获取一个域名的主域名

class DomainService
{
    protected $cacheKey = 'domain-cache';

    protected $domainList;

    public function getDomainSuffix()
    {
        if (!$this->domainList) {
            $cacheList = Yii::$app->cacheFile->get($this->cacheKey);
            if ($cacheList) {
                $this->domainList = $cacheList;
            } else {
                $this->domainList = $this->syncRemoteDomain();
                Yii::$app->cacheFile->set($this->cacheKey, $this->domainList);
            }
        }

        return $this->domainList;
    }

    public function syncRemoteDomain()
    {
        $res = CurlService::getIns()->get('https://publicsuffix.org/list/effective_tld_names.dat');
        if ($res->getErrorMsg()) {
            return [];
        }

        $body = $res->getBody();
        $domainSuffixList = explode("
", $body);
        $domainSuffixList = array_filter($domainSuffixList, function ($row) {
            $row = trim($row);
            if (!empty($row) && substr($row, 0, 2) != '//') {
                return true;
            }
            return false;
        });

        return $domainSuffixList;
    }

    public function getMain(string $domain)
    {
        $domainList = $this->getDomainSuffix();
        $domainMap = array_flip($domainList);
        $origin = $domainSep = explode('.', $domain);
        $len = count($domainSep);
        for ($i = 0; $i < $len; $i++) {
            unset($domainSep[$i]);
            if (count($domainSep) == 0) {
                break;
            }
            $s = implode('.', $domainSep);
            if (isset($domainMap[$s])) {
                return '*.'.$origin[$i].'.'.$s;
            }
        }

        return $domain;
    }
}