<?php
/**
 * Piwik - Open source web analytics
 *
 * @link http://piwik.org
 * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
 * @version $Id$
 *
 * @category Piwik
 * @package Piwik
 */

/**
 * Code originally inspired from OpenX
 * - openx/plugins_repo/openXDeliveryCacheStore/extensions/deliveryCacheStore/oxCacheFile/oxCacheFile.class.php
 * - openx/plugins_repo/openXDeliveryCacheStore/extensions/deliveryCacheStore/oxCacheFile/oxCacheFile.delivery.php
 *
 * We may want to add support for cache expire, storing last modification time in the file. See code in:
 * - openx/lib/max/Delivery/cache.php
 *
 * @package Piwik
 */
class Piwik_CacheFile
{
	/**
	 * @var string
	 */
	protected $cachePath;
	/**
	 * @var
	 */
	protected $cachePrefix;

	/**
	 * @param string  $directory  directory to use
	 */
	function __construct($directory)
	{
		$this->cachePath = PIWIK_USER_PATH . '/tmp/cache/' . $directory . '/';
	}

	/**
	 * Function to fetch a cache entry
	 *
	 * @param string  $id  The cache entry ID
	 * @return array|bool  False on error, or array the cache content
	 */
	function get($id)
	{
		if(empty($id)) {
			return false;
		}
		$cache_complete = false;
		$content = '';

		// We are assuming that most of the time cache will exists
		$ok = @include($this->cachePath . $id . '.php');

		if ($ok && $cache_complete == true) {
			return $content;
		}

		return false;
	}

	/**
	 * A function to store content a cache entry.
	 *
	 * @param string  $id       The cache entry ID
	 * @param array   $content  The cache content
	 * @return bool  True if the entry was succesfully stored
	 */
	function set($id, $content)
	{
		if(empty($id)) {
			return false;
		}
		if( !is_dir($this->cachePath))
		{
			Piwik_Common::mkdir($this->cachePath);
		}
		if (!is_writable($this->cachePath)) {
			return false;
		}
	
		$id = $this->cachePath . $id . '.php';

		$cache_literal  = "<"."?php\n\n";
		$cache_literal .= "$"."content   = ".var_export($content, true).";\n\n";
		$cache_literal .= "$"."cache_complete   = true;\n\n";
		$cache_literal .= "?".">";

		// Write cache to a temp file, then rename it, overwriting the old cache
		// On *nix systems this should guarantee atomicity
		$tmp_filename = tempnam($this->cachePath, 'tmp_');
		@chmod($tmp_filename, 0640);
		if ($fp = @fopen($tmp_filename, 'wb')) {
			@fwrite ($fp, $cache_literal, strlen($cache_literal));
			@fclose ($fp);
			
			if (!@rename($tmp_filename, $id)) {
				// On some systems rename() doesn't overwrite destination
				@unlink($id);
				if (!@rename($tmp_filename, $id)) {
					// Make sure that no temporary file is left over
					// if the destination is not writable
					@unlink($tmp_filename);
				}
			}
			return true;
		}
		return false;
	}

	/**
	 * A function to delete a single cache entry
	 *
	 * @param string  $id  The cache entry ID
	 * @return bool  True if the entry was succesfully deleted
	 */
	function delete($id)
	{
		if(empty($id)) {
			return false;
		}
		$filename = $this->cachePath . $id . '.php';
		if (file_exists($filename)) {
			@unlink ($filename);
			return true;
		}
		return false;
	}

	/**
	 * A function to delete all cache entries in the directory
	 */
	function deleteAll()
	{
		Piwik::unlinkRecursive($this->cachePath, $deleteRootToo = false);
	}
}