class.ilChatroom.php

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<?php

declare(strict_types=1);

use ILIAS\Notifications\Identification\NotificationIdentification;
use ILIAS\Notifications\Model\ilNotificationConfig;
use ILIAS\Notifications\Model\ilNotificationLink;
use ILIAS\Notifications\Model\ilNotificationParameter;
use ILIAS\Chatroom\GlobalScreen\ChatInvitationNotificationProvider;

class ilChatroom
{
    public const ROOM_INVITATION = 'invitation_to_room';
    private static string $settingsTable = 'chatroom_settings';
    private static string $historyTable = 'chatroom_history';
    private static string $userTable = 'chatroom_users';
    private static string $sessionTable = 'chatroom_sessions';
    private static string $banTable = 'chatroom_bans';
    private static string $uploadTable = 'chatroom_uploads';
    private array $settings = [];
    private array $availableSettings = [
        'object_id' => 'integer',
        'allow_anonymous' => 'boolean',
        'allow_custom_usernames' => 'boolean',
        'enable_history' => 'boolean',
        'autogen_usernames' => 'string',
        'room_type' => 'string',
        'display_past_msgs' => 'integer',
    ];
    private int $roomId = 0;
    private ?ilObjChatroom $object = null;

    public static function checkUserPermissions($permissions, int $ref_id, bool $send_info = true): bool
    {
        global $DIC;
        $main_tpl = $DIC->ui()->mainTemplate();

        if (!is_array($permissions)) {
            $permissions = [$permissions];
        }

        $hasPermissions = self::checkPermissions($DIC->user()->getId(), $ref_id, $permissions);
        if (!$hasPermissions && $send_info) {
            $main_tpl->setOnScreenMessage('failure', $DIC->language()->txt('permission_denied'), true);

            return false;
        }

        return $hasPermissions;
    }

    public static function checkPermissionsOfUser(int $usr_id, $permissions, int $ref_id): bool
    {
        if (!is_array($permissions)) {
            $permissions = [$permissions];
        }

        return self::checkPermissions($usr_id, $ref_id, $permissions);
    }

    protected static function checkPermissions(int $usr_id, int $ref_id, array $permissions): bool
    {
        global $DIC;

        $pub_ref_id = ilObjChatroom::_getPublicRefId();

        if ($pub_ref_id === $ref_id) {
            $obj_id = ilObject::_lookupObjId($ref_id);
            foreach ($permissions as $permission) {
                $no_access = !$DIC->rbac()->system()->checkAccessOfUser($usr_id, $permission, $ref_id) || (
                    !$DIC->rbac()->system()->checkAccessOfUser($usr_id, 'write', $ref_id) &&
                    ilObjChatroomAccess::_isOffline($obj_id) &&
                    in_array($permission, ['read', 'visible'], true)
                );

                if ($no_access) {
                    return false;
                }
            }
        } else {
            foreach ($permissions as $permission) {
                if (!$DIC->access()->checkAccessOfUser($usr_id, $permission, '', $ref_id)) {
                    return false;
                }
            }
        }

        return true;
    }

    public static function byObjectId(int $object_id): ?ilChatroom
    {
        global $DIC;

        $query = 'SELECT * FROM ' . self::$settingsTable . ' WHERE object_id = %s';
        $types = [ilDBConstants::T_INTEGER];
        $values = [$object_id];
        $rset = $DIC->database()->queryF($query, $types, $values);

        if ($row = $DIC->database()->fetchAssoc($rset)) {
            $room = new self();
            $room->initialize($row);
            return $room;
        }

        return null;
    }

    public function initialize(array $rowdata): void
    {
        $this->roomId = (int) $rowdata['room_id'];

        foreach ($this->availableSettings as $setting => $type) {
            if (isset($rowdata[$setting])) {
                settype($rowdata[$setting], $this->availableSettings[$setting]);
                $this->setSetting($setting, $rowdata[$setting]);
            }
        }
    }

    public function setSetting(string $name, $value): void
    {
        $this->settings[$name] = $value;
    }

    public static function byRoomId(int $room_id, bool $initObject = false): ?ilChatroom
    {
        global $DIC;

        $query = 'SELECT * FROM ' . self::$settingsTable . ' WHERE room_id = %s';

        $types = [ilDBConstants::T_INTEGER];
        $values = [$room_id];

