From 19d47784bde7f5d8cfc06f868350ed6ac69c8a21 Mon Sep 17 00:00:00 2001
From: Wim <wim@42.be>
Date: Thu, 31 Dec 2020 16:59:47 +0100
Subject: [PATCH] Add threading support with token (discord) (#1342)

Webhooks don't support the threading yet, so this is token only.
In discord you can reply on each message of a thread, but this is not possible in mattermost (so some changes added there to make sure we always answer on the rootID of the thread).

Also needs some more testing with slack.

update : It now also uses the token when replying to a thread (even if webhooks are enabled), until webhooks have support for threads.
---
 bridge/discord/discord.go       | 17 +++++++++++++++--
 bridge/discord/handlers.go      |  5 +++++
 bridge/mattermost/handlers.go   |  2 +-
 bridge/mattermost/mattermost.go |  9 +++++++++
 gateway/router.go               |  2 +-
 5 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/bridge/discord/discord.go b/bridge/discord/discord.go
index d63006a7..c8b810c6 100644
--- a/bridge/discord/discord.go
+++ b/bridge/discord/discord.go
@@ -244,7 +244,7 @@ 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 {
+	if useWebhooks && msg.Event != config.EventMsgDelete && msg.ParentID == "" {
 		return b.handleEventWebhook(&msg, channelID)
 	}
 
@@ -287,11 +287,24 @@ func (b *Bdiscord) handleEventBotUser(msg *config.Message, channelID string) (st
 		return msg.ID, err
 	}
 
+	m := discordgo.MessageSend{
+		Content: msg.Username + msg.Text,
+	}
+
+	if msg.ParentID != "" && msg.ParentID != "msg-parent-not-found" {
+		m.Reference = &discordgo.MessageReference{
+			MessageID: msg.ParentID,
+			ChannelID: channelID,
+			GuildID:   b.guildID,
+		}
+	}
+
 	// Post normal message
-	res, err := b.c.ChannelMessageSend(channelID, msg.Username+msg.Text)
+	res, err := b.c.ChannelMessageSendComplex(channelID, &m)
 	if err != nil {
 		return "", err
 	}
+
 	return res.ID, nil
 }
 
diff --git a/bridge/discord/handlers.go b/bridge/discord/handlers.go
index 370b8912..d2b38538 100644
--- a/bridge/discord/handlers.go
+++ b/bridge/discord/handlers.go
@@ -127,6 +127,11 @@ func (b *Bdiscord) messageCreate(s *discordgo.Session, m *discordgo.MessageCreat
 	// Replace emotes
 	rmsg.Text = replaceEmotes(rmsg.Text)
 
+	// Add our parent id if it exists
+	if m.MessageReference != nil {
+		rmsg.ParentID = m.MessageReference.MessageID
+	}
+
 	b.Log.Debugf("<= Sending message from %s on %s to gateway", m.Author.Username, b.Account)
 	b.Log.Debugf("<= Message is %#v", rmsg)
 	b.Remote <- rmsg
diff --git a/bridge/mattermost/handlers.go b/bridge/mattermost/handlers.go
index 67e68d02..58af43a8 100644
--- a/bridge/mattermost/handlers.go
+++ b/bridge/mattermost/handlers.go
@@ -108,7 +108,7 @@ func (b *Bmattermost) handleMatterClient(messages chan *config.Message) {
 			Channel:  message.Channel,
 			Text:     message.Text,
 			ID:       message.Post.Id,
-			ParentID: message.Post.ParentId,
+			ParentID: message.Post.RootId, // ParentID is obsolete with mattermost
 			Extra:    make(map[string][]interface{}),
 		}
 
diff --git a/bridge/mattermost/mattermost.go b/bridge/mattermost/mattermost.go
index e41b19d7..2c11b79e 100644
--- a/bridge/mattermost/mattermost.go
+++ b/bridge/mattermost/mattermost.go
@@ -127,6 +127,15 @@ func (b *Bmattermost) Send(msg config.Message) (string, error) {
 		msg.Text = fmt.Sprintf("[thread]: %s", msg.Text)
 	}
 
+	// we only can reply to the root of the thread, not to a specific ID (like discord for example does)
+	if msg.ParentID != "" {
+		post, res := b.mc.Client.GetPost(msg.ParentID, "")
+		if res.Error != nil {
+			b.Log.Errorf("getting post %s failed: %s", msg.ParentID, res.Error.DetailedError)
+		}
+		msg.ParentID = post.RootId
+	}
+
 	// Upload a file if it exists
 	if msg.Extra != nil {
 		for _, rmsg := range helper.HandleExtra(&msg, b.General) {
diff --git a/gateway/router.go b/gateway/router.go
index b07e5781..468f02c8 100644
--- a/gateway/router.go
+++ b/gateway/router.go
@@ -160,7 +160,7 @@ func (r *Router) handleReceive() {
 				// For some bridges we always add/update the message ID.
 				// This is necessary as msgIDs will change if a bridge returns
 				// a different ID in response to edits.
-				if !exists || msg.Protocol == "discord" {
+				if !exists {
 					gw.Messages.Add(msg.Protocol+" "+msg.ID, msgIDs)
 				}
 			}