rfqmsg: populate transfer type field in request message

rfqmsg/messages.go

@@ -90,6 +90,63 @@ func (id *ID) Record() tlv.Record {
 	return tlv.MakeStaticRecord(0, id, recordSize, IdEncoder, IdDecoder)
 }
 
+// TransferType defines the type of transaction which will be performed if the
+// quote request leads to an accepted agreement.
+type TransferType uint8
+
+const (
+	// UnspecifiedTransferType represents an undefined or transfer type.
+	UnspecifiedTransferType TransferType = iota
+
+	// PayInvoiceTransferType indicates that the requesting peer wants to
+	// pay a Lightning Network invoice using a taproot asset.
+	PayInvoiceTransferType
+
+	// RecvPaymentTransferType indicates that the requesting peer wants
+	// to receive taproot asset funds linked to a Lightning Network invoice.
+	RecvPaymentTransferType
+)
+
+// Record returns a TLV record that can be used to encode/decode a transfer type
+// to/from a TLV stream.
+//
+// NOTE: This is part of the tlv.RecordProducer interface.
+func (t *TransferType) Record() tlv.Record {
+	// Note that we set the type here as zero, as when used with a
+	// tlv.RecordT, the type param will be used as the type.
+	return tlv.MakeStaticRecord(
+		0, t, 1, TransferTypeEncoder, TransferTypeDecoder,
+	)
+}
+
+// TransferTypeEncoder is a function that can be used to encode a TransferType
+// to a writer.
+func TransferTypeEncoder(w io.Writer, val any, buf *[8]byte) error {
+	if transferType, ok := val.(*TransferType); ok {
+		transferTypeInt := uint8(*transferType)
+		return tlv.EUint8(w, &transferTypeInt, buf)
+	}
+
+	return tlv.NewTypeForEncodingErr(val, "TransferType")
+}
+
+// TransferTypeDecoder is a function that can be used to decode a TransferType
+// from a reader.
+func TransferTypeDecoder(r io.Reader, val any, buf *[8]byte, l uint64) error {
+	if transferType, ok := val.(*TransferType); ok {
+		var transferTypeInt uint8
+		err := tlv.DUint8(r, &transferTypeInt, buf, l)
+		if err != nil {
+			return err
+		}
+
+		*transferType = TransferType(transferTypeInt)
+		return nil
+	}
+
+	return tlv.NewTypeForDecodingErr(val, "TransferType", l, 8)
+}
+
 // AssetRate represents the exchange rate of an asset to BTC, encapsulating
 // both the rate in fixed-point format and an expiration timestamp.
 //

rfqmsg/request.go

@@ -64,7 +64,9 @@ type requestWireMsgData struct {
 	// ID is the unique identifier of the quote request.
 	ID tlv.RecordT[tlv.TlvType2, ID]
 
-	// TODO(ffranr): Add transfer type field with TLV type 4.
+	// TransferType defines the type of transaction which will be performed
+	// if the quote request leads to an accepted agreement.
+	TransferType tlv.RecordT[tlv.TlvType4, TransferType]
 
 	// Expiry is the Unix timestamp (in seconds) when the quote expires.
 	// The quote becomes invalid after this time.
@@ -129,6 +131,7 @@ type requestWireMsgData struct {
 func newRequestWireMsgDataFromBuy(q BuyRequest) (requestWireMsgData, error) {
 	version := tlv.NewRecordT[tlv.TlvType0](q.Version)
 	id := tlv.NewRecordT[tlv.TlvType2](q.ID)
+	transferType := tlv.NewRecordT[tlv.TlvType4](RecvPaymentTransferType)
 
 	// Set the expiry to the default request lifetime unless an asset rate
 	// hint is provided.
@@ -179,6 +182,7 @@ func newRequestWireMsgDataFromBuy(q BuyRequest) (requestWireMsgData, error) {
 	return requestWireMsgData{
 		Version:          version,
 		ID:               id,
+		TransferType:     transferType,
 		Expiry:           expiryTlv,
 		InAssetID:        inAssetID,
 		InAssetGroupKey:  inAssetGroupKey,
@@ -194,6 +198,7 @@ func newRequestWireMsgDataFromBuy(q BuyRequest) (requestWireMsgData, error) {
 func newRequestWireMsgDataFromSell(q SellRequest) (requestWireMsgData, error) {
 	version := tlv.NewPrimitiveRecord[tlv.TlvType0](q.Version)
 	id := tlv.NewRecordT[tlv.TlvType2](q.ID)
+	transferType := tlv.NewRecordT[tlv.TlvType4](PayInvoiceTransferType)
 
 	// Set the expiry to the default request lifetime unless an asset rate
 	// hint is provided.
@@ -247,6 +252,7 @@ func newRequestWireMsgDataFromSell(q SellRequest) (requestWireMsgData, error) {
 	return requestWireMsgData{
 		Version:          version,
 		ID:               id,
+		TransferType:     transferType,
 		Expiry:           expiryTlv,
 		InAssetID:        inAssetID,
 		OutAssetID:       outAssetID,
@@ -328,6 +334,7 @@ func (m *requestWireMsgData) Encode(w io.Writer) error {
 	records := []tlv.Record{
 		m.Version.Record(),
 		m.ID.Record(),
+		m.TransferType.Record(),
 		m.Expiry.Record(),
 		m.MaxInAsset.Record(),
 	}
@@ -408,6 +415,7 @@ func (m *requestWireMsgData) Decode(r io.Reader) error {
 	tlvStream, err := tlv.NewStream(
 		m.Version.Record(),
 		m.ID.Record(),
+		m.TransferType.Record(),
 		m.Expiry.Record(),
 
 		inAssetID.Record(),