<?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;

	}

}