all entities being processed by this system.
	 *
	 * @return a bag containing all active entities of the system
	 * @deprecated This method allocates a new Bag each time, refer to {@link #getActives(com.artemis.utils.Bag)}
	 */
	@Deprecated
	public ImmutableBag getActives() {
		return getActives(new Bag());
	}
}