// One finite response per delivered observation at this battery. Cancellation
// does not turn the same radio message into new ammunition authorization.
class ERR_MortarReportLedger
{
 protected ref map<int, float> m_Attempts = new map<int, float>();

 bool Available(int messageId, float observedAt, float now)
 {
  if (messageId <= 0 || observedAt < 0 || now < observedAt || now - observedAt > ERR_MortarPrediction.MAX_REPORT_AGE_MS) return false;
  for (int i = m_Attempts.Count() - 1; i >= 0; i--)
   if (now - m_Attempts.GetElement(i) > ERR_MortarPrediction.MAX_REPORT_AGE_MS) m_Attempts.Remove(m_Attempts.GetKey(i));
  return !m_Attempts.Contains(messageId) && m_Attempts.Count() < 128;
 }
 bool Claim(int messageId, float observedAt, float now)
 {
  if (!Available(messageId, observedAt, now)) return false;
  m_Attempts.Insert(messageId, observedAt);
  return true;
 }
}