From c79648e4e1ee907a689d12b5f797bddfcf72a491 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      | 15 ++++++++++-----
 channeldb/revocation_log_test.go | 12 ++++++++----
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/channeldb/revocation_log.go b/channeldb/revocation_log.go
index a3fcf25db..db6cf9281 100644
--- a/channeldb/revocation_log.go
+++ b/channeldb/revocation_log.go
@@ -163,19 +163,17 @@ 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.RecordT[tlv.TlvType6, uint16]
 }
 
 // toTlvStream converts an HTLCEntry record into a tlv representation.
@@ -186,12 +184,15 @@ func (h *HTLCEntry) toTlvStream() (*tlv.Stream, error) {
 		h.OutputIndex.Record(),
 		h.Incoming.Record(),
 		h.Amt.Record(),
+		h.HtlcIndex.Record(),
 	}
 
 	h.CustomBlob.WhenSome(func(r tlv.RecordT[tlv.TlvType5, tlv.Blob]) {
 		records = append(records, r.Record())
 	})
 
+	tlv.SortRecords(records)
+
 	return tlv.NewStream(records...)
 }
 
@@ -211,6 +212,9 @@ func NewHTLCEntryFromHTLC(htlc HTLC) *HTLCEntry {
 		Amt: tlv.NewRecordT[tlv.TlvType4](
 			tlv.NewBigSizeT(htlc.Amt.ToSatoshis()),
 		),
+		HtlcIndex: tlv.NewPrimitiveRecord[tlv.TlvType6](
+			uint16(htlc.HtlcIndex),
+		),
 	}
 
 	if len(htlc.ExtraData) != 0 {
@@ -520,6 +524,7 @@ func deserializeHTLCEntries(r io.Reader) ([]*HTLCEntry, error) {
 			htlc.Incoming.Record(),
 			htlc.Amt.Record(),
 			customBlob.Record(),
+			htlc.HtlcIndex.Record(),
 		}
 
 		tlvStream, err := tlv.NewStream(records...)
diff --git a/channeldb/revocation_log_test.go b/channeldb/revocation_log_test.go
index 33f20c45c..01088757e 100644
--- a/channeldb/revocation_log_test.go
+++ b/channeldb/revocation_log_test.go
@@ -52,10 +52,11 @@ var (
 		CustomBlob: tlv.SomeRecordT(
 			tlv.NewPrimitiveRecord[tlv.TlvType5](blobBytes),
 		),
+		HtlcIndex: tlv.NewPrimitiveRecord[tlv.TlvType6, uint16](3),
 	}
 	testHTLCEntryBytes = []byte{
-		// Body length 28.
-		0x1c,
+		// Body length 32.
+		0x20,
 		// Rhash tlv.
 		0x0, 0x0,
 		// RefundTimeout tlv.
@@ -68,6 +69,8 @@ var (
 		0x4, 0x5, 0xfe, 0x0, 0xf, 0x42, 0x40,
 		// Custom blob tlv.
 		0x5, 0x4, 0x1, 0x2, 0x3, 0x4,
+		// HLTC index tlv.
+		0x6, 0x2, 0x0, 0x03,
 	}
 
 	localBalance  = lnwire.MilliSatoshi(9000)
@@ -84,6 +87,7 @@ var (
 		Htlcs: []HTLC{{
 			RefundTimeout: testHTLCEntry.RefundTimeout.Val,
 			OutputIndex:   int32(testHTLCEntry.OutputIndex.Val),
+			HtlcIndex:     uint64(testHTLCEntry.HtlcIndex.Val),
 			Incoming:      testHTLCEntry.Incoming.Val,
 			Amt: lnwire.NewMSatFromSatoshis(
 				testHTLCEntry.Amt.Val.Int(),
@@ -235,7 +239,7 @@ func TestSerializeHTLCEntries(t *testing.T) {
 	partialBytes := testHTLCEntryBytes[3:]
 
 	// Write the total length and RHash tlv.
-	expectedBytes := []byte{0x3c, 0x0, 0x20}
+	expectedBytes := []byte{0x40, 0x0, 0x20}
 	expectedBytes = append(expectedBytes, rHashBytes...)
 
 	// Append the rest.
@@ -350,7 +354,7 @@ func TestDerializeHTLCEntries(t *testing.T) {
 	partialBytes := testHTLCEntryBytes[3:]
 
 	// Write the total length and RHash tlv.
-	testBytes := append([]byte{0x3c, 0x0, 0x20}, rHashBytes...)
+	testBytes := append([]byte{0x40, 0x0, 0x20}, rHashBytes...)
 
 	// Append the rest.
 	testBytes = append(testBytes, partialBytes...)