From 094bc9bd77202de2a6e798acca67c1cfe1e9a0a6 Mon Sep 17 00:00:00 2001
From: Skip R <tinyslices@gmail.com>
Date: Tue, 3 Feb 2026 21:55:58 -0800
Subject: [PATCH] connector: support transaction IDs

---
 pkg/connector/connector.go     | 13 +++++++++++--
 pkg/connector/handlediscord.go | 10 +++++++++-
 pkg/discordid/id.go            | 11 +++++++++++
 pkg/msgconv/from-matrix.go     | 16 +++++-----------
 4 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/pkg/connector/connector.go b/pkg/connector/connector.go
index d866e49..25070b7 100644
--- a/pkg/connector/connector.go
+++ b/pkg/connector/connector.go
@@ -20,7 +20,11 @@ import (
 	"context"
 
 	"maunium.net/go/mautrix/bridgev2"
+	"maunium.net/go/mautrix/bridgev2/networkid"
+	"maunium.net/go/mautrix/event"
+	"maunium.net/go/mautrix/id"
 
+	"go.mau.fi/mautrix-discord/pkg/discordid"
 	"go.mau.fi/mautrix-discord/pkg/msgconv"
 )
 
@@ -31,8 +35,9 @@ type DiscordConnector struct {
 }
 
 var (
-	_ bridgev2.NetworkConnector      = (*DiscordConnector)(nil)
-	_ bridgev2.MaxFileSizeingNetwork = (*DiscordConnector)(nil)
+	_ bridgev2.NetworkConnector               = (*DiscordConnector)(nil)
+	_ bridgev2.MaxFileSizeingNetwork          = (*DiscordConnector)(nil)
+	_ bridgev2.TransactionIDGeneratingNetwork = (*DiscordConnector)(nil)
 )
 
 func (d *DiscordConnector) Init(bridge *bridgev2.Bridge) {
@@ -59,3 +64,7 @@ func (d *DiscordConnector) GetName() bridgev2.BridgeName {
 		DefaultPort:      29334,
 	}
 }
+
+func (d *DiscordConnector) GenerateTransactionID(_ id.UserID, _ id.RoomID, _ event.Type) networkid.RawTransactionID {
+	return networkid.RawTransactionID(discordid.GenerateNonce())
+}
diff --git a/pkg/connector/handlediscord.go b/pkg/connector/handlediscord.go
index 2826d64..9516779 100644
--- a/pkg/connector/handlediscord.go
+++ b/pkg/connector/handlediscord.go
@@ -59,11 +59,19 @@ type DiscordMessage struct {
 }
 
 var (
-	_ bridgev2.RemoteMessage = (*DiscordMessage)(nil)
+	_ bridgev2.RemoteMessage                  = (*DiscordMessage)(nil)
+	_ bridgev2.RemoteMessageWithTransactionID = (*DiscordMessage)(nil)
 	// _ bridgev2.RemoteEdit    = (*DiscordMessage)(nil)
 	// _ bridgev2.RemoteMessageRemove    = (*DiscordMessage)(nil)
 )
 
+func (m *DiscordMessage) GetTransactionID() networkid.TransactionID {
+	if m.Data.Nonce == "" {
+		return ""
+	}
+	return networkid.TransactionID(m.Data.Nonce)
+}
+
 func (m *DiscordMessage) ConvertMessage(ctx context.Context, portal *bridgev2.Portal, intent bridgev2.MatrixAPI) (*bridgev2.ConvertedMessage, error) {
 	return m.Client.connector.MsgConv.ToMatrix(ctx, portal, intent, m.Client.UserLogin, m.Client.Session, m.Data), nil
 }
diff --git a/pkg/discordid/id.go b/pkg/discordid/id.go
index 42d4321..346604a 100644
--- a/pkg/discordid/id.go
+++ b/pkg/discordid/id.go
@@ -17,10 +17,21 @@
 package discordid
 
 import (
+	"strconv"
+	"time"
+
 	"github.com/bwmarrin/discordgo"
 	"maunium.net/go/mautrix/bridgev2/networkid"
 )
 
+const DiscordEpochMillis = 1420070400000
+
+// GenerateNonce creates a Discord-style snowflake nonce for message idempotency.
+func GenerateNonce() string {
+	snowflake := (time.Now().UnixMilli() - DiscordEpochMillis) << 22
+	return strconv.FormatInt(snowflake, 10)
+}
+
 func MakeUserID(userID string) networkid.UserID {
 	return networkid.UserID(userID)
 }
diff --git a/pkg/msgconv/from-matrix.go b/pkg/msgconv/from-matrix.go
index 8e328f8..d717377 100644
--- a/pkg/msgconv/from-matrix.go
+++ b/pkg/msgconv/from-matrix.go
@@ -22,8 +22,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"strconv"
-	"time"
 
 	"github.com/bwmarrin/discordgo"
 	"github.com/rs/zerolog"
@@ -35,14 +33,6 @@ import (
 	"go.mau.fi/mautrix-discord/pkg/discordid"
 )
 
-const discordEpochMillis = 1420070400000
-
-func generateMessageNonce() string {
-	snowflake := (time.Now().UnixMilli() - discordEpochMillis) << 22
-	// Nonce snowflakes don't have internal IDs or increments
-	return strconv.FormatInt(snowflake, 10)
-}
-
 func parseAllowedLinkPreviews(raw map[string]any) []string {
 	if raw == nil {
 		return nil
@@ -102,7 +92,11 @@ func (mc *MessageConverter) ToDiscord(
 	ctx = context.WithValue(ctx, contextKeyPortal, msg.Portal)
 	ctx = context.WithValue(ctx, contextKeyDiscordClient, session)
 	var req discordgo.MessageSend
-	req.Nonce = generateMessageNonce()
+	if msg.InputTransactionID != "" {
+		req.Nonce = string(msg.InputTransactionID)
+	} else {
+		req.Nonce = discordid.GenerateNonce()
+	}
 	log := zerolog.Ctx(ctx)
 
 	if msg.ReplyTo != nil {