fn select_cardinal_utxo(
    &mut self,
    target_value: Amount,
    prefer_under: bool,
  ) -> Result<(OutPoint, Amount)> {
    tprintln!(
      "looking for {} cardinal worth {target_value}",
      if prefer_under { "smaller" } else { "bigger" }
    );

    let inscribed_utxos = self
      .inscriptions
      .keys()
      .map(|satpoint| satpoint.outpoint)
      .collect::<BTreeSet<OutPoint>>();

    let mut best_match = None;
    for utxo in &self.utxos {
      if inscribed_utxos.contains(utxo) || self.locked_utxos.contains(utxo) {
        continue;
      }

      let current_value = self.amounts[utxo];

      let (_, best_value) = match best_match {
        Some(prev) => prev,
        None => {
          best_match = Some((*utxo, current_value));
          (*utxo, current_value)
        }
      };

      let abs_diff = |a: Amount, b: Amount| -> Amount { max(a, b) - min(a, b) };
      let is_closer = abs_diff(current_value, target_value) < abs_diff(best_value, target_value);

      let not_preference_but_closer = if prefer_under {