bufferA.writeUtf8(normalized)

  // 3. For each label, convert/validate Punycode.
  val decoded = Punycode.decode(bufferA.readUtf8()) ?: return null

  // 4.1 Validate.

  // Must be NFC.
  if (decoded != normalizeNfc(decoded)) return null

  // TODO: Must not begin with a combining mark.
  // TODO: Each character must be 'valid' or 'deviation'. Not mapped.
  // TODO: CheckJoiners from IDNA 2008

  }

  /**
   * UTS 46 Validity Criteria: Decoded punycode must be NFC.
   *
   * https://www.unicode.org/reports/tr46/#Validity_Criteria
   */
  @Test
  fun hostnameInPunycodeNfcAndNfd() {
    // café can be NFC (é is one code point) or NFD (e plus ´ as two code points).
    val hostNfc = "café.com"
    val hostNfcPunycode = "xn--caf-dma.com"