webmentions/src/EndpointParser.php

<?php declare(strict_types=1);

namespace Lewisdale\Webmentions;

use Symfony\Contracts\HttpClient\ResponseInterface;
use Symfony\Component\DomCrawler\Crawler;

class EndpointParser {
    public static function parse(ResponseInterface $response) : string | null
    {
        $headers = $response->getHeaders();
        $endpoint = null;

        if (isset($headers["link"])) {
            $link = $headers["link"][0];
            if (preg_match('/rel=("?)webmention("?)/', $link)) {
                $matches = [];
                preg_match('/\<(..*?)\>/', $link, $matches);

                if (count($matches) > 1) {
                    $endpoint = $matches[1];
                }
            }
        }

        if (!$endpoint) {
            $doc = new Crawler($response->getContent());
            $webmention = $doc->filter('rel="webmention"')->first();
        }

        if ($endpoint && !str_contains($endpoint, "https://")) {
            $res = parse_url($response->getInfo('url'));
            $endpoint = $res["scheme"] . "://" . $res["host"] . $endpoint;
        }
        return $endpoint;
    }
}