<?php
/**
 * EGroupware API: Caching provider storing data in PHP's APC or APCu extension
 *
 * @link http://www.egroupware.org
 * @license http://opensource.org/licenses/gpl-license.php GPL - GNU General Public License
 * @package api
 * @subpackage cache
 * @author Ralf Becker <RalfBecker-AT-outdoor-training.de>
 * @copyright (c) 2010-16 by Ralf Becker <RalfBecker-AT-outdoor-training.de>
 * @version $Id$
 */

namespace EGroupware\Api\Cache;

/**
 * Caching provider storing data in PHP's APC or APCu extension / shared memory.
 *
 * The provider concats all $keys with '::' to get a single string.
 *
 * This provider is used by default, if it is available or explicit enabled in your header.inc.php:
 * $GLOBALS['egw_info']['server']['cache_provider_instance'] = array('EGroupware\Api\Cache\Apc');
 * and optional also $GLOBALS['egw_info']['server']['cache_provider_tree'] (defaults to instance)
 *
 * APC(u) and CLI:
 * --------------
 * APC(u) is not enabled by default for CLI (apc.enable_cli), nor would it access same shared memory!
 * It makes no sense to fall back to files cache, as this is probably quite outdated,
 * if PHP via Webserver uses APC. Better to use no cache at all.
 * Api\Cache::get*() will return NULL for not found and Api\Cache::[un]set*()
 * false for not being able to (un)set anything.
 * It also does not make sense to report failure by throwing an Exception and filling
 * up cron logs.
 * --> if APC(u) is available for Webserver, we report availability for CLI too,
 *     but use no cache at all!
 */
class Apc extends Base implements Provider
{
	/**
	 * Constructor, eg. opens the connection to the backend
	 *
	 * @throws Exception if connection to backend could not be established
	 * @param array $params eg. array('localhost'[,'localhost:11211',...])
	 */
	function __construct(array $params)
	{
		if (!function_exists('apc_fetch'))	// apc >= 3.0
		{
			throw new Exception (__METHOD__.'('.array2string($params).") No function apc_fetch()!");
		}
	}

	/**
	 * Check if APC is available for caching user data
	 *
	 * Default shared memory size of 32M is just enough for the byte code cache,
	 * but not for caching user data, we only use APC by default if we have at least 64M.
	 *
	 * @return boolean true: apc available, false: not
	 */
	public static function available()
	{
		if (($available = (bool)ini_get('apc.enabled') && function_exists('apc_fetch')))
		{
			$size = ini_get('apc.shm_size');
			// ancent APC (3.1.3) in Debian 6/Squezze has size in MB without a unit
			if (is_numeric($size) && $size <= 1048576) $size .= 'M';

			switch(strtoupper(substr($size, -1)))
			{
				case 'G':
					$size *= 1024;
				case 'M':
					$size *= 1024;
				case 'K':
					$size *= 1024;
			}
			$size *= ini_get('apc.shm_segments');

			// only cache in APC, if we have at least 64M available (default is 32M)
			$available = $size >= 67108864;
		}
		//error_log(__METHOD__."() size=$size returning ".array2string($available));
		return $available;
	}

	/**
	 * Stores some data in the cache, if it does NOT already exists there
	 *
	 * @param array $keys eg. array($level,$app,$location)
	 * @param mixed $data
	 * @param int $expiration =0
	 * @return boolean true on success, false on error, incl. key already exists in cache
	 */
	function add(array $keys,$data,$expiration=0)
	{
		return apc_add(self::key($keys),$data,$expiration);
	}

	/**
	 * Stores some data in the cache
	 *
	 * @param array $keys eg. array($level,$app,$location)
	 * @param mixed $data
	 * @param int $expiration =0
	 * @return boolean true on success, false on error
	 */
	function set(array $keys,$data,$expiration=0)
	{
		return apc_store(self::key($keys),$data,$expiration);
	}

	/**
	 * Get some data from the cache
	 *
	 * @param array $keys eg. array($level,$app,$location)
	 * @return mixed data stored or NULL if not found in cache
	 */
	function get(array $keys)
	{
		$success = null;
		$data = apc_fetch($key=self::key($keys),$success);

		if (!$success)
		{
			//error_log(__METHOD__."(".array2string($keys).") key='$key' NOT found!");
			return null;
		}
		//error_log(__METHOD__."(".array2string($keys).") key='$key' found ".bytes(serialize($data))." bytes).");
		return $data;
	}

	/**
	 * Delete some data from the cache
	 *
	 * @param array $keys eg. array($level,$app,$location)
	 * @return boolean true on success, false on error (eg. $key not set)
	 */
	function delete(array $keys)
	{
		return apc_delete(self::key($keys));
	}

	/**
	 * Delete all data under given keys
	 *
	 * If no keys are given whole APC cache is cleared, which should allways
	 * work and can not run out of memory as the iterator sometimes does.
	 *
	 * @param array $keys eg. array($level,$app,$location)
	 * @return boolean true on success, false on error (eg. on iterator available)
	 */
	function flush(array $keys)
	{
		// APC >= 3.1.1, but also seems to be missing if apc is disabled eg. for cli
		if (!class_exists('APCIterator') || !$keys)
		{
			if (function_exists('apc_clear_cache')) apc_clear_cache('user');

			return false;
		}
		//error_log(__METHOD__."(".array2string($keys).")");
		foreach(new \APCIterator('user', $preg='/^'.preg_quote(self::key($keys).'/')) as $item)
		{
			//error_log(__METHOD__."(".array2string($keys).") preg='$preg': calling apc_delete('$item[key]')");
			apc_delete($item['key']);
		}
		return true;
	}

	/**
	 * Create a single key from $keys
	 *
	 * @param array $keys
	 * @return string
	 */
	private static function key(array $keys)
	{
		return implode('::',$keys);
	}
}