NotificationsQueue.php

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<?php

namespace Elgg\Notifications;

use Elgg\Config;
use Elgg\Database\Delete;
use Elgg\Database\Select;
use Elgg\Database\Update;
use Elgg\Queue\DatabaseQueue;

class NotificationsQueue extends DatabaseQueue {
    
    const QUEUE_NAME = 'notifications';
    
    protected $config;
    
    public function __construct(string $name, \Elgg\Database $db, \Elgg\Config $config) {
        parent::__construct($name, $db);
        
        $this->config = $config;
    }
    
    public function dequeue() {
        $delay = (int) $this->config->notifications_queue_delay;
        if ($delay < 1) {
            // no delay, so rely on parent logic
            return parent::dequeue();
        }
        
        // get a record for processing
        $select = Select::fromTable(self::TABLE_NAME);
        $select->select('*')
            ->where($select->compare('name', '=', $this->name, ELGG_VALUE_STRING))
            ->andWhere($select->expr()->isNull('worker'))
            ->andWhere($select->compare('timestamp', '<', $this->getCurrentTime("-{$delay} seconds")->getTimestamp(), ELGG_VALUE_TIMESTAMP))
            ->orderBy('id', 'ASC')
            ->setMaxResults(1);
        
        $row = $this->db->getDataRow($select);
        if (empty($row)) {
            return;
        }
        
        // lock a record for processing
        $update = Update::table(self::TABLE_NAME);
        $update->set('worker', $update->param($this->workerId, ELGG_VALUE_STRING))
            ->where($update->compare('name', '=', $this->name, ELGG_VALUE_STRING))
            ->andWhere($update->compare('id', '=', $row->id, ELGG_VALUE_ID))
            ->andWhere($update->expr()->isNull('worker'));
        
        if ($this->db->updateData($update, true) !== 1) {
            return;
        }
        
        // remove locked record from database
        $delete = Delete::fromTable(self::TABLE_NAME);
        $delete->where($delete->compare('id', '=', $row->id, ELGG_VALUE_ID));
        
        $this->db->deleteData($delete);
        
        return unserialize($row->data);
    }
}