MM-16258: Adds new API endpoint + (App & Client & Store) to retrieve … (#11176)

* MM-16258: Adds new API endpoint + (App & Client & Store) to retrieve Users who would be removed from a list of hypothetical group IDs representing the synced groups.

* MM-16258: Adds roles to JSON response.

* MM-16258: Updates GetByIDs to use Squirrel.

* MM-16258: Puts as much as possible into Squirrel.

* MM-16258: Changes names of methods, functions, and route.

* MM-16258: Updates some comments.

* MM-16258: Extra validation of group_ids parameter.

* MM-16258: Changes validation of group_ids query param.

* MM-16258: Rename a variable and a constant.

* MM-16258: Fix test.

store/sqlstore/group_store.go

@@ -7,8 +7,10 @@ import (
 	"database/sql"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/Masterminds/squirrel"
+	sq "github.com/Masterminds/squirrel"
 
 	"github.com/mattermost/mattermost-server/model"
 	"github.com/mattermost/mattermost-server/store"
@@ -132,6 +134,19 @@ func (s *SqlGroupStore) Get(groupId string) store.StoreChannel {
 	})
 }
 
+func (s *SqlGroupStore) GetByIDs(groupIDs []string) ([]*model.Group, *model.AppError) {
+	var groups []*model.Group
+	query := s.getQueryBuilder().Select("*").From("UserGroups").Where(sq.Eq{"Id": groupIDs})
+	queryString, args, err := query.ToSql()
+	if err != nil {
+		return nil, model.NewAppError("SqlGroupStore.GetByIDs", "store.sql_group.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	if _, err := s.GetReplica().Select(&groups, queryString, args...); err != nil {
+		return nil, model.NewAppError("SqlGroupStore.GetByIDs", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+	return groups, nil
+}
+
 func (s *SqlGroupStore) GetByRemoteID(remoteID string, groupSource model.GroupSource) store.StoreChannel {
 	return store.Do(func(result *store.StoreResult) {
 
@@ -1035,3 +1050,81 @@ func (s *SqlGroupStore) GetGroups(page, perPage int, opts model.GroupSearchOpts)
 
 	return groups, nil
 }
+
+func (s *SqlGroupStore) teamMembersMinusGroupMembersQuery(teamID string, groupIDs []string, isCount bool) squirrel.SelectBuilder {
+	var selectStr string
+
+	if isCount {
+		selectStr = "count(DISTINCT Users.Id)"
+	} else {
+		tmpl := "Users.*, TeamMembers.SchemeGuest, TeamMembers.SchemeAdmin, TeamMembers.SchemeUser, %s AS GroupIDs"
+		if s.DriverName() == model.DATABASE_DRIVER_MYSQL {
+			selectStr = fmt.Sprintf(tmpl, "group_concat(UserGroups.Id)")
+		} else {
+			selectStr = fmt.Sprintf(tmpl, "string_agg(UserGroups.Id, ',')")
+		}
+	}
+
+	subQuery := s.getQueryBuilder().Select("GroupMembers.UserId").
+		From("GroupMembers").
+		Join("UserGroups ON UserGroups.Id = GroupMembers.GroupId").
+		Where("GroupMembers.DeleteAt = 0").
+		Where(fmt.Sprintf("GroupMembers.GroupId IN ('%s')", strings.Join(groupIDs, "', '")))
+
+	sql, _ := subQuery.MustSql()
+
+	query := s.getQueryBuilder().Select(selectStr).
+		From("TeamMembers").
+		Join("Teams ON Teams.Id = TeamMembers.TeamId").
+		Join("Users ON Users.Id = TeamMembers.UserId").
+		LeftJoin("Bots ON Bots.UserId = TeamMembers.UserId").
+		Join("GroupMembers ON GroupMembers.UserId = Users.Id").
+		Join("UserGroups ON UserGroups.Id = GroupMembers.GroupId").
+		Where("TeamMembers.DeleteAt = 0").
+		Where("Teams.DeleteAt = 0").
+		Where("Users.DeleteAt = 0").
+		Where("Bots.UserId IS NULL").
+		Where("Teams.Id = ?", teamID).
+		Where(fmt.Sprintf("Users.Id NOT IN (%s)", sql))
+
+	if !isCount {
+		query = query.GroupBy("Users.Id, TeamMembers.SchemeGuest, TeamMembers.SchemeAdmin, TeamMembers.SchemeUser")
+	}
+
+	return query
+}
+
+// TeamMembersMinusGroupMembers returns the set of users on the given team minus the set of users in the given
+// groups.
+func (s *SqlGroupStore) TeamMembersMinusGroupMembers(teamID string, groupIDs []string, page, perPage int) ([]*model.UserWithGroups, *model.AppError) {
+	query := s.teamMembersMinusGroupMembersQuery(teamID, groupIDs, false)
+	query = query.OrderBy("Users.Id").Limit(uint64(perPage)).Offset(uint64(page * perPage))
+
+	queryString, args, err := query.ToSql()
+	if err != nil {
+		return nil, model.NewAppError("SqlGroupStore.TeamMembersMinusGroupMembers", "store.sql_group.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	var users []*model.UserWithGroups
+	if _, err = s.GetReplica().Select(&users, queryString, args...); err != nil {
+		return nil, model.NewAppError("SqlGroupStore.TeamMembersMinusGroupMembers", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return users, nil
+}
+
+// CountTeamMembersMinusGroupMembers returns the count of the set of users on the given team minus the set of users
+// in the given groups.
+func (s *SqlGroupStore) CountTeamMembersMinusGroupMembers(teamID string, groupIDs []string) (int64, *model.AppError) {
+	queryString, args, err := s.teamMembersMinusGroupMembersQuery(teamID, groupIDs, true).ToSql()
+	if err != nil {
+		return 0, model.NewAppError("SqlGroupStore.CountTeamMembersMinusGroupMembers", "store.sql_group.app_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	var count int64
+	if count, err = s.GetReplica().SelectInt(queryString, args...); err != nil {
+		return 0, model.NewAppError("SqlGroupStore.CountTeamMembersMinusGroupMembers", "store.select_error", nil, err.Error(), http.StatusInternalServerError)
+	}
+
+	return count, nil
+}