rpc: for DecodeAssetPayReq hit the oracle directly

We just want to map the amount in BTC to asset units. So we rely on our
local oracle. Otherwise if we hit the peer directly, then it's more
similar to `EstimateRouteFee`.

config.go

@@ -195,6 +195,8 @@ type Config struct {
 
 	RfqManager *rfq.Manager
 
+	PriceOracle rfq.PriceOracle
+
 	UniverseStats universe.Telemetry
 
 	AuxLeafSigner *tapchannel.AuxLeafSigner

rpcserver.go

@@ -7732,25 +7732,40 @@ func (r *rpcServer) getInboundPolicy(ctx context.Context, chanID uint64,
 
 // assetInvoiceAmt calculates the amount of asset units to pay for an invoice
 // which is expressed in sats.
-func (r *rpcServer) assetInvoiceAmt(ctx context.Context, assetID asset.ID,
-	invoiceAmt lnwire.MilliSatoshi, peerPubKey *route.Vertex,
-	expiryTimestamp time.Time) (uint64, error) {
+func (r *rpcServer) assetInvoiceAmt(ctx context.Context, targetAsset asset.Specifier,
+	invoiceAmt lnwire.MilliSatoshi) (uint64, error) {
+
+	oracle := r.cfg.PriceOracle
 
-	acceptedQuote, err := r.fetchSendRfqQuote(
-		ctx, assetID, invoiceAmt, peerPubKey, expiryTimestamp,
+	oracleResp, err := oracle.QueryAskPrice(
+		ctx, targetAsset, fn.None[uint64](), fn.Some(invoiceAmt),
+		fn.None[rfqmsg.AssetRate](),
 	)
 	if err != nil {
-		return 0, fmt.Errorf("error sending RFQ quote: %w", err)
+		return 0, fmt.Errorf("error querying ask price: %w", err)
+	}
+	if oracleResp.Err != nil {
+		return 0, fmt.Errorf("error querying ask price: %w", err)
 	}
 
-	return acceptedQuote.AssetAmount, nil
+	assetRate := oracleResp.AssetRate.Rate
+
+	numAssetUnits := rfqmath.MilliSatoshiToUnits(
+		invoiceAmt, assetRate,
+	).ScaleTo(0)
+
+	return numAssetUnits.ToUint64(), nil
 }
 
 // DecodeAssetPayReq decodes an incoming invoice, then uses the RFQ system to
 // map the BTC amount to the amount of asset units for the specified asset ID.
 func (r *rpcServer) DecodeAssetPayReq(ctx context.Context,
 	payReq *tchrpc.AssetPayReqString) (*tchrpc.AssetPayReq, error) {
 
+	if r.cfg.PriceOracle == nil {
+		return nil, fmt.Errorf("price oracle is not set")
+	}
+
 	// First, we'll perform some basic input validation.
 	switch {
 	case len(payReq.AssetId) == 0:
@@ -7783,28 +7798,6 @@ func (r *rpcServer) DecodeAssetPayReq(ctx context.Context,
 
 	resp.PayReq = payReqInfo
 
-	// TODO(roasbeef): add dry run mode?
-	//  * obtains quote, but doesn't actually treat as standing order
-
-	// Now that we have the basic invoice information, we'll query the RFQ
-	// system to obtain a quote to send this amount of BTC. Note that this
-	// doesn't factor in the fee limit, so this attempts just to map the
-	// sats amount to an asset unit.
-	timestamp := time.Unix(payReqInfo.Timestamp, 0)
-	expiryTimestamp := timestamp.Add(time.Duration(payReqInfo.Expiry))
-	numMsat := lnwire.NewMSatFromSatoshis(
-		btcutil.Amount(payReqInfo.NumSatoshis),
-	)
-	invoiceAmt, err := r.assetInvoiceAmt(
-		ctx, assetID, numMsat, nil,
-		expiryTimestamp,
-	)
-	if err != nil {
-		return nil, fmt.Errorf("error deriving asset amount: %w", err)
-	}
-
-	resp.AssetAmount = invoiceAmt
-
 	// Next, we'll fetch the information for this asset ID through the addr
 	// book. This'll automatically fetch the asset if needed.
 	assetGroup, err := r.cfg.AddrBook.QueryAssetInfo(ctx, assetID)
@@ -7841,6 +7834,23 @@ func (r *rpcServer) DecodeAssetPayReq(ctx context.Context,
 		}
 	}
 
+	// Now that we have the basic invoice information, we'll query the RFQ
+	// system to obtain a quote to send this amount of BTC. Note that this
+	// doesn't factor in the fee limit, so this attempts just to map the
+	// sats amount to an asset unit.
+	numMsat := lnwire.NewMSatFromSatoshis(
+		btcutil.Amount(payReqInfo.NumSatoshis),
+	)
+	targetAsset := asset.NewSpecifierOptionalGroupKey(
+		assetGroup.ID(), assetGroup.GroupKey,
+	)
+	invoiceAmt, err := r.assetInvoiceAmt(ctx, targetAsset, numMsat)
+	if err != nil {
+		return nil, fmt.Errorf("error deriving asset amount: %w", err)
+	}
+
+	resp.AssetAmount = invoiceAmt
+
 	// The final piece of information we need is the decimal display
 	// information for this asset ID.
 	decDisplay, err := r.DecDisplayForAssetID(ctx, assetID)

tapcfg/server.go

@@ -582,6 +582,7 @@ func genServerConfig(cfg *Config, cfgLogger btclog.Logger,
 		UniverseQueriesPerSecond: cfg.Universe.UniverseQueriesPerSecond,
 		UniverseQueriesBurst:     cfg.Universe.UniverseQueriesBurst,
 		RfqManager:               rfqManager,
+		PriceOracle:              priceOracle,
 		AuxLeafSigner:            auxLeafSigner,
 		AuxFundingController:     auxFundingController,
 		AuxChanCloser:            auxChanCloser,