package org.apache.archiva.event;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

import java.util.Set;

/**
 * Allows implementer to emit to, subscribe and unsubscribe EventObservers
 */
public interface EventBus
{
    /**
     * Emit a event
     * @param emitter
     * @param message
     */
    void emit(EventEmitter emitter, EventMessage message);

    /**
     * Allows the subscriber to receive messages from this event bus
     * @param observer
     */
    void subscribe(EventObserver observer);

    /**
     * Stops the observer from receiving any messages
     * @param observer
     */
    void unsubscribe(EventObserver observer);

    /**
     * Get the set of registered EventObservers
     * @return
     */
    Set<EventObserver> getObservers();
}