package com.atlassian.event.legacy;
   
   import com.atlassian.event.Event;
   import com.atlassian.event.EventListener;
   import com.atlassian.event.spi.ListenerHandler;
   import com.atlassian.event.spi.ListenerInvoker;
   import com.google.common.collect.Sets;
   
   import java.util.Collections;
  import java.util.List;
  import java.util.Set;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  /**
   * A listener handler to deal with legacy {@link com.atlassian.event.EventListener event listeners}
   *
   * @see com.atlassian.event.EventListener
   * @see Event
   * @since 2.0
   */
  public class LegacyListenerHandler implements ListenerHandler {
      public List<? extends ListenerInvoker> getInvokers(Object listener) {
          return checkNotNull(listener) instanceof EventListener
                  ? getLegacyListenerInvoker((EventListener) listener)
                  : Collections.<ListenerInvoker>emptyList();
      }
  
      private List<? extends ListenerInvoker> getLegacyListenerInvoker(EventListener eventListener) {
          return Collections.singletonList(new LegacyListenerInvoker(eventListener));
      }
  
      private static class LegacyListenerInvoker implements ListenerInvoker {
          private final EventListener eventListener;
  
          public LegacyListenerInvoker(EventListener eventListener) {
              this.eventListener = checkNotNull(eventListener);
          }
  
          public Set<Class<?>> getSupportedEventTypes() {
              Class[] classes = eventListener.getHandledEventClasses();
              if (classes.length == 0)
                  return Collections.<Class<?>>singleton(Event.class);
              else
                  return Sets.<Class<?>>newHashSet(classes);
          }
  
          public void invoke(Object event) {
              eventListener.handleEvent((Event) event);
          }
  
          public boolean supportAsynchronousEvents() {
              return true;
          }
  
          @Override
          public String toString() {
              return "LegacyListenerInvoker{eventListener=" + eventListener + '}';
          }
      }
  }