<?php
class Util_Common_Session implements Util_Session_SaveHandler_Interface 
{
    const LIFETIME = 1800;
    const DOMAIN = '.yoho.cn';
    
    protected $prefix = 'yh_session_';
    
    protected $domain = '.yoho.cn';
    
    protected $_lifetime = false;
    
    protected $_overrideLifetime = false;
    
    protected $_sessionSavePath = '';
    
    protected $_sessionName = '';
    
    protected $mem = null;
    
    /**
     * 初始化
     * 
     * @param array $options
     */
    public function __construct(array $options = array())
    {
        $this->domain = defined('SITE_DOMAIN') ? SITE_DOMAIN : self::DOMAIN;
        
        ini_set('session.cookie_domain', $this->domain);
        // 使用 COOKIE 保存 SESSION ID 的方式
        ini_set('session.use_cookies', 1);
        // 兼容使用 GET/POST 变量方式
        ini_set('session.use_trans_sid', 1);
        // 设置垃圾收集的触发几率
        ini_set('session.gc_probability', 1);
        // 设置垃圾收集的触发几率除数
        ini_set('session.gc_divisor', 100);
        // 设置垃圾回收最大生存时间,浏览器生存周期
        ini_set('session.gc_maxlifetime', self::LIFETIME);
        
        ini_set('session.cookie_path', '/');
        
        // 多主机共享保存 SESSION ID 的 COOKIE
        // 将 session.save_handler 设置为 user
        // session_module_name ( 'user' );
        // 定义 SESSION 各项操作所对应的方法名;
        $this->createCacheObj();
        $this->setLifetime(self::LIFETIME);
        $this->setOverrideLifetime(true);
    }
    
    /**
     * 析构函数
     * 
     * @return void
     */
    public function __destruct()
    {
        session_write_close();
        
        $this->mem = null;
    }
    
    /**
     * 创建Cache对象
     *
     * @return Instance of cache | false
     */
    private function createCacheObj() 
    {
        $this->mem = Util_Cache::factory ( array ('domain' => 'www' . $this->domain, 'class' => 'session') );
        if (! isset ( $this->mem ) || ! $this->mem) 
        {
            throw new Framework_YException ( 'All cache servers down.' );
        }
        return $this->mem;
    }
    
    /**
     * Set session lifetime and optional whether or not the lifetime of an existing session should be overridden
     *
     * $lifetime === false resets lifetime to session.gc_maxlifetime
     *
     * @param int $lifetime
     * @param boolean $overrideLifetime (optional)
     * @return Zend_Session_SaveHandler_Memcached
     */
    public function setLifetime($lifetime, $overrideLifetime = null)
     {
        if ($lifetime < 0) 
        {
            throw new Framework_YException ( '生存周期不能设置为小于0!' );
        } 
        else if (empty ( $lifetime ))
        {
            $this->_lifetime = ( int ) ini_get ( 'session.gc_maxlifetime' );
        }
        else
        {
            $this->_lifetime = ( int ) $lifetime;
        }
        if ($overrideLifetime != null)
        {
            $this->setOverrideLifetime ( $overrideLifetime );
        }
        return $this;
    }
    
    /**
     * Retrieve session lifetime
     *
     * @return int
     */
    public function getLifetime() 
    {
        return $this->_lifetime;
    }
    
    /**
     * Set whether or not the lifetime of an existing session should be overridden
     *
     * @param boolean $overrideLifetime
     * @return Zend_Session_SaveHandler_Memcached
     */
    public function setOverrideLifetime($overrideLifetime)
    {
        $this->_overrideLifetime = ( boolean ) $overrideLifetime;
        
        return $this;
    }
    
    public function getOverrideLifetime() 
    {
        return $this->_overrideLifetime;
    }
    
    /**
     * Retrieve session lifetime considering
     *
     * @param array $value
     * @return int
     */
    public function open($save_path, $name)
    {
        $this->_sessionSavePath = $save_path;
        $this->_sessionName = $name;
        return true;
    }
    
    /**
     * Retrieve session expiration time
     *
     * @param * @param array $value
     * @return int
     */
    public function close() 
    {
        return true;
    }
    
    /**
     * 读取接口
     *
     * @param string $id
     * @return mixed | false
     */
    public function read($id)
    {
        $return = '';
        $value = $this->mem->get ( $this->prefix . $id ); //获取数据
        if ($value) 
        {
            if ($this->_getExpirationTime ( $value ) > time ())
            {
                $return = $value ['data'];
            }
            else
            {
                $this->destroy ( $id );
            }
        }
        return $return;
    }
    
    /**
     * 写入接口
     *
     * @param string $id
     * @param mixed $data
     * @return boolean
     */
    public function write($id, $data)
    {
        $return = false;
        $insertDate = array ('modified' => time (), 'data' => ( string ) $data );
        $value = $this->mem->get ( $this->prefix . $id ); //获取数据
        if ($value) 
        {
            $insertDate ['lifetime'] = $this->_getLifetime ( $value );
            $return = $this->_overrideLifetime ? $this->mem->set ( $this->prefix . $id, $insertDate, 0, $insertDate ['lifetime'] ) : $this->mem->set ( $this->prefix . $id, $insertDate );
        } 
        else 
        {
            $insertDate ['lifetime'] = $this->_lifetime;
            $return = $this->mem->set ( $this->prefix . $id, $insertDate, 0, $this->_lifetime );
        }
        return $return;
    }
    
    /**
     * 摧毁ITEM
     *
     * @param string $id
     * @return boolean
     */
    public function destroy($id)
    {
        return $this->mem->delete ( $this->prefix . $id );
    }
    
    /**
     * 垃圾收集
     *
     * @param integer $maxlifetime
     * @return true
     */
    public function gc($maxlifetime) 
    {
        return true;
    }
    
    /**
     * 获取生存时间
     *
     * @param String $value
     * @return Integer
     */
    protected function _getLifetime($value)
    {
        $return = $this->_lifetime;
        if (! $this->_overrideLifetime)
        {
            $return = ( int ) $value ['lifetime'];
        }
        return $return;
    }
    
    protected function _getExpirationTime($value) 
    {
        return ( int ) $value ['modified'] + $this->_getLifetime ( $value );
    }
}