/**
    * 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.hadoop.hbase.ipc;
  
  import com.google.common.base.Preconditions;
  
  import io.netty.channel.Channel;
  import io.netty.channel.EventLoopGroup;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.util.Pair;
  
  /**
   * Helper class for passing config to {@link NettyRpcClient}.
   * <p>
   * As hadoop Configuration can not pass an Object directly, we need to find a way to pass the
   * EventLoopGroup to {@code AsyncRpcClient} if we want to use a single {@code EventLoopGroup} for
   * the whole process.
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public class NettyRpcClientConfigHelper {
  
    public static final String EVENT_LOOP_CONFIG = "hbase.rpc.client.event-loop.config";
  
    private static final String CONFIG_NAME = "global-event-loop";
  
    private static final Map<String, Pair<EventLoopGroup, Class<? extends Channel>>>
      EVENT_LOOP_CONFIG_MAP = new HashMap<>();
  
    /**
     * Set the EventLoopGroup and channel class for {@code AsyncRpcClient}.
     */
    public static void setEventLoopConfig(Configuration conf, EventLoopGroup group,
        Class<? extends Channel> channelClass) {
      Preconditions.checkNotNull(group, "group is null");
      Preconditions.checkNotNull(channelClass, "channel class is null");
      conf.set(EVENT_LOOP_CONFIG, CONFIG_NAME);
      EVENT_LOOP_CONFIG_MAP.put(CONFIG_NAME,
        Pair.<EventLoopGroup, Class<? extends Channel>> newPair(group, channelClass));
    }
  
    /**
     * The {@code AsyncRpcClient} will create its own {@code NioEventLoopGroup}.
     */
    public static void createEventLoopPerClient(Configuration conf) {
      conf.set(EVENT_LOOP_CONFIG, "");
      EVENT_LOOP_CONFIG_MAP.clear();
    }
  
    static Pair<EventLoopGroup, Class<? extends Channel>> getEventLoopConfig(Configuration conf) {
      String name = conf.get(EVENT_LOOP_CONFIG);
      if (name == null) {
        return DefaultNettyEventLoopConfig.GROUP_AND_CHANNEL_CLASS;
      }
      if (StringUtils.isBlank(name)) {
        return null;
      }
      return EVENT_LOOP_CONFIG_MAP.get(name);
    }
  
  }