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

// 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;
}


// called to read a file from the server
function process(city)
{
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // try to connect to the server
    try
    {
      var itinerary = document.getElementById(city + 'Itinerary').value;
      var start = document.getElementById(city + 'start-date').value;
      var end = document.getElementById(city + 'end-date').value;
      var params = '?it=' + itinerary + '&st= ' + start + '&end=' +end+'&ct='+city;
      // initiate reading the async.txt file from the server
      xmlHttp.open("GET", "http://www.tours-venice-italy.com/venice-events/js/ajax/quick-search.php" + params, true);
      switch(city)
      {
      case 'Venice': 
      xmlHttp.onreadystatechange = handleRequestStateChangeVenice;
      break;
      
      case 'Florence': 
      xmlHttp.onreadystatechange = handleRequestStateChangeFlorence;
      break;
      
      case 'Rome': 
      xmlHttp.onreadystatechange = handleRequestStateChangeRome;
      break;
      
      default:break;
      }
      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 handleRequestStateChangeVenice() 
{
  // obtain a reference to the <div> element on the page
  myDiv = document.getElementById('buttonVenice');
  // display the status of the request 
 if (xmlHttp.readyState == 4) 
  {
    //document.getElementById('buttonVenice').disabled = false;
    // continue only if HTTP status is "OK"
    if (xmlHttp.status == 200) 
    {
      try
      {
      	 // read the message from the server
        response = xmlHttp.responseText;
        // display the message 
        myDiv.href = response;
        document.getElementById('loadingvenice').style.display='none';
      }
      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);
        setTimeout("process()",1000);
    }
  }
  else
  {
  	 // document.getElementById('loadingvenice').style.display='inline';
  	  document.getElementById('buttonVenice').href ='javascript:void(0);';
  }
}

// function that handles the HTTP response
function handleRequestStateChangeFlorence() 
{
  // obtain a reference to the <div> element on the page
  myDiv = document.getElementById('buttonFlorence');
  // display the status of the request 
 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;
        // display the message 
        myDiv.href = response;
        document.getElementById('loadingflorence').style.display='none'; 
      }
      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);
        setTimeout("process()",1000);
    }
  }
   else
  {
  	//  document.getElementById('loadingflorence').style.display='inline';
  	  document.getElementById('buttonFlorence').href ='javascript:void(0);';
  }
}

// function that handles the HTTP response
function handleRequestStateChangeRome() 
{
  // obtain a reference to the <div> element on the page
  myDiv = document.getElementById('buttonRome');
  // display the status of the request 
 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;
        // display the message 
        myDiv.href = response;
        document.getElementById('loadingrome').style.display='none'; 
      }
      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);
       setTimeout("process()",1000);
    }
  }
   else
  {
  	  //document.getElementById('loadingrome').style.display='inline';
  	  document.getElementById('buttonRome').href ='javascript:void(0);';
  }
}