<?php

/*
 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between
 * Copyright (C) 2006-2009 Dan Fuhry
 *
 * This program is Free Software; you can redistribute and/or modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
 *
 * This program 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 details.
 */
 
/**
 * Framework for caching arbitrary data around the site.
 * @package Enano
 * @subpackage Core
 * @author Dan Fuhry <dan@enanocms.org>
 * @license GNU General Public License
 */

class CacheManager
{
  /**
   * Fetch a cached piece of data.
   * @param string Cache ID. The timestamp is checked automatically.
   */
  
  public function fetch($cache_id)
  {
    if ( !preg_match('/^[a-z0-9_]+$/', $cache_id) )
    {
      throw new Exception('Cache ID must be letters, numbers, and underscores.');
    }
    $cache_file = ENANO_ROOT . "/cache/cache_$cache_id.php";
    if ( file_exists($cache_file) )
    {
      require($cache_file);
      if ( isset($_cache_data) && isset($_cache_ttl) && isset($_cache_timestamp) )
      {
        $cache_expire = $_cache_timestamp + ( 60 * $_cache_ttl);
        if ( $cache_expire >= time() || $_cache_ttl === -1 )
        {
          return $_cache_data;
        }
      }
    }
    return false;
  }
  
  /**
   * Stores an array by var_export()ing it and saving it to disk.
   * @param string Cache ID - human readable name for this store (letters, numbers, underscores)
   * @param array Data to store
   * @param int TTL for the cached array, in minutes. Defaults to 20. If set to -1, caches indefinitely.
   * @return bool True on success, false on failure
   */
  
  public function store($cache_id, $data, $ttl = 20)
  {
    if ( getConfig('cache_thumbs') != '1' )
    {
      // caching disabled
      return false;
    }
    if ( !preg_match('/^[a-z0-9_]+$/', $cache_id) )
    {
      throw new Exception('Cache ID must be letters, numbers, and underscores.');
    }
    if ( !is_int($ttl) )
    {
      throw new Exception('TTL must be an integer');
    }
    
    $cache_file = ENANO_ROOT . "/cache/cache_$cache_id.php";
    if ( file_exists($cache_file) )
    {
      @unlink($cache_file);
    }
    $fh = @fopen($cache_file, 'w');
    if ( !$fh )
    {
      throw new Exception('Failed to open file for writing.');
    }
    $exported = Language::var_export_string($data);
    $now = time();
    $content = <<<EOF
<?php
/**
 * Automatically generated cache file.
 * Do not edit this file as it will expire and be overwritten $ttl minutes from its creation.
 */

\$_cache_ttl = $ttl;
\$_cache_timestamp = $now;
\$_cache_data = $exported;

EOF;
    fwrite($fh, $content);
    fclose($fh);
    
    return true;
  }
  
  /**
   * Deletes a cached item.
   * @param string Cache ID.
   * @return bool true on success or if item doesn't exist, false on failure
   */
  
  public function purge($cache_id)
  {
    if ( !preg_match('/^[a-z0-9_]+$/', $cache_id) )
    {
      throw new Exception('Cache ID must be letters, numbers, and underscores.');
    }
    
    $cache_file = ENANO_ROOT . "/cache/cache_$cache_id.php";
    if ( file_exists($cache_file) )
    {
      if ( unlink($cache_file) )
      {
        return true;
      }
      return false;
    }
    return true;
  }
}