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// 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.grid.server;

import org.openqa.selenium.events.EventBus;
import org.openqa.selenium.grid.config.Config;
import org.openqa.selenium.internal.Require;

public class EventBusOptions {

  static final String EVENTS_SECTION = "events";
  private static final String DEFAULT_CLASS = "org.openqa.selenium.events.zeromq.ZeroMqEventBus";
  private final Config config;
  private volatile EventBus bus;

  public EventBusOptions(Config config) {
    this.config = Require.nonNull("Config", config);
  }

  public EventBus getEventBus() {
    EventBus localBus = bus;
    if (localBus == null) {
      synchronized (this) {
        localBus = bus;
        if (localBus == null) {
          localBus = createBus();
          bus = localBus;
        }
      }
    }

    return localBus;
  }

  private EventBus createBus() {
    return config.getClass(EVENTS_SECTION, "implementation", EventBus.class, DEFAULT_CLASS);
  }
}
