<?php

namespace App\BusProNet;

use Symfony\Component\DomCrawler\Crawler;

/**
 * Builds a Crawler over BusPro's XML payloads.
 *
 * The Crawler constructor parses its content as HTML5, which flattens the
 * nesting BusPro's exports and API responses rely on, so XML has to be added
 * through addXmlContent() instead.
 */
final class XmlCrawlerFactory
{
    public static function create(string $xml): Crawler
    {
        $crawler = new Crawler();
        $crawler->addXmlContent($xml);

        return $crawler;
    }

    /**
     * Explains why create() returned an empty Crawler. addXmlContent() discards the
     * libxml errors, so an empty, a malformed and a truncated payload are
     * indistinguishable afterwards; this re-parses to recover the reason. Only worth
     * calling on the failure path.
     */
    public static function diagnose(string $xml): string
    {
        if ('' === trim($xml)) {
            return sprintf('empty response (%d bytes)', strlen($xml));
        }

        $previousUseErrors = libxml_use_internal_errors(true);
        libxml_clear_errors();

        try {
            simplexml_load_string($xml);

            $messages = [];
            foreach (libxml_get_errors() as $error) {
                $messages[] = sprintf('%s (line %d, column %d)', trim($error->message), $error->line, $error->column);
            }

            if ([] === $messages) {
                return sprintf('unknown XML error (%d bytes)', strlen($xml));
            }

            return sprintf('%s (%d bytes)', implode('; ', array_unique($messages)), strlen($xml));
        } finally {
            libxml_clear_errors();
            libxml_use_internal_errors($previousUseErrors);
        }
    }
}