//
// ========================================================================
// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//

package org.eclipse.jetty.ee10.servlets;

import java.io.IOException;

/**
 * <p>{@link EventSource} is the passive half of an event source connection, as defined by the
 * <a href="http://www.w3.org/TR/eventsource/">EventSource Specification</a>.</p>
 * <p>{@link EventSource.Emitter} is the active half of the connection and allows to operate on the connection.</p>
 * <p>{@link EventSource} allows applications to be notified of events happening on the connection;
 * two events are being notified: the opening of the event source connection, where method
 * {@link EventSource#onOpen(Emitter)} is invoked, and the closing of the event source connection,
 * where method {@link EventSource#onClose()} is invoked.</p>
 *
 * @see EventSourceServlet
 */
public interface EventSource
{
    /**
     * <p>Callback method invoked when an event source connection is opened.</p>
     *
     * @param emitter the {@link Emitter} instance that allows to operate on the connection
     * @throws IOException if the implementation of the method throws such exception
     */
    public void onOpen(Emitter emitter) throws IOException;

    /**
     * <p>Callback method invoked when an event source connection is closed.</p>
     */
    public void onClose();

    /**
     * <p>{@link Emitter} is the active half of an event source connection, and allows applications
     * to operate on the connection by sending events, data or comments, or by closing the connection.</p>
     * <p>An {@link Emitter} instance will be created for each new event source connection.</p>
     * <p>{@link Emitter} instances are fully thread safe and can be used from multiple threads.</p>
     */
    public interface Emitter
    {
        /**
         * <p>Sends a named event with data to the client.</p>
         * <p>When invoked as: <code>event("foo", "bar")</code>, the client will receive the lines:</p>
         * <pre>
         * event: foo
         * data: bar
         * </pre>
         *
         * @param name the event name
         * @param data the data to be sent
         * @throws IOException if an I/O failure occurred
         * @see #data(String)
         */
        public void event(String name, String data) throws IOException;

        /**
         * <p>Sends a default event with data to the client.</p>
         * <p>When invoked as: <code>data("baz")</code>, the client will receive the line:</p>
         * <pre>
         * data: baz
         * </pre>
         * <p>When invoked as: <code>data("foo\r\nbar\rbaz\nbax")</code>, the client will receive the lines:</p>
         * <pre>
         * data: foo
         * data: bar
         * data: baz
         * data: bax
         * </pre>
         *
         * @param data the data to be sent
         * @throws IOException if an I/O failure occurred
         */
        public void data(String data) throws IOException;

        /**
         * <p>Sends a comment to the client.</p>
         * <p>When invoked as: <code>comment("foo")</code>, the client will receive the line:</p>
         * <pre>
         * : foo
         * </pre>
         *
         * @param comment the comment to send
         * @throws IOException if an I/O failure occurred
         */
        public void comment(String comment) throws IOException;

        /**
         * <p>Closes this event source connection.</p>
         */
        public void close();
    }
}
