*/
package org.codelibs.fess.util;

import java.net.Inet6Address;
import java.net.InetAddress;

/**
 * Utility class for handling IP addresses, particularly IPv6 addresses in URLs.
 * This class provides methods to properly format IPv6 addresses for use in URLs
 * by adding brackets where necessary.
 */
public final class IpAddressUtil {

    /**

    /**
     * Resolves the given host name to an array of IP addresses.
     * The host name is first converted to ASCII using IDN before resolution.
     * IPv6 addresses in bracket notation (e.g., [::1] or [2001:db8::1]) are
     * handled specially by removing the brackets before resolution.
     *
     * @param host the host name to resolve
     * @return an array of IP addresses for the host

  private var nextAddress = 0xff000064L // 255.0.0.100 in IPv4; ::ff00:64 in IPv6.

  /** Sets the results for `hostname`.  */
  operator fun set(
    hostname: String,
    addresses: List<InetAddress>,
  ): FakeDns {
    hostAddresses[hostname] = addresses
    return this
  }

  /** Clears the results for `hostname`.  */
  fun clear(hostname: String): FakeDns {
    hostAddresses.remove(hostname)
    return this
  }

    /**
     * Resolves the given host name to an array of IP addresses.
     * The host name is first converted to ASCII using IDN before resolution.
     * IPv6 addresses in bracket notation (e.g., [::1] or [2001:db8::1]) are
     * handled specially by removing the brackets before resolution.
     *
     * @param host the host name to resolve
     * @return an array of IP addresses for the host

   * an IPv4 address or not.
   *
   * <p>IPv6 addresses are <b>coerced</b> to IPv4 addresses before being converted to integers.
   *
   * <p>As long as there are applications that assume that all IP addresses are IPv4 addresses and
   * can therefore be converted safely to integers (for whatever purpose) this function can be used
   * to handle IPv6 addresses as well until the application is suitably fixed.
   *

They're also concrete: each URL identifies a specific path (like `/square/okhttp`) and query (like `?q=sharks&lang=en`). Each webserver hosts many URLs.

### [Addresses](https://square.github.io/okhttp/5.x/okhttp/okhttp3/-address/)

Addresses specify a webserver (like `github.com`) and all of the **static** configuration necessary to connect to that server: the port number, HTTPS settings, and preferred network protocols (like HTTP/2).

    @Test
    public void testIsIPv6Address() {
        // IPv6 addresses
        assertTrue(IpAddressUtil.isIPv6Address("::1"));
        assertTrue(IpAddressUtil.isIPv6Address("2001:db8::1"));
        assertTrue(IpAddressUtil.isIPv6Address("fe80::1"));
        assertTrue(IpAddressUtil.isIPv6Address("2001:0db8:0000:0000:0000:ff00:0042:8329"));

        // IPv4 addresses
        assertFalse(IpAddressUtil.isIPv6Address("127.0.0.1"));

     * fallbacks to prevent the host machine's various IP addresses from interfering.
     */
    private val SINGLE_INET_ADDRESS_DNS =
      Dns { hostname ->
        val addresses = Dns.SYSTEM.lookup(hostname)
        listOf(addresses[0])
      }

    private operator fun Throwable?.plus(throwable: Throwable): Throwable {
      if (this != null) {

    // 2 6to4 addresses differing in the embedded IPv4 address should
    // hash to the different values.
    assertThat(InetAddresses.getCoercedIPv4Address(InetAddresses.forString("2002:0102:0304::1")))
        .isNotEqualTo(
            InetAddresses.getCoercedIPv4Address(InetAddresses.forString("2002:0506:0708::1")));

    // 2 6to4 addresses NOT differing in the embedded IPv4 address should

/**
 * This test binds two different web servers (IPv4 and IPv6) to the same port, but on different
 * local IP addresses. Requests made to `127.0.0.1` will reach the IPv4 server, and requests made to
 * `::1` will reach the IPv6 server.
 *
 * By orchestrating two different servers with the same port but different IP addresses, we can
 * test what OkHttp does when both are reachable, or if only one is reachable.
 *