# send.ludic - every frame: a batch when one is due, its answer when it lands, the wait doubled
# when it failed, the queue on disk every few seconds. One request at a time; nothing waits on it.

export function telemetry_tick(telemetry_st: mut TelemetryState) -> void {
  if not telemetry_st.telemetry__ready { return }
  telemetry__id_tick(telemetry_st)
  if not telemetry__enabled() {
    if telemetry_st.telemetry__n > 0 or telemetry_st.telemetry__h >= 0 { telemetry_forget(telemetry_st) }
    return
  }
  if not telemetry__can_send(telemetry_st) { return }
  let now = telemetry__now()
  let c = telemetry__conf(telemetry_st)
  if not telemetry_st.telemetry__clock_on {
    telemetry_st.telemetry__clock_on = true
    telemetry_st.telemetry__next_ms = now + c.flush_ms
    telemetry_st.telemetry__saved_ms = now
  }
  if now - telemetry_st.telemetry__saved_ms >= c.save_ms {
    telemetry_save(telemetry_st)
    telemetry_st.telemetry__saved_ms = now
  }
  if telemetry_st.telemetry__h >= 0 {
    telemetry__answer(telemetry_st, now)
    return
  }
  if telemetry_st.telemetry__n == 0 { return }
  let early = telemetry_st.telemetry__fails == 0 and telemetry_st.telemetry__n >= c.flush_at
  if early or now >= telemetry_st.telemetry__next_ms {
    telemetry_save(telemetry_st)
    telemetry__flush(telemetry_st, now)
    if telemetry_st.telemetry__fails == 0 { telemetry_st.telemetry__next_ms = now + c.flush_ms }
  }
}

function telemetry__answer(telemetry_st: mut TelemetryState, now: int) -> void {
  let st = telemetry__poll(telemetry_st.telemetry__h)
  if st < 0 { return }
  telemetry_st.telemetry__h = -1
  if st > 0 {
    tr_drop(telemetry_st, telemetry_st.telemetry__sent_n)
    telemetry_st.telemetry__fails = 0
    telemetry_st.telemetry__next_ms = now + telemetry__conf(telemetry_st).flush_ms
    telemetry__fact(telemetry_st, TELEMETRY_SENT, telemetry_st.telemetry__sent_n, st, 0)
  } else {
    telemetry__backoff(telemetry_st, now)
    telemetry__fact(telemetry_st, TELEMETRY_FAILED, telemetry_st.telemetry__sent_n, st, telemetry_st.telemetry__next_ms - now)
  }
  telemetry_save(telemetry_st)
}

function telemetry__flush(telemetry_st: mut TelemetryState, now: int) -> void {
  if telemetry_st.telemetry__h >= 0 or len(telemetry_st.telemetry__id) == 0 or telemetry_st.telemetry__n == 0 { return }
  let n = min(telemetry__conf(telemetry_st).batch, telemetry_st.telemetry__n)
  tb_batch(telemetry_st, n)
  let h = telemetry__send(telemetry_st, telemetry_st.telemetry__out.b, sb_len(telemetry_st.telemetry__out))
  if h < 0 {
    telemetry__backoff(telemetry_st, now)
    telemetry__fact(telemetry_st, TELEMETRY_FAILED, n, 0, telemetry_st.telemetry__next_ms - now)
    return
  }
  telemetry_st.telemetry__h = h
  telemetry_st.telemetry__sent_n = n
}

# a failed send: wait twice as long next time, up to backoff_max doublings
function telemetry__backoff(telemetry_st: mut TelemetryState, now: int) -> void {
  if telemetry_st.telemetry__fails < telemetry__conf(telemetry_st).backoff_max { telemetry_st.telemetry__fails += 1 }
  telemetry_st.telemetry__next_ms = now + (telemetry__conf(telemetry_st).flush_ms << telemetry_st.telemetry__fails)
}