Fix the fedimint sweep fee for max balance

mutiny-core/src/federation.rs

@@ -571,7 +571,7 @@ impl<S: MutinyStorage> FederationClient<S> {
                 }
             }
         };
-        inv.fees_paid = Some(outgoing_payment.fee.sats_round_down());
+        inv.fees_paid = Some(sats_round_up(&outgoing_payment.fee));
 
         self.maybe_update_after_checking_fedimint(inv.clone())
             .await?;
@@ -617,6 +617,11 @@ impl<S: MutinyStorage> FederationClient<S> {
     }
 }
 
+fn sats_round_up(amount: &Amount) -> u64 {
+    let rounded = Amount::from_msats(amount.msats + 999).sats_round_down();
+    rounded
+}
+
 // Get a preferred gateway from a federation
 fn get_gateway_preference(
     gateways: Vec<fedimint_ln_common::LightningGatewayAnnouncement>,

mutiny-core/src/lib.rs

@@ -1232,6 +1232,7 @@ impl<S: MutinyStorage> MutinyWallet<S> {
         );
 
         let fees = fedimint_client.gateway_fee().await?;
+        // FIXME: this is still producing off by one. check round down
         let amt = max_spendable_amount(current_balance, &fees)
             .map_or(Err(MutinyError::InsufficientBalance), Ok)?;
         log_debug!(self.logger, "max spendable: {}", amt);
@@ -1276,9 +1277,10 @@ impl<S: MutinyStorage> MutinyWallet<S> {
             );
         }
 
+        let total_fees = first_invoice_res.fees_paid.unwrap_or(0) + fee;
         Ok(FedimintSweepResult {
-            amount: first_invoice_amount,
-            fees: Some(first_invoice_res.fees_paid.unwrap_or(0) + fee),
+            amount: current_balance - total_fees,
+            fees: Some(total_fees),
         })
     }