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

// Display error messages (true) or degrade to non-AJAX behavior (false)
var showErrors = true;

// Contains the link or form clicked or submitted by the visitor
var actionObject = '';

// initialize the validation requests cache
var cache = new Array();

// Creates an XMLHttpRequest instance
function createXmlHttpRequestObject()
{
  // Will store the XMLHttpRequest object
  var xmlHttp;

  // Create the XMLHttpRequest object
  try
  {
    // Try to create native 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 id until one works
    for (i = 0; i < XmlHttpVersions.length && !xmlHttp; i++)
    {
      try
      {
        // Try to create XMLHttpRequest object
        xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
      }
      catch (e) {} // Ignore potential error
    }
  }

  // If the XMLHttpRequest object was created successfully, return it
  if (xmlHttp)
  {
    return xmlHttp;
  }
  // If an error happened, pass it to handleError
  else
  {
    handleError("Error creating the XMLHttpRequest object.");
  }
}

// Displays an the error message or degrades to non-AJAX behavior
function handleError($message)
{
  // Ignore errors if showErrors is false
  if (showErrors)
  {
    // Display error message
    alert("Error encountered: \n" + $message);
    return false;
  }
  // Fall back to non-AJAX behavior
  else if (!actionObject.tagName)
  {
    return true;
  }
  // Fall back to non-AJAX behavior by following the link
  else if (actionObject.tagName == 'A')
  {
    window.location = actionObject.href;
  }
  // Fall back to non-AJAX behavior by submitting the form
  else if (actionObject.tagName == 'FORM')
  {
    actionObject.submit();
  }
}

// Adds a product to the shopping cart
function addProductToCart(form)
{
  // Display "Updating" message
  document.getElementById('updating').style.visibility = 'visible';

  // Degrade to classical form submit if XMLHttpRequest is not available
  if (!xmlHttp) return true;

  // Create the URL we open asynchronously
  request = form.action + '&AjaxRequest';
  params  = '';

  // obtain selected attributes
  formSelects = form.getElementsByTagName('SELECT');
  if (formSelects)
  {
    for (i = 0; i < formSelects.length; i++)
    {
      params += '&' + formSelects[i].name + '=';
      selected_index = formSelects[i].selectedIndex;
      params += encodeURIComponent(formSelects[i][selected_index].text);
    }
  }

  // Try to connect to the server
  try
  {
    // Continue only if the XMLHttpRequest object isn't busy
    if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
    {
      // Make a server request to validate the extracted data
      xmlHttp.open("POST", request, true);
      xmlHttp.setRequestHeader("Content-Type",
                               "application/x-www-form-urlencoded");
      xmlHttp.onreadystatechange = addToCartStateChange;
      xmlHttp.send(params);
    }
  }
  catch (e)
  {
    // Handle error
    handleError(e.toString());
  }

  // Stop classical form submit if AJAX action succeeded
  return false;
}

// Function that retrieves the HTTP response
function addToCartStateChange()
{
  // 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
      {
        updateCartSummary();
      }
      catch (e)
      {
        handleError(e.toString());
      }
    }
    else
    {
      handleError(xmlHttp.statusText);
    }
  }
}

// Process server's response
function updateCartSummary()
{
  // Read the response
  response = xmlHttp.responseText;

  // Server error?
  if (response.indexOf("ERRNO") >= 0 || response.indexOf("error") >= 0)
  {
    handleError(response);
  }
  else
  {
    // Extract the contents of the cart_summary div element
    var cartSummaryRegEx = /^<div id="cart_summary">([\s\S]*)<\/div>$/m;
    matches = cartSummaryRegEx.exec(response);
    response = matches[1];

    // Update the cart summary box and hide the Loading message
    document.getElementById("cart_summary").innerHTML = response;
    // Hide the "Updating..." message
    document.getElementById('updating').style.visibility = 'hidden';
  }
}

// Called on shopping cart update actions
function executeCartAction(obj)
{
  // Display "Updating..." message
  document.getElementById('updating').style.visibility = 'visible';

  // Degrade to classical form submit if XMLHttpRequest is not available
  if (!xmlHttp) return true;

  // Save object reference
  actionObject = obj;

  // Initialize response and parameters
  response = '';
  params = '';

  // If a link was clicked we get its href attribute
  if (obj.tagName == 'A')
  {
    url = obj.href + '&AjaxRequest';
  }
  // If the form was submitted we get its elements
  else
  {
    url = obj.action + '&AjaxRequest';
    formElements = obj.getElementsByTagName('INPUT');

    if (formElements)
    {
      for (i = 0; i < formElements.length; i++)
      {
        params += '&' + formElements[i].name + '=';
        params += encodeURIComponent(formElements[i].value);
      }
    }
  }

