<?php

namespace IndieWeb;

use DOMDocument;
use DOMXPath;
use Mf2;

/**
 * Unparse URL
 *
 * Given an assoc. array of the form produced by parse_url, return a string
 *
 * Adapted from http://www.php.net/manual/en/function.parse-url.php#106731
 *
 * Note: the scheme and host are forced to lowercase to avoid case-sensitive issues.
 *
 * @param  array $parsed_url
 * @return string
 */
function unparseUrl(array $parsed_url)
{
    $user = isset($parsed_url['user']) ? $parsed_url['user'] : '';
    $pass = isset($parsed_url['pass']) ? ':' . $parsed_url['pass'] : '';

    return implode('', array(
        isset($parsed_url['scheme']) ? strtolower($parsed_url['scheme']) . '://' : '',
        $user,
        ($user || $pass) ? "$pass@" : '',
        isset($parsed_url['host']) ? strtolower($parsed_url['host']) : '',
        isset($parsed_url['port']) ? ':' . $parsed_url['port'] : '',
        isset($parsed_url['path']) ? $parsed_url['path'] : '/',
        isset($parsed_url['query']) ? '?' . $parsed_url['query'] : '',
        isset($parsed_url['fragment']) ? '#' . $parsed_url['fragment'] : '',
    ));
}

function normaliseUrl($url)
{
    return $url === null ? null : unparseUrl(parse_url($url));
}

function httpGet($url)
{
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_HEADER, 1);
    $response = curl_exec($ch);
    $info = curl_getinfo($ch);
    curl_close($ch);

    $rawHeaders = mb_substr($response, 0, $info['header_size']);
    $headers = http_parse_headers($rawHeaders);
    $body = mb_substr($response, $info['header_size']);

    return array($body, $headers, $info);
}

function followOneRedirect($url)
{
    list($body, $headers, $info) = httpGet($url);

    if (strpos($info['http_code'], '3') === 0 and isset($headers['Location'])) {
        return is_array($headers['Location'])
            ? current($headers['Location'])
            : $headers['Location'];
    } else {
        return null;
    }
}

/**
 * rel-me Document URL
 *
 * Given a URL, resolves any redirects and returns the resolved URL, whether or not
 * the redirect chain is secure (doesn’t change protocol) and the redirect chain,
 * for inspection.
 *
 * Example usage:
 *
 *     list($profileUrl, $isSecure, $redirectChain) = IndieWeb\relMeDocumentUrl($me);
 *
 * $followOneRedirect defaults to IndieWeb\followOneRedirect but can be replaced for
 * testing purposes.
 *
 * Returns [string URL, bool isSecure, array redirectChain]
 * @return array
 */
function relMeDocumentUrl($url, $followOneRedirect = null)
{
    if (!is_callable($followOneRedirect))
        $followOneRedirect = __NAMESPACE__ . '\followOneRedirect';

    $previous = array();
    $secure = true;
    $is_https = false;
    $currentUrl = $url;
    while (true) {
        // TODO: is resolving this URL correct behaviour here?
        // should it be resolved just to the host?
        $redirectedUrl = Mf2\resolveUrl($currentUrl, $followOneRedirect($currentUrl));
        if ($redirectedUrl === null):
            break;
        elseif (in_array($redirectedUrl, $previous)):
            break;
        elseif ($is_https && parse_url($currentUrl, PHP_URL_SCHEME) !== parse_url($redirectedUrl, PHP_URL_SCHEME)):
            $secure = false;
            $previous[] = $currentUrl = $redirectedUrl;
            break;
        else:
            if (parse_url($currentUrl, PHP_URL_SCHEME) == 'https') {
                $is_https = true;
            }
            $currentUrl = $redirectedUrl;
            $previous[] = $currentUrl;
        endif;
    }

    return array($currentUrl, $secure, $previous);
}

/**
 * rel-me links
 * given the HTML and URL of a page, returns all the rel-me links found on that page
 * @return array
 */
function relMeLinks($html, $url)
{
    $parser = new Mf2\Parser($html, $url);
    $mf = $parser->parse();
    $relMeLinks = @($mf['rels']['me'] ?: array());

    return array_unique($relMeLinks);
}

/**
 * URLs match other than scheme
 * Given two URLs, checks if they are the same, ignorning their schemes
 * @todo write tests for this
 * @return bool
 */
function urlsMatchOtherThanScheme($url1, $url2)
{
    $p1 = parse_url($url1);
    $p2 = parse_url($url2);
    $p1['scheme'] = 'http';
    $p2['scheme'] = 'http';

    return unparseUrl($p1) === unparseUrl($p2);
}

/**
 * Backlinking rel-me URL matches
 *
 * Used to check whether an inbound (silo to indie homepage) rel-me link can securely
 * be considered to link to the indie profile URL. Given a back-linking URL and a profile
 * URL, returns an array of [(bool) matches, (bool) secure, (array) redirect chain)]
 *
 * Example Usage:
 *
 *     list($matches, $secure, $previous) = IndieWeb\backlinkingRelMeUrlMatches($inboundRelMeUrl, $meUrl);
 *
 * $followOneRedirect defaults to IndieWeb\followOneRedirect but can be replaced for
 * testing purposes.
 * @return array [matches, secure, previous]
 */
function backlinkingRelMeUrlMatches($backlinking, $meUrl, $followOneRedirect = null)
{
    if ($followOneRedirect === null)
        $followOneRedirect = __NAMESPACE__ . '\followOneRedirect';

    $meUrl = normaliseUrl($meUrl);
    $previous = array();
    $currentUrl = normaliseUrl($backlinking);
    while (true) {
        if ($currentUrl === $meUrl)
            return array(true, true, $previous); // the URLs match and are secure

        $redirectedUrl = normaliseUrl($followOneRedirect($currentUrl));

        if ($redirectedUrl === null or in_array($redirectedUrl, $previous)):
            return array(false, true, $previous); // The URLs don’t match but are secure
        elseif (parse_url($redirectedUrl, PHP_URL_SCHEME) !== parse_url($currentUrl, PHP_URL_SCHEME)):
            if (urlsMatchOtherThanScheme($redirectedUrl, $meUrl)):
                return array(true, false, $previous);
            else:
                return array(false, false, $previous);
            endif;
        else:
            $currentUrl = $redirectedUrl;
            $previous[] = $currentUrl;
        endif;
    }
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