import java.net.InetAddress;
import java.text.ParseException;
import org.jspecify.annotations.Nullable;

/**
 * A syntactically valid host specifier, suitable for use in a URI. This may be either a numeric IP
 * address in IPv4 or IPv6 notation, or a domain name.
 *
 * <p>Because this class is intended to represent host specifiers which can reasonably be used in a

            return false;
        }
    }

    /**
     * Formats an IP address string for use in a URL.
     * IPv6 addresses are wrapped in brackets, IPv4 addresses are returned as-is.
     *
     * @param address the IP address string to format
     * @return the formatted address (IPv6 with brackets, IPv4 unchanged)
     */
    public static String formatForUrl(final String address) {
        if (address == null) {

    }
  }

  /** No SNI for literal IPv6 addresses. */
  @Test
  fun ipv6() {
    val recordedRequest = requestToHostnameViaProxy("2607:f8b0:400b:804::200e")
    assertThat(recordedRequest.url.host).isEqualTo("2607:f8b0:400b:804::200e")
    assertThat(recordedRequest.handshakeServerNames).isEmpty()
  }

  /** No SNI for literal IPv4 addresses. */
  @Test
  fun ipv4() {

				// Number of probes.
				// ~ cat /proc/sys/net/ipv4/tcp_keepalive_probes (defaults to 9, we reduce it to 5)
				_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPCNT, 5)

				// Wait time after successful probe in seconds.
				// ~ cat /proc/sys/net/ipv4/tcp_keepalive_intvl (defaults to 75 secs, we reduce it to 15 secs)

		// 127.0.0.1 is moved to the end of the list.
		if ipV4s[i].IsLoopback() {
			return false
		}
		if ipV4s[j].IsLoopback() {
			return true
		}
		return []byte(ipV4s[i].To4())[3] > []byte(ipV4s[j].To4())[3]
	})

	var ips []string
	for _, ip := range ipV4s {
		ips = append(ips, ip.String())
	}

	return append(nonIPs, ips...)
}

  private fun decodeIpv6(input: String): ByteArray? = decodeIpv6(input, 0, input.length)

  @Test
  fun testToCanonicalHost() {
    // IPv4
    assertThat("127.0.0.1".toCanonicalHost()).isEqualTo("127.0.0.1")
    assertThat("1.2.3.4".toCanonicalHost()).isEqualTo("1.2.3.4")

    // IPv6
    assertThat("::1".toCanonicalHost()).isEqualTo("::1")
    assertThat("2001:db8::1".toCanonicalHost()).isEqualTo("2001:db8::1")

     * @return IP address
     */
    public InetAddress getAddress() {
        return address;
    }

    /**
     * Check if this is an IPv6 address
     *
     * @return true if IPv6, false if IPv4
     */
    public boolean isIpv6() {
        return ipv6;
    }

    /**
     * Check if RSS is supported
     *
     * @return true if RSS capable
     */
    public boolean isRssCapable() {

    /** Kerberos protocol version */
    String KERBEROS_VERSION = "5";

    /** Kerberos AP-REQ message type */
    String KERBEROS_AP_REQ = "14";

    /** Address family: Internet (IPv4) */
    int AF_INTERNET = 2;
    /** Address family: CHANET */
    int AF_CHANET = 5;
    /** Address family: XNS */
    int AF_XNS = 6;
    /** Address family: ISO */
    int AF_ISO = 7;

 * [system DNS service][SYSTEM], which is the default. Some applications may provide their own
 * implementation to use a different DNS server, to prefer IPv6 addresses, to prefer IPv4 addresses,
 * or to force a specific known IP address.
 *
 * Implementations of this interface must be safe for concurrent use.
 */
fun interface Dns {
  /**

        IdnDnsResolver resolver = new IdnDnsResolver();

        // Test IPv6 loopback address with brackets
        String host = "[::1]";
        InetAddress[] addresses = resolver.resolve(host);
        assertNotNull(addresses);
        assertTrue(addresses.length > 0);
        // IPv6 loopback can be represented as ::1 or 0:0:0:0:0:0:0:1
        String hostAddress = addresses[0].getHostAddress();