<?php

/**
 * Kunena Component
 *
 * @package         Kunena.Framework
 * @subpackage      Integration
 *
 * @copyright       Copyright (C) 2008 - @currentyear@ Kunena Team. All rights reserved.
 * @license         https://www.gnu.org/copyleft/gpl.html GNU/GPL
 * @link            https://www.kunena.org
 **/

namespace Kunena\Forum\Libraries\Access;

\defined('_JEXEC') or die();

use Exception;
use Joomla\CMS\Factory;
use Joomla\CMS\HTML\HTMLHelper;
use Joomla\CMS\Language\Text;
use Joomla\CMS\Plugin\PluginHelper;
use Joomla\Database\Exception\ExecutionFailureException;
use Joomla\Utilities\ArrayHelper;
use Kunena\Forum\Libraries\Config\KunenaConfig;
use Kunena\Forum\Libraries\Error\KunenaError;
use Kunena\Forum\Libraries\Factory\KunenaFactory;
use Kunena\Forum\Libraries\Forum\Category\KunenaCategory;
use Kunena\Forum\Libraries\Forum\Category\KunenaCategoryHelper;
use Kunena\Forum\Libraries\Forum\Category\User\KunenaCategoryUserHelper;
use Kunena\Forum\Libraries\Forum\KunenaForum;
use Kunena\Forum\Libraries\Forum\Topic\KunenaTopic;
use Kunena\Forum\Libraries\Forum\Topic\KunenaTopicHelper;
use Kunena\Forum\Libraries\Profiler\KunenaProfiler;
use Kunena\Forum\Libraries\User\KunenaUser;
use Kunena\Forum\Libraries\User\KunenaUserHelper;

/**
 * Class KunenaAccess
 *
 * @since   Kunena 6.0
 */
class KunenaAccess
{
    /**
     * @return  void
     *
     * @since   Kunena 6.0
     */
    const CATEGORY_SUBSCRIPTION = 1;

    /**
     * @return  void
     *
     * @since   Kunena 6.0
     */
    const TOPIC_SUBSCRIPTION = 2;

    /**
     * @var     null
     * @since   Kunena 6.0
     */
    protected static $instance = null;

    /**
     * @var     string
     * @since   Kunena 6.0
     */
    protected static $cacheKey = 'com_kunena.access.global.v1';

    /**
     * @var     array
     * @since   Kunena 6.0
     */
    protected $accesstypes = ['all' => []];

    /**
     * @var     array|null
     * @since   Kunena 6.0
     */
    protected $adminsByCatid = null;

    /**
     * @var     array|null
     * @since   Kunena 6.0
     */
    protected $adminsByUserid = null;

    /**
     * @var     array|null
     * @since   Kunena 6.0
     */
    protected $moderatorsByCatid = null;

    /**
     * @var     array|null
     * @since   Kunena 6.0
     */
    protected $moderatorsByUserid = null;

    /**
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function __construct()
    {
        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->start('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;
        PluginHelper::importPlugin('kunena');

        $classes = Factory::getApplication()->triggerEvent('onKunenaGetAccessControl');

        foreach ($classes as $class) {
            if (!\is_object($class)) {
                continue;
            }

            $types                      = $class->getAccessTypes();
            $this->accesstypes['all'][] = $class;
            unset($types['all']);

            foreach ($types as $type) {
                $this->accesstypes[$type][] = $class;
            }
        }

        // If values were not cached (or users permissions have been changed), force reload
        if (!isset($this->adminsByCatid)) {
            $this->clearCache();
        }

        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->stop('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;
    }

    /**
     * @return  void
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function clearCache()
    {
        $this->adminsByCatid      = [];
        $this->adminsByUserid     = [];
        $this->moderatorsByCatid  = [];
        $this->moderatorsByUserid = [];

        // Reset read KunenaAccess for the current session
        $me  = KunenaUserHelper::getMyself();
        $app = KunenaFactory::getApplication();
        $app->setUserState("com_kunena.user{$me->userid}_read", null);

        // @var KunenaAccess $access

        foreach ($this->accesstypes['all'] as $access) {
            if (method_exists($access, 'loadCategoryRoles')) {
                $this->storeRoles((array) $access->loadCategoryRoles());
            }
        }

