content: /*
   * Copyright (C) 2020 ActiveJ LLC.
   *
   * Licensed 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 io.activej.dns;
  
  import io.activej.common.annotation.ComponentInterface;
  import io.activej.dns.protocol.*;
  import io.activej.http.HttpUtils;
  import io.activej.promise.Promise;
  import org.jetbrains.annotations.Nullable;
  
  import java.net.InetAddress;
  
  /**
   * Components implementing this interface can resolve given domain names into
   * their respective IP addresses.
   * If host is not recognized or connection to DNS server timed out it will
   * fail with a respective {@link DnsQueryException}.
   */
  @ComponentInterface
  public interface IDnsClient {
  	/**
  	 * Searches for an IPv4 for the given domain
  	 *
  	 * @param domainName domain name for to get IP for
  	 */
  	default Promise<DnsResponse> resolve4(String domainName) {
  		return resolve(DnsQuery.ipv4(domainName));
  	}
  
  	/**
  	 * Searches for an IPv6 for the given domain
  	 *
  	 * @param domainName domain name for to get IP for
  	 */
  	default Promise<DnsResponse> resolve6(String domainName) {
  		return resolve(DnsQuery.ipv6(domainName));
  	}
  
  	/**
  	 * Searches for an IP for the given query
  	 *
  	 * @param query domain and IP version
  	 */
  	Promise<DnsResponse> resolve(DnsQuery query);
  
  	/**
  	 * Closes the underlying UDP socket if it's open.
  	 * Note that on next {@link #resolve} call it will be created again.
  	 * Any pending requests will be completed with timeout exception.
  	 */
  	void close();
  
  	/**
  	 * Checks if query already contains an IP and returns fake {@link DnsResponse} for it and <code>null</code> otherwise.
  	 *
  	 * @param query query which might contain an IP
  	 * @return fake query response if is does and <code>null</code> if it does not
  	 */
  	static @Nullable DnsResponse resolveFromQuery(DnsQuery query) {
  		if ("localhost".equals(query.getDomainName())) {
  			InetAddress[] ips = {InetAddress.getLoopbackAddress()};
  			return DnsResponse.of(DnsTransaction.of((short) 0, query), DnsResourceRecord.of(ips, 0));
  		}
  		if (HttpUtils.isInetAddress(query.getDomainName())) {
  			InetAddress[] ips = {HttpUtils.inetAddress(query.getDomainName())};
  			return DnsResponse.of(DnsTransaction.of((short) 0, query), DnsResourceRecord.of(ips, 0));
  		}
  		return null;
  	}
  }
  