<?php
/**
 * Converts an array-represented URL to a string
 *
 * Source: http://php.net/manual/en/function.parse-url.php#106731
 *
 * @see http://php.net/manual/en/function.parse-url.php
 *
 * @param array $parsedUrl an array-represented URL
 *
 * @return string the string representation of the URL
 */
function unparse_url($parsedUrl)
{
    $scheme   = isset($parsedUrl['scheme']) ? $parsedUrl['scheme'].'://' : '';
    $host     = isset($parsedUrl['host']) ? $parsedUrl['host'] : '';
    $port     = isset($parsedUrl['port']) ? ':'.$parsedUrl['port'] : '';
    $user     = isset($parsedUrl['user']) ? $parsedUrl['user'] : '';
    $pass     = isset($parsedUrl['pass']) ? ':'.$parsedUrl['pass']  : '';
    $pass     = ($user || $pass) ? "$pass@" : '';
    $path     = isset($parsedUrl['path']) ? $parsedUrl['path'] : '';
    $query    = isset($parsedUrl['query']) ? '?'.$parsedUrl['query'] : '';
    $fragment = isset($parsedUrl['fragment']) ? '#'.$parsedUrl['fragment'] : '';

    return "$scheme$user$pass$host$port$path$query$fragment";
}

/**
 * Removes undesired query parameters and fragments
 *
 * @param string url Url to be cleaned
 *
 * @return string the string representation of this URL after cleanup
 */
function cleanup_url($url)
{
  $obj_url = new Url($url);
  return $obj_url->cleanup();
}

/**
 * Get URL scheme.
 *
 * @param string url Url for which the scheme is requested
 *
 * @return mixed the URL scheme or false if none is provided.
 */
function get_url_scheme($url)
{
  $obj_url = new Url($url);
  return $obj_url->getScheme();
}

/**
 * Adds a trailing slash at the end of URL if necessary.
 *
 * @param string $url URL to check/edit.
 *
 * @return string $url URL with a end trailing slash.
 */
function add_trailing_slash($url)
{
    return $url . (!endsWith($url, '/') ? '/' : '');
}

/**
 * Replace not whitelisted protocols by 'http://' from given URL.
 *
 * @param string $url       URL to clean
 * @param array  $protocols List of allowed protocols (aside from http(s)).
 *
 * @return string URL with allowed protocol
 */
function whitelist_protocols($url, $protocols)
{
    if (startsWith($url, '?') || startsWith($url, '/')) {
        return $url;
    }
    $protocols = array_merge(['http', 'https'], $protocols);
    $protocol = preg_match('#^(\w+):/?/?#', $url, $match);
    // Protocol not allowed: we remove it and replace it with http
    if ($protocol === 1 && ! in_array($match[1], $protocols)) {
        $url = str_replace($match[0], 'http://', $url);
    } elseif ($protocol !== 1) {
        $url = 'http://' . $url;
    }
    return $url;
}

/**
 * URL representation and cleanup utilities
 *
 * Form
 *   scheme://[username:password@]host[:port][/path][?query][#fragment]
 *
 * Examples
 *   http://username:password@hostname:9090/path?arg1=value1&arg2=value2#anchor
 *   https://host.name.tld
 *   https://h2.g2/faq/?vendor=hitchhiker&item=guide&dest=galaxy#answer
 *
 * @see http://www.faqs.org/rfcs/rfc3986.html
 */
class Url
{
    private static $annoyingQueryParams = array(
        // Facebook
        'action_object_map=',
        'action_ref_map=',
        'action_type_map=',
        'fb_',
        'fb=',
        'PHPSESSID=',

        // Scoop.it
        '__scoop',

        // Google Analytics & FeedProxy
        'utm_',

        // ATInternet
        'xtor=',

        // Other
        'campaign_'
    );

    private static $annoyingFragments = array(
        // ATInternet
        'xtor=RSS-',

        // Misc.
        'tk.rss_all'
    );

    /*
     * URL parts represented as an array
     *
     * @see http://php.net/parse_url
     */
    protected $parts;

    /**
     * Parses a string containing a URL
     *
     * @param string $url a string containing a URL
     */
    public function __construct($url)
    {
        $url = self::cleanupUnparsedUrl(trim($url));
        $this->parts = parse_url($url);

        if (!empty($url) && empty($this->parts['scheme'])) {
            $this->parts['scheme'] = 'http';
        }
    }

    /**
     * Clean up URL before it's parsed.
     * ie. handle urlencode, url prefixes, etc.
     *
     * @param string $url URL to clean.
     *
     * @return string cleaned URL.
     */
    protected static function cleanupUnparsedUrl($url)
    {
        return self::removeFirefoxAboutReader($url);
    }

    /**
     * Remove Firefox Reader prefix if it's present.
     *
     * @param string $input url
     *
     * @return string cleaned url
     */
    protected static function removeFirefoxAboutReader($input)
    {
        $firefoxPrefix = 'about://reader?url=';
        if (startsWith($input, $firefoxPrefix)) {
            return urldecode(ltrim($input, $firefoxPrefix));
        }
        return $input;
    }
    
    /**
     * Returns a string representation of this URL
     */
    public function toString()
    {
        return unparse_url($this->parts);
    }

    /**
     * Removes undesired query parameters
     */
    protected function cleanupQuery()
    {
        if (! isset($this->parts['query'])) {
            return;
        }

        $queryParams = explode('&', $this->parts['query']);

        foreach (self::$annoyingQueryParams as $annoying) {
            foreach ($queryParams as $param) {
                if (startsWith($param, $annoying)) {
                    $queryParams = array_diff($queryParams, array($param));
                    continue;
                }
            }
        }

        if (count($queryParams) == 0) {
            unset($this->parts['query']);
            return;
        }

        $this->parts['query'] = implode('&', $queryParams);
    }    

    /**
     * Removes undesired fragments
     */
    protected function cleanupFragment()
    {
        if (! isset($this->parts['fragment'])) {
            return;
        }

        foreach (self::$annoyingFragments as $annoying) {
            if (startsWith($this->parts['fragment'], $annoying)) {
                unset($this->parts['fragment']);
                break;
            }
        }
    }

    /**
     * Removes undesired query parameters and fragments
     *
     * @return string the string representation of this URL after cleanup
     */
    public function cleanup()
    {
        $this->cleanupQuery();
        $this->cleanupFragment();
        return $this->toString();
    }

    /**
     * Converts an URL with an International Domain Name host to a ASCII one.
     * This requires PHP-intl. If it's not available, just returns this->cleanup().
     *
     * @return string converted cleaned up URL.
     */
    public function idnToAscii()
    {
        $out = $this->cleanup();
        if (! function_exists('idn_to_ascii') || ! isset($this->parts['host'])) {
            return $out;
        }
        $asciiHost = idn_to_ascii($this->parts['host'], 0, INTL_IDNA_VARIANT_UTS46);
        return str_replace($this->parts['host'], $asciiHost, $out);
    }

    /**
     * Get URL scheme.
     *
     * @return string the URL scheme or false if none is provided.
     */
    public function getScheme() {
        if (!isset($this->parts['scheme'])) {
            return false;
        }
        return $this->parts['scheme'];
    }

    /**
     * Get URL host.
     *
     * @return string the URL host or false if none is provided.
     */
    public function getHost() {
        if (empty($this->parts['host'])) {
            return false;
        }
        return $this->parts['host'];
    }

    /**
     * Test if the Url is an HTTP one.
     *
     * @return true is HTTP, false otherwise.
     */
    public function isHttp() {
        return strpos(strtolower($this->parts['scheme']), 'http') !== false;
    }
}
