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The core HTTP and composition mechanisms of Ratpack
There is a newer version: 2.0.0-rc-1
/*
 * Copyright 2015 the original author 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 ratpack.sse;

import ratpack.func.Function;

/**
 * An individual event in a server sent event stream.
 * 
 * The {@link #getItem() item} is the item in the data stream being emitted as a server sent event.
 * It can be used to derive values for the {@link #id}, {@link #event} and/or {@link #data} fields.
 * 

 * By default, the {@code id}, {@code event} and {@code data} fields are set to {@code null}.
 *
 * @param  the item type contained in the event
 * @see ratpack.sse.ServerSentEvents#serverSentEvents
 */
public interface Event {
  /**
   * The stream item that this event.
   *
   * @return a supporting object
   */
  T getItem();

  /**
   * The “id” value of the event.
   * 

   * {@code null} by default.
   *
   * @return the “id” value of the event
   */
  String getId();

  /**
   * The “event” value of the event.
   * 

   * {@code null} by default.
   *
   * @return the “event” value of the event
   */
  String getEvent();

  /**
   * The “data” value of the event.
   * 

   * {@code null} by default.
   *
   * @return the “data” value of the event
   */
  String getData();

  /**
   * Sets the “id” value of the event to the return value of the given function.
   * 

   * The function receives the {@link #getItem() item} and is executed immediately.
   *
   * @param function a generator for the “id” value of the event
   * @return this
   * @throws Exception any thrown by {@code function}
   */
  Event id(Function function) throws Exception;

  /**
   * Specify the event id for the server sent event.
   *
   * @param id the event id
   * @return this
   */
  Event id(String id);

  /**
   * Sets the “event” value of the event to the return value of the given function.
   * 

   * The function receives the {@link #getItem() item} and is executed immediately.
   *
   * @param function a generator for the “event” value of the event
   * @return this
   * @throws Exception any thrown by {@code function}
   */
  Event event(Function function) throws Exception;

  /**
   * Specify the event type for the server sent event.
   *
   * @param event the event type
   * @return this
   */
  Event event(String event);

  /**
   * Sets the “data” value of the event to the return value of the given function.
   * 
   * The function receives the {@link #getItem() item} and is executed immediately.
   *
   * @param function a generator for the “data” value of the event
   * @return this
   * @throws Exception any thrown by {@code function}
   */
  Event data(Function function) throws Exception;

  /**
   * Specify the event data for the server sent event.
   *
   * @param data the event data
   * @return this
   */
  Event data(String data);
}