Fix Mattermost event deduplication

Mattermost assigns its own IDs to messages, thus when sending a message
to Mattermost the event_seen key that has to be written must take into
account that ID and not the one that we put in the event (which was the
Matrix event ID)

Note that for XMPP anything can be used as an ID, so using the Matrix
event ID there worked, but it's actually not so good.

1 files changed, 12 insertions, 12 deletions

diff --git a/connector/mattermost/mattermost.go b/connector/mattermost/mattermost.go
index 12ac604..52eb40f 100644
--- a/connector/mattermost/mattermost.go
+++ b/connector/mattermost/mattermost.go
@@ -243,7 +243,7 @@ func (mm *Mattermost) Leave(roomId RoomID) {
 	// Not supported? TODO
 }
 
-func (mm *Mattermost) Send(event *Event) error {
+func (mm *Mattermost) Send(event *Event) (string, error) {
 	post := &model.Post{
 		Message: event.Text,
 	}
@@ -254,29 +254,29 @@ func (mm *Mattermost) Send(event *Event) error {
 	if event.Room != "" {
 		ch, err := mm.checkRoomId(event.Room)
 		if err != nil {
-			return err
+			return "", err
 		}
 		post.ChannelId = ch
 	} else if event.Recipient != "" {
 		ui, err := mm.checkUserId(event.Recipient)
 		if err != nil {
-			return err
+			return "", err
 		}
 
 		_, resp := mm.conn.Client.CreateDirectChannel(mm.conn.User.Id, ui)
 		if resp.Error != nil {
-			return resp.Error
+			return "", resp.Error
 		}
 		channelName := model.GetDMNameFromIds(ui, mm.conn.User.Id)
 
 		err = mm.conn.UpdateChannels()
 		if err != nil {
-			return err
+			return "", err
 		}
 
 		post.ChannelId = mm.conn.GetChannelId(channelName, "")
 	} else {
-		return fmt.Errorf("Invalid target")
+		return "", fmt.Errorf("Invalid target")
 	}
 
 	if event.Attachments != nil {
@@ -284,28 +284,28 @@ func (mm *Mattermost) Send(event *Event) error {
 		for _, file := range event.Attachments {
 			rdr, err := file.Read()
 			if err != nil {
-				return err
+				return "", err
 			}
 			defer rdr.Close()
 			data, err := ioutil.ReadAll(rdr)
 			if err != nil {
-				return err
+				return "", err
 			}
 			up_file, err := mm.conn.UploadFile(data, post.ChannelId, file.Filename())
 			if err != nil {
 				log.Warnf("UploadFile error: %s", err)
-				return err
+				return "", err
 			}
 			post.FileIds = append(post.FileIds, up_file)
 		}
 	}
 
-	_, resp := mm.conn.Client.CreatePost(post)
+	created_post, resp := mm.conn.Client.CreatePost(post)
 	if resp.Error != nil {
 		log.Warnf("CreatePost error: %s", resp.Error)
-		return resp.Error
+		return "", resp.Error
 	}
-	return nil
+	return created_post.Id, nil
 }
 
 func (mm *Mattermost) Close() {