/*------------------------------------------------------------------------------

Copyright(c) 2005 Google Inc. All rights reserved.

------------------------------------------------------------------------------*/

// are we playing with an int?
function isInt (str)
{
	var i = parseInt (str);
	if (isNaN (i)) return false;
	i = i . toString ();
	if (i != str) return false;
	return true;
}

// find out the value of a given query string variable
function getQueryVariable(variable) {
	var query = window.location.search.substring(1);
	var vars = query.split("&");
	for (var i=0;i<vars.length;i++) {
		var pair = vars[i].split("=");
		if (pair[0] == variable) {
			return pair[1];
		}
	} 
}

// here is are little innerHTML function
function refreshTip(direction)
{

	// check to see if we are playing with ints
	if(isInt(direction)) {
		var myTip = direction; // we can randomize these
	} else {
		if(direction == "prev"){ // move back
			var myTip = parseInt(document.getElementById("currentTip").value)-1;
		} else if(direction == "next"){ // move forward
			var myTip = parseInt(document.getElementById("currentTip").value)+1;
		}
	}

	// this is where we loop the tips
	if(myTip == 0) {
		var myTip = 25;
	} else if(myTip > 25){ // put your max tip number here
		var myTip = 1;
	}
	
	// keep track of the new tip number here
	document.getElementById("currentTip").value = myTip;
	
	var Field = document.getElementById("tip"); // selects the given element

        if(window.XMLHttpRequest) {
                xmlhttp = new XMLHttpRequest();
        } else if(window.ActiveXObject) {
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        } else {
                return false;
        }
        xmlhttp.open("GET", "./tips/"+myTip+".html", true);
		  
        xmlhttp.onreadystatechange=function() {
                if (xmlhttp.readyState == 4) {

                        Field.innerHTML = xmlhttp.responseText; // puts the result into the element
                }
        }
        xmlhttp.send(null);
}

function getRandomTip() // this is only called onLoad
{
	// set this value to the total number of tips + 1
	var randomnumber=Math.floor(Math.random()*25)+1;
	
		// here we return a random tip 
		return refreshTip(randomnumber);
	
}

function getRandomHeader() // this is only called onLoad
{
   //-------------
   var n = 7;
   var names = new Array(n);
   names[0] = "gmail";
   names[1] = "talk";
   names[2] = "sms";
   names[3] = "blogger";
   names[4] = "desktop";
   names[5] = "scholar";
   names[6] = "picasa";
   //-------------

   //-- look for preset target
   var target = getQueryVariable("target");
   if (target) {
      for (i=0; i<n; i++) {
         if (target == names[i]) return(changeHeader(names[i]));
      }
   }
   //-- otherwise pick one randomly
   var x = Math.floor(Math.random()*7);
   return(changeHeader(names[x]));

}
function changeHeader(whichHeader) {

   //-------------
   var n = 7;
   var names = new Array(n);
   names[0] = "gmail";
   names[1] = "