<?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;
	protected static $reinforced_enable_threshold = 10;
	protected static $reinforced_disable_threshold = 5;
	protected static $reinforced_prob = 20;

	/**
	 * Check if the current page should be cached.
	 *
	 * @param string $page The current page
	 * @return boolean
	 */
	protected static function shouldCache($page = '')
	{
		// never cache for admins
		if (session::isAdmin() || session::isCachingForciblyDisabled()) {
			return false;
		}
		// Don't cache the image files.
		if ($page == 'thumb' || $page == 'sig') {
			return false;
		}

		$cacheignore = explode(',', config::get('cache_ignore'));
		if (config::get('cache_enabled')
				&& count($_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();
		}  elseif (defined('DB_USE_REDIS') && DB_USE_REDIS == true) {
			$cachehandler = new CacheHandlerHashedRedis();
		} 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())) {
			$cachetime = self::expiry($page);
			$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 ((isset($_SERVER['HTTP_IF_NONE_MATCH'])
								&& strpos($_SERVER['HTTP_IF_NONE_MATCH'], $etag) !== false)
						|| (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) 
								&& @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 ($usegz) {
				ob_start("ob_gzhandler");
			} else {
				ob_start();
			}
		}
		// If the page cache is off we still compress pages if asked.
		else if ($usegz) {
			ob_start("ob_gzhandler");
		}
	}

	/**
	 * Generate the cache for the current page.
	 */
	public static function generate($page = null)
	{
		if (!is_string($page)) {
			$page = null;
		}
		if (cache::shouldCache()) {
			$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();
			} elseif (defined('DB_USE_REDIS') && DB_USE_REDIS == true) {
				$cachehandler = new CacheHandlerHashedRedis();
			} else {
				$cachehandler = new CacheHandlerHashed();
			}
			$cachehandler->put($cachefile,
					preg_replace('/profile -->.*<!-- \/profile/',
							'profile -->Cached '
							.gmdate("d M Y H:i:s").'<!-- /profile', ob_get_contents()), null,
					self::expiry($page));

			$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.
	 */
	protected 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 (defined('DB_USE_MEMCACHE') && DB_USE_MEMCACHE == true) {
			$cachehandler = new CacheHandlerHashedMem();
		}  elseif (defined('DB_USE_REDIS') && DB_USE_REDIS == true) {
			$cachehandler = new CacheHandlerHashedRedis();
		} 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');
	}

	/**
	 * Get the expiry time for a given page.
	 * @param string $page
	 *
	 * @return integer timestamp for the page's expiry time
	 */
	protected static function expiry($page)
	{
		$cachetimes = array();
		if (config::get('cache_times')) {
			$times = explode(',', config::get('cache_times'));
			foreach ($times as $string) {
				$array = explode(':', $string);
				$cachetimes[$array[0]] = $array[1];
			}
		}

		if (isset($cachetimes[$page])) {
			$cachetime = $cachetimes[$page];
		} else {
			$cachetime = config::get('cache_time');
		}

		$cachetime = $cachetime * 60;

		return $cachetime;
	}

}