getLowestSmartRate function

Implementation

SmartRate getLowestSmartRate(List<SmartRate> smartRates, int deliveryDays,
    SmartRateAccuracy deliveryAccuracy) {
  SmartRate? lowestRate;

  for (SmartRate rate in smartRates) {
    if (rate.price == null) {
      continue; // Skip this rate if it doesn't have a price
    }

    if (lowestRate != null && lowestRate.price == null) {
      // somehow a rate with null got selected in the last iteration, throw an error
      // the guard clause above should have prevented this, so this should never happen
      throw FilteringException(
          'A smart rate with null price was selected in the last iteration');
    }

    if (rate.timeInTransit == null) {
      continue; // Skip this rate if it doesn't have a time in transit
    }

    int? estimatedDeliveryDays =
        rate.timeInTransit?.bySmartRateAccuracy(deliveryAccuracy);

    if (estimatedDeliveryDays == null) {
      continue; // Skip this rate if it doesn't have a time in transit for the given accuracy
    }

    if (estimatedDeliveryDays > deliveryDays) {
      continue; // Skip this rate if the estimated delivery days is greater than the given delivery days
    }

    // if there's no lowest rate yet, use it
    if (lowestRate == null) {
      lowestRate = rate;
      continue;
    }

    // if the rate is lower than the current lowest rate, use it
    if (rate.price! < lowestRate.price!) {
      lowestRate = rate;
      continue;
    }
  }

  if (lowestRate == null) {
    throw FilteringException(ErrorMessages.noMatchingRatesFound);
  }

  return lowestRate;
}