<?PHP
/*
 * (c) Etienne Bagnoud 2010 
 *
 * Wpad-php generates wpad.pac file based on configuration. It checks if 
 * proxies are alive and distribute them equally at each request by a client
 *
 * This file is part of Wpad-php. 
 *
 * Wpad-php is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version.
 *
 * Wpad-php is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Wpad-php.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Good doc : http://findproxyforurl.com/pac_functions_explained.html
 */

/*
 * Strings for replacement
 */
$fstring['shexp'] = 'shExpMatch(url, \'%s\')';
$fstring['innet'] = 'isInNet(host, \'%s\', \'%s\')';
$fstring['protocol'] = 'url.substring(0, %s)=="%s"';
$fstring['others'] = '%s';

$strings = array('innet', 'shexp', 'protocol', 'others');

/*
 * Load configuration 
 */
if(is_readable('wpad.conf.php')) {
	$include = 'wpad.conf.php';
} else if(is_readable('/etc/wpad.conf.php')) {
	$include = '/etc/wpad.conf.php';
} else if(is_readable(getenv('WPADCONF'))) {
	$include = getenv('WPADCONF');
}
include($include);

/*
 * if $_wpad wasn't set we just tell to always run direct
*/
$conf_loaded = true; 
if(!isset($_wpad)) {
	$conf_loaded = false;
}

/*
 * Check an URL to see if proxy is alive. The file must contain OK
 */
function checkProxyIsAlive($proxy, $url)
{
	$ret = false;
	$fp = fsockopen($proxy[0], $proxy[1], $errno, $errstr);
	if($fp) {
		fwrite($fp, 'GET ' . "$url\r\n");
		$data = '';
		while(!feof($fp)) {
			$data .= fgets($fp, 128);
		}
		fclose($fp);
		if($data == 'OK') 
			$ret = true;
	}

	return $ret;
}

/*
 * Proxy Round Robin selection. Each time this script is ran, change order for
 * each proxy in the list. This will load-balance proxies.
 */
function getProxyRR($file, $sem, $maxProxy) {
	$ret = 0;
	$s = sem_get($sem);
	sem_acquire($s);
	$fp = fopen($file, 'r');
	if($fp) {
		$last = fgets($fp);
		if(intval($last) >= $maxProxy - 1) {
			$next = 0;
		} else {
			$next = intval($last)+1;
		}
		fclose($fp);
		$fp = fopen($file, 'w');
		if($fp) {
			fwrite($fp, $next);
			fclose($fp);
		}
		$ret = $next;
	}
	sem_release($s);
	return $next;
}

/*
 * Prepare time and expire time
 */
$now = time();
if($conf_loaded) {
	$expire = $now + $_wpad['expire'];
	$max_age = $_wpad['expire'];
} else {
	$expire = $now + 3600; // default to 1 h
	$max_age = 3600;
}

/*
 * Expire now in debug mode
 */
if($_wpad['debug'] == true) {
	$expire = $now;
	$max_age = 0;
}

/*
 * Header for wpad.dat 
 * Firefox doesn't follow max-age and expire and I haven't try with others
 * In debug mode we send text/plain
 */
if($_wpad['debug'] == true) {
	header('Content-Type: text/plain; charset=utf-8');
} else {
	header('Content-Type: application/x-ns-proxy-autoconfig');
}
header('Cache-Control: must-revalidate, max-age=' . $max_age );
/*
 * Thanks http://ch.php.net/manual/en/function.gmdate.php#25031
 */
header('Date: '. gmdate('D, d M Y H:i:s \G\M\T', $now));
header('Last-Modified: '. gmdate('D, d M Y H:i:s \G\M\T', $now));
header('Expires: '. gmdate('D, d M Y H:i:s \G\M\T', $expire));

$wpad_txt = 'function FindProxyForURL(url, host) {' . "\n";
$wpad_txt .= "\t" . 'var direct="DIRECT";' . "\n";

if(!$conf_loaded) {
	$wpad_txt .= "\t" . 'return direct;' . "\n";
} else {
	/*
	 * Our proxies list
	 */
	$proxies = $_wpad['proxies']; 

	$av = array();
	foreach($proxies as $proxy) {
		if(checkProxyIsAlive($proxy, $_wpad['proxy_check_url']))
			$av[] = $proxy;
	}

	$proxiesNum = count($av);

   /*
    * Generate list of proxies for wpad.pac, do round-robin selection of the
    * first proxy in the list.
    */
	$wpad_txt .= "\t" . 'var proxies = "';
	if($proxiesNum > 0) {
		$proxyFirst = getProxyRR($_wpad['proxyrr_file'], $_wpad['semkey'], 
		  $proxiesNum);
		for($i = $proxyFirst; $i < $proxiesNum; $i++) {
			$wpad_txt .= 'PROXY ' . $av[$i][0] . ':' . $av[$i][1] .'; ';
		}
		for($i = 0; $i < $proxyFirst; $i++) {
			$wpad_txt .= 'PROXY ' . $av[$i][0] . ':' . $av[$i][1] .'; ';
		}
	}
	$wpad_txt .= 'DIRECT";' . "\n\n";

   /*
    * Prepare the protocol replacement array
    */
	$protocol = array();
	if(count($_wpad['protocol'])) {
		foreach($_wpad['protocol'] as $p) {
			$protocol[] = array(strval(strlen($p)), $p);
		}
	}
	$_wpad['protocol'] = $protocol;

   /*
    * Goes through each seaction and generate conditions for it
    */
	foreach($strings as $s) {
		if(count($_wpad[$s])>0) {
			$wpad_txt .= "\t" . 'if(';
			$first=true;
			foreach($_wpad[$s] as $exp) {
				if(!$first) {
					$wpad_txt .= "\n\t    " . '|| ';
				}
				if(is_array($exp)) {
					$wpad_txt .= vsprintf($fstring[$s], $exp); 
				} else {
					$wpad_txt .= sprintf($fstring[$s], $exp);
				}
				$first=false;
			}
			$wpad_txt .= ")\n\t{\n\t\treturn direct;\n\t}\n\n";
		}
	}
}

$wpad_txt .= "\n\t" . 'return proxies;'. "\n". '}' . "\n";

/*
 * Here we are
 */
echo $wpad_txt;
exit(0);
?>