        $rset = $DIC->database()->queryF($query, $types, $values);

        if ($row = $DIC->database()->fetchAssoc($rset)) {
            $room = new self();
            $room->initialize($row);

            if ($initObject) {
                $room->object = ilObjectFactory::getInstanceByObjId((int) $row['object_id']);
            }

            return $room;
        }

        return null;
    }

    public function getDescription(): string
    {
        if (!$this->object) {
            $this->object = ilObjectFactory::getInstanceByObjId((int) $this->getSetting('object_id'));
        }

        return $this->object->getDescription();
    }

    public function getSetting(string $name)
    {
        return $this->settings[$name];
    }

    public function save(): void
    {
        $this->saveSettings($this->settings);
    }

    public function saveSettings(array $settings): void
    {
        global $DIC;

        $localSettings = [];

        foreach ($this->availableSettings as $setting => $type) {
            if (array_key_exists($setting, $settings)) {
                if ($type === 'boolean') {
                    $settings[$setting] = (bool) $settings[$setting];
                }
                $localSettings[$setting] = [$this->phpTypeToMDBType($type), $settings[$setting]];
            }
        }

        if (!isset($localSettings['room_type']) || !$localSettings['room_type'][1]) {
            $localSettings['room_type'][0] = ilDBConstants::T_TEXT;
            $localSettings['room_type'][1] = 'repository';
        }

        if ($this->roomId > 0) {
            $DIC->database()->update(
                self::$settingsTable,
                $localSettings,
                ['room_id' => [ilDBConstants::T_INTEGER, $this->roomId]]
            );
        } else {
            $this->roomId = $DIC->database()->nextId(self::$settingsTable);

            $localSettings['room_id'] = [
                ilDBConstants::T_INTEGER,
                $this->roomId
            ];

            $DIC->database()->insert(self::$settingsTable, $localSettings);
        }
    }

    private function phpTypeToMDBType(string $type): string
    {
        return match ($type) {
            'string' => ilDBConstants::T_TEXT,
            'boolean' => ilDBConstants::T_INTEGER,
            default => $type,
        };
    }

    public function addHistoryEntry($message): void
    {
        global $DIC;

        $timestamp = 0;
        if (is_array($message)) {
            $timestamp = (int) $message['timestamp'];
        } elseif (is_object($message)) {
            $timestamp = (int) $message->timestamp;
        }

        $id = $DIC->database()->nextId(self::$historyTable);
        $DIC->database()->insert(
            self::$historyTable,
            [
                'hist_id' => [ilDBConstants::T_INTEGER, $id],
                'room_id' => [ilDBConstants::T_INTEGER, $this->roomId],
                'message' => [ilDBConstants::T_TEXT, json_encode($message, JSON_THROW_ON_ERROR)],
                'timestamp' => [ilDBConstants::T_INTEGER, ($timestamp > 0 ? $timestamp : time())],
            ]
        );
    }

    public function connectUser(ilChatroomUser $user): bool
    {
        global $DIC;

        $userdata = [
            'login' => $user->getUsername(),
            'id' => $user->getUserId()
        ];

        $query = 'SELECT user_id FROM ' . self::$userTable . ' WHERE room_id = %s AND user_id = %s';
        $types = [ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER];
        $values = [$this->roomId, $user->getUserId()];

        if (!$DIC->database()->fetchAssoc($DIC->database()->queryF($query, $types, $values))) {
            // Notice: Using replace instead of insert looks strange, because we actually know whether the selected data exists or not
            // But we occasionally found some duplicate key errors although the data set should not exist when the following code is reached
            $DIC->database()->replace(
                self::$userTable,
                [
                    'room_id' => [ilDBConstants::T_INTEGER, $this->roomId],
                    'user_id' => [ilDBConstants::T_INTEGER, $user->getUserId()]
                ],
                [
                    'userdata' => [ilDBConstants::T_TEXT, json_encode($userdata, JSON_THROW_ON_ERROR)],
                    'connected' => [ilDBConstants::T_INTEGER, time()],
                ]
            );

            return true;
        }

        return false;
    }

    public function getConnectedUsers(bool $only_data = true): array
    {
        global $DIC;

