<?php

/*

http://www.cs.tufts.edu/g/20/notes/php_dangers.php
Directory creation is atomic

*/

class LightPressCache {
    
    /*
    
    What we do not cache:
    
    - any page with an HTTP method != GET
    
    - any page with a REQUEST_URI containing an unescaped '?'
    
    */
    
    var $constructor_args = array('validity', 'gc_probability', 'dir', 'track_users', 'include_or_exclude', 'url_list', 'base_path');
    
    // configuration
    var $validity = 300;       // seconds
    var $gc_probability = 250;   // one in n+1 chances of doing garbage collection
    var $dir = '/tmp/';
    var $track_users = false;
    var $include_or_exclude = 'exclude';
    var $url_list = '';
    var $base_path = '/';
    
    var $active = true;    // is this cache active?
    
    // set by constructor
    var $_valid;    // earliest valid timestamp for a cache item
    
    var $page_id;
    var $user_id = '';
    
    function LightPressCache($args, $dummy_run=false) {
        
        if (is_array($args)) {
            foreach ($this->constructor_args as $k) {
                if (isset($args[$k]))
                    $this->$k = stripslashes($args[$k]);
            }
        } else {
            $this->raiseError('non-array first argument passed to constructor (dummy mode: ' . $dummy_run . ')', 'LightPressCache', __LINE__);
        }
        
        $this->validity = (int)$this->validity;
        $this->gc_probability = (int)$this->gc_probability;
        $this->track_users = (bool)$this->track_users;
        
        if ($dummy_run)
            return;
        
        $this->url_list = explode(' ', $this->url_list);
        
        if (!is_dir($this->dir)) {
            $this->raiseError('cache directory ' . $this->dir . ' not found', 'LightPressCache', __LINE__);
            $this->active = false;
            return;
        }
        if (!is_writable($this->dir)) {
            $this->raiseError('cache directory ' . $this->dir . ' not writable', 'LightPressCache', __LINE__);
            $this->active = false;
            return;
        }
        
    }
    
    function activate() {
        $this->page_id =& $this->_getId($_SERVER['REQUEST_URI'], $_SERVER['REQUEST_METHOD']);
        $this->user_id =& $this->_getUserId();
        if (!empty($this->user_id) && !$this->track_users)
            $this->active = false;
    }
    
    function _getId($uri, $method='GET') {
        // get the page id
        
        if ($method != 'GET' || strpos($uri, '?') !== false)
            return;
        
        if (substr($uri, -1) != '/')
            $uri = "$uri/";
        
        $found = false;
        foreach ($this->url_list as $url) {
            if ($url == $uri || $url == "$uri/") {
                $found = true;
                break;
            }
        }
        
        if ($this->include_or_exclude == 'include') {
            if (!$found)
                return;
        } else {
            if ($found)
                return;
        }
        
        return urlencode(preg_replace('/#.*$/', '', $uri)); // thanks to wp-cache for the regexp
        
        return '';
    }
    
    function _getUserId() {
        // get the user id
        
        $user_id = '';
        
        $cookies = array_keys($_COOKIE);
        sort($cookies);
        foreach ($cookies as $k) {
            if ($k == 'lp_identity')
                $user_id .= $_COOKIE[$k];
            else if (strpos($k, 'wordpressuser_') === 0)
                $user_id .= $_COOKIE[$k];
        }
        if (!empty($user_id))
            $user_id = md5($user_id);
        
        return $user_id;
    }
    
    function getCache($page_id=null, $user_id=null) {
        // TODO: return cache-friendly headers, eg Cache-Control: max-age=3600
        //       together with the page content
        //       have a look at http://www.mnot.net/cache_docs/ for reference
        if (is_null($page_id))
            $page_id = $this->page_id;
        if (is_null($user_id))
            $user_id = $this->user_id;
        
        if (is_null($page_id))
            return;
        
        $filename = $this->dir . DIRECTORY_SEPARATOR . "lpcache_${page_id}_${user_id}";
        
        $file_stat = @stat($filename);
        
        if (!$file_stat)
            return;
        
