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 org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.*;
  import java.util.concurrent.ConcurrentHashMap;
  
  public class EventManager implements EventSource
  {
  
      private static final Logger log = LoggerFactory.getLogger(EventManager.class);
  
      private final ConcurrentHashMap<EventType<? extends Event>, Set<EventHandler>> handlerMap = new ConcurrentHashMap<>();
  
      private final Object source;
  
      public EventManager(Object source) {
          if (source==null) {
              throw new IllegalArgumentException("The source may not be null");
          }
          this.source = source;
      }
  
      @Override
      public <T extends Event> void registerEventHandler(EventType<T> type, EventHandler<? super T> eventHandler) {
          Set<EventHandler> handlers = handlerMap.computeIfAbsent(type, t -> new LinkedHashSet<>());
          if (!handlers.contains(eventHandler)) {
              handlers.add(eventHandler);
          }
      }
  
      @Override
      public <T extends Event> void unregisterEventHandler(EventType<T> type, EventHandler<? super T> eventHandler) {
          if (handlerMap.containsKey(type)) {
              handlerMap.get(type).remove(eventHandler);
          }
      }
  
      public void fireEvent(Event fireEvent) {
          final EventType<? extends Event> type = fireEvent.getType();
          Event event;
          if (fireEvent.getSource()!=source) {
              event = fireEvent.copyFor(source);
          } else {
              event = fireEvent;
          }
          for (EventType<? extends Event> handlerType : handlerMap.keySet()) {
              if (EventType.isInstanceOf(type, handlerType)) {
                      for (EventHandler handler : handlerMap.get(handlerType)) {
                          try {
                              handler.handle(event);
                          } catch (Exception e) {
                              // We catch all errors from handlers
                              log.error("An error occured during event handling: {}", e.getMessage(), e);
                          }
                      }
              }
          }
      }
  }