* no data frames to follow.
   *
   * @param streamId server-initiated stream ID: an even number.
   * @param responseHeaders minimally includes `:status`.
   * @param last when true, there is no response data.
   */
  fun onHeaders(
    streamId: Int,
    responseHeaders: List<Header>,
    last: Boolean,
  ): Boolean

  /**

      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      Headers responseHeaders = response.headers();
      for (int i = 0; i < responseHeaders.size(); i++) {
        System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
      }

      System.out.println(response.body().string());
    }
  }

    try (Response response = client.newCall(request).execute()) {
      if (!response.isSuccessful()) {
        Headers responseHeaders = response.headers();
        for (int i = 0; i < responseHeaders.size(); i++) {
          System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
        }

        throw new IOException("Unexpected code " + response);
      }

  }

  private fun send404(
    stream: Http2Stream,
    path: String,
  ) {
    val responseHeaders =
      listOf(
        Header(":status", "404"),
        Header(":version", "HTTP/1.1"),
        Header("content-type", "text/plain"),
      )
    stream.writeHeaders(
      responseHeaders = responseHeaders,
      outFinished = false,
      flushHeaders = false,
    )

      var unexpectedValues = false

      // Parse each header.
      for (i in 0 until responseHeaders.size) {
        if (!responseHeaders.name(i).equals(HEADER_WEB_SOCKET_EXTENSION, ignoreCase = true)) {
          continue // Not a header we're interested in.
        }
        val header = responseHeaders.value(i)

        // Parse each extension.
        var pos = 0
        while (pos < header.length) {

          if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

          Headers responseHeaders = response.headers();
          for (int i = 0, size = responseHeaders.size(); i < size; i++) {
            System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
          }

          System.out.println(responseBody.string());
        }
      }
    });
  }

    client.newCall(request)
      .execute()
      .use { response ->
        if (!response.isSuccessful) {
          val responseHeaders = response.headers
          for (i in 0 until responseHeaders.size) {
            println(responseHeaders.name(i) + ": " + responseHeaders.value(i))
          }
          throw IOException("Unexpected code $response")
        }
        println(response.body.string())