From 2510c190241df65d0efcbf52c783b3c7f2362d61 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Mon, 1 Apr 2024 17:44:14 -0700
Subject: [PATCH] channeldb: add HtlcIndex to HTLCEntry

This may be useful for custom channel types that base everything off the index (a global value) rather than the output index (can change with each state).
---
 channeldb/revocation_log.go      | 23 ++++++++++++++++++-----
 channeldb/revocation_log_test.go | 17 +++++++++++++----
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/channeldb/revocation_log.go b/channeldb/revocation_log.go
index b7b73a35a..3abc73f81 100644
--- a/channeldb/revocation_log.go
+++ b/channeldb/revocation_log.go
@@ -155,19 +155,17 @@ type HTLCEntry struct {
 
 	// Incoming denotes whether we're the receiver or the sender of this
 	// HTLC.
-	//
-	// NOTE: this field is the memory representation of the field
-	// incomingUint.
 	Incoming tlv.RecordT[tlv.TlvType3, bool]
 
 	// Amt is the amount of satoshis this HTLC escrows.
-	//
-	// NOTE: this field is the memory representation of the field amtUint.
 	Amt tlv.RecordT[tlv.TlvType4, tlv.BigSizeT[btcutil.Amount]]
 
 	// CustomBlob is an optional blob that can be used to store information
 	// specific to revocation handling for a custom channel type.
 	CustomBlob tlv.OptionalRecordT[tlv.TlvType5, tlv.Blob]
+
+	// HtlcIndex is the index of the HTLC in the channel.
+	HtlcIndex tlv.OptionalRecordT[tlv.TlvType6, uint16]
 }
 
 // toTlvStream converts an HTLCEntry record into a tlv representation.
@@ -184,6 +182,12 @@ func (h *HTLCEntry) toTlvStream() (*tlv.Stream, error) {
 		records = append(records, r.Record())
 	})
 
+	h.HtlcIndex.WhenSome(func(r tlv.RecordT[tlv.TlvType6, uint16]) {
+		records = append(records, r.Record())
+	})
+
+	tlv.SortRecords(records)
+
 	return tlv.NewStream(records...)
 }
 
@@ -203,6 +207,9 @@ func NewHTLCEntryFromHTLC(htlc HTLC) (*HTLCEntry, error) {
 		Amt: tlv.NewRecordT[tlv.TlvType4](
 			tlv.NewBigSizeT(htlc.Amt.ToSatoshis()),
 		),
+		HtlcIndex: tlv.SomeRecordT(tlv.NewPrimitiveRecord[tlv.TlvType6](
+			uint16(htlc.HtlcIndex),
+		)),
 	}
 
 	if len(htlc.CustomRecords) != 0 {
@@ -509,6 +516,7 @@ func deserializeHTLCEntries(r io.Reader) ([]*HTLCEntry, error) {
 		var htlc HTLCEntry
 
 		customBlob := htlc.CustomBlob.Zero()
+		htlcIndex := htlc.HtlcIndex.Zero()
 
 		// Create the tlv stream.
 		records := []tlv.Record{
@@ -518,6 +526,7 @@ func deserializeHTLCEntries(r io.Reader) ([]*HTLCEntry, error) {
 			htlc.Incoming.Record(),
 			htlc.Amt.Record(),
 			customBlob.Record(),
+			htlcIndex.Record(),
 		}
 
 		tlvStream, err := tlv.NewStream(records...)
@@ -539,6 +548,10 @@ func deserializeHTLCEntries(r io.Reader) ([]*HTLCEntry, error) {
 			htlc.CustomBlob = tlv.SomeRecordT(customBlob)
 		}
 
+		if t, ok := parsedTypes[htlcIndex.TlvType()]; ok && t == nil {
+			htlc.HtlcIndex = tlv.SomeRecordT(htlcIndex)
+		}
+
 		// Append the entry.
 		htlcs = append(htlcs, &htlc)
 	}
diff --git a/channeldb/revocation_log_test.go b/channeldb/revocation_log_test.go
index 139a02d52..4290552ee 100644
--- a/channeldb/revocation_log_test.go
+++ b/channeldb/revocation_log_test.go
@@ -59,10 +59,13 @@ var (
 		CustomBlob: tlv.SomeRecordT(
 			tlv.NewPrimitiveRecord[tlv.TlvType5](blobBytes),
 		),
+		HtlcIndex: tlv.SomeRecordT(
+			tlv.NewPrimitiveRecord[tlv.TlvType6, uint16](0x33),
+		),
 	}
 	testHTLCEntryBytes = []byte{
-		// Body length 41.
-		0x29,
+		// Body length 45.
+		0x2d,
 		// Rhash tlv.
 		0x0, 0x0,
 		// RefundTimeout tlv.
@@ -76,6 +79,8 @@ var (
 		// Custom blob tlv.
 		0x5, 0x11, 0xfe, 0x00, 0x01, 0x00, 0x01, 0x0b, 0x63, 0x75, 0x73,
 		0x74, 0x6f, 0x6d, 0x20, 0x64, 0x61, 0x74, 0x61,
+		// HLTC index tlv.
+		0x6, 0x2, 0x0, 0x33,
 	}
 
 	testHTLCEntryHash = HTLCEntry{
@@ -126,7 +131,11 @@ var (
 		Htlcs: []HTLC{{
 			RefundTimeout: testHTLCEntry.RefundTimeout.Val,
 			OutputIndex:   int32(testHTLCEntry.OutputIndex.Val),
-			Incoming:      testHTLCEntry.Incoming.Val,
+			HtlcIndex: uint64(
+				testHTLCEntry.HtlcIndex.ValOpt().
+					UnsafeFromSome(),
+			),
+			Incoming: testHTLCEntry.Incoming.Val,
 			Amt: lnwire.NewMSatFromSatoshis(
 				testHTLCEntry.Amt.Val.Int(),
 			),
@@ -294,7 +303,7 @@ func TestSerializeHTLCEntries(t *testing.T) {
 	partialBytes := testHTLCEntryBytes[3:]
 
 	// Write the total length and RHash tlv.
-	expectedBytes := []byte{0x49, 0x0, 0x20}
+	expectedBytes := []byte{0x4d, 0x0, 0x20}
 	expectedBytes = append(expectedBytes, rHashBytes...)
 
 	// Append the rest.