{
      Some((outpoint, utxo_amount)) => (outpoint, utxo_amount),
      _ => return Err(Self::not_found()),
    };

    let mut transaction = Transaction {
      version: 1,
      lock_time: LockTime::ZERO,
      input: vec![TxIn {
        previous_output: *outpoint,
        script_sig: ScriptBuf::new(),
        sequence: Sequence::ENABLE_RBF_NO_LOCKTIME,
        witness: Witness::new(),
      }],
      output: vec![
        TxOut {
          value: value.to_sat(),
          script_pubkey: address.payload.script_pubkey(),
        },
        TxOut {
          value: (*utxo_amount - value).to_sat(),
          script_pubkey: address.payload.script_pubkey(),
        },
      ],
    };

    #[allow(clippy::cast_possible_truncation)]
    #[allow(clippy::cast_sign_loss)]
    let fee = (fee_rate.unwrap_or(1.0) * transaction.vsize() as f64).round() as u64;

    transaction.output[1].value -= fee;

    state.mempool.push(transaction);

    state.sent.push(Sent {
      address: address.assume_checked(),
      amount,