// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();
var navrat = 0;
// 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;
}

// na druhy formular pouzijeme jinou funkci

function roomterms(room, type)
{
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // TODO: sem zkusime vrazit pominku na PARAMS podle toho co obsahje nastavime parametry getTerms
       params = 'typ=' + type + '&room=' + room;
       navrat = 1;

    try
    {
      // get the two values entered by the user
      //var firstNumber = document.getElementById("firstNumber").value;
      //var secondNumber = document.getElementById("secondNumber").value;

      // create the params string
     // var params = "firstNumber=" + firstNumber +
     //              "&secondNumber=" + secondNumber;
      // initiate the asynchronous HTTP request
      xmlHttp.open("GET", "getTerms.php?" + params, 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());
    }
  }
}




// read a file from the server
function process(params)
{
  // disablneme submit 
  document.Rezervacem.SRezervacem.disabled = true;
  // deletneme hlaseni ostatnich terminu
  document.getElementById('OstatniHlaseni').innerHTML = '';
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // TODO: sem zkusime vrazit pominku na PARAMS podle toho co obsahje nastavime parametry getTerms
    if (params == 'vikend' || params == 'tyden') {
        document.Rezervacem.Pokoj.disabled = true;
        document.Rezervacem.Pokoj.selectedIndex = 0;

        navrat = 1;
    }
    else if (params == 'termin') {
    // zjistit selcted option a vrazit jeho value jako params
      if (document.Rezervacem.Termin.selectedIndex == 0) {
              params = 'pokoj=undefined';
      }
      else {
        params = 'pokoj=' + document.Rezervacem.Termin.options[document.Rezervacem.Termin.selectedIndex].value;
        navrat = 2;
      }
    }
    
    try
    {
      // get the two values entered by the user
      //var firstNumber = document.getElementById("firstNumber").value;
      //var secondNumber = document.getElementById("secondNumber").value;
      
      // create the params string
     // var params = "firstNumber=" + firstNumber +
     //              "&secondNumber=" + secondNumber;
      // initiate the asynchronous HTTP request
      xmlHttp.open("GET", "getTerms.php?" + params, 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 called when the state of the HTTP request changes
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
      {
        // do something with the response from the server
        handleServerResponse();
      }
      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);
    }
  }
}

// handles the response received from the server
function handleServerResponse()
{
   var response = xmlHttp.responseText;
   
/*  // retrieve the server's response packaged as an XML DOM object
  var xmlResponse = xmlHttp.responseXML;
  // catching potential errors with IE and Opera
  if (!xmlResponse || !xmlResponse.documentElement)
    throw("Invalid XML structure:\n" + xmlHttp.responseText);

  // catching potential errors with Firefox
  var rootNodeName = xmlResponse.documentElement.nodeName;
  if (rootNodeName == "parsererror")
    throw("Invalid XML structure:\n" + xmlHttp.responseText);
  // getting the root element (the document element)
  xmlRoot = xmlResponse.documentElement;
  // testing that we received the XML document we expect
  if (rootNodeName != "response" || !xmlRoot.firstChild)        // TODO: podle nazvu elementu provedeme zpracovani dat
    throw("Invalid XML structure:\n" + xmlHttp.responseText);
  // the value we need to display is the child of the root <response> element
  responseText = xmlRoot.firstChild.data;
  // display the user message
  //myDiv = document.getElementById("myDivElement");
  //myDiv.innerHTML = "Server says the answer is: " + responseText;
  */
  if (navrat == 1) {
  terminy = document.getElementById('SelTermin');
  terminy.innerHTML = "";
  terminy.innerHTML = response;
 }
 else {


    pokoje = document.getElementById('SelPokoj');
    pokoje.innerHTML = "";
    pokoje.innerHTML = response;
  }

}