<?php
namespace Lib\StoreDriver;

/**
 * 
 * 这里用php数组文件来存储数据，
 * 为了获取高性能需要用类似memcache的存储
 * @author walkor <workerman.net>
 * 
 */

class File
{
    // 为了避免频繁读取磁盘，增加了缓存机制
    protected $dataCache = array();
    // 上次缓存时间
    protected $lastCacheTime = 0;
    // 保存数据的文件
    protected $dataFile = '';
    // 打开文件的句柄
    protected $dataFileHandle = null;
    
    // 缓存过期时间
    const CACHE_EXP_TIME = 1;
    
    /**
     * 构造函数
     * @param 配置名 $config_name
     */
    public function __construct($config_name)
    {
        $this->dataFile = \Config\Store::$storePath . "/$config_name.store.cache.php";
        if(!is_file($this->dataFile))
        {
            touch($this->dataFile);
        }
        $this->dataFileHandle = fopen($this->dataFile, 'r+');
        if(!$this->dataFileHandle)
        {
            $error_msg = "can not fopen($this->dataFile, 'r+')";
            throw new \Exception($error_msg);
        }
    }
    
    /**
     * 设置
     * @param string $key
     * @param mixed $value
     * @param int $ttl
     * @return number
     */
    public function set($key, $value, $ttl = 0)
    {
        flock($this->dataFileHandle, LOCK_EX);
        $this->readDataFromDisk();
        $this->dataCache[$key] = $value;
        $ret = $this->writeToDisk();
        flock($this->dataFileHandle, LOCK_UN);
        return $ret;
    }
    
    /**
     * 读取
     * @param string $key
     * @param bool $use_cache
     * @return Ambigous <NULL, multitype:>
     */
    public function get($key, $use_cache = true)
    {
        if(!$use_cache || time() - $this->lastCacheTime > self::CACHE_EXP_TIME)
        {
            flock($this->dataFileHandle, LOCK_EX);
            $this->readDataFromDisk();
            flock($this->dataFileHandle, LOCK_UN);
        }
        return isset($this->dataCache[$key]) ? $this->dataCache[$key] : null;
    }
   
    /**
     * 删除
     * @param string $key
     * @return number
     */
    public function delete($key)
    {
        flock($this->dataFileHandle, LOCK_EX);
        $this->readDataFromDisk();
        unset($this->dataCache[$key]);
        $ret = $this->writeToDisk();
        flock($this->dataFileHandle, LOCK_UN);
        return $ret;
    }
    
    /**
     * 写入磁盘
     * @return number
     */
    protected function writeToDisk()
    {
        return file_put_contents($this->dataFile, "<?php \n return " . var_export($this->dataCache, true). ';');
    }
    
    /**
     * 从磁盘读
     */
    protected function readDataFromDisk()
    {
        $cache = include $this->dataFile;
        if(is_array($cache))
        {
            $this->dataCache = $cache;
        }
        $this->lastCacheTime = time();
    }
}