ServerResolver.php

<?php declare(strict_types=1);


final class ServerResolver
{

    private const CONFIG = [
        'free_space' => 500,
        'tcp_connection' => 300,
        'upload_speed' => 200,
        'download_speed' => 200,
    ];

    /**
     * @return StorageServer|null
     */
    public function findBestUploadServer()
    {
        $servers = $this->getOnlineServers();

        foreach (self::CONFIG as $field => $points) {
            $this->updateAvailabilityIndex($servers, $field, $points);
        }

        return $servers[0];
    }

    private function updateAvailabilityIndex(array &$servers, string $field, int $points)
    {
        usort($servers, function ($a, $b, $field) {
            return $b[$field] <=> $a[$field];
        });
        foreach ($servers as $key => $server) {
            $currIndex = $servers[$key]['availabilityIndex'] ?? 0;
            $servers[$key]['availabilityIndex'] = $currIndex + ($points / ($key + 2));
        }
    }

    private function getOnlineServers(): array
    {
        /** @var StorageServer[] $servers */
        $servers = StorageServer::find(['online = 1']);
        if (count($servers) === 0) {
            throw new LogicException('No servers available');
        }
        return $servers->toArray();
    }
}