        // Load native category moderators and administrators
        $db    = Factory::getContainer()->get('DatabaseDriver');
        $query = $db->createQuery()
            ->select($db->quoteName(['user_id', 'category_id', 'role']))
            ->from($db->quoteName('#__kunena_user_categories'))
            ->where($db->quoteName('role') . ' IN (1,2)');
        $db->setQuery($query);

        try {
            $this->storeRoles((array) $db->loadObjectList());
        } catch (ExecutionFailureException $e) {
            KunenaError::displayDatabaseError($e);
        }
    }

    /**
     * @param   array|null  $list  list
     *
     * @return  void
     *
     * @since   Kunena 6.0
     */
    protected function storeRoles(?array $list = null)
    {
        if (empty($list)) {
            return;
        }

        foreach ($list as $item) {
            $userid = \intval($item->user_id);
            $catid  = \intval($item->category_id);

            if (!$userid) {
                continue;
            }

            if ($item->role == KunenaForum::ADMINISTRATOR) {
                $this->adminsByUserid[$userid][$catid] = 1;
                $this->adminsByCatid[$catid][$userid]  = 1;
            } elseif ($item->role == KunenaForum::MODERATOR) {
                $this->moderatorsByUserid[$userid][$catid] = 1;
                $this->moderatorsByCatid[$catid][$userid]  = 1;
            }
        }
    }

    /**
     * @return  KunenaAccess|null
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public static function getInstance(): ?KunenaAccess
    {
        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->start('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;

        if (!self::$instance) {
            self::$instance = new KunenaAccess();
        }

        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->stop('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;

        return self::$instance;
    }

    /**
     * @param   KunenaCategory  $category  category
     *
     * @return  array
     *
     * @since   Kunena 6.0
     */
    public function getAccessOptions(KunenaCategory $category): array
    {
        $list = [];

        // @var KunenaAccess $access

        foreach ($this->accesstypes['all'] as $access) {
            if (method_exists($access, 'getAccessOptions')) {
                $list += $access->getAccessOptions(null, $category);
            }
        }

        // User has disabled KunenaAccess control
        $key = preg_replace('/[^\w\d]/', '-', $category->accesstype);

        if (!isset($list[$key])) {
            $list[$key]['access'] = [
                'title' => Text::_('COM_KUNENA_ACCESS_UNKNOWN'),
                'desc'  => Text::sprintf('COM_KUNENA_ACCESS_UNKNOWN_DESC', $category->accesstype),
                'input' => $category->access,
            ];
        }

        return $list;
    }

    /**
     * @param   KunenaCategory  $category  category
     *
     * @return  string
     *
     * @throws Exception
     * @since   Kunena 6.0
     */
    public function getAccessTypesList(KunenaCategory $category): string
    {
        static $enabled = false;

        if (!$enabled) {
            $enabled = true;
            Factory::getApplication()->getDocument()->addScriptDeclaration(
                "function kShowAccessType(htmlclass, el) {
	var selectedvalue = el.find(\":selected\").val();

	name = selectedvalue.replace(/[^\\w\\d]+/, '-');

$('.'+htmlclass).each(function() {
  $( this ).hide();
});

$('.'+htmlclass+'-'+name).each(function() {
  $( this ).show();
});

}
jQuery(document).ready(function ($) {
	var item = $('#accesstype');
	if (item) {
		kShowAccessType('kaccess', item);
	}
});"
            );
        }

        $exists      = 0;
        $accesstypes = [];

        foreach ($this->accesstypes as $type => $list) {
            if ($type == 'all') {
                continue;
            }

            foreach ($list as $access) {
                if (method_exists($access, 'getAccessOptions')) {
                    $string               = Text::_('COM_KUNENA_INTEGRATION_TYPE_' . preg_replace('/[^\w\d]/', '_', $type));
                    $accesstypes[$string] = HTMLHelper::_('select.option', $type, $string);
                    $exists               |= $type == $category->accesstype;

                    break;
                }
            }
        }

        ksort($accesstypes);

