var xmlHttp = createXmlHttpRequestObject();
//alert (xmlHttp);

// creates an XMLHttpRequest instance
function createXmlHttpRequestObject()
{
    // will store the reference to the XMLHttpRequest object
    var xmlHttp;
    // this should work for all browsers except IE6 and older
    try
    {
        // try to create XMLHttpRequest object
        xmlHttp = new XMLHttpRequest();
    }
    catch(e)
    {
        // assume IE6 or older
        var XmlHttpVersions = new Array('MSXML2.XMLHTTP.6.0',
                                        'MSXML2.XMLHTTP.5.0',
                                        'MSXML2.XMLHTTP.4.0',
                                        'MSXML2.XMLHTTP.3.0',
                                        'MSXML2.XMLHTTP',
                                        'Microsoft.XMLHTTP');
        // try every prog id until one works
        for (var i=0; i<XmlHttpVersions.length && !xmlHttp; i++)
        {
            try

            {
                // try to create XMLHttpRequest object
                xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
            }
            catch (e) {}
        }
    }
    // return the created object or display an error message
    if (!xmlHttp)
        alert("Error creating the XMLHttpRequest object.");
    else
        return xmlHttp;
}

function auto_calc(form){

    if (xmlHttp)
    {
    	set_progress_bar('calc_res');
        try
        {
            var url = 'calc.php?' +
                    'cost=' + form.cost.value +
                    '&volume=' + form.volume.value +
                    '&currency=' + form.currency.value +
                    '&power=' + form.power.value +
                    '&power_edizm=' + form.xpower_edizm.value +
                    '&country=' + form.xcountry.value +
                    '&engine_type=' + form.xengine_type.value +
                    '&age=' + form.xage.value +
                    '&face=' + form.xface.value +
                    '&mode=ajax';
            // initiate reading a file from the server
            xmlHttp.open("GET", url, true);
            xmlHttp.onreadystatechange = handleRequestStateChange;
            xmlHttp.send(null);
        }

        catch (e)
        {
            alert("Can't connect to server:\n" + e.toString());
        }
    }

  /*var div = xGetElementById('auto_res_div');
  div.innerHTML='<br /><br /><br /><br /><p>считаю...</p>'+
                '<br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br />';


  var ajax = new Ajax.Updater(
                               div,
                               url,
                               {
                                method: 'get'
                               }
                            );
 */
  return false;
}

function handleRequestStateChange()
{
    // when readyState is 4, we are ready to read the server response
    if (xmlHttp.readyState == 4)
    {
        // continue only if HTTP status is "OK"
        if (xmlHttp.status == 200)
        {
            try
            {
                calc_output();
            }
            catch(e)
            {
				clear_html('calc_res');
            	// display error message
                alert("Error reading the response: " + e.toString());
            }
        }
        else
        {
			clear_html('calc_res');
        	// display status message
            alert("There was a problem retrieving the data:\n" +
                xmlHttp.statusText);
        }
    }
}

function calc_output()
{
    var taken_arr = new Array();
    taken_arr = xmlHttp.responseText.split('@_@_@');
    var status = taken_arr[0];
    var msg = taken_arr[1];
    if (status == 0)
    {
        clear_html('calc_res');
    	alert(msg);
    }
    else if (status == 1)
    {
        cr_obj = document.getElementById('calc_res');
        cr_obj.innerHTML = msg;
    }
}

function clear_html(div_id)
{
	document.getElementById(div_id).innerHTML = '';
}

function set_progress_bar(div_id)
{
	document.getElementById(div_id).innerHTML = '<center><img src="progress.gif" /></center>';
}