limonte / spam-link-analyser

src/SpamLinkAnalyser.php

<?php
namespace Limonte;

use PHPHtmlParser\Dom;

class SpamLinkAnalyser
{
    const OK = 0;
    const GOOGLE_BOT_DIFFERENT_REDIRECT = 101;
    const TOO_MUCH_REDIRECTS = 102;

    const GOOGLE_BOT_USER_AGENT = 'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)';
    const GOOGLE_CHROME_USER_AGENT = 'Mozilla/5.0 AppleWebKit/537.36 (like Gecko) Chrome/55.0.2883.75 Safari/537.36';

    private $whitelist;

    public function __construct()
    {
        $this->whitelist = [
            '*://google.*',
        ];
    }

    /**
     * @param string $url
     *
     * @return int
     */
    public function check($url)
    {
        $url = trim($url);
        if (filter_var($url, FILTER_VALIDATE_URL) === false) {
            throw new \Exception("Invalid URL");
        }

        if ($this->inWhitelist($url)) {
            return self::OK;
        }

        for ($i = 0; $i <= 3; $i++) {
            if ($i === 3) {
                return self::TOO_MUCH_REDIRECTS;
            }

            $botRedirect = $this->getRedirectUrl($url, self::GOOGLE_BOT_USER_AGENT);
            $chromeRedirect = $this->getRedirectUrl($url, self::GOOGLE_CHROME_USER_AGENT);

            if ($botRedirect || $chromeRedirect) {
                if ($botRedirect !== $chromeRedirect) {
                    return self::GOOGLE_BOT_DIFFERENT_REDIRECT;
                }
            } else {
                return self::OK;
            }

            $url = $chromeRedirect;
        }
    }

    /**
     * @param  string $url
     * @param  string $userAgent
     *
     * @return string $redurectUrl
     */
    private function getRedirectUrl($url, $userAgent)
    {
        $curlInfo = $this->getCurlInfo($url, $userAgent);

        $redurectUrl = $this->removeQueryString(@$curlInfo['redirect_url']);

        if (trim($url, '/') === trim($redurectUrl, '/')) {
            $redurectUrl = '';
        }

        // look for meta http-equiv="refresh"
        if (!$redurectUrl) {
            $dom = new Dom;
            $dom->load($url);
            $metaTags = $dom->find('meta');
            foreach ($metaTags as $meta) {

The expression $metaTags of type array|object<PHPHtmlParser\Dom\AbstractNode> is not guaranteed to be traversable. How about adding an additional type check?

                if ($meta->getAttribute('http-equiv') === 'refresh') {
                    $redurectUrl = preg_replace(
                        '/\s*\d+\s*;\s*url\s*=\s*(\'|\")(.+)(\'|\")/i',
                        '$2',
                        $meta->getAttribute('content')
                    );
                    break;
                }
            }
        }

        return $redurectUrl;
    }

    /**
     * @param  string  $url
     *
     * @return boolean
     */
    private function inWhitelist($url)
    {
        foreach ($this->whitelist as $whitelistItem) {
            if (fnmatch($whitelistItem, $url)) {
                return true;
            }
        }
        return false;
    }

    /**
     * @param string $url
     * @param string $userAgent
     *
     * @return array $curlInfo
     */
    private function getCurlInfo($url, $userAgent)
    {
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_URL, $url);
        curl_setopt($curl, CURLOPT_FILETIME, true);
        curl_setopt($curl, CURLOPT_NOBODY, true);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl, CURLOPT_HEADER, true);
        curl_setopt($curl, CURLOPT_USERAGENT, $userAgent);
        curl_exec($curl);
        $curlInfo = curl_getinfo($curl);
        return $curlInfo;
    }

    /**
     * @param  string $url
     *
     * @return string
     */
    private function removeQueryString($url)
    {
        return preg_replace('/\?.*/', '', $url);
    }
}