  // Try to connect to the server
  try
  {
    // Make server request only if the XMLHttpRequest object isn't busy
    if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
    {
      xmlHttp.open("POST", url, true);
      xmlHttp.setRequestHeader("Content-Type",
                               "application/x-www-form-urlencoded");
      xmlHttp.onreadystatechange = cartActionStateChange;
      xmlHttp.send(params);
    }
  }
  catch (e)
  {
    // Handle error
    handleError(e.toString());
  }

  // Stop classical form submit if AJAX action succeeded
  return false;
}

// the function handles the validation for any form field
function validate(inputValue, fieldID, reqTarget, isRequired, urlParam)
{
  // only continue if xmlHttp isn't void
  if (xmlHttp)
  {
    // if we received non-null parameters, we add them to cache in the
    // form of the query string to be sent to the server for validation
    if (fieldID)
    {
    	urlParam = encodeURIComponent(urlParam);
   		reqTarget = encodeURI(reqTarget);
    	// encode values for safely adding them to an HTTP request query string
    	if (urlParam == "ajax-request")
    	{
    		actionObject = reqTarget + "ajax-request/";

    	}
    	else
    	{
    		actionObject = reqTarget + "&AjaxRequest";
    	}
    	inputValue = encodeURIComponent(inputValue);
    	fieldID = encodeURIComponent(fieldID);
  		isRequired = encodeURIComponent(isRequired);
      // add the values to the queue
      cache.push("inputValue=" + inputValue + "&fieldID=" + fieldID + "&isRequired=" + isRequired);
    }
    // try to connect to the server
    try
    {
      // continue only if the XMLHttpRequest object isn't busy
      // and the cache is not empty
      if ((xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
         && cache.length > 0)
      {
        // get a new set of parameters from the cache
        var cacheEntry = cache.shift();
        // make a server request to validate the extracted data
        xmlHttp.open("POST", actionObject, true);
        xmlHttp.setRequestHeader("Content-Type",
                                 "application/x-www-form-urlencoded");
        xmlHttp.onreadystatechange = handleRequestStateChange;
        xmlHttp.send(cacheEntry);
      }
    }
    catch (e)
    {
      // display an error when failing to connect to the server
      handleError(e.toString());
    }
  }
}

// function that handles the HTTP response
function handleRequestStateChange()
{
  // when readyState is 4, we read the server response
  if (xmlHttp.readyState == 4)
  {
    // continue only if HTTP status is "OK"
    if (xmlHttp.status == 200)
    {
      try
      {
        // read the response from the server
        readResponse();
      }
      catch(e)

      {
        // display error message
        handleError(e.toString());
      }
    }
    else
    {
      // display error message
      handleError(xmlHttp.statusText);
    }
  }
}

// read server's response
function readResponse()
{
  // retrieve the server's response
  var response = xmlHttp.responseText;
  // server error?
  if (response.indexOf("ERRNO") >= 0
      || response.indexOf("error:") >= 0
      || response.length == 0)
    throw(response.length == 0 ? "Server error." : response);
  // get response in XML format (assume the response is valid XML)
  responseXml = xmlHttp.responseXML;
  // get the document element
  xmlDoc = responseXml.documentElement;
  result = xmlDoc.getElementsByTagName("result")[0].firstChild.data;
  fieldID = xmlDoc.getElementsByTagName("fieldid")[0].firstChild.data;
  // find the HTML element that displays the error
  message = document.getElementById(fieldID + "Failed");
  // show the error or hide the error - 0 = false, 1 = true
  message.className = (result == "1") ? "error" : "hidden";
  // call validate() again, in case there are values left in the cache
  setTimeout("validate();", 500);
}

// Function that retrieves the HTTP response
function cartActionStateChange()
{
  // 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
      {
        // Read the response
        response = xmlHttp.responseText;

        // Server error?
        if (response.indexOf("ERRNO") >= 0 || response.indexOf("error") >= 0)
        {
          handleError(response);
        }
        else
        {
          // Update the cart
          document.getElementById("wrap_main_content").innerHTML = response;
          // Hide the "Updating..." message
          document.getElementById('updating').style.visibility = 'hidden';
        }
      }
      catch (e)
      {
        // Handle error
        handleError(e.toString());
      }
    }
    else
    {
      // Handle error
      handleError(xmlHttp.statusText);
    }
  }
}