Add support for incoming webhook deletions on Discord

bridge/discord/discord.go

@@ -278,7 +278,7 @@ func (b *Bdiscord) Send(msg config.Message) (string, error) {
 
 	// Use webhook to send the message
 	useWebhooks := b.shouldMessageUseWebhooks(&msg)
-	if useWebhooks && msg.Event != config.EventMsgDelete && msg.ParentID == "" {
+	if useWebhooks && msg.ParentID == "" {
 		return b.handleEventWebhook(&msg, channelID)
 	}
 

bridge/discord/transmitter/transmitter.go

@@ -94,6 +94,23 @@ func (t *Transmitter) Edit(channelID string, messageID string, params *discordgo
 	return nil
 }
 
+// Delete will delete a message from a channel, if possible.
+func (t *Transmitter) Delete(channelID string, messageID string) error {
+	wh := t.getWebhook(channelID)
+
+	if wh == nil {
+		return ErrWebhookNotFound
+	}
+
+	uri := discordgo.EndpointWebhookToken(wh.ID, wh.Token) + "/messages/" + messageID
+	_, err := t.session.RequestWithBucketID("DELETE", uri, nil, discordgo.EndpointWebhookToken("", ""))
+	if err != nil {
+		return fmt.Errorf("delete failed: %w", err)
+	}
+
+	return nil
+}
+
 // HasWebhook checks whether the transmitter is using a particular webhook.
 func (t *Transmitter) HasWebhook(id string) bool {
 	t.mutex.RLock()

bridge/discord/webhook.go

@@ -109,6 +109,21 @@ func (b *Bdiscord) webhookSend(msg *config.Message, channelID string) (*discordg
 }
 
 func (b *Bdiscord) handleEventWebhook(msg *config.Message, channelID string) (string, error) {
+	if msg.Event == config.EventMsgDelete {
+		if msg.ID == "" {
+			return "", nil
+		}
+
+		err := b.transmitter.Delete(channelID, msg.ID)
+		if err != nil {
+			b.Log.Errorf("Could not delete message: %s", err)
+			return "", err
+		}
+
+		b.Log.Infof("Message deleted successfully")
+		return "", nil
+	}
+
 	// skip events
 	if msg.Event != "" && msg.Event != config.EventUserAction && msg.Event != config.EventJoinLeave && msg.Event != config.EventTopicChange {
 		return "", nil