<?php
/*
 * Project:     MagpieRSS: a simple RSS integration tool
 * File:        rss_cache.inc, a simple, rolling(no GC), cache 
 *				for RSS objects, keyed on URL.
 * Author:      Kellan Elliott-McCrea <kellan@protest.net>
 * Version:		0.51
 * License:		GPL
 *
 * The lastest version of MagpieRSS can be obtained from:
 * http://magpierss.sourceforge.net
 *
 * For questions, help, comments, discussion, etc., please join the
 * Magpie mailing list:
 * http://lists.sourceforge.net/lists/listinfo/magpierss-general
 *
 */

class RSSCache {
    var $BASE_CACHE = './cache'; // where the cache files are stored
    var $MAX_AGE = 3600; // when are files stale, default one hour
    var $ERROR = ""; // accumulate error messages
    function RSSCache ($base = '', $age = '')
    {
        if ($base) {
            $this->BASE_CACHE = $base;
        } 
        if ($age) {
            $this->MAX_AGE = $age;
        } 
        // attempt to make the cache directory
        if (! file_exists($this->BASE_CACHE)) {
            $status = @mkdir($this->BASE_CACHE, 0755); 
            // if make failed
            if (! $status) {
                $this->error("Cache couldn't make dir '" . $this->BASE_CACHE . "'."
                    );
            } 
        } 
    } 

    /*=======================================================================*\
	Function:	set
	Purpose:	add an item to the cache, keyed on url
	Input:		url from wich the rss file was fetched
	Output:		true on sucess	
\*=======================================================================*/
    function set ($url, $rss)
    {
        $this->ERROR = "";
        $cache_file = $this->file_name($url);
        $fp = @fopen($cache_file, 'w');

        if (! $fp) {
            $this->error("Cache unable to open file for writing: $cache_file"
                );
            return 0;
        } 

        $data = $this->serialize($rss);
        fwrite($fp, $data);
        fclose($fp);

        return $cache_file;
    } 

    /*=======================================================================*\
	Function:	get
	Purpose:	fetch an item from the cache
	Input:		url from wich the rss file was fetched
	Output:		cached object on HIT, false on MISS	
\*=======================================================================*/
    function get ($url)
    {
        $this->ERROR = "";
        $cache_file = $this->file_name($url);

        if (! file_exists($cache_file)) {
            $this->debug("Cache doesn't contain: $url (cache file: $cache_file)"
                );
            return 0;
        } 

        $fp = @fopen($cache_file, 'r');
        if (! $fp) {
            $this->error("Failed to open cache file for reading: $cache_file"
                );
            return 0;
        } 

        $data = fread($fp, filesize($cache_file));
        $rss = $this->unserialize($data);

        return $rss;
    } 

    /*=======================================================================*\
	Function:	check_cache
	Purpose:	check a url for membership in the cache
				and whether the object is older then MAX_AGE (ie. STALE)
	Input:		url from wich the rss file was fetched
	Output:		cached object on HIT, false on MISS	
\*=======================================================================*/
    function check_cache ($url)
    {
        $this->ERROR = "";
        $filename = $this->file_name($url);

        if (file_exists($filename)) {
            // find how long ago the file was added to the cache
            // and whether that is longer then MAX_AGE
            $mtime = filemtime($filename);
            $age = time() - $mtime;
            if ($this->MAX_AGE > $age) {
                // object exists and is current
                return 'HIT';
            } else {
                // object exists but is old
                return 'STALE';
            } 
        } else {
            // object does not exist
            return 'MISS';
        } 
    } 

    /*=======================================================================*\
	Function:	serialize
\*=======================================================================*/
    function serialize ($rss)
    {
        return serialize($rss);
    } 

    /*=======================================================================*\
	Function:	unserialize
\*=======================================================================*/
    function unserialize ($data)
    {
        return unserialize($data);
    } 

    /*=======================================================================*\
	Function:	file_name
	Purpose:	map url to location in cache
	Input:		url from wich the rss file was fetched
	Output:		a file name
\*=======================================================================*/
    function file_name ($url)
    {
        $filename = md5($url);
        return join(DIRECTORY_SEPARATOR, array($this->BASE_CACHE, $filename));
    } 

    /*=======================================================================*\
	Function:	error
	Purpose:	register error
\*=======================================================================*/
    function error ($errormsg, $lvl = E_USER_WARNING)
    { 
        // append PHP's error message if track_errors enabled
        if (isset($php_errormsg)) {
            $errormsg .= " ($php_errormsg)";
        } 
        $this->ERROR = $errormsg;
        if (MAGPIE_DEBUG) {
            trigger_error($errormsg, $lvl);
        } else {
            error_log($errormsg, 0);
        } 
    } 

    function debug ($debugmsg, $lvl = E_USER_NOTICE)
    {
        if (MAGPIE_DEBUG) {
            $this->error("MagpieRSS [debug] $debugmsg", $lvl);
        } 
    } 
} 

?>