MM-11700 Clean up handling of user display names for notifications (#9343)

* MM-11700 Clean up handling of user display names for notifications

app/notification.go

@@ -157,32 +157,11 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 		updateMentionChans = append(updateMentionChans, a.Srv.Store.Channel().IncrementMentionCount(post.ChannelId, id))
 	}
 
-	var senderUsername string
-	senderName := ""
-	channelName := ""
-	if post.IsSystemMessage() {
-		senderName = utils.T("system.message.name")
-	} else {
-		if value, ok := post.Props["override_username"]; ok && post.Props["from_webhook"] == "true" && channel.Type != model.CHANNEL_DIRECT {
-			senderName = value.(string)
-			senderUsername = value.(string)
-		} else {
-			senderName = sender.Username
-			senderUsername = sender.Username
-		}
-	}
-
-	if channel.Type == model.CHANNEL_GROUP {
-		userList := []*model.User{}
-		for _, u := range profileMap {
-			if u.Id != sender.Id {
-				userList = append(userList, u)
-			}
-		}
-		userList = append(userList, sender)
-		channelName = model.GetGroupDisplayNameFromUsers(userList, false)
-	} else {
-		channelName = channel.DisplayName
+	notification := &postNotification{
+		post:       post,
+		channel:    channel,
+		profileMap: profileMap,
+		sender:     sender,
 	}
 
 	if a.Config().EmailSettings.SendEmailNotifications {
@@ -227,7 +206,7 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 			autoResponderRelated := status.Status == model.STATUS_OUT_OF_OFFICE || post.Type == model.POST_AUTO_RESPONDER
 
 			if userAllowsEmails && status.Status != model.STATUS_ONLINE && profileMap[id].DeleteAt == 0 && !autoResponderRelated {
-				a.sendNotificationEmail(post, profileMap[id], channel, team, channelName, senderName, sender)
+				a.sendNotificationEmail(notification, profileMap[id], team)
 			}
 		}
 	}
@@ -310,12 +289,8 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 				}
 
 				a.sendPushNotification(
-					post,
+					notification,
 					profileMap[id],
-					channel,
-					channelName,
-					sender,
-					senderName,
 					mentionedUserIds[id],
 					(channelNotification || hereNotification || allNotification),
 					replyToThreadType,
@@ -337,12 +312,8 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 
 				if ShouldSendPushNotification(profileMap[id], channelMemberNotifyPropsMap[id], false, status, post) {
 					a.sendPushNotification(
-						post,
+						notification,
 						profileMap[id],
-						channel,
-						channelName,
-						sender,
-						senderName,
 						false,
 						false,
 						"",
@@ -355,9 +326,9 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 	message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POSTED, "", post.ChannelId, "", nil)
 	message.Add("post", a.PostWithProxyAddedToImageURLs(post).ToJson())
 	message.Add("channel_type", channel.Type)
-	message.Add("channel_display_name", channelName)
+	message.Add("channel_display_name", notification.GetChannelName(model.SHOW_USERNAME, ""))
 	message.Add("channel_name", channel.Name)
-	message.Add("sender_name", senderUsername)
+	message.Add("sender_name", notification.GetSenderName(model.SHOW_USERNAME, a.Config().ServiceSettings.EnablePostUsernameOverride))
 	message.Add("team_id", team.Id)
 
 	if len(post.FileIds) != 0 && fchan != nil {
@@ -628,3 +599,50 @@ func (a *App) GetMentionKeywordsInChannel(profiles map[string]*model.User, lookF
 
 	return keywords
 }
+
+// Represents either an email or push notification and contains the fields required to send it to any user.
+type postNotification struct {
+	channel    *model.Channel
+	post       *model.Post
+	profileMap map[string]*model.User
+	sender     *model.User
+}
+
+// Returns the name of the channel for this notification. For direct messages, this is the sender's name
+// preceeded by an at sign. For group messages, this is a comma-separated list of the members of the
+// channel, with an option to exclude the recipient of the message from that list.
+func (n *postNotification) GetChannelName(userNameFormat string, excludeId string) string {
+	switch n.channel.Type {
+	case model.CHANNEL_DIRECT:
+		return fmt.Sprintf("@%s", n.sender.GetDisplayName(userNameFormat))
+	case model.CHANNEL_GROUP:
+		names := []string{}
+		for _, user := range n.profileMap {
+			if user.Id != excludeId {
+				names = append(names, user.GetDisplayName(userNameFormat))
+			}
+		}
+
+		sort.Strings(names)
+
+		return strings.Join(names, ", ")
+	default:
+		return n.channel.DisplayName
+	}
+}
+
+// Returns the name of the sender of this notification, accounting for things like system messages
+// and whether or not the username has been overridden by an integration.
+func (n *postNotification) GetSenderName(userNameFormat string, overridesAllowed bool) string {
+	if n.post.IsSystemMessage() {
+		return utils.T("system.message.name")
+	}
+
+	if overridesAllowed && n.channel.Type != model.CHANNEL_DIRECT {
+		if value, ok := n.post.Props["override_username"]; ok && n.post.Props["from_webhook"] == "true" {
+			return value.(string)
+		}
+	}
+
+	return n.sender.GetDisplayName(userNameFormat)
+}