code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC 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.openqa.selenium.events.local;
  
  import com.google.common.eventbus.EventBus;
  import com.google.common.eventbus.Subscribe;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.function.Consumer;
  import org.openqa.selenium.events.Event;
  import org.openqa.selenium.events.EventListener;
  import org.openqa.selenium.events.EventName;
  import org.openqa.selenium.grid.config.Config;
  import org.openqa.selenium.internal.Require;
  
  public class GuavaEventBus implements org.openqa.selenium.events.EventBus {
  
    private final EventBus guavaBus;
    private final List<Listener> allListeners = new LinkedList<>();
  
    public GuavaEventBus() {
      guavaBus = new EventBus();
    }
  
    @Override
    public boolean isReady() {
      return true;
    }
  
    @Override
    public void addListener(EventListener<?> listener) {
      Require.nonNull("Listener", listener);
  
      Listener guavaListener = new Listener(listener.getEventName(), listener);
      allListeners.add(guavaListener);
      guavaBus.register(guavaListener);
    }
  
    @Override
    public void fire(Event event) {
      guavaBus.post(Require.nonNull("Event", event));
    }
  
    @Override
    public void close() {
      allListeners.forEach(guavaBus::unregister);
      allListeners.clear();
    }
  
    public static GuavaEventBus create(Config config) {
      return new GuavaEventBus();
    }
  
    private static class Listener {
  
      private final EventName eventName;
      private final Consumer<Event> onType;
  
      public Listener(EventName eventName, Consumer<Event> onType) {
        this.eventName = Require.nonNull("Event type", eventName);
        this.onType = Require.nonNull("Event listener", onType);
      }
  
      @Subscribe
      public void handle(Event event) {
        if (eventName.equals(event.getType())) {
          onType.accept(event);
        }
      }
    }
  }
  