        $query = 'SELECT ' . ($only_data ? 'userdata' : '*') . ' FROM ' . self::$userTable . ' WHERE room_id = %s';
        $types = [ilDBConstants::T_INTEGER];
        $values = [$this->roomId];
        $rset = $DIC->database()->queryF($query, $types, $values);
        $users = [];

        while ($row = $DIC->database()->fetchAssoc($rset)) {
            $users[] = $only_data ? json_decode($row['userdata'], false, 512, JSON_THROW_ON_ERROR) : $row;
        }

        return $users;
    }

    public function disconnectUser(int $user_id): void
    {
        $this->disconnectUsers([$user_id]);
    }

    public function disconnectUsers(array $userIds): void
    {
        global $DIC;

        $query = 'SELECT * FROM ' . self::$userTable . ' WHERE room_id = %s AND ' .
            $DIC->database()->in('user_id', $userIds, false, ilDBConstants::T_INTEGER);

        $types = [ilDBConstants::T_INTEGER];
        $values = [$this->roomId];
        $res = $DIC->database()->queryF($query, $types, $values);

        if ($row = $DIC->database()->fetchAssoc($res)) {
            $query = 'DELETE FROM ' . self::$userTable . ' WHERE room_id = %s AND ' .
                $DIC->database()->in('user_id', $userIds, false, ilDBConstants::T_INTEGER);

            $types = [ilDBConstants::T_INTEGER];
            $values = [$this->roomId];
            $DIC->database()->manipulateF($query, $types, $values);

            do {
                if ($this->getSetting('enable_history')) {
                    $id = $DIC->database()->nextId(self::$sessionTable);
                    $DIC->database()->insert(
                        self::$sessionTable,
                        [
                            'sess_id' => [ilDBConstants::T_INTEGER, $id],
                            'room_id' => [ilDBConstants::T_INTEGER, $this->roomId],
                            'user_id' => [ilDBConstants::T_INTEGER, $row['user_id']],
                            'userdata' => [ilDBConstants::T_TEXT, $row['userdata']],
                            'connected' => [ilDBConstants::T_INTEGER, $row['connected']],
                            'disconnected' => [ilDBConstants::T_INTEGER, time()]
                        ]
                    );
                }
            } while ($row = $DIC->database()->fetchAssoc($res));
        }
    }

    public function getSettings(): array
    {
        return $this->settings;
    }

    public function isSubscribed(int $chat_userid): bool
    {
        global $DIC;

        $query = 'SELECT COUNT(user_id) as cnt FROM ' . self::$userTable .
            ' WHERE room_id = %s AND user_id = %s';

        $types = [ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER];
        $values = [$this->roomId, $chat_userid];
        $res = $DIC->database()->queryF($query, $types, $values);

        return ($row = $DIC->database()->fetchAssoc($res)) && (int) $row['cnt'] === 1;
    }

    public function getHistory(
        ilDateTime $from = null,
        ilDateTime $to = null,
        int $restricted_session_userid = null,
        bool $respect_target = true
    ): array {
        global $DIC;

        $join = '';

        $query =
            'SELECT historyTable.* ' .
            'FROM ' . self::$historyTable . ' historyTable ' . $join . ' ' .
            'WHERE historyTable.room_id = ' . $this->getRoomId();

        $filter = [];

        if ($from !== null) {
            $filter[] = 'timestamp >= ' . $DIC->database()->quote($from->getUnixTime(), ilDBConstants::T_INTEGER);
        }

        if ($to !== null) {
            $filter[] = 'timestamp <= ' . $DIC->database()->quote($to->getUnixTime(), ilDBConstants::T_INTEGER);
        }

        if ($filter) {
            $query .= ' AND ' . implode(' AND ', $filter);
        }
        $query .= ' ORDER BY timestamp ASC';

        $rset = $DIC->database()->query($query);
        $result = [];

        while ($row = $DIC->database()->fetchAssoc($rset)) {
            try {
                $message = json_decode($row['message'], false, 512, JSON_THROW_ON_ERROR);
            } catch (JsonException) {
                $message = null;
            } finally {
                if ($message === null) {
                    $message = json_decode('{}', false, 512, JSON_THROW_ON_ERROR);
                }
            }

            $row['message'] = $message;
            $row['message']->timestamp = $row['timestamp'];
            if (
                $respect_target &&
                property_exists($row['message'], 'target') &&
                $row['message']->target !== null &&
                !$row['message']->target->public && (
                    !isset($row['recipients']) ||
                    !in_array($DIC->user()->getId(), explode(',', (string) $row['recipients']), false)
                )
            ) {
                continue;
            }

