<?php

/**
 * Limb Web Application Framework
 *
 * @link http://limb-project.com
 *
 * @copyright  Copyright &copy; 2004-2007 BIT
 * @license    LGPL http://www.gnu.org/copyleft/lesser.html
 * @version    $Id: lmbHttpCache.class.php 5001 2007-02-08 15:36:45Z pachanga $
 * @package    net
 */

//inspired by http://alexandre.alapetite.net/doc-alex/php-http-304/



define('LIMB_HTTP_CACHE_TYPE_PRIVATE', 0);

define('LIMB_HTTP_CACHE_TYPE_PUBLIC', 1);



class lmbHttpCache

{

  protected $etag;

  protected $last_modified_time;

  protected $cache_time;

  protected $cache_type;



  function __construct()

  {

    $this->reset();

  }



  function reset()

  {

    $this->last_modified_time = time();

    $this->etag = null;

    $this->cache_time = 0;

    $this->cache_type = LIMB_HTTP_CACHE_TYPE_PRIVATE;

  }



  function checkAndWrite($response)

  {

    if($this->is412())

    {

      $this->_write412Response($response);

      return true;

    }

    elseif($this->is304())

    {

      $this->_write304Response($response);

      return true;

    }

    else

    {

      $this->_writeCachingResponse($response);



      return isset($_SERVER['REQUEST_METHOD']) && $_SERVER['REQUEST_METHOD'] == 'HEAD'; //rfc2616-sec9.html#sec9.4

    }

  }



  function is412()

  {

    if (isset($_SERVER['HTTP_IF_MATCH'])) //rfc2616-sec14.html#sec14.24

    {

      $etag_client = stripslashes($_SERVER['HTTP_IF_MATCH']);

      return (($etag_client != '*') &&  (strpos($etag_client, $this->getEtag()) === false));

    }



    if (isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE'])) //http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.28

    {

      return (strcasecmp($_SERVER['HTTP_IF_UNMODIFIED_SINCE'], $this->formatLastModifiedTime()) != 0);

    }



    return false;

  }



  function is304()

  {

    if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) //rfc2616-sec14.html#sec14.25 //rfc1945.txt

    {

      return ($_SERVER['HTTP_IF_MODIFIED_SINCE'] == $this->formatLastModifiedTime());

    }



    if (isset($_SERVER['HTTP_IF_NONE_MATCH'])) //rfc2616-sec14.html#sec14.26

    {

      $etag_client = stripslashes($_SERVER['HTTP_IF_NONE_MATCH']);

      return (($etag_client == $this->getEtag()) ||  ($etag_client == '*'));

    }



    return false;

  }



  protected function _write412Response($response)

  {

    $response->header('HTTP/1.1 412 Precondition Failed');

    $response->header('Cache-Control: protected, max-age=0, must-revalidate');

    $response->header('Content-Type: text/plain');



    $response->write("HTTP/1.1 Error 412 Precondition Failed: Precondition request failed positive evaluation\n");

  }



  protected function _write304Response($response)

  {

    $response->header('HTTP/1.0 304 Not Modified');

    $response->header('Etag: ' . $this->getEtag());

    $response->header('Pragma: ');

    $response->header('Cache-Control: ');

    $response->header('Last-Modified: ');

    $response->header('Expires: ');

  }



  protected function _writeCachingResponse($response)

  {

    $response->header('Cache-Control: ' . $this->_getCacheControl()); //rfc2616-sec14.html#sec14.9

    $response->header('Last-Modified: ' . $this->formatLastModifiedTime());

    $response->header('Etag: ' . $this->getEtag());

    $response->header('Pragma: ');

    $response->header('Expires: ');

  }



  protected function _getCacheControl()

  {

    if ($this->cache_time == 0)

      $cache = 'protected, must-revalidate, ';

    elseif ($this->cache_type == LIMB_HTTP_CACHE_TYPE_PRIVATE)

      $cache = 'protected, ';

    elseif ($this->cache_type == LIMB_HTTP_CACHE_TYPE_PUBLIC)

      $cache = 'public, ';

    else

      $cache = '';

    $cache .= 'max-age=' . floor($this->cache_time);

    return $cache;

  }



  function formatLastModifiedTime()

  {

    return $this->_formatGmtTime($this->last_modified_time);

  }



  protected function _formatGmtTime($time)

  {

    return gmdate('D, d M Y H:i:s \G\M\T', $time);

  }



  function setLastModifiedTime($last_modified_time)

  {

    $this->last_modified_time = $last_modified_time;

  }



  function getLastModifiedTime()

  {

    return $this->last_modified_time;

  }



  function setEtag($etag)

  {

    $this->etag = $etag;

  }



  function getEtag()

  {

    if($this->etag)

      return $this->etag;



    //rfc2616-sec14.html#sec14.19 //='"0123456789abcdef0123456789abcdef"'

    if (isset($_SERVER['QUERY_STRING']))

      $query = '?' . $_SERVER['QUERY_STRING'];

    else

      $query = '';



    $this->etag = '"' . md5($this->_getScriptName() . $query . '#' . $this->last_modified_time ) . '"';



    return $this->etag;

  }



  protected function _getScriptName()

  {

    if (isset($_SERVER['SCRIPT_FILENAME']))

      return $_SERVER['SCRIPT_FILENAME'];

    elseif (isset($_SERVER['PATH_TRANSLATED']))

      return $_SERVER['PATH_TRANSLATED'];

    else

      return '';

  }



  function setCacheTime($cache_time)

  {

    $this->cache_time = $cache_time;

  }



  function getCacheTime()

  {

    return $this->cache_time;

  }



  function setCacheType($cache_type)

  {

    $this->cache_type = $cache_type;

  }



  function getCacheType()

  {

    return $this->cache_type;

  }

}



?>