val reader = ServerSentEventReader(body.source(), this)
      try {
        if (!canceled) {
          listener.onOpen(this, response)
          while (!canceled && reader.processNextEvent()) {
          }
        }
      } catch (e: Exception) {
        val exception =
          when {
            canceled -> IOException("canceled", e)
            else -> e
          }

   * data section was empty. Any number of calls to [Callback.onRetryChange] may occur while
   * processing an event.
   *
   * @return false when EOF is reached
   */
  @Throws(IOException::class)
  fun processNextEvent(): Boolean {
    var id = lastId
    var type: String? = null
    val data = Buffer()

    while (true) {
      when (source.select(options)) {
        in 0..2 -> {
          completeEvent(id, type, data)

          callbacks.add(timeMs)
        }
      }
    val buffer = Buffer().writeUtf8(source)
    val reader = ServerSentEventReader(buffer, callback)
    while (reader.processNextEvent()) {
    }
    assertThat(buffer.size, "Unconsumed buffer: ${buffer.readUtf8()}")
      .isEqualTo(0)
  }