cmd/quote: add asset rate to display

Author: sputn1ck

cmd/loop/main.go

@@ -103,6 +103,13 @@ const (
 	//      Amount:                                    50 USD
 	assetAmtFmt = "%-36s %12d %s\n"
 
+	// rateFmt formats an exchange rate into a one line string, intended to
+	// prettify the terminal output. For Instance,
+	// 	fmt.Printf(f, "Exchange rate:", rate, "USD")
+	// prints out as,
+	//      Exchange rate:                            0.0002 USD/SAT
+	rateFmt = "%-36s %12.4f %s/SAT\n"
+
 	// blkFmt formats the number of blocks into a one line string, intended
 	// to prettify the terminal output. For Instance,
 	// 	fmt.Printf(f, "Conf target", target)

cmd/loop/quote.go

@@ -3,12 +3,15 @@ package main
 import (
 	"context"
 	"fmt"
+	"math/big"
 	"os"
 	"time"
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightninglabs/loop"
 	"github.com/lightninglabs/loop/looprpc"
+	"github.com/lightninglabs/taproot-assets/rfqmath"
+	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/urfave/cli"
 )
@@ -268,7 +271,19 @@ func printQuoteOutResp(req *looprpc.QuoteRequest,
 	totalFee := resp.HtlcSweepFeeSat + resp.SwapFeeSat
 
 	if resp.AssetRfqInfo != nil {
+		assetAmtSwap, err := getAssetAmt(
+			req.Amt, resp.AssetRfqInfo.SwapAssetRate,
+		)
+		if err != nil {
+			fmt.Printf("Error converting asset amount: %v\n", err)
+			return
+		}
+		exchangeRate := float64(assetAmtSwap) / float64(req.Amt)
 		fmt.Printf(assetAmtFmt, "Send off-chain:",
+			assetAmtSwap, resp.AssetRfqInfo.AssetName)
+		fmt.Printf(rateFmt, "Exchange rate:",
+			exchangeRate, resp.AssetRfqInfo.AssetName)
+		fmt.Printf(assetAmtFmt, "Limit Send off-chain:",
 			resp.AssetRfqInfo.MaxSwapAssetAmt,
 			resp.AssetRfqInfo.AssetName)
 	} else {
@@ -288,7 +303,17 @@ func printQuoteOutResp(req *looprpc.QuoteRequest,
 	fmt.Printf(satAmtFmt, "Estimated total fee:", totalFee)
 	fmt.Println()
 	if resp.AssetRfqInfo != nil {
+		assetAmtPrepay, err := getAssetAmt(
+			resp.PrepayAmtSat, resp.AssetRfqInfo.PrepayAssetRate,
+		)
+		if err != nil {
+			fmt.Printf("Error converting asset amount: %v\n", err)
+			return
+		}
 		fmt.Printf(assetAmtFmt, "No show penalty (prepay):",
+			assetAmtPrepay,
+			resp.AssetRfqInfo.AssetName)
+		fmt.Printf(assetAmtFmt, "Limit no show penalty (prepay):",
 			resp.AssetRfqInfo.MaxPrepayAssetAmt,
 			resp.AssetRfqInfo.AssetName)
 	} else {
@@ -302,3 +327,43 @@ func printQuoteOutResp(req *looprpc.QuoteRequest,
 		time.Unix(int64(req.SwapPublicationDeadline), 0),
 	)
 }
+
+// getAssetAmt returns the asset amount for the given amount in satoshis and
+// the asset rate.
+func getAssetAmt(amt int64, assetRate *looprpc.FixedPoint) (
+	uint64, error) {
+
+	askAssetRate, err := unmarshalFixedPoint(
+		assetRate,
+	)
+	if err != nil {
+		return 0, err
+	}
+	msatAmt := lnwire.MilliSatoshi(
+		(amt * 1000),
+	)
+	assetAmt := rfqmath.MilliSatoshiToUnits(
+		msatAmt, *askAssetRate,
+	)
+
+	return assetAmt.ToUint64(), nil
+}
+
+// unmarshalFixedPoint converts an RPC FixedPoint to a BigIntFixedPoint.
+func unmarshalFixedPoint(fp *looprpc.FixedPoint) (*rfqmath.BigIntFixedPoint,
+	error) {
+	// Return an error is the scale component of the fixed point is greater
+	// than the max value of uint8.
+	if fp.Scale > 255 {
+		return nil, fmt.Errorf("scale value overflow: %v", fp.Scale)
+	}
+	scale := uint8(fp.Scale)
+
+	cBigInt := new(big.Int)
+	cBigInt.SetString(fp.Coefficient, 10)
+
+	return &rfqmath.BigIntFixedPoint{
+		Coefficient: rfqmath.NewBigInt(cBigInt),
+		Scale:       scale,
+	}, nil
+}