content: /*
   *  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.
   */
  package org.apache.causeway.extensions.sse.applib.annotations;
  
  import org.apache.causeway.extensions.sse.applib.service.SseChannel;
  
  /**
   * Server-sent events.
   *
   * @see <a href="https://www.w3schools.com/html/html5_serversentevents.asp">www.w3schools.com</a>
   *
   * @since 2.0 {@index}
   */
  public interface SseSource {
  
      void run(SseChannel channel);
  
      String getPayload();
  
      // -- PROPERTY ANNOTATION DEFAULT
  
      /**
       * This class is the default for the
       * {@link ServerSentEvents#observe()} annotation attribute.
       */
      public static final class Noop implements SseSource {
  
          @Override
          public void run(SseChannel channel) {
              // just do nothing
          }
  
          @Override
          public String getPayload() {
              return "";
          }
  
      }
  
      // -- BASIC PREDICATES
  
      public static boolean isObservable(Class<?> type) {
          if(type==null) {
              return false;
          }
          if(!SseSource.class.isAssignableFrom(type)) {
              return false;
          }
          return !type.equals(Noop.class);
      }
  
  }
  