<?php
/**
 * $Date$
 * $Revision$
 * $HeadURL$
 * @package EDK
 */

/**
 * Page caching class
 *
 * Contains methods to create and retrieve a complete cache of the current page.
 * @package EDK
 */
class cache
{
	private static $cacheName = null;
	private static $reinforced_enable_threshold = 10;
	private static $reinforced_disable_threshold = 5;
	private static $reinforced_prob	= 20;

	/**
	 * Check the server load using /proc/loadavg.
	 * 
	 * Changes reinforced statust depending on load where supported.
	 */
	public static function checkLoad()
	{
		if (PHP_OS != 'Linux') {
			return;
		}

		$load = @file_get_contents('/proc/loadavg');
		if (false === $load) {
			return;
		}
		$array = explode(' ', $load);
		// If load is high put killboard into RF
		if ((float)$array[0] > self::$reinforced_enable_threshold) {
			config::set('is_reinforced', true);
		}
		// If load is consistently low cancel reinforced
		else if (config::get('is_reinforced')
				&& (float)$array[0] < self::$reinforced_disable_threshold
				&& rand(1, self::$reinforced_prob) == 1) {
			config::set('is_reinforced', false);
		}
		return true;
	}
	/**
	 * Check if the current page should be cached.
	 *
	 * @param string $page The current page
	 * @return boolean
	 */
	private static function shouldCache($page = '')
	{
		// never cache for admins
		if (session::isAdmin())
		{
			return false;
		}
		// Don't cache the image files.
		if ($page == 'thumb' ||
				$page == 'mapview' ||
				$page == 'sig') return false;
		self::checkLoad();
		if (config::get('is_reinforced') && count($_POST) == 0)
		{
			return true;
		}

		$cacheignore = explode(',', config::get('cache_ignore'));
		if (config::get('cache_enabled')
				&& count($_POST) == 0
				&& !($page != '' && in_array($page, $cacheignore))) {
			return true;
		}
		return false;
	}
	/**
	 * Check if the current page is cached and valid then send it if so.
	 *
	 * @param string $page The current page.
	 */
	public static function check($page)
	{
		// Set an old expiry date to discourage the browser from trying to
		// cache the page.
		if($page != 'mapview' && $page != 'sig')
		{
			header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");
			header('Cache-Control: no-cache');
		}
		$usegz = config::get('cfg_compress')
			&& !ini_get('zlib.output_compression');
		$cachefile = cache::genCacheName();
		if(defined('DB_USE_MEMCACHE') && DB_USE_MEMCACHE == true) $cachehandler = new CacheHandlerHashedMem();
		else $cachehandler = new CacheHandlerHashed();

		// If the cache doesn't exist then we don't need to check times.
		if (cache::shouldCache($page) && $cachehandler->exists(cache::genCacheName()))
		{
			$times = explode(',', config::get('cache_times'));
			foreach ($times as $string)
			{
				$array = explode(':', $string);
				$cachetimes[$array[0]] = $array[1];
			}

			if ($cachetimes[$page])
			{
				$cachetime = $cachetimes[$page];
			}
			else
			{
				$cachetime = config::get('cache_time');
			}

			$cachetime = $cachetime * 60;

			if (config::get('is_reinforced'))
			{
				//global $smarty;
				//$smarty->assign('message', 'Note: This killboard has entered reinforced operation mode.');
				// cache is extended in reinforced mode
				$cachetime = $cachetime * 20;
				if($cachetime < 60) $cachetime = 60;
			}
			$timestamp = time() - $cachehandler->age($cachefile);
			
			if(config::get('cache_update') == '*'
				&& file_exists(KB_CACHEDIR.'/killadded.mk')
				&& $timestamp < @filemtime(KB_CACHEDIR.'/killadded.mk'))
					$timestamp = 0;
			else
			{
				$cacheupdate = explode(',', config::get('cache_update'));
				if (($page != '' && in_array($page, $cacheupdate))
					&& file_exists(KB_CACHEDIR.'/killadded.mk')
					&& $timestamp < @filemtime(KB_CACHEDIR.'/killadded.mk'))
						$timestamp = 0;
			}
			if (time() - $cachetime < $timestamp)
			{
				// Alternatively, use a hash of the file. More cpu for a little
				// less bandwidth. Possibly more useful if we keep an index.
				// filename, age, hash. Age would be used for cache clearing.
				$etag=md5($cachefile.$timestamp);
				if($usegz
					&& strpos($_SERVER['HTTP_ACCEPT_ENCODING'],"gzip") !== false)
						$etag .= 'gz';
				header("Etag: \"".$etag."\"");

				header("Last-Modified: ".gmdate("D, d M Y H:i:s", $timestamp)." GMT");

