multi: revise rfq.SellOrder fields

This commit removes the `max_asset_amount` and `min_ask` fields from the
`SellOrder` type and introduces a new `payment_max_amt` field.

The removed fields were not used correctly. The new `payment_max_amt`
field allows us to leverage the `MaxInAmount` from the RFQ request wire
message.

itest/rfq_test.go

@@ -264,7 +264,6 @@ func testRfqAssetSellHtlcIntercept(t *harnessTest) {
 
 	// Alice sends a sell order to Bob for some amount of the newly minted
 	// asset.
-	purchaseAssetAmt := uint64(200)
 	askAmt := uint64(42000)
 	sellOrderExpiry := uint64(time.Now().Add(24 * time.Hour).Unix())
 
@@ -275,9 +274,8 @@ func testRfqAssetSellHtlcIntercept(t *harnessTest) {
 					AssetId: mintedAssetIdBytes,
 				},
 			},
-			MaxAssetAmount: purchaseAssetAmt,
-			MinAsk:         askAmt,
-			Expiry:         sellOrderExpiry,
+			PaymentMaxAmt: askAmt,
+			Expiry:        sellOrderExpiry,
 
 			// Here we explicitly specify Bob as the destination
 			// peer for the sell order. This will prompt Alice's

rfq/manager.go

@@ -739,14 +739,15 @@ type SellOrder struct {
 	// AssetGroupKey is the public key of the asset group to sell.
 	AssetGroupKey *btcec.PublicKey
 
-	// MaxAssetAmount is the maximum amount of the asset that can be sold as
-	// part of the order.
-	MaxAssetAmount uint64
-
-	// MinAsk is the minimum ask price that the seller is willing to accept.
-	MinAsk lnwire.MilliSatoshi
+	// PaymentMaxAmt is the maximum msat amount that the responding peer
+	// must agree to pay.
+	PaymentMaxAmt lnwire.MilliSatoshi
 
 	// Expiry is the unix timestamp at which the order expires.
+	//
+	// TODO(ffranr): This is the invoice expiry unix timestamp in seconds.
+	//  We should make use of this field to ensure quotes are valid for the
+	//  duration of the invoice.
 	Expiry uint64
 
 	// Peer is the peer that the buy order is intended for. This field is

rfq/negotiator.go

@@ -489,13 +489,10 @@ func (n *Negotiator) HandleOutgoingSellOrder(order SellOrder) {
 
 		if n.cfg.PriceOracle != nil && assetSpecifier.IsSome() {
 			// Query the price oracle for an asking price.
-			//
-			// TODO(ffranr): Add paymentMaxAmt to SellOrder and use
-			//  as arg here.
 			assetRate, err := n.queryAskFromPriceOracle(
 				order.Peer, assetSpecifier,
 				fn.None[uint64](),
-				fn.None[lnwire.MilliSatoshi](),
+				fn.Some(order.PaymentMaxAmt),
 				fn.None[rfqmsg.AssetRate](),
 			)
 			if err != nil {
@@ -508,12 +505,9 @@ func (n *Negotiator) HandleOutgoingSellOrder(order SellOrder) {
 			assetRateHint = fn.Some[rfqmsg.AssetRate](*assetRate)
 		}
 
-		// TODO(ffranr): Add paymentMaxAmt to SellOrder and use as arg
-		//  here.
 		request, err := rfqmsg.NewSellRequest(
 			*order.Peer, order.AssetID, order.AssetGroupKey,
-			lnwire.MilliSatoshi(order.MaxAssetAmount),
-			assetRateHint,
+			order.PaymentMaxAmt, assetRateHint,
 		)
 		if err != nil {
 			err := fmt.Errorf("unable to create sell request "+

rpcserver.go

@@ -6405,12 +6405,10 @@ func unmarshalAssetSellOrder(
 	}
 
 	return &rfq.SellOrder{
-		AssetID:        assetId,
-		AssetGroupKey:  assetGroupKey,
-		MaxAssetAmount: req.MaxAssetAmount,
-		MinAsk:         lnwire.MilliSatoshi(req.MinAsk),
-		Expiry:         req.Expiry,
-		Peer:           peer,
+		AssetID:       assetId,
+		AssetGroupKey: assetGroupKey,
+		PaymentMaxAmt: lnwire.MilliSatoshi(req.PaymentMaxAmt),
+		Peer:          peer,
 	}, nil
 }
 
@@ -6922,11 +6920,36 @@ func (r *rpcServer) SendPayment(req *tchrpc.SendPaymentRequest,
 		// set.
 		peerPubKey = &assetChan.channelInfo.PubKeyBytes
 
-		// TODO(guggero): This should actually be the max BTC amount
-		// (invoice amount plus fee limit) in milli-satoshi, not the
-		// asset amount. Need to change the whole RFQ API to do that
-		// though.
-		maxAssetAmount := assetChan.assetInfo.LocalBalance
+		// paymentMaxAmt is the maximum amount that the counterparty is
+		// expected to pay. This is the amount that the invoice is
+		// asking for plus the fee limit in milli-satoshis.
+		var paymentMaxAmt lnwire.MilliSatoshi
+		if invoice.MilliSat == nil {
+			amt, err := lnrpc.UnmarshallAmt(pReq.Amt, pReq.AmtMsat)
+			if err != nil {
+				return fmt.Errorf("error unmarshalling "+
+					"amount: %w", err)
+			}
+			if amt == 0 {
+				return errors.New("amount must be specified " +
+					"when paying a zero amount invoice")
+			}
+
+			paymentMaxAmt = amt
+		} else {
+			paymentMaxAmt = *invoice.MilliSat
+		}
+
+		// Calculate the fee limit that should be used for this payment.
+		feeLimit, err := lnrpc.UnmarshallAmt(
+			pReq.FeeLimitSat, pReq.FeeLimitMsat,
+		)
+		if err != nil {
+			return fmt.Errorf("error unmarshalling fee limit: %w",
+				err)
+		}
+
+		paymentMaxAmt += feeLimit
 
 		expiryTimestamp := invoice.Timestamp.Add(invoice.Expiry())
 		resp, err := r.AddAssetSellOrder(
@@ -6936,10 +6959,9 @@ func (r *rpcServer) SendPayment(req *tchrpc.SendPaymentRequest,
 						AssetId: assetID[:],
 					},
 				},
-				MaxAssetAmount: maxAssetAmount,
-				MinAsk:         uint64(*invoice.MilliSat),
-				Expiry:         uint64(expiryTimestamp.Unix()),
-				PeerPubKey:     peerPubKey[:],
+				PaymentMaxAmt: uint64(paymentMaxAmt),
+				Expiry:        uint64(expiryTimestamp.Unix()),
+				PeerPubKey:    peerPubKey[:],
 				TimeoutSeconds: uint32(
 					rfq.DefaultTimeout.Seconds(),
 				),