        $mtime =& $file_stat[9];
        if (($mtime + $this->validity) < time())
            return;
        
        if (!($f = @fopen($filename, 'rb')))
            return;
        
        $data = @fread($f, $file_stat[7]);
        
        @fclose($f);
        
        if (substr($data, -1) == chr(0)) {
            return (
                substr($data, 0, -1) .
                '<!-- served by FileCache on ' . date('r') . ' -->'
            );
        }

    }
    
    function setCache(&$content, $page_id=null, $user_id=null) {

        if (is_null($page_id))
            $page_id = $this->page_id;
        if (is_null($user_id))
            $user_id = $this->user_id;
        
        if (is_null($page_id))
            return;

        $filename = $this->dir . DIRECTORY_SEPARATOR . "lpcache_${page_id}_${user_id}";
        $dirname = $this->dir . DIRECTORY_SEPARATOR . "lpcache_${page_id}_lock";
        
        if (!$this->_lock($dirname))
            return;
        
        $f = @fopen($filename, 'wb');
        @fwrite($f,
               $content . 
               '<!-- cached by FileCache on ' . date('r') . ' expires on ' . date('r', (time() + $this->validity)) . " -->\n" . chr(0));
        @fclose($f);
        
        $this->_unlock($dirname);
        
        $r = rand(0, $this->gc_probability);
        
        if ($r == 0)
            $this->garbageCollect();
        
    }
    
    function _lock($dirname) {
        // we don't care for retries, worst thing that happens is we don't
        // write the cache file in this request
        return @mkdir($dirname,0755);
    } 

    function _unlock($dirname) {
        @rmdir($dirname);
    } 
    
    function clearCache($id=null) {
        $this->garbageCollect(null, true);
    }
    
    function clearCacheComment($comment_id=null) {
        
        if (!is_null($comment_id)) {
            global $postdata;
            if (isset($postdata) && isset($postdata->ID))
                $this->clearCachePost($postdata->ID);
        }
        
    }
    
    function clearCachePost($post_id=null) {

        if (!is_null($post_id)) {
            // clear only cache files related to this post id
            // if we have this it means we are running as an action inside WP
            $permalink = get_permalink($post_id);
            $url_tokens = parse_url($permalink);
            if (isset($url_tokens['path'])) {
                $page_id = $this->_getId($url_tokens['path']);
                if (!empty($page_id)) {
                    $this->garbageCollect($page_id, true);
                    $this->garbageCollect($this->_getId($this->base_path), true);
                }
            }
        }

    }
    
    function clearCachePostUri($post_uri) {
        $page_id = $this->_getId($post_uri);
        if (!empty($page_id))
            $this->garbageCollect($page_id, true);
    }
    
    function garbageCollect($page_id=null, $clean_all=false) {
        // TODO: grab the list first, then delete so as to interfere less
        //       with new saves
        
        if (!is_null($page_id))
            $page_id = 'lpcache_' . $page_id . '_';

        $dir =& $this->dir;
        
        if ($handle = @opendir($dir)) {
            
            $valid = $this->_valid;
            
            clearstatcache();
            
            while (($file = readdir($handle)) !== false) {
                if (!substr($file, 0, 9) == 'lp_cache_')
                    continue;
                if ($page_id && strpos($file, $page_id) !== 0)
                    continue;
                
                $file_name = "$dir/$file";
                $mtime = @filemtime($file_name); // might have been a lockdir, or garbage collected
                if ($clean_all || (!$mtime || ($mtime + $this->validity) >= time())) {
                    // old cache or stale lock dir
                    if (@is_dir($file_name))
                        @rmdir($file_name);
                    else
                        @unlink($file_name);
                }
            }
            closedir($handle);
        } else {
            return $this->raiseError(
                "cannot get directory handle for '$dir'",
                'garbageCollect',
                __LINE__);
        }

    }
    
    function raiseError($message, $method, $line, $type=E_USER_WARNING) {
        trigger_error(
            sprintf("%s.%s() line %d: %s", get_class($this), $method, $line, $message),
            $type);
    }

}

?>