fossbilling-mailgateway/NotificationCooldown.php

<?php

declare(strict_types=1);

namespace Box\Mod\Mailgateway;

use Doctrine\DBAL\Connection;
use Doctrine\DBAL\Exception\UniqueConstraintViolationException;

class NotificationCooldown
{
    private int $seconds;

    public function __construct(private Connection $connection, ?int $seconds = null)
    {
        $this->seconds = $seconds ?? RuntimeConfig::get('notification_cooldown_seconds');
    }

    /** Atomically reserve a sender's notification slot and queue the email. */
    public function run(string $sender, callable $queue): bool
    {
        $key = hash('sha256', strtolower(trim($sender)));
        $now = time();

        return $this->connection->transactional(function () use ($key, $now, $queue): bool {
            try {
                $this->connection->insert('mailgateway_notification', ['sender_key' => $key, 'last_notified_at' => 0]);
            } catch (UniqueConstraintViolationException) {
                // Existing sender; the conditional update decides who owns the slot.
            }
            $claimed = $this->connection->executeStatement(
                'UPDATE mailgateway_notification SET last_notified_at = ? WHERE sender_key = ? AND last_notified_at <= ?',
                [$now, $key, $now - $this->seconds],
            );
            if ($claimed !== 1) {
                return false;
            }
            if ($queue() === false) {
                // Disabled templates do not consume the sender's notification slot.
                $this->connection->delete('mailgateway_notification', ['sender_key' => $key]);
                return false;
            }

            return true;
        });
    }
}