public function unbindStudent(Request $request)
{
    $groupId = $request->input('groupId');
    $studentId = $request->input('studentId');

    DB::beginTransaction();

    try {
        $groupName = Group::where('id', $groupId)->first()->name;
        GroupStudent::where(['group_id' => $groupId, 'student_id' => $studentId])->delete();
        $studentProducts = StudentProduct::where(['group_id' => $groupId, 'student_id' => $studentId])->get();
        foreach ($studentProducts as $sp) {
            $sp->group_id = null;
            $sp->save();
        }

        $currentDate = date('Y-m-d');
        $currentHour = date('H');

        $events = Event::where('date', '>=', $currentDate)
            ->where('hour', '>=', $currentHour)
            ->where('group_name', $groupName)
            ->get();

        $ids = [];
        foreach ($events as $e) {
            $ids[] = $e->id;
        }

        EventLesson::whereIn('event_id', $ids)
            ->where('student_id',  $studentId)
            ->where('attendance_status', '=', 0)
            ->delete();

        DB::commit();
    } catch (\Exception $e) {
        DB::rollback();
        $mes = $e->getMessage();
        $result['error'] = $mes;
        return $result;
    }

    $result['success'] = 'Deleted';
    return $result;
}