Event.java

/*
 * $Id$
 *
 * SARL is an general-purpose agent programming language.
 * More details on http://www.sarl.io
 *
 * Copyright (C) 2014-2017 the original authors or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.sarl.lang.core;

import java.io.Serializable;
import java.util.UUID;

import org.eclipse.xtext.xbase.lib.Pure;

/** Elementary interaction unit inside an {@link EventSpace} An event is the
 * specification of some occurrence in a Space that may potentially trigger
 * effects by a listener. Within a Space, the notion of {@link Scope} enables to
 * precisely control/filter the potential recipients of an event.
 *
 * @author $Author: srodriguez$
 * @version $FullVersion$
 * @mavengroupid $GroupId$
 * @mavenartifactid $ArtifactId$
 */
public abstract class Event implements Serializable {

	private static final long serialVersionUID = -4314428111329600890L;

	private Address source;

	/** Constructs an Event without source.
	 * The source must be set with {@link #setSource(Address)}
	 * by the creator of the event, or by the emitting mechanism,
	 * before sending the event on the event bus.
	 */
	public Event() {
		//
	}

	/** Constructs an Event with a source.
	 * @param source - source of the event.
	 */
	public Event(Address source) {
		this.source = source;
	}

	@Override
	@Pure
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj != null && getClass().equals(obj.getClass())) {
			final Event event = (Event) obj;
			return (this.source == null && event.source == null)
					|| (this.source != null && this.source.equals(event.source));
		}
		return false;
	}

	@Override
	@Pure
	public int hashCode() {
		int hash = 31 + getClass().hashCode();
		if (this.source != null) {
			hash = hash * 31 + this.source.hashCode();
		}
		return hash;
	}

	/**
	 * The source of the event.
	 *
	 * @return the source of the event.
	 */
	@Pure
	public Address getSource() {
		return this.source;
	}

	/**
	 * The address of the source of this event.
	 *
	 * @param source - the source of the event.
	 */
	public void setSource(Address source) {
		this.source = source;
	}

	/**
	 * Returns a String representation of the Event E1 attributes only.
	 *
	 * @return the string representation of the attributes of this Event.
	 */
	@Pure
	protected String attributesToString() {
		final StringBuilder result = new StringBuilder();
		result.append("source = "); //$NON-NLS-1$
		result.append(this.source);
		return result.toString();
	}

	@Override
	@Pure
	public String toString() {
		return getClass().getSimpleName()
				+ " [" + attributesToString() //$NON-NLS-1$
				+ "]"; //$NON-NLS-1$
	}

	/** Replies if the event was emitted by an entity with the given address.
	 *
	 * @param address - the address of the emitter to test.
	 * @return <code>true</code> if the given event was emitted by
	 *     an entity with the given address; otherwise <code>false</code>.
	 * @since 0.2
	 */
	@Pure
	public boolean isFrom(Address address) {
		return (address != null) && address.equals(getSource());
	}

	/** Replies if the event was emitted by an entity with the given identifier.
	 *
	 * @param entityId - the identifier of the emitter to test.
	 * @return <code>true</code> if the given event was emitted by
	 *     an entity with the given identifier; otherwise <code>false</code>.
	 * @since 0.2
	 */
	@Pure
	public boolean isFrom(UUID entityId) {
		final Address iSource = getSource();
		return (entityId != null) && (iSource != null)
				&& entityId.equals(iSource.getUUID());
	}

}