        // User has disabled KunenaAccess control
        if (!$exists) {
            $string               = Text::sprintf('COM_KUNENA_INTEGRATION_UNKNOWN', $category->accesstype);
            $accesstypes[$string] = HTMLHelper::_('select.option', $category->accesstype, $string);
        }

        return HTMLHelper::_('select.genericlist', $accesstypes, 'accesstype', 'class="form-select" onchange="kShowAccessType(\'kaccess\', $(this))"', 'value', 'text', $category->accesstype);
    }

    /**
     * Get KunenaAccess groups for the selected category.
     *
     * @param   KunenaCategory  $category  Category
     *
     * @return  array|null
     *
     * @since   Kunena 6.0
     */
    public function getCategoryAccess(KunenaCategory $category): ?array
    {
        $list = [];

        $accesstype = $category->accesstype;

        if (!isset($this->accesstypes[$accesstype])) {
            return $list;
        }

        foreach ($this->accesstypes[$accesstype] as $access) {
            if (method_exists($access, 'getCategoryAccess')) {
                $list += $access->getCategoryAccess($category);
            }
        }

        return $list;
    }

    /**
     * Get category administrators.
     *
     * @param   int   $catid  Category Id
     * @param   bool  $all    all
     *
     * @return  array
     *
     * @since   Kunena 6.0
     */
    public function getAdmins($catid = 0, $all = false): array
    {
        $list = !empty($this->adminsByCatid[$catid]) ? $this->adminsByCatid[$catid] : [];

        if ($all && !empty($this->adminsByCatid[0])) {
            $list += $this->adminsByCatid[0];
        }

        return $list;
    }

    /**
     * Get category moderators.
     *
     * @param   int   $catid  Category Id
     * @param   bool  $all    all
     *
     * @return  array
     *
     * @since   Kunena 6.0
     */
    public function getModerators($catid = 0, $all = false): array
    {
        $list = !empty($this->moderatorsByCatid[$catid]) ? $this->moderatorsByCatid[$catid] : [];

        if ($all && !empty($this->moderatorsByCatid[0])) {
            $list += $this->moderatorsByCatid[0];
        }

        return $list;
    }

    /**
     * @param   mixed  $user  user
     *
     * @return  array
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function getAdminStatus($user = null): array
    {
        if (!($user instanceof KunenaUser)) {
            $user = KunenaFactory::getUser($user);
        }

        return !empty($this->adminsByUserid[$user->userid]) ? $this->adminsByUserid[$user->userid] : [];
    }

    /**
     * Assign user as moderator or resign him.
     *
     * @param   KunenaCategory|int  $category  KunenaCategory object
     *
     * @param   mixed               $user      KunenaUser object
     * @param   bool                $status    status
     *
     * @return  boolean
     *
     * @throws Exception
     * @since   Kunena 6.0
     *
     * @example if ($category->isAuthorised('admin')) $category->setModerator($user, true);
     */
    public function setModerator($category, $user = null, $status = true): bool
    {
        // Check if category exists
        if ($category && !$category->exists()) {
            return false;
        }

        $categoryId = $category ? $category->id : 0;
        $status     = \intval($status);

        // Check if user exists
        if (!($user instanceof KunenaUser)) {
            $user = KunenaUserHelper::get($user);
        }

        if (!$user->exists()) {
            return false;
        }

        $success      = true;
        $userCategory = KunenaCategoryUserHelper::get($categoryId, $user);

        if (($userCategory->role == 0 && $status) || ($userCategory->role == 1 && !$status)) {
            $userCategory->role = $status;

            $success = $userCategory->save();

            // Clear role cache
            $this->clearCache();

            // Change user moderator status
            $moderator = $this->getModeratorStatus($user);

            if ($user->moderator != !empty($moderator)) {
                $user->moderator = \intval(!empty($moderator));
                $success         = $user->save();
            }
        }

        return $success;
    }

    /**
     * @param   mixed  $user  user
     *
     * @return  array
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function getModeratorStatus($user = null): array
    {
        if (!($user instanceof KunenaUser)) {
            $user = KunenaFactory::getUser($user);
        }

        return !empty($this->moderatorsByUserid[$user->userid]) ? $this->moderatorsByUserid[$user->userid] : [];
    }

