/*
 * Copyright 2014 Open Networking Laboratory
 *
 * 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 org.onlab.onos.event;

/**
 * Abstraction of an of a time-stamped event pertaining to an arbitrary subject.
 */
public interface Event<T extends Enum, S extends Object> {

    /**
     * Returns the timestamp of when the event occurred, given in milliseconds
     * since the start of epoch.
     *
     * @return timestamp in milliseconds
     */
    long time();

    /**
     * Returns the type of the event.
     *
     * @return event type
     */
    T type();

    /**
     * Returns the subject of the event.
     *
     * @return subject to which this event pertains
     */
    S subject();

}