// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();

function escapeParams(param){
  return param.replace(/&/g, "%26");
}

// 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 odber(email)
{
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // try to connect to the server
    try
    { 
      xmlHttp.open("GET", "ajax/odber.php?EMAIL="+escapeParams(email), true);
      xmlHttp.onreadystatechange = handleRequestStateChange;
            
      xmlHttp.send(null);
    }
    // display the error in case of failure
    catch (e)
 
    {
      alert("Can't connect to server:\n" + e.toString());
    }
  }
}

// function that handles the HTTP response
function handleRequestStateChange() 
{
  // obtain a reference to the <div> element on the page
  if (xmlHttp.readyState == 4) 
  {
    // continue only if HTTP status is "OK"
    if (xmlHttp.status == 200) 
    {
      try
      {
        // read the message from the server
        response = xmlHttp.responseText;  
        eval(response);
        
        if ( ajax_result.status == "successful" ){
          document.getElementById('odber-input').value = "@";
        }
        else{
          if ( ajax_result.error == "FORMAT" ){
            alert('Nesprávny formát');
          }
          else document.getElementById('odber-input').value = "@";
        }
        //alert("AJAX: "+ajax_result.function+", "+ajax_result.status);
      }
      catch(e)
      {
        // display error message
        alert("Error reading the response: " + e.toString());
      }
    } 
    else
    {
      // display status message
      alert("There was a problem retrieving the data:\n" + 
            xmlHttp.statusText);
    }
  }
}