// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();
// when set to true, display detailed error messages
var showErrors = true;
// initialize the requests cache 
var cache = new Array();

// 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) {} // ignore potential error
    }
  }
  // return the created object or display an error message
  if (!xmlHttp)
    alert("Error creating the XMLHttpRequest object.");
  else 
    return xmlHttp;
}

// function that displays an error message
function displayError($message)
{
  // ignore errors if showErrors is false
  if (showErrors)
  {
    // turn error displaying Off
    showErrors = false;
    // display error message
    alert("Error encountered: \n" + $message);
 
  }
}

// Send request to server
function process(content, action)
{
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // initialize the request query string to empty string 
    params = "";
    // escape the values to be safely sent to the server 
    content = encodeURIComponent(content);
    // prepare the task for sending to the server
    params = "content=" + content + "&action=" + action;
    // don't add null params to cache            
    if (params) cache.push(params);

    // try to connect to the server
    try
    {
      // only continue if the connection is clear and cache is not empty
      if ((xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
           && cache.length>0)
      {
        // get next set of values from cache
        var cacheEntry = cache.shift();
        // definice vlastni hlavicky parametru
        // initiate the request
        xmlHttp.open("POST", "/ajax", true);
        xmlHttp.setRequestHeader("Content-Type", 
                                 "application/x-www-form-urlencoded");
        xmlHttp.onreadystatechange = handleRequestStateChange;
        // null pouziju pokud odesilam metodou get a parametry pisu primo za adresu
        xmlHttp.send(params);
        //xmlHttp.send(null);
      }
      else
      {
        setTimeout("process();", 1000);  
      }
    }
    // display the error in case of failure
    catch (e)
    {
      displayError(e.toString());
    }
  }
}

// function that retrieves the HTTP response
function handleRequestStateChange() 
{
  // when readyState is 4, we also read the server response
  if (xmlHttp.readyState == 4) 
  {
    // continue only if HTTP status is "OK"
    if (xmlHttp.status == 200) 
    {
      try
      {
        postUpdateProcess();
      }
      catch(e)
      {
        // display error message
        displayError(e.toString());
      }
    } 
    else 
    {
      displayError(xmlHttp.statusText);
    }
  }
}
// Processes server's response
function postUpdateProcess()
{
  // read the response
  var response = xmlHttp.responseText;
  // server error?
  // pokud se vranti jako prni znaky ERRNO nebo error, vypis se zastavi a generuje se chyba

  if(response.slice(0,2)=='ER'){
    var winInfo = new WindowInfo();
    document.getElementById("ErrorBar").style.top = (winInfo.scrollOffsetTop+100)+"px";
    document.getElementById("ErrorBar").innerHTML = response.slice(2,response.length);
    new Effect.Appear(document.getElementById("ErrorBar")); // zobrazi informacni pole 
    setTimeout("new Effect.Fade(document.getElementById('ErrorBar'));", 7000); // nastavi skryti po nekolika sekundach
  }else if(response.slice(0,2)=='IN'){
    // vymaze formular byl-li korektne prijaty
    document.getElementById("FormNews").reset();
    // nastavi pozici zobrazeni panelu
    var winInfo = new WindowInfo();
    document.getElementById("InfoBar").style.top = (winInfo.scrollOffsetTop+100)+"px";
    document.getElementById("InfoBar").innerHTML = response.slice(2,response.length);
    new Effect.Appear(document.getElementById("InfoBar")); // zobrazi informacni pole 
    setTimeout("new Effect.Fade(document.getElementById('InfoBar'));", 7000); // nastavi skryti po nekolika sekundach
  }else if(response.slice(0,2)=='GR'){
    // vymaze formular byl-li korektne prijaty
    document.getElementById("FormKontakt").reset();
    // nastavi pozici zobrazeni panelu
    var winInfo = new WindowInfo();
    document.getElementById("GreenBar").style.top = (winInfo.scrollOffsetTop+100)+"px";
    document.getElementById("GreenBar").innerHTML = response.slice(2,response.length);
    new Effect.Appear(document.getElementById("GreenBar")); // zobrazi informacni pole 
    setTimeout("new Effect.Fade(document.getElementById('GreenBar'));", 7000); // nastavi skryti po nekolika sekundach
  }
  //if (response.indexOf("ERRNO") >= 0 || response.indexOf("error") >= 0 || response.indexOf("PHP5") >= 0) alert('chyba error!!!'+response);
  // pokud neni prihlaseny uz presmeruje ho na root
}