Add support for Telegram topics (telegram) (#1942)

Topics are surfaced by appending /<topic-id> to the channel setting for the gateway. 
An example for the topic with ID of 16 would be:

```
[[gateway.inout]]
account="telegram.mytelegram"
channel="-100xxxxxxxxxx/16"
```

2 files changed, 69 insertions, 17 deletions

diff --git a/bridge/telegram/handlers.go b/bridge/telegram/handlers.go
index 5ffb1eca..985397ef 100644
--- a/bridge/telegram/handlers.go
+++ b/bridge/telegram/handlers.go
@@ -11,7 +11,7 @@ import (
 	"github.com/42wim/matterbridge/bridge/config"
 	"github.com/42wim/matterbridge/bridge/helper"
 	"github.com/davecgh/go-spew/spew"
-	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+	tgbotapi "github.com/matterbridge/telegram-bot-api/v6"
 )
 
 func (b *Btelegram) handleUpdate(rmsg *config.Message, message, posted, edited *tgbotapi.Message) *tgbotapi.Message {
@@ -20,6 +20,11 @@ func (b *Btelegram) handleUpdate(rmsg *config.Message, message, posted, edited *
 		if posted.Text == "/chatId" {
 			chatID := strconv.FormatInt(posted.Chat.ID, 10)
 
+			// Handle chat topics
+			if posted.IsTopicMessage {
+				chatID = chatID + "/" + strconv.Itoa(posted.MessageThreadID)
+			}
+
 			_, err := b.Send(config.Message{
 				Channel: chatID,
 				Text:    fmt.Sprintf("ID of this chat: %s", chatID),
@@ -91,7 +96,8 @@ func (b *Btelegram) handleForwarded(rmsg *config.Message, message *tgbotapi.Mess
 
 // handleQuoting handles quoting of previous messages
 func (b *Btelegram) handleQuoting(rmsg *config.Message, message *tgbotapi.Message) {
-	if message.ReplyToMessage != nil {
+	// Used to check if the message was a reply to the root topic
+	if message.ReplyToMessage != nil && !(message.ReplyToMessage.MessageID == message.MessageThreadID) { //nolint:nestif
 		usernameReply := ""
 		if message.ReplyToMessage.From != nil {
 			if b.GetBool("UseFirstName") {
@@ -211,9 +217,14 @@ func (b *Btelegram) handleRecv(updates <-chan tgbotapi.Update) {
 		// set the ID's from the channel or group message
 		rmsg.ID = strconv.Itoa(message.MessageID)
 		rmsg.Channel = strconv.FormatInt(message.Chat.ID, 10)
+		if message.MessageThreadID != 0 {
+			rmsg.Channel += "/" + strconv.Itoa(message.MessageThreadID)
+		}
 
 		// preserve threading from telegram reply
-		if message.ReplyToMessage != nil {
+		if message.ReplyToMessage != nil &&
+			// Used to check if the message was a reply to the root topic
+			!(message.ReplyToMessage.MessageID == message.MessageThreadID) {
 			rmsg.ParentID = strconv.Itoa(message.ReplyToMessage.MessageID)
 		}
 
@@ -326,12 +337,12 @@ func (b *Btelegram) maybeConvertWebp(name *string, data *[]byte) {
 
 // handleDownloadFile handles file download
 func (b *Btelegram) handleDownload(rmsg *config.Message, message *tgbotapi.Message) error {
-	size := 0
+	size := int64(0)
 	var url, name, text string
 	switch {
 	case message.Sticker != nil:
 		text, name, url = b.getDownloadInfo(message.Sticker.FileID, ".webp", true)
-		size = message.Sticker.FileSize
+		size = int64(message.Sticker.FileSize)
 	case message.Voice != nil:
 		text, name, url = b.getDownloadInfo(message.Voice.FileID, ".ogg", true)
 		size = message.Voice.FileSize
@@ -348,7 +359,7 @@ func (b *Btelegram) handleDownload(rmsg *config.Message, message *tgbotapi.Messa
 		text = " " + message.Document.FileName + " : " + url
 	case message.Photo != nil:
 		photos := message.Photo
-		size = photos[len(photos)-1].FileSize
+		size = int64(photos[len(photos)-1].FileSize)
 		text, name, url = b.getDownloadInfo(photos[len(photos)-1].FileID, "", true)
 	}
 
@@ -452,7 +463,7 @@ func (b *Btelegram) handleEdit(msg *config.Message, chatid int64) (string, error
 }
 
 // handleUploadFile handles native upload of files
-func (b *Btelegram) handleUploadFile(msg *config.Message, chatid int64, parentID int) (string, error) {
+func (b *Btelegram) handleUploadFile(msg *config.Message, chatid int64, threadid int, parentID int) (string, error) {
 	var media []interface{}
 	for _, f := range msg.Extra["file"] {
 		fi := f.(config.FileInfo)
@@ -502,7 +513,7 @@ func (b *Btelegram) handleUploadFile(msg *config.Message, chatid int64, parentID
 		}
 	}
 
