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   /*
    * Copyright 2020 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty.resolver.dns;
  
  import io.netty.handler.codec.dns.DnsQuestion;
  import io.netty.handler.logging.LogLevel;
  import io.netty.util.internal.logging.InternalLogLevel;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  /**
   * A {@link DnsQueryLifecycleObserverFactory} that enables detailed logging in the {@link DnsNameResolver}.
   * <p>
   * When {@linkplain DnsNameResolverBuilder#dnsQueryLifecycleObserverFactory(DnsQueryLifecycleObserverFactory)
   * configured on the resolver}, detailed trace information will be generated so that it is easier to understand the
   * cause of resolution failure.
   */
  public final class LoggingDnsQueryLifeCycleObserverFactory implements DnsQueryLifecycleObserverFactory {
      private static final InternalLogger DEFAULT_LOGGER =
              InternalLoggerFactory.getInstance(LoggingDnsQueryLifeCycleObserverFactory.class);
      private final InternalLogger logger;
      private final InternalLogLevel level;
  
      /**
       * Create {@link DnsQueryLifecycleObserver} instances that log events at the default {@link LogLevel#DEBUG} level.
       */
      public LoggingDnsQueryLifeCycleObserverFactory() {
          this(LogLevel.DEBUG);
      }
  
      /**
       * Create {@link DnsQueryLifecycleObserver} instances that log events at the given log level.
       * @param level The log level to use for logging resolver events.
       */
      public LoggingDnsQueryLifeCycleObserverFactory(LogLevel level) {
          this.level = checkAndConvertLevel(level);
          logger = DEFAULT_LOGGER;
      }
  
      /**
       * Create {@link DnsQueryLifecycleObserver} instances that log events to a logger with the given class context,
       * at the given log level.
       * @param classContext The class context for the logger to use.
       * @param level The log level to use for logging resolver events.
       */
      public LoggingDnsQueryLifeCycleObserverFactory(Class<?> classContext, LogLevel level) {
          this.level = checkAndConvertLevel(level);
          logger = InternalLoggerFactory.getInstance(checkNotNull(classContext, "classContext"));
      }
  
      /**
       * Create {@link DnsQueryLifecycleObserver} instances that log events to a logger with the given name context,
       * at the given log level.
       * @param name The name for the logger to use.
       * @param level The log level to use for logging resolver events.
       */
      public LoggingDnsQueryLifeCycleObserverFactory(String name, LogLevel level) {
          this.level = checkAndConvertLevel(level);
          logger = InternalLoggerFactory.getInstance(checkNotNull(name, "name"));
      }
  
      private static InternalLogLevel checkAndConvertLevel(LogLevel level) {
          return checkNotNull(level, "level").toInternalLevel();
      }
  
      @Override
      public DnsQueryLifecycleObserver newDnsQueryLifecycleObserver(DnsQuestion question) {
          return new LoggingDnsQueryLifecycleObserver(question, logger, level);
      }
  }