/*
 * Copyright (c) 2012, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.ws.rs.sse;

import java.util.concurrent.CompletionStage;

Outbound Server-Sent Events stream.
 The instance of SseEventSink can be only acquired by injection of a resource method parameter: 
@GET
@Path("eventStream")
@Produces(MediaType.SERVER_SENT_EVENTS)
public void eventStream(@Context SseEventSink eventSink) {
    // ...
}

The injected instance is then considered as a return type, so the resource method doesn't return anything,
similarly as in server-side async processing.

The underlying client connection is kept open and the application code
is able to send events. A server-side instance implementing the interface
corresponds exactly to a single client HTTP connection.

The injected instance is thread safe.
Author:
Marek Potociar (marek.potociar at oracle.com)
Since:
2.1/**
 * Outbound Server-Sent Events stream.
 * <p>
 * The instance of {@link SseEventSink} can be only acquired by injection of a resource method parameter:
 * <pre>
 * &#64;GET
 * &#64;Path("eventStream")
 * &#64;Produces(MediaType.SERVER_SENT_EVENTS)
 * public void eventStream(@Context SseEventSink eventSink) {
 *     // ...
 * }
 * </pre>
 * The injected instance is then considered as a return type, so the resource method doesn't return anything,
 * similarly as in server-side async processing.
 * <p>
 * The underlying client connection is kept open and the application code
 * is able to send events. A server-side instance implementing the interface
 * corresponds exactly to a single client HTTP connection.
 * <p>
 * The injected instance is thread safe.
 *
 * @author Marek Potociar (marek.potociar at oracle.com)
 * @since 2.1
 */
public interface SseEventSink extends AutoCloseable {

    
Check if the stream has been closed already.
 Please note that the client connection represented by this SseServerSink can be closed by the client side when a client decides to close connection and disconnect from the server. 
Returns:
true when closed, false otherwise./**
     * Check if the stream has been closed already.
     * <p>
     * Please note that the client connection represented by this {@code SseServerSink} can be closed by the
     * client side when a client decides to close connection and disconnect from the server.
     *
     * @return {@code true} when closed, {@code false} otherwise.
     */
    boolean isClosed();

    
Send an outbound Server-sent event to this sink.

Event will be serialized and sent to the client.
Params:
event – event to be written.
Returns:
completion stage that completes when the event has been sent. If there is a problem during sending of
an event, completion stage will be completed exceptionally./**
     * Send an outbound Server-sent event to this sink.
     * <p>
     * Event will be serialized and sent to the client.
     *
     * @param event event to be written.
     * @return completion stage that completes when the event has been sent. If there is a problem during sending of
     * an event, completion stage will be completed exceptionally.
     */
    public CompletionStage<?> send(OutboundSseEvent event);

    
Close the SseEventSink instance and release all associated resources. 
 Subsequent calls have no effect and are ignored. Once the SseEventSink is closed, invoking any method other than this one and isClosed() would result in an IllegalStateException being thrown. /**
     * Close the {@link SseEventSink} instance and release all associated resources.
     * <p>
     * Subsequent calls have no effect and are ignored. Once the {@link SseEventSink} is closed,
     * invoking any method other than this one and {@link #isClosed()} would result in
     * an {@link IllegalStateException} being thrown.
     */
    @Override
    void close();
}