-	return b.sendMediaFiles(msg, chatid, parentID, media)
+	return b.sendMediaFiles(msg, chatid, threadid, parentID, media)
 }
 
 func (b *Btelegram) handleQuote(message, quoteNick, quoteMessage string) string {
diff --git a/bridge/telegram/telegram.go b/bridge/telegram/telegram.go
index 43cb818f..e7885ca3 100644
--- a/bridge/telegram/telegram.go
+++ b/bridge/telegram/telegram.go
@@ -10,7 +10,7 @@ import (
 	"github.com/42wim/matterbridge/bridge"
 	"github.com/42wim/matterbridge/bridge/config"
 	"github.com/42wim/matterbridge/bridge/helper"
-	tgbotapi "github.com/go-telegram-bot-api/telegram-bot-api/v5"
+	tgbotapi "github.com/matterbridge/telegram-bot-api/v6"
 )
 
 const (
@@ -86,11 +86,41 @@ func TGGetParseMode(b *Btelegram, username string, text string) (textout string,
 	return textout, parsemode
 }
 
+func (b *Btelegram) getIds(channel string) (int64, int, error) {
+	var chatid int64
+	topicid := 0
+
+	// get the chatid
+	if strings.Contains(channel, "/") { //nolint:nestif
+		s := strings.Split(channel, "/")
+		if len(s) < 2 {
+			b.Log.Errorf("Invalid channel format: %#v\n", channel)
+			return 0, 0, nil
+		}
+		id, err := strconv.ParseInt(s[0], 10, 64)
+		if err != nil {
+			return 0, 0, err
+		}
+		chatid = id
+		tid, err := strconv.Atoi(s[1])
+		if err != nil {
+			return 0, 0, err
+		}
+		topicid = tid
+	} else {
+		id, err := strconv.ParseInt(channel, 10, 64)
+		if err != nil {
+			return 0, 0, err
+		}
+		chatid = id
+	}
+	return chatid, topicid, nil
+}
+
 func (b *Btelegram) Send(msg config.Message) (string, error) {
 	b.Log.Debugf("=> Receiving %#v", msg)
 
-	// get the chatid
-	chatid, err := strconv.ParseInt(msg.Channel, 10, 64)
+	chatid, topicid, err := b.getIds(msg.Channel)
 	if err != nil {
 		return "", err
 	}
@@ -123,13 +153,13 @@ func (b *Btelegram) Send(msg config.Message) (string, error) {
 	// Upload a file if it exists
 	if msg.Extra != nil {
 		for _, rmsg := range helper.HandleExtra(&msg, b.General) {
-			if _, msgErr := b.sendMessage(chatid, rmsg.Username, rmsg.Text, parentID); msgErr != nil {
+			if _, msgErr := b.sendMessage(chatid, topicid, rmsg.Username, rmsg.Text, parentID); msgErr != nil {
 				b.Log.Errorf("sendMessage failed: %s", msgErr)
 			}
 		}
 		// check if we have files to upload (from slack, telegram or mattermost)
 		if len(msg.Extra["file"]) > 0 {
-			return b.handleUploadFile(&msg, chatid, parentID)
+			return b.handleUploadFile(&msg, chatid, topicid, parentID)
 		}
 	}
 
@@ -143,7 +173,7 @@ func (b *Btelegram) Send(msg config.Message) (string, error) {
 	// Ignore empty text field needs for prevent double messages from whatsapp to telegram
 	// when sending media with text caption
 	if msg.Text != "" {
-		return b.sendMessage(chatid, msg.Username, msg.Text, parentID)
+		return b.sendMessage(chatid, topicid, msg.Username, msg.Text, parentID)
 	}
 
 	return "", nil
@@ -157,9 +187,12 @@ func (b *Btelegram) getFileDirectURL(id string) string {
 	return res
 }
 
-func (b *Btelegram) sendMessage(chatid int64, username, text string, parentID int) (string, error) {
+func (b *Btelegram) sendMessage(chatid int64, topicid int, username, text string, parentID int) (string, error) {
 	m := tgbotapi.NewMessage(chatid, "")
 	m.Text, m.ParseMode = TGGetParseMode(b, username, text)
+	if topicid != 0 {
+		m.BaseChat.MessageThreadID = topicid
+	}
 	m.ReplyToMessageID = parentID
 	m.DisableWebPagePreview = b.GetBool("DisableWebPagePreview")
 
@@ -171,11 +204,19 @@ func (b *Btelegram) sendMessage(chatid int64, username, text string, parentID in
 }
 
 // sendMediaFiles native upload media files via media group
-func (b *Btelegram) sendMediaFiles(msg *config.Message, chatid int64, parentID int, media []interface{}) (string, error) {
+func (b *Btelegram) sendMediaFiles(msg *config.Message, chatid int64, threadid int, parentID int, media []interface{}) (string, error) {
 	if len(media) == 0 {
 		return "", nil
 	}
-	mg := tgbotapi.MediaGroupConfig{ChatID: chatid, ChannelUsername: msg.Username, Media: media, ReplyToMessageID: parentID}
+	mg := tgbotapi.MediaGroupConfig{
+		BaseChat: tgbotapi.BaseChat{
+			ChatID:           chatid,
+			MessageThreadID:  threadid,
+			ChannelUsername:  msg.Username,
+			ReplyToMessageID: parentID,
+		},
+		Media: media,
+	}
 	messages, err := b.c.SendMediaGroup(mg)
 	if err != nil {
 		return "", err