    /**
     * @param   mixed  $user  user
     *
     * @return  mixed
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function getAllowedCategories($user = null)
    {
        static $read = [];

        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->start('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;

        if (!($user instanceof KunenaUser)) {
            $user = KunenaFactory::getUser($user);
        }

        if (!isset($read[$user->userid])) {
            $id  = $user->userid;
            $app = KunenaFactory::getApplication();

            // TODO: handle guests/bots with no userstate
            $read[$id] = $app->getUserState("com_kunena.user{$id}_read");

            if ($read[$id] === null) {
                $list       = [];
                $categories = KunenaCategoryHelper::getCategories(false, false, 'none');

                foreach ($categories as $category) {
                    // Remove unpublished categories
                    if ($category->published != 1) {
                        unset($categories[$category->id]);
                    }

                    // Moderators have always KunenaAccess
                    if (self::isModerator($user, $category->id)) {
                        $list[$category->id] = $category->id;
                        unset($categories[$category->id]);
                    }
                }

                // Get external authorization
                if (!empty($categories)) {
                    // @var KunenaAccess $access

                    foreach ($this->accesstypes['all'] as $access) {
                        if (method_exists($access, 'authoriseCategories')) {
                            $list += $access->authoriseCategories($id, $categories);
                        }
                    }
                }

                // Clean up and filter the resulting list by using only array keys.
                $list      = array_keys($list);
                $list      = ArrayHelper::toInteger($list);
                $read[$id] = array_combine($list, $list);
                unset($read[$id][0]);
                $app->setUserState("com_kunena.user{$id}_read", $read[$id]);
            }
        }

        KunenaProfiler::getInstance() ? KunenaProfiler::instance()->stop('function ' . __CLASS__ . '::' . __FUNCTION__ . '()') : null;

        return $read[$user->userid];
    }

    /**
     * @param   mixed  $user   user
     * @param   int    $catid  catid
     *
     * @return  boolean
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function isModerator($user = null, $catid = 0): bool
    {
        if (!($user instanceof KunenaUser)) {
            $user = KunenaUserHelper::get($user);
        }

        // Guests and banned users cannot be moderators
        if (!$user->exists() || $user->isBanned()) {
            return false;
        }

        // Administrators are always moderators
        if ($this->isAdmin($user, $catid)) {
            return true;
        }

        if (!empty($this->moderatorsByUserid[$user->userid])) {
            // Is user a global moderator?
            if (!empty($this->moderatorsByUserid[$user->userid][0])) {
                return true;
            }

            // Is user a category moderator?
            if (!empty($this->moderatorsByUserid[$user->userid][$catid])) {
                return true;
            }
        }

        return false;
    }

    /**
     * @param   mixed  $user   user
     * @param   int    $catid  catid
     *
     * @return  boolean
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function isAdmin($user = null, $catid = 0): bool
    {
        if (!($user instanceof KunenaUser)) {
            $user = KunenaFactory::getUser($user);
        }

        // Guests and banned users cannot be administrators
        if (!$user->exists() || $user->isBanned()) {
            return false;
        }

        // In backend every logged in user has global admin rights (for now)
        if (Factory::getApplication()->isClient('administrator') && $user->userid == KunenaUserHelper::getMyself()->userid) {
            return true;
        }

        // Is user a global administrator?
        if (!empty($this->adminsByUserid[$user->userid][0])) {
            return true;
        }

        // Is user a category administrator?
        if (!empty($this->adminsByUserid[$user->userid][$catid])) {
            return true;
        }

        return false;
    }

    /**
     * Authorise user actions in a category.
     *
     * Function returns a list of authorised actions. Missing actions are threaded as inherit.
     *
     * @param   KunenaCategory  $category  category
     * @param   int             $userid    user id
     *
     * @return  array
     *
     * @since   Kunena 6.0
     */
    public function authoriseActions(KunenaCategory $category, int $userid): array
    {
        $list = [];

        if (empty($this->accesstypes[$category->accesstype])) {
            return $list;
        }

        foreach ($this->accesstypes[$category->accesstype] as $access) {
            // @var KunenaAccess $access

