[MM-59519] preserve DM/GM unread/read state over export and import (#27707)

server/channels/app/export.go

@@ -815,7 +815,7 @@ func (a *App) exportAllDirectChannels(ctx request.CTX, job *model.Job, writer io
 			afterId = channel.Id
 
 			// Skip if there are no active members in the channel
-			if len(*channel.Members) == 0 {
+			if len(channel.Members) == 0 {
 				continue
 			}
 
@@ -829,7 +829,12 @@ func (a *App) exportAllDirectChannels(ctx request.CTX, job *model.Job, writer io
 				return err
 			}
 
-			channelLine := ImportLineFromDirectChannel(channel, favoritedBy)
+			shownBy, err := a.buildShownByList(channel)
+			if err != nil {
+				return err
+			}
+
+			channelLine := ImportLineFromDirectChannel(channel, favoritedBy, shownBy)
 			if err := a.exportWriteLine(writer, channelLine); err != nil {
 				return err
 			}
@@ -862,6 +867,55 @@ func (a *App) buildFavoritedByList(channelID string) ([]string, *model.AppError)
 	return userIDs, nil
 }
 
+func (a *App) buildShownByList(channel *model.DirectChannelForExport) ([]string, *model.AppError) {
+	shownBy := make([]string, 0)
+	switch channel.Type {
+	case model.ChannelTypeGroup:
+		for _, member := range channel.Members {
+			prefs, err := a.Srv().Store().Preference().GetCategory(member.UserId, model.PreferenceCategoryGroupChannelShow)
+			if err != nil {
+				return nil, model.NewAppError("buildShownByList", "app.preference.get_category.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
+			}
+
+			for i := range prefs {
+				if prefs[i].Name == channel.Id && prefs[i].Value == "true" {
+					user, err := a.Srv().Store().User().Get(context.Background(), member.UserId)
+					if err != nil {
+						return nil, model.NewAppError("buildShownByList", "app.user.get.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
+					}
+
+					shownBy = append(shownBy, user.Username)
+				}
+			}
+		}
+	case model.ChannelTypeDirect:
+		for i, member := range channel.Members {
+			otherMember := member // in case it's a channel with self
+			if len(channel.Members) == 2 {
+				// since the are only two members, the other member is should be the remainder of i+1/2
+				otherMember = channel.Members[(i+1)%2]
+			}
+			prefs, err := a.Srv().Store().Preference().GetCategoryAndName(model.PreferenceCategoryDirectChannelShow, otherMember.UserId)
+			if err != nil {
+				return nil, model.NewAppError("buildShownByList", "app.preference.get_category.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
+			}
+
+			for _, pref := range prefs {
+				if pref.Value == "true" && pref.UserId == member.UserId {
+					user, err := a.Srv().Store().User().Get(context.Background(), member.UserId)
+					if err != nil {
+						return nil, model.NewAppError("buildShownByList", "app.user.get.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
+					}
+
+					shownBy = append(shownBy, user.Username)
+				}
+			}
+		}
+	}
+
+	return shownBy, nil
+}
+
 func (a *App) exportAllDirectPosts(ctx request.CTX, job *model.Job, writer io.Writer, withAttachments, includeArchivedChannels bool) ([]imports.AttachmentImportData, *model.AppError) {
 	var attachments []imports.AttachmentImportData
 	afterId := strings.Repeat("0", 26)