				// There was a reason for having both checks. etag not always
				// checked maybe?
				if (strpos($_SERVER['HTTP_IF_NONE_MATCH'], $etag) !== false ||
						@strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) == $timestamp)
				{
					header($_SERVER["SERVER_PROTOCOL"]." 304 Not Modified");
					exit;
				}

				if($usegz) ob_start("ob_gzhandler");
				else ob_start();
				echo $cachehandler->get($cachefile);
				ob_end_flush();
				exit();
			}
			if($usegz) ob_start("ob_gzhandler");
			else ob_start();
		}
		// Don't turn on gzip when sending images.
		elseif (cache::shouldCache($page))
		{
			if($usegz) ob_start("ob_gzhandler");
			else ob_start();
		}
		// If the page cache is off we still compress pages if asked.
		elseif($usegz) ob_start("ob_gzhandler");
	}
	/**
	 * Generate the cache for the current page.
	 */
	public static function generate()
	{
		if (cache::shouldCache())
		{
			$usegz = config::get('cfg_compress')
				&& !ini_get('zlib.output_compression');
			$cachefile = cache::genCacheName();

			if(DB_USE_MEMCACHE) $cachehandler = new CacheHandlerHashedMem();
			else $cachehandler = new CacheHandlerHashed();
			$cachehandler->put($cachefile, preg_replace('/profile -->.*<!-- \/profile/','profile -->Cached '.gmdate("d M Y H:i:s").'<!-- /profile',ob_get_contents()));
			$timestamp = time() - $cachehandler->age($cachefile);
			$etag = md5($cachefile.$timestamp );
			if($usegz && strpos($_SERVER['HTTP_ACCEPT_ENCODING'],"gzip") !== false)
				$etag .= 'gz';

			header("Etag: \"".$etag."\"");
			header("Last-Modified: ".gmdate("D, d M Y H:i:s", $timestamp)." GMT");
			ob_end_flush();
		}
	}
	/**
	 * Generate the cache filename.
	 *
	 * Security modification could change this function to generate access
	 * level specific cache files.
	 *
	 * @return string string of path and filename for the current page's cachefile.
	 */
	private static function genCacheName()
	{
		if(isset(self::$cacheName)) return self::$cacheName;

		global $themename, $stylename;
		$basename = $_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'].IS_IGB.$themename.$stylename;
		event::call('cacheNaming', $basename);
		self::$cacheName = KB_SITE.$basename;
		return self::$cacheName;
	}
	/**
	 * Remove the cache of the current page.
	 */
	public static function deleteCache()
	{
		$cachefile = cache::genCacheName();

		if(DB_USE_MEMCACHE) $cachehandler = new CacheHandlerHashedMem();
		else $cachehandler = new CacheHandlerHashed();
		$cachehandler->remove($cachefile);
	}
	/**
	 * Mark the cached page as still current without rebuilding it.
	 */
	public static function touchCache()
	{
		if(! config::get('cache_enabled') ) return;
		if (!file_exists(KB_PAGECACHEDIR.'/'.KB_SITE))
			mkdir(KB_PAGECACHEDIR.'/'.KB_SITE);
		touch(cache::genCacheName());
	}
	/**
	 * Notify the cache that a kill has been added.
	 */
	public static function notifyKillAdded()
	{
		if(! config::get('cache_enabled') ) return;
		if (!file_exists(KB_PAGECACHEDIR))
			mkdir(KB_PAGECACHEDIR);
		touch(KB_CACHEDIR.'/killadded.mk');
	}
}