/** The socket that carries this exchange. */
  val socket: Socket

  /** Returns an output stream where the request body can be streamed. */
  @Throws(IOException::class)
  fun createRequestBody(
    request: Request,
    contentLength: Long,
  ): Sink

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

  @Volatile
  private var canceled = false

  override val isResponseComplete: Boolean
    get() = stream?.isSourceComplete == true

  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

            exchange.flushRequest()
            val bufferedRequestBody = exchange.createRequestBody(request, true).buffer()
            requestBody.writeTo(bufferedRequestBody)
          } else {
            // Write the request body if the "Expect: 100-continue" expectation was met.
            val bufferedRequestBody = exchange.createRequestBody(request, false).buffer()
            requestBody.writeTo(bufferedRequestBody)