rpcserver: AddInvoice uses new helper methods

Author: GeorgeTsagk

rpcserver.go

@@ -7717,13 +7717,6 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 			"amount")
 	}
 
-	// In order to avoid repeating the following check let's assign it to a
-	// boolean for easier access.
-	var satsMode bool
-	if amtMsat != 0 {
-		satsMode = true
-	}
-
 	// The peer public key is optional if there is only a single asset
 	// channel.
 	var peerPubKey *route.Vertex
@@ -7758,60 +7751,14 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 		time.Duration(expirySeconds) * time.Second,
 	)
 
-	maxUnits := req.AssetAmount
-
-	// If the invoice defines the desired amount in satoshis, we need to
-	// query our oracle first to get an estimation on the asset rate. This
-	// will help us establish a quote with the correct amount of asset
-	// units.
-	if satsMode {
-		oracleRes, err := r.cfg.PriceOracle.QueryBidPrice(
-			ctx, specifier, fn.None[uint64](), fn.Some(amtMsat),
-			fn.None[rfqmsg.AssetRate](),
-		)
-		if err != nil {
-			return nil, err
-		}
-
-		if oracleRes.Err != nil {
-			return nil, fmt.Errorf("cannot query oracle: %v",
-				oracleRes.Err.Error())
-		}
-
-		assetUnits := rfqmath.MilliSatoshiToUnits(
-			amtMsat, oracleRes.AssetRate.Rate,
-		)
-
-		maxUnits = assetUnits.ToUint64()
-	}
-
-	// Since we used a different oracle price query above calculate the max
-	// amount of units, we want to add some breathing room to account for
-	// price fluctuations caused by the small time delay, plus the fact that
-	// the agreed upon quote may be different. If we don't add this safety
-	// window the peer may allow a routable amount that evaluates to less
-	// than what we ask for.
-	tolerance := rfqmath.NewBigIntFromUint64(
+	maxUnits, err := calculateAssetMaxAmount(
+		ctx, r.cfg.PriceOracle, specifier, req.AssetAmount, iReq,
 		r.cfg.RfqManager.GetPriceDeviationPpm(),
 	)
-
-	// Parse the max asset units to the rfqmath type.
-	maxMathUnits := rfqmath.NewBigIntFromUint64(maxUnits)
-
-	// Calculate the tolerance margin.
-	toleranceUnits := maxMathUnits.Mul(tolerance).Div(
-		rfqmath.NewBigIntFromUint64(1_000_000),
-	)
-
-	// Apply the tolerance margin twice. Once due to the ask/bid price
-	// deviation that may occur during rfq negotiation, and once for the
-	// price movement that may occur between querying the oracle and
-	// acquiring the quote. We don't really care about this margin being too
-	// big, this only affects the max units our peer agrees to route.
-	maxMathUnits = maxMathUnits.Add(toleranceUnits).Add(toleranceUnits)
-
-	// Now parse the result back to uint64.
-	maxUnits = maxMathUnits.ToUint64()
+	if err != nil {
+		return nil, fmt.Errorf("error calculating asset max "+
+			"amount: %w", err)
+	}
 
 	rpcSpecifier := marshalAssetSpecifier(specifier)
 
@@ -7847,68 +7794,14 @@ func (r *rpcServer) AddInvoice(ctx context.Context,
 		return nil, fmt.Errorf("unexpected response type: %T", r)
 	}
 
-	// Now that we have the accepted quote, we know the amount in Satoshi
-	// that we need to pay. We can now update the invoice with this amount.
-	//
-	// First, un-marshall the ask asset rate from the accepted quote.
-	askAssetRate, err := rfqrpc.UnmarshalFixedPoint(
-		acceptedQuote.AskAssetRate,
+	invoiceAmtMsat, err := validateInvoiceAmount(
+		acceptedQuote, req.AssetAmount, iReq,
 	)
 	if err != nil {
-		return nil, fmt.Errorf("error unmarshalling ask asset rate: %w",
-			err)
-	}
-
-	invUnits := req.AssetAmount
-
-	if satsMode {
-		// If the invoice was created over a satoshi amount, we need to
-		// calculate the units.
-		invUnits = rfqmath.MilliSatoshiToUnits(
-			amtMsat, *askAssetRate,
-		).ScaleTo(0).ToUint64()
-
-		// Now let's see if the negotiated quote can actually route the
-		// amount we need in msat.
-		maxFixedUnits := rfqmath.NewBigIntFixedPoint(
-			acceptedQuote.AssetMaxAmount, 0,
-		)
-		maxRoutableMsat := rfqmath.UnitsToMilliSatoshi(
-			maxFixedUnits, *askAssetRate,
-		)
-
-		if maxRoutableMsat <= amtMsat {
-			return nil, fmt.Errorf("cannot create invoice for %v "+
-				"msat, max routable amount is %v msat", amtMsat,
-				maxRoutableMsat)
-		}
-	}
-
-	// If the invoice is for an asset unit amount smaller than the minimal
-	// transportable amount, we'll return an error, as it wouldn't be
-	// payable by the network.
-	if acceptedQuote.MinTransportableUnits > invUnits {
-		return nil, fmt.Errorf("cannot create invoice over %d asset "+
-			"units, as the minimal transportable amount is %d "+
-			"units with the current rate of %v units/BTC",
-			invUnits, acceptedQuote.MinTransportableUnits,
-			acceptedQuote.AskAssetRate)
-	}
-
-	switch {
-	case satsMode:
-		iReq.ValueMsat = int64(amtMsat)
-
-	default:
-		// Convert the asset amount into a fixed-point.
-		assetAmount := rfqmath.NewBigIntFixedPoint(req.AssetAmount, 0)
-
-		// Calculate the invoice amount in msat.
-		valMsat := rfqmath.UnitsToMilliSatoshi(
-			assetAmount, *askAssetRate,
-		)
-		iReq.ValueMsat = int64(valMsat)
+		return nil, fmt.Errorf("error validating invoice "+
+			"amount: %w", err)
 	}
+	iReq.ValueMsat = invoiceAmtMsat
 
 	// The last step is to create a hop hint that includes the fake SCID of
 	// the quote, alongside the channel's routing policy. We need to choose