            if (method_exists($access, 'getAuthoriseActions')) {
                $sublist = $access->getAuthoriseActions($category, $userid);

                foreach ($sublist as $key => $value) {
                    $list[$key] = !empty($list[$key]) || $value;
                }
            }
        }

        return $list;
    }

    /**
     * @param   mixed  $user    user
     * @param   int    $catid   catid
     * @param   bool   $string  string
     *
     * @return  string|array
     *
     * @throws Exception
     * @since   Kunena 6.0
     */
    public function getAllowedHold($user, int $catid, $string = true)
    {
        /**
         * Hold = 0: normal
         * Hold = 1: unapproved
         * Hold = 2: deleted
         */

        if (!($user instanceof KunenaUser)) {
            $user = KunenaFactory::getUser($user);
        }

        $config = KunenaFactory::getConfig();

        $hold[0] = 0;

        if ($this->isModerator($user, $catid)) {
            $hold[1] = 1;
        }

        if (
            ($config->modSeeDeleted == '0' && $this->isAdmin($user, $catid))
            || ($config->modSeeDeleted == '1' && $this->isModerator($user, $catid))
        ) {
            $hold[2] = 2;
            $hold[3] = 3;
        }

        if ($string) {
            $hold = implode(',', $hold);
        }

        return $hold;
    }

    /**
     * @param   int    $catid        catid
     * @param   mixed  $topic        topic
     * @param   mixed  $type         type
     * @param   bool   $moderators   moderators
     * @param   bool   $admins       admins
     * @param   mixed  $excludeList  exclude list
     *
     * @return  array
     *
     * @throws Exception
     * @since   Kunena 6.0
     */
    public function getSubscribers($catid, $topic, $type = false, $moderators = false, $admins = false, $excludeList = null): array
    {
        $topic    = KunenaTopicHelper::get($topic);
        $category = $topic->getCategory();

        if (!$topic->exists()) {
            return [];
        }

        $modlist = [];

        if (!empty($this->moderatorsByCatid[0])) {
            $modlist += $this->moderatorsByCatid[0];
        }

        if (!empty($this->moderatorsByCatid[$catid])) {
            $modlist += $this->moderatorsByCatid[$catid];
        }

        $adminlist = [];

        if (!empty($this->adminsByCatid[0])) {
            $adminlist += $this->adminsByCatid[0];
        }

        if (!empty($this->adminsByCatid[$catid])) {
            $adminlist += $this->adminsByCatid[$catid];
        }

        if ($type) {
            $subscribers = $this->loadSubscribers($topic, $type);
            $allow       = $deny = [];

            if (!empty($subscribers)) {
                // @var KunenaAccess $access

                foreach ($this->accesstypes[$category->accesstype] as $access) {
                    if (method_exists($access, 'authoriseUsers')) {
                        list($a, $d) = $access->authoriseUsers($topic, $subscribers);

                        if (!empty($a)) {
                            $allow += array_combine($a, $a);
                        }

                        if (!empty($d)) {
                            $deny += array_combine($d, $d);
                        }
                    }
                }
            }

            $subsList = array_diff($allow, $deny);

            // Category administrators and moderators override ACL
            $subsList += array_intersect_key($adminlist, array_flip($subscribers));
            $subsList += array_intersect_key($modlist, array_flip($subscribers));
        }

        if (!$moderators) {
            $modlist = [];
        } else {
            // If category has no moderators, send email to admins instead
            if (empty($modlist)) {
                $admins = true;
            }
        }

        if (!$admins) {
            $adminlist = [];
        }

        $db    = Factory::getContainer()->get('DatabaseDriver');
        $query = $db->createQuery();
        $query->select('u.id, u.name, u.username, u.email')
            ->from('#__users AS u')
            ->where("u.block=0");
        $userlist = [];

        if (!empty($subsList)) {
            $userlist += $subsList;
            $subsList = implode(',', array_keys($subsList));
            $query->select("IF( u.id IN ({$subsList}), 1, 0 ) AS subscription");
        } else {
            $query->select("0 AS subscription");
        }

        if (!empty($modlist)) {
            $userlist += $modlist;
            $modlist  = implode(',', array_keys($modlist));
            $query->select("IF( u.id IN ({$modlist}), 1, 0 ) AS moderator");
        } else {
            $query->select("0 AS moderator");
        }

