fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink

  /** This should update the HTTP engine's sentRequestMillis field. */
  @Throws(IOException::class)
  fun writeRequestHeaders(request: Request)

  /** Flush the request to the underlying socket. */
  @Throws(IOException::class)
  fun flushRequest()

    val hasRequestBody = HttpMethod.permitsRequestBody(request.method) && requestBody != null
    val isUpgradeRequest = "upgrade".equals(request.header("Connection"), ignoreCase = true)
    try {
      exchange.writeRequestHeaders(request)

      if (hasRequestBody) {
        // If there's a "Expect: 100-continue" header on the request, wait for a "HTTP/1.1 100

  override val socket: Socket
    get() = stream!!

  override fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink = stream!!.sink

  override fun writeRequestHeaders(request: Request) {
    if (stream != null) return

    val hasRequestBody = request.body != null
    val requestHeaders = http2HeadersList(request)
    stream = http2Connection.newStream(requestHeaders, hasRequestBody)