/**
 * Ajax.js
 *
 * Collection of Scripts to allow in page communication from browser to (struts) server
 * ie can reload part instead of full page
 *
 * How to use
 * ==========
 * 1) Call retrieveURL from the relevant event on the HTML page (e.g. onclick)
 * 2) Pass the url to contact (e.g. Struts Action) and the name of the HTML form to post
 * 3) When the server responds ...
 *     - the script loops through the response , looking for <span id="name">newContent</span>
 *      - each <span> tag in the *existing* document will be replaced with newContent
 *
 * NOTE: <span id="name"> is case sensitive. Name *must* follow the first quote mark and end in a quote
 *     Everything after the first '>' mark until </span> is considered content.
 *     Empty Sections should be in the format <span id="name"></span>
 */

//global variables
  var req;
  var which;
  var index;
  var obj;


  /**
   * Get the contents of the URL via an Ajax call
   * url - to get content from (e.g. /struts-ajax/sampleajax.do?ask=COMMAND_NAME_1) 
   * nodeToOverWrite - when callback is made
   * nameOfFormToPost - which form values will be posted up to the server as part 
   *          of the request (can be null)
   */
  function processURL( type, url, nameOfFormToPost) 
  {

    if ( nameOfFormToPost)
    {
      url = url + getFormAsString( nameOfFormToPost);
    }

    if ( type == 'value')
    {
      retrieveURL( url, processStateChangeValue);
    }
    else if ( type == 'html')
    {
      retrieveURL( url, processStateChange);
    }
    else
    {
      retrieveURL( url, processStateChangeMixed);
    }
  }

  function retrieveURL( url, callback) 
  {
    
    //Do the Ajax call
    if (window.XMLHttpRequest) { // Non-IE browsers
      req = new XMLHttpRequest();
      req.onreadystatechange = callback;
      try {
        req.open("GET", url, true); //was get
      } catch (e) {
        alert("Problem Communicating with Server\n"+e);
      }
      req.send(null);
    } else if (window.ActiveXObject) { // IE
      
      req = new ActiveXObject("Microsoft.XMLHTTP");
      if (req) {
        req.onreadystatechange = callback;
        req.open("GET", url, true);
        req.send();
      }
    }
  }

/**
 * Set as the callback method for when XmlHttpRequest State Changes 
 * used by retrieveUrl
 */
  function processStateChange() 
  {
  
    if (req.readyState == 4) 
    { // Complete
      if (req.status == 200) 
      { // OK response
        //alert("Ajax response:"+req.responseText);
        //Split the text response into Span elements
        spanElements = splitTextIntoSpan(req.responseText);
        
        //Use these span elements to update the page
        replaceHtml(spanElements);
        
      } else 
      {
        alert("Problem with server response:\n " + req.statusText);
      }
    }
  }
 
  function processStateChangeValue() 
  {
    if (req.readyState == 4) 
    { // Complete
      if (req.status == 200) 
      { // OK response
        //alert("Ajax response:"+req.responseText);
        replaceValues( req.responseText)
      }
      else
      {
        alert("Problem with server response:\n " + req.statusText);
      }
    }
  }

  function processStateChangeMixed() 
  {
  
    if (req.readyState == 4) 
    { // Complete
      if (req.status == 200) 
      { // OK response
        //alert("Ajax response:"+req.responseText);
        //Split the text response into Span elements
        spanElements = splitTextIntoSpan(req.responseText);
        
        //Use these span elements to update the page
        special = replaceHtml(spanElements);
        if ( special != null)
        {
          replaceValues( special)
        }
      } else 
      {
        alert("Problem with server response:\n " + req.statusText);
      }
    }
  }
 /**
  * gets the contents of the form as a URL encoded String
  * suitable for appending to a url
  * @param formName to encode
  * @return string with encoded form values , beings with &
  */ 
 function getFormAsString(formName){
   
   //Setup the return String
   returnString ="";
   
    //Get the form values
   formElements=document.forms[formName].elements;
   
