import okhttp3.Dns.Companion.SYSTEM

/**
 * A domain name service that resolves IP addresses for host names. Most applications will use the
 * [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.
 */

 * addresses nor hostnames; they will be verified as IP addresses (which is a more strict
 * verification).
 */
private val VERIFY_AS_IP_ADDRESS = "([0-9a-fA-F]*:[0-9a-fA-F:.]*)|([\\d.]+)".toRegex()

/** Returns true if this string is not a host name and might be an IP address. */
fun String.canParseAsIpAddress(): Boolean = VERIFY_AS_IP_ADDRESS.matches(this)

/**

 * limitations under the License.
 */
package okhttp3.internal

import java.net.InetAddress
import okhttp3.Dns

/**
 * A network that always resolves two IP addresses per host. Use this when testing route selection
 * fallbacks to guarantee that a fallback address is available.
 */
class DoubleInetAddressDns : Dns {
  override fun lookup(hostname: String): List<InetAddress> {

    rather than the duration specified in the response's cache-control header.
 *  Fix: Verify certificate IP addresses in canonical form. When a server presents a TLS certificate
    containing an IP address we must match that address against the URL's IP address, even when the
    two addresses are encoded differently, such as `192.168.1.1` and `0::0:0:FFFF:C0A8:101`. Note

    // https://daniel.haxx.se/blog/2016/08/18/http2-connection-coalescing/

    // 1. This connection must be HTTP/2.
    if (http2Connection == null) return false

    // 2. The routes must share an IP address.
    if (routes == null || !routeMatchesAny(routes)) return false

    // 3. This connection's server certificate's must cover the new host.
    if (address.hostnameVerifier !== OkHostnameVerifier) return false

  companion object {
    /** Obtain a host string containing either an actual host name or a numeric IP address. */
    val InetSocketAddress.socketHost: String get() {
      // The InetSocketAddress was specified with a string (either a numeric IP or a host name). If
      // it is a name, all IPs for that name should be tried. If it is an IP address, only that IP
      // address should be tried.
      val address = address ?: return hostName

        derReader.readOctetString()
      }
    }.also { expected ->
      assertThat(expected).hasMessage("constructed octet strings not supported for DER")
    }
  }

  @Test fun `choice IP address`() {
    val bytes = "8704c0a80201".decodeHex()
    val localhost = InetAddress.getByName("192.168.2.1").address.toByteString()
    assertThat(CertificateAdapters.generalName.fromDer(bytes))

/**
 * 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.
 *

There may be many routes for a single address. For example, a webserver that is hosted in multiple datacenters may yield multiple IP addresses in its DNS response.

 *    [proxy selector][java.net.ProxySelector] is used. It may return multiple proxies to attempt.
 *  * **IP address:** whether connecting directly to an origin server or a proxy, opening a socket
 *    requires an IP address. The DNS server may return multiple IP addresses to attempt.
 *
 * Each route is a specific selection of these options.
 */
class Route(
  @get:JvmName("address") val address: Address,