/*
    * Copyright 2019 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.channel.socket.SocketProtocolFamily;
  
  import java.net.Inet4Address;
  import java.net.Inet6Address;
  import java.net.InetAddress;
  import java.util.Comparator;
  
  final class PreferredAddressTypeComparator implements Comparator<InetAddress> {
  
      private static final PreferredAddressTypeComparator IPv4 = new PreferredAddressTypeComparator(Inet4Address.class);
      private static final PreferredAddressTypeComparator IPv6 = new PreferredAddressTypeComparator(Inet6Address.class);
  
      static PreferredAddressTypeComparator comparator(SocketProtocolFamily family) {
          switch (family) {
              case INET:
                  return IPv4;
              case INET6:
                  return IPv6;
              default:
                  throw new IllegalArgumentException();
          }
      }
  
      private final Class<? extends InetAddress> preferredAddressType;
  
      private PreferredAddressTypeComparator(Class<? extends InetAddress> preferredAddressType) {
          this.preferredAddressType = preferredAddressType;
      }
  
      @Override
      public int compare(InetAddress o1, InetAddress o2) {
          if (o1.getClass() == o2.getClass()) {
              return 0;
          }
          return preferredAddressType.isAssignableFrom(o1.getClass()) ? -1 : 1;
      }
  }