val headers =
      Headers.Builder()
        .add("WWW-Authenticate: Basic realm=\"protected area\", charset=\"US-ASCII\"")
        .build()
    val expectedAuthParams = mutableMapOf<String?, String>()
    expectedAuthParams["realm"] = "protected area"
    expectedAuthParams["charset"] = "US-ASCII"
    assertThat(headers.parseChallenges("WWW-Authenticate"))
      .isEqualTo(listOf(Challenge("Basic", expectedAuthParams)))
  }

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

import okio.Buffer
import okio.ByteString.Companion.encodeUtf8

/**
 * An [RFC 3492] punycode decoder for converting ASCII to Unicode domain name labels. This is
 * intended for use in Internationalized Domain Names (IDNs).
 *
 * This class contains a Kotlin implementation of the pseudocode specified by RFC 3492. It includes

 * example this converts `☃.net` to `xn--n3h.net`, and `WwW.GoOgLe.cOm` to `www.google.com`.
 * `null` will be returned if the host cannot be ToASCII encoded or if the result contains
 * unsupported ASCII characters.
 */
internal fun String.toCanonicalHost(): String? {
  val host: String = this

  // If the input contains a :, it’s an IPv6 address.
  if (":" in host) {

    encapsulation enabled.
 *  Fix: Strictly verify hostnames used with OkHttp's `HostnameVerifier`. Programs that make direct
    manual calls to `HostnameVerifier` could be defeated if the hostnames they pass in are not
    strictly ASCII. This issue is tracked as [CVE-2021-0341].


## Version 4.9.1

_2021-01-30_

 *  Fix: Work around a crash in Android 10 and 11 that may be triggered when two threads

internal object DnsRecordCodec {
  private const val SERVFAIL = 2
  private const val NXDOMAIN = 3
  const val TYPE_A = 0x0001
  const val TYPE_AAAA = 0x001c
  private const val TYPE_PTR = 0x000c
  private val ASCII = Charsets.US_ASCII

  fun encodeQuery(
    host: String,
    type: Int,
  ): ByteString =
    Buffer().apply {
      writeShort(0) // query id
      writeShort(256) // flags with recursion

  }

  @Test fun prohibitionCharactersSpaces() {
    assertThat(stringPrep(" ")).isEqualTo(" ") // ASCII space not prohibited.
    assertThat(stringPrep("\u2003")).isNull() // EM SPACE
  }

  @Test fun prohibitionControlCharacters() {
    assertThat(stringPrep("\u007f")).isEqualTo("\u007f") // ASCII delete not prohibited.
    assertThat(stringPrep("\u0080")).isNull()
    assertThat(stringPrep("\u2029")).isNull()

 *
 * Mappings may overlap.
 *
 * ASCII-Only
 * ==========
 *
 * Neither the section index nor the ranges data use bit 0x80 anywhere. That means the data is
 * strictly ASCII. This is intended to make it efficient to encode this data as a string, and to
 * index into it as a string.
 *
 * The mappings data contains non-ASCII characters.
 */
internal class IdnaMappingTable internal constructor(

 *
 *  * In queries, ' ' is encoded to '+' and '+' is encoded to "%2B".
 *
 *  * Characters in `encodeSet` are percent-encoded.
 *
 *  * Control characters and non-ASCII characters are percent-encoded.
 *
 *  * All other characters are copied without transformation.
 *
 * @param alreadyEncoded true to leave '%' as-is; false to convert it to '%25'.

    // Less than 16,384 chars, because we index on a 14-bit index in the ranges table.
    assertThat(compactTable.mappings.length).isLessThan(1 shl 14)

    // Confirm the data strings are ASCII.
    for (dataString in listOf<String>(compactTable.sections, compactTable.ranges)) {
      for (codePoint in dataString.codePoints()) {
        assertThat(codePoint and 0x7f).isEqualTo(codePoint)
      }
    }

    /** Arbitrary code point that's 4 bytes in UTF-8 and valid in IdnaMappingTable.txt. */
    private const val UNICODE_4 = 0x1d11e

    /**
     * Returns a new instance configured with a default encode set for the ASCII range. The specific
     * rules vary per-component: for example, '?' may be identity-encoded in a fragment, but must be
     * percent-encoded in a path.
     *
     * See https://url.spec.whatwg.org/#percent-encoded-bytes