        if (!empty($adminlist)) {
            $userlist  += $adminlist;
            $adminlist = implode(',', array_keys($adminlist));
            $query->select("IF( u.id IN ({$adminlist}), 1, 0 ) AS admin");
        } else {
            $query->select("0 AS admin");
        }

        if (empty($excludeList)) {
            // False, null, '', 0 and array(): get all subscribers
            $excludeList = [];
        } elseif (\is_array($excludeList)) {
            // Array() needs to be flipped to get userids into keys
            $excludeList = array_flip($excludeList);
        } else {
            // Others: let's assume that we have comma separated list of values (string)
            $excludeList = array_flip(explode(',', (string) $excludeList));
        }

        $userlist = array_diff_key($userlist, $excludeList);
        $userids  = [];

        if (!empty($userlist)) {
            $userlist = implode(',', array_keys($userlist));
            $query->where("u.id IN ({$userlist})");

            // Only send to users whose Joomla account is enabled to Receive System Emails
            if (KunenaConfig::getInstance()->useSystemEmails) {
                $query->where("u.sendEmail = 1");
            }

            $db = Factory::getContainer()->get('DatabaseDriver');
            $db->setQuery($query);

            try {
                $userids = (array) $db->loadObjectList();
            } catch (ExecutionFailureException $e) {
                KunenaError::displayDatabaseError($e);
            }
        }

        return $userids;
    }

    /**
     * @param   KunenaTopic  $topic  loadSubscribers
     * @param   bool         $type   type
     *
     * @return  array
     *
     * @throws  Exception
     * @since   Kunena 6.0
     */
    public function loadSubscribers(KunenaTopic $topic, $type)
    {
        $category = $topic->getCategory();
        $db       = Factory::getContainer()->get('DatabaseDriver');
        $query    = [];

        if ($type & self::TOPIC_SUBSCRIPTION) {
            // Get topic subscriptions
            $querytopic = $db->createQuery()
                ->select($db->quoteName('user_id'))
                ->from($db->quoteName('#__kunena_user_topics', 'ut'))
                ->leftJoin($db->quoteName('#__kunena_users', 'ku') . ' ON ' . $db->quoteName('ut.user_id') . ' = ' . $db->quoteName('ku.userid'))
                ->where($db->quoteName('ut.topic_id') . ' = ' . $db->quote($topic->id))
                ->andWhere($db->quoteName('ut.subscribed') . ' = 1')
                ->andWhere($db->quoteName('ku.banned') . ' = ' . $db->quote('1000-01-01 00:00:00'))
                ->andWhere($db->quoteName('ut.topic_id') . ' = ' . $db->quote($topic->id))
                ->andWhere($db->quoteName('ut.subscribed') . ' = 1')
                ->group($db->quoteName('user_id'));

            $query[] = $querytopic;
        }

        if ($type & self::CATEGORY_SUBSCRIPTION) {
            // Get category subscriptions
            $querycat = $db->createQuery()
                ->select($db->quoteName('user_id'))
                ->from($db->quoteName('#__kunena_user_categories', 'ut'))
                ->leftJoin($db->quoteName('#__kunena_users', 'ku') . ' ON ' . $db->quoteName('ut.user_id') . ' = ' . $db->quoteName('ku.userid'))
                ->where($db->quoteName('category_id') . ' = ' . $db->quote($category->id))
                ->andWhere($db->quoteName('ut.subscribed') . ' = 1')
                ->andWhere($db->quoteName('ku.banned') . ' = ' . $db->quote('1000-01-01 00:00:00'))
                ->andWhere($db->quoteName('category_id') . ' = ' . $db->quote($category->id))
                ->andWhere($db->quoteName('ut.subscribed') . ' = 1')
                ->group($db->quoteName('user_id'));
            $query[]  = $querycat;
        }

        $query = implode(' UNION ', $query);
        $db->setQuery($query);

        try {
            $userids = (array) $db->loadColumn();
        } catch (ExecutionFailureException $e) {
            KunenaError::displayDatabaseError($e);
        }

        return $userids;
    }
}