<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Caching;

/**
 * ZendDataCache provides Zend data caching in terms of an application component.
 *
 * To use this application component, the [Zend Data Cache PHP extension](http://www.zend.com/en/products/server/)
 * must be loaded.
 *
 * See [[Cache]] for common cache operations that ZendDataCache supports.
 *
 * For more details and usage information on Cache, see the [guide article on caching](guide:caching-overview).
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class ZendDataCache extends Cache
{

    /**
     * Retrieves a value from cache with a specified key.
     * This is the implementation of the method declared in the parent class.
     * 
     * @param string $key
     *            a unique key identifying the cached value
     * @return mixed|false the value stored in cache, false if the value is not in the cache or expired.
     */
    protected function getValue($key)
    {
        $result = zend_shm_cache_fetch($key);
        
        return $result === null ? false : $result;
    }

    /**
     * Stores a value identified by a key in cache.
     * This is the implementation of the method declared in the parent class.
     *
     * @param string $key
     *            the key identifying the value to be cached
     * @param mixed $value
     *            the value to be cached. Most often it's a string. If you have disabled [[serializer]],
     *            it could be something else.
     * @param int $duration
     *            the number of seconds in which the cached value will expire. 0 means never expire.
     * @return bool true if the value is successfully stored into cache, false otherwise
     */
    protected function setValue($key, $value, $duration)
    {
        return zend_shm_cache_store($key, $value, $duration);
    }

    /**
     * Stores a value identified by a key into cache if the cache does not contain this key.
     * This is the implementation of the method declared in the parent class.
     *
     * @param string $key
     *            the key identifying the value to be cached
     * @param mixed $value
     *            the value to be cached. Most often it's a string. If you have disabled [[serializer]],
     *            it could be something else.
     * @param int $duration
     *            the number of seconds in which the cached value will expire. 0 means never expire.
     * @return bool true if the value is successfully stored into cache, false otherwise
     */
    protected function addValue($key, $value, $duration)
    {
        return zend_shm_cache_fetch($key) === null ? $this->setValue($key, $value, $duration) : false;
    }

    /**
     * Deletes a value with the specified key from cache
     * This is the implementation of the method declared in the parent class.
     * 
     * @param string $key
     *            the key of the value to be deleted
     * @return bool if no error happens during deletion
     */
    protected function deleteValue($key)
    {
        return zend_shm_cache_delete($key);
    }

    /**
     * Deletes all values from cache.
     * This is the implementation of the method declared in the parent class.
     * 
     * @return bool whether the flush operation was successful.
     */
    protected function flushValues()
    {
        return zend_shm_cache_clear();
    }
}