   //loop through the array , building up the url
   //in the form /strutsaction.do&name=value
   
   for ( var i=formElements.length-1; i>=0; --i ){
     //we escape (encode) each value
    //alert( 'Name=' + formElements[i].name + ' Type=' + formElements[i].type);
    if ( formElements[i].type == 'radio' ||
         formElements[i].type == 'checkbox')
    {
      if ( formElements[i].checked)
      {
        returnString=returnString+"&"+escape(formElements[i].name)+"="+escape(formElements[i].value);
      }
    }
    else
    {
      returnString=returnString+"&"+escape(formElements[i].name)+"="+escape(formElements[i].value);
    }
   }
   
   //return the values
   return returnString; 
 }
 
  function replaceValues( text) 
  {
    lines = text.split('\n');
    for (var i=0; i < lines.length; ++i)
    {
      if ( lines[i].length > 1)
      {
        replaceValue( lines[i]);
      }
    }
  }

  function replaceValue( text) 
  {
    index = text.indexOf("=");
    if ( index > -1) 
    {
      name = text.substring( 0, index);
      //alert("Ajax element name: "+name);
      if( document.getElementById( name))
      {
        //alert("Replacing Element:"+name);
        document.getElementById( name).innerHTML = text.substring( index+1);
      }
      else if ( parent.document.getElementById( name))
      {
        //alert("Replacing Parent Element:"+name);
        parent.document.getElementById( name).innerHTML = text.substring( index+1);
      }
      else
      {
        //alert("Element: "+name+" not found in existing/parent document");
      }
    }
  }

 /**
 * Splits the text into <span> elements
 * @param the text to be parsed
 * @return array of <span> elements - this array can contain nulls
 */
 function splitTextIntoSpan(textToSplit)
 {
 
    //Split the document
   returnElements=textToSplit.split("</span>")
   
   //Process each of the elements   
   for ( var i=0; i < returnElements.length; ++i )
   {
     
     //Remove everything before the 1st span
     spanPos = returnElements[i].indexOf("<span");    
     
     //if we find a match , take out everything before the span
     if( spanPos > 0)
     {
       subString=returnElements[i].substring(spanPos);
       returnElements[i]=subString;
     } 
   }
   
   return returnElements;
 }
 
 /*
  * Replace html elements in the existing (ie viewable document)
  * with new elements (from the ajax requested document)
  * WHERE they have the same name AND are <span> elements
  * @param newTextElements (output of splitTextIntoSpan)
  *          in the format <span id=name>texttoupdate
  */
 function replaceHtml(newTextElements)
 {
 
   specialCase = null;
   //loop through newTextElements
   for ( var i=0; i < newTextElements.length; ++i )
   {
  
     //check that this begins with <span
     if(newTextElements[i].indexOf("<span") > -1)
     {
       
       //get the name - between the 1st and 2nd quote mark
       startNamePos=newTextElements[i].indexOf('"')+1;
       endNamePos=newTextElements[i].indexOf('"',startNamePos);
       name=newTextElements[i].substring(startNamePos,endNamePos);
       //get the content - everything after the first > mark
       startContentPos=newTextElements[i].indexOf('>')+1;
       content=newTextElements[i].substring(startContentPos);

       //alert('Name: ' + name + ' Content: ' + content);
       //Now update the existing Document with this element
       if ( name == 'specialCase')
       {
         specialCase = content;
       }
       else if ( name == 'alert')
       {
         alert( content);
       }
       else
       {
         //check that this element exists in the document
         if(document.getElementById(name))
         {
  
           //alert("Replacing Element:"+name);
           document.getElementById(name).innerHTML = content;
         }
         else if( parent.document.getElementById(name))
         {
  
           //alert("Replacing Parent Element:"+name);
           parent.document.getElementById(name).innerHTML = content;
         }
         else
         {
         //alert("Element:"+name+"not found in existing document");
         }
       }
     }
   }

   return specialCase;
 }