<?php // vim:ts=4:sw=4:noet
/*====================================================================== 
Copyright (C) 2006-2009, Walter Doekes
This file is part of KjwLib-php45.
 
KjwLib-php45 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 
(at your option) any later version. 

KjwLib-php45 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 KjwLib-php45.  If not, see <http://www.gnu.org/licenses/>. 
======================================================================*/

/**
 * FIXME: needs documentation
 */
class KjwCache {
	var $_cachePath = null;
	var $_cacheFile = null;
	var $_enabled = false;
	var $_expire = null;
	
	function KjwCache($cachePath = 'cache') {
		$this->_cachePath = $cachePath;
	}

	function expire($seconds) {
		$this->_expire = $seconds;
	}

	function start() {
		// Check if we're in a session by checking SESSID,
		// if we're in a session, do not cache anything..
//		echo "<!-- " . session_name();
//		print_r($_REQUEST);
//		echo " -->";
		if (!isset($_REQUEST[session_name()])) {
		
			$this->_cacheFile = $this->_cachePath . '/' . md5($_SERVER['REQUEST_URI']) . '.cache';

			// We have a file that is recent enough, output it and die.
			if (@file_exists($this->_cacheFile)
					&& ($this->_expire === null || filemtime($this->_cacheFile) + $this->_expire > time())) {
				// Send last-modified
				header('Last-Modified: ' . gmdate('D, d M Y H:i:s T', filemtime($this->_cacheFile)));
				if ($this->_expire !== null)
					header('Expires: ' . gmdate('D, d M Y H:i:s T', filemtime($this->_cacheFile) + $this->_expire));
				
				// Enable 304 not modified.
				if (function_exists('apache_request_headers')) {
					$headers = apache_request_headers();
					if (isset($headers['If-Modified-Since'])
							&& filemtime($this->_cacheFile) <= strtotime($headers['If-Modified-Since'])) {
						header("HTTP/1.0 304 Not Modified");
						exit;
					}
				}

				// Write file for those that didn't have it already.
				readfile($this->_cacheFile);
				exit;
			}

			// Send expires header if we have it set.
			if ($this->_expire !== null)
				header('Expires: ' . gmdate('D, d M Y H:i:s T', time() + $this->_expire));
				
			// Start output buffering so we can store the page.
			ob_start();
			$this->_enabled = true;
			
		} else {

			// When we use sessions, we're doing dynamic data,
			// and we won't be doing caching.
			header('Cache-Control: no-cache, must-revalidate'); // HTTP/1.1
			header('Last-Modified: ' . gmdate('D, d M Y H:i:s T', time()));
			header('Expires: Mon, 26 Jul 1997 05:00:00 GMT'); // Date in the past

		}
	}

	/**
	 * "delete" .cache files.. call saveCache first if you plan to undo..
	 * @return amount of files deleted
	 */
	function setDirty() {
		$n = 0;
		$dp = opendir($this->_cachePath);
		while (($entry = readdir($dp)) !== false)
			if (substr($entry, -6) == '.cache')
				if (unlink($this->_cachePath . '/' . $entry))
					++$n;
		closedir($dp);
		return $n;
	}

	/**
	 * store cache files by copying the .cache to .cache.bak.
	 * removes old .bak files first, so we know this cache contains only newly cached items.
	 * @return amount of files stored/pushed
	 */
	function saveCache() {
		$n = 0;
		$dp = opendir($this->_cachePath);
		while (($entry = readdir($dp)) !== false)
			if (substr($entry, -10) == '.cache.bak')
				unlink($this->_cachePath . '/' . $entry);
		rewinddir($dp);
		while (($entry = readdir($dp)) !== false)
			if (substr($entry, -6) == '.cache')
				if (copy($this->_cachePath . '/' . $entry, $this->_cachePath . '/' . $entry . '.bak'))
					++$n;
		closedir($dp);
		return $n;
	}

	/**
     * deletes current .cache files. copies .cache.bak to .cache.
	 * @return amount of files "restored"
	 */
	function loadCache() {
		$n = 0;
		$dp = opendir($this->_cachePath);
		while (($entry = readdir($dp)) !== false)
			if (substr($entry, -6) == '.cache')
				unlink($this->_cachePath . '/' . $entry);
		rewinddir($dp);
		while (($entry = readdir($dp)) !== false)
			if (substr($entry, -10) == '.cache.bak')
				if (copy($this->_cachePath . '/' . $entry, $this->_cachePath . '/' . substr($entry, 0, -4)))
					++$n;
		closedir($dp);
		return $n;
	}

	function destroy() {
		if ($this->_enabled) {
			echo "<!-- cached file created: " . gmdate("Y-m-d H:i") . " UTC -->";
			if (($fp = @fopen($this->_cacheFile, 'w')) !== false) {
				$success = @fwrite($fp, ($towrite = ob_get_contents())) === strlen($towrite);
				@fclose($fp);
				if ($success === false)
					unlink($this->_cacheFile);
			}
			ob_end_flush();
		}
	}
}

?>