<?php
class cache {
    
    //cache path
    private $cache_path = './cache/';
    
    /**
     * static method
     * can refer to static
     *
     * @access public
     * @return static obiect
     *
     */
     
    public static function factory()
    {
        return new cache;
    }
    
    /**
     * methos allows you to save cache
     *
     * @access public
     * @param string $name - filename of cache
     * @param mixed $value - value of cache
     * @param integer $time - time expired cache
     *
     */
     
    public function save( $name, $value, $time)
    {
        
        //if is all ok
        if( $this -> _findCache( $name) == false)
        {
            $time = $time + time();
            $name = $name . '~' . $time;
            file_put_contents( $this -> cache_path . $name, serialize( $value));
        }
        
        //if time expired
        elseif( $this -> expired( $name) < time())
        {
            $this -> flush( $name);
            $this -> save( $name, $value, $time);
        }
        
        //if cache exists and time no expired
        else
        {
            echo 'cach exists';
        }
    }
    
    /**
     * load cache
     *
     * @access public
     * @param string $name - filename of cache
     *
     */
     
    public function load( $name)
    {
        if( $this -> state( $name) === true)
        {
            return unserialize( file_get_contents( $this -> _findCache( $name)));
        }
        else
        {
            return false;
        }
    }
    
    /**
     * delete cache
     *
     * @access public
     * @param string $name - filename of cache
     *
     */
    
    public function flush( $name = false)
    {
        if( $name == true)
        {
            //delete one selected cache
            if( file_exists( $this -> _findCache( $name)))
            {
               $this -> _findCache( $name);
                unlink( $this -> _findCache( $name));
            }
            
            //delete all cache
            else
            {
                echo 'file no\'t exists';
            }
        }
        else
        {
            $files = glob( $this -> cache_path . '*');
            foreach( $files as $item)
            {
                unlink( $item);
            }
        }
    }
    
    /**
     * return expired time to left
     *
     * @access public
     * @param string $name - filename of cache
     *
     */
     
    public function expired( $name)
    {
        $expired = substr( strstr($this -> _findCache( $name), '~'), 1);
        return ($expired > time()) ? $expired - time() : false;
    }
    
    /**
     * check state
     *
     * @access private
     * @param string $name - filename of cache
     *
     */
     
    private function state( $name)
    {
        if( $this -> _findCache( $name) == true)
        {
            $r = explode('~', $this -> _findCache( $name)); //0 = filename; 1 = time
            
            if( $r[1] > time())
            {
                return true;
            }
            else
            {
                return false;
            }
        } else { return false; }
    }
    
    /**
     * find all name of cache
     *
     * @accessprivate
     * @param string $name - filename of cache
     *
     */
    
    private function _findCache( $name)
    {
        $files = glob( $this -> cache_path . $name . '~*');
        
        if( $files == false) 
        {
            return false;
        }
        else
        {
            return $files[0];
        }
    }
}