            $result[] = $row;
        }
        return $result;
    }

    public function getRoomId(): int
    {
        return $this->roomId;
    }

    public function saveFileUploadToDb(int $user_id, string $filename, string $type): void
    {
        global $DIC;

        $upload_id = $DIC->database()->nextId(self::$uploadTable);
        $DIC->database()->insert(
            self::$uploadTable,
            [
                'upload_id' => [ilDBConstants::T_INTEGER, $upload_id],
                'room_id' => [ilDBConstants::T_INTEGER, $this->roomId],
                'user_id' => [ilDBConstants::T_INTEGER, $user_id],
                'filename' => [ilDBConstants::T_TEXT, $filename],
                'filetype' => [ilDBConstants::T_TEXT, $type],
                'timestamp' => [ilDBConstants::T_INTEGER, time()]
            ]
        );
    }

    public function banUser(int $user_id, int $actor_id, string $comment = ''): void
    {
        global $DIC;

        $DIC->database()->replace(
            self::$banTable,
            [
                'room_id' => [ilDBConstants::T_INTEGER, $this->roomId],
                'user_id' => [ilDBConstants::T_INTEGER, $user_id]
            ],
            [
                'actor_id' => [ilDBConstants::T_INTEGER, $actor_id],
                'timestamp' => [ilDBConstants::T_INTEGER, time()],
                'remark' => [ilDBConstants::T_TEXT, $comment]
            ]
        );
    }

    public function unbanUser($user_id): int
    {
        global $DIC;

        if (!is_array($user_id)) {
            $user_id = [$user_id];
        }

        $query = 'DELETE FROM ' . self::$banTable . ' WHERE room_id = %s AND ' . $DIC->database()->in('user_id', $user_id, false, ilDBConstants::T_INTEGER);
        $types = [ilDBConstants::T_INTEGER];
        $values = [$this->getRoomId()];

        return $DIC->database()->manipulateF($query, $types, $values);
    }

    public function isUserBanned(int $user_id): bool
    {
        global $DIC;

        $query = 'SELECT COUNT(user_id) cnt FROM ' . self::$banTable . ' WHERE user_id = %s AND room_id = %s';
        $types = [ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER];
        $values = [$user_id, $this->getRoomId()];

        $res = $DIC->database()->queryF($query, $types, $values);

        return ($row = $DIC->database()->fetchAssoc($res)) && $row['cnt'];
    }

    public function getBannedUsers(): array
    {
        global $DIC;

        $query = 'SELECT chb.* FROM ' . self::$banTable . ' chb INNER JOIN usr_data ud ON chb.user_id = ud.usr_id WHERE chb.room_id = %s ';
        $types = [ilDBConstants::T_INTEGER];
        $values = [$this->getRoomId()];
        $res = $DIC->database()->queryF($query, $types, $values);
        $result = [];

        while ($row = $DIC->database()->fetchAssoc($res)) {
            if ($row['user_id'] > 0) {
                $user = new ilObjUser((int) $row['user_id']);
                $userdata = [
                    'user_id' => $user->getId(),
                    'firstname' => $user->getFirstname(),
                    'lastname' => $user->getLastname(),
                    'login' => $user->getLogin(),
                    'timestamp' => (int) $row['timestamp'],
                    'actor_id' => (int) $row['actor_id'],
                    'remark' => $row['remark']
                ];

                $result[] = $userdata;
            }
        }

        return $result;
    }

    public function getLastSession(ilChatroomUser $user): ?array
    {
        global $DIC;

        $query = 'SELECT * FROM ' . self::$sessionTable . ' WHERE user_id = ' .
            $DIC->database()->quote($user->getUserId(), ilDBConstants::T_INTEGER) .
            ' ORDER BY connected DESC';

        $DIC->database()->setLimit(1);
        $res = $DIC->database()->query($query);

        if ($row = $DIC->database()->fetchAssoc($res)) {
            return $row;
        }

        return null;
    }

    public function getSessions(ilChatroomUser $user): array
    {
        global $DIC;

        $query = 'SELECT * FROM ' . self::$sessionTable
            . ' WHERE room_id = ' .
            $DIC->database()->quote($this->getRoomId(), ilDBConstants::T_INTEGER) .
            ' ORDER BY connected DESC';

        $res = $DIC->database()->query($query);

        $result = [];
        while ($row = $DIC->database()->fetchAssoc($res)) {
            $result[] = $row;
        }

        return $result;
    }

    public function sendInvitationNotification(
        ?ilChatroomObjectGUI $gui,
        $sender,
        int $recipient_id,
        string $invitationLink = ''
    ): void {
        $links = [];

        if ($gui && $invitationLink === '') {
            $invitationLink = $this->getChatURL($gui);
        }

        $links[] = new ilNotificationLink(
            new ilNotificationParameter('chat_join', [], 'chatroom'),
            $invitationLink
        );

        if ($recipient_id > 0 && ANONYMOUS_USER_ID !== $recipient_id) {
            if (is_numeric($sender) && $sender > 0) {
                $sender_id = $sender;
                $usr = ilObjectFactory::getInstanceByObjId($sender);
                $public_name = $usr->getPublicName();
            } elseif ($sender instanceof ilChatroomUser) {
                if ($sender->getUserId() > 0) {
                    $sender_id = $sender->getUserId();
                } else {
                    $sender_id = ANONYMOUS_USER_ID;
                }
                $public_name = $sender->getUsername();
            } else {
                throw new InvalidArgumentException(
                    '$sender must be an instance of ilChatroomUser or an id of an ilObjUser instance'
                );
            }

            $userLang = ilLanguageFactory::_getLanguageOfUser($recipient_id);
            $userLang->loadLanguageModule('mail');
            $bodyParams = [
                'link' => $invitationLink,
                'inviter_name' => $public_name,
                'room_name' => $this->getTitle(),
                'salutation' => ilMail::getSalutation($recipient_id, $userLang),
                'BR' => "\n",
            ];

            $notification = new ilNotificationConfig(ChatInvitationNotificationProvider::NOTIFICATION_TYPE);
            $notification->setTitleVar('chat_invitation', $bodyParams, 'chatroom');
            $notification->setShortDescriptionVar('chat_invitation_short', $bodyParams, 'chatroom');
            $notification->setLongDescriptionVar('chat_invitation_long', $bodyParams, 'chatroom');
            $notification->setLinks($links);
            $notification->setIconPath('templates/default/images/standard/icon_chtr.svg');
            $notification->setValidForSeconds(ilNotificationConfig::TTL_LONG);
            $notification->setVisibleForSeconds(ilNotificationConfig::DEFAULT_TTS);
            $notification->setIdentification(new NotificationIdentification(
                ChatInvitationNotificationProvider::NOTIFICATION_TYPE,
                self::ROOM_INVITATION . '_' . $this->getRefIdByRoomId($this->getRoomId()),
            ));
            $notification->setHandlerParam('mail.sender', (string) $sender_id);

            $notification->notifyByUsers([$recipient_id]);
        }
    }

    public function getChatURL(ilChatroomObjectGUI $gui): string
    {
        return ilLink::_getStaticLink($gui->getObject()->getRefId(), $gui->getObject()->getType());
    }

    public function getTitle(): string
    {
        if (!$this->object) {
            $this->object = ilObjectFactory::getInstanceByObjId((int) $this->getSetting('object_id'));
        }

        return $this->object->getTitle();
    }

    public function countActiveUsers(): int
    {
        global $DIC;

        $query = 'SELECT COUNT(user_id) cnt FROM ' . self::$userTable . ' WHERE room_id = %s';
        $types = [ilDBConstants::T_INTEGER];
        $values = [$this->roomId];
        $res = $DIC->database()->queryF($query, $types, $values);

        if ($row = $DIC->database()->fetchAssoc($res)) {
            return (int) $row['cnt'];
        }

        return 0;
    }

    public function getAccessibleRoomIdByTitleMap(int $user_id): array
    {
        global $DIC;

        $query = "
                        SELECT room_id, od.title, objr.ref_id
                        FROM object_data od
                        INNER JOIN  " . self::$settingsTable . "
                                ON object_id = od.obj_id
                        INNER JOIN object_reference objr
                                ON objr.obj_id = od.obj_id
                                AND objr.deleted IS NULL
                        INNER JOIN tree
                                ON tree.child = objr.ref_id
                                AND tree.tree = %s
                        WHERE od.type = %s
       ";

        $types = [ilDBConstants::T_INTEGER, ilDBConstants::T_TEXT];
        $values = [1, 'chtr'];
        $res = $DIC->database()->queryF($query, $types, $values);

        $rooms = [];
        while ($row = $DIC->database()->fetchAssoc($res)) {
            if (self::checkPermissionsOfUser($user_id, 'read', (int) $row['ref_id'])) {
                $rooms[(int) $row['room_id']] = $row['title'];
            }
        }

        return $rooms;
    }

    public function getRefIdByRoomId(int $room_id): int
    {
        global $DIC;

        $query = "
       SELECT      objr.ref_id
       FROM        object_reference    objr

       INNER JOIN  chatroom_settings   cs
           ON      cs.object_id = objr.obj_id

       INNER JOIN  object_data     od
           ON      od.obj_id = cs.object_id

       WHERE       cs.room_id = %s
       ";

        $types = [ilDBConstants::T_INTEGER];
        $values = [$room_id];

        $res = $DIC->database()->queryF($query, $types, $values);

        $row = $DIC->database()->fetchAssoc($res);

        return (int) ($row['ref_id'] ?? 0);
    }

    public function getLastMessages(int $number, ilChatroomUser $chatuser): array
    {
        global $DIC;

        // There is currently no way to check if a message is private or not
        // by sql. So we fetch twice as much as we need and hope that there
        // are not more than $number private messages.
        $DIC->database()->setLimit($number);
        $rset = $DIC->database()->query(
            'SELECT *
                        FROM ' . self::$historyTable . '
                        WHERE room_id = ' . $DIC->database()->quote($this->roomId, ilDBConstants::T_INTEGER) . '
                        AND (
                                (' . $DIC->database()->like('message', ilDBConstants::T_TEXT, '%"type":"message"%') . ' AND NOT ' . $DIC->database()->like('message', ilDBConstants::T_TEXT, '%"public":0%') . ')
                                OR ' . $DIC->database()->like('message', ilDBConstants::T_TEXT, '%"target":{%"id":"' . $chatuser->getUserId() . '"%') . '
                                OR ' . $DIC->database()->like('message', ilDBConstants::T_TEXT, '%"from":{"id":' . $chatuser->getUserId() . '%') . '
                        )
                        ORDER BY timestamp DESC'
        );

        $result_count = 0;
        $results = [];
        while (($row = $DIC->database()->fetchAssoc($rset)) && $result_count < $number) {
            $tmp = json_decode($row['message'], false, 512, JSON_THROW_ON_ERROR);
            if (property_exists($tmp, 'target') && $tmp->target instanceof stdClass && (int) $tmp->target->public === 0) {
                if (in_array($chatuser->getUserId(), [(int) $tmp->target->id, (int) $tmp->from->id], true)) {
                    $results[] = $tmp;
                    ++$result_count;
                }
            } else {
                $results[] = $tmp;
                ++$result_count;
            }
        }

        if ($results !== []) {
            $rset = $DIC->database()->queryF(
                'SELECT *
                 FROM ' . self::$historyTable . '
                 WHERE room_id = %s
                 AND ' . $DIC->database()->like('message', ilDBConstants::T_TEXT, '%%"type":"notice"%%') . '
                 AND timestamp <= %s AND timestamp >= %s
                 ORDER BY timestamp DESC',
                [ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER],
                [$this->roomId, $results[0]->timestamp, $results[$result_count - 1]->timestamp]
            );

            while (($row = $DIC->database()->fetchAssoc($rset))) {
                $tmp = json_decode($row['message'], false, 512, JSON_THROW_ON_ERROR);
                $results[] = $tmp;
            }
        }

        usort($results, static function (stdClass $a, stdClass $b): int {
            $a_timestamp = strlen((string) $a->timestamp) === 13 ? ((int) substr((string) $a->timestamp, 0, -3)) : $a->timestamp;
            $b_timestamp = strlen((string) $b->timestamp) === 13 ? ((int) substr((string) $b->timestamp, 0, -3)) : $b->timestamp;

            return $b_timestamp - $a_timestamp;
        });

        return $results;
    }

    public function clearMessages(): void
    {
        global $DIC;

        $DIC->database()->queryF(
            'DELETE FROM ' . self::$historyTable . ' WHERE room_id = %s',
            [ilDBConstants::T_INTEGER],
            [$this->roomId]
        );

        $DIC->database()->queryF(
            'DELETE FROM ' . self::$sessionTable . ' WHERE room_id = %s AND disconnected < %s',
            [ilDBConstants::T_INTEGER, ilDBConstants::T_INTEGER],
            [$this->roomId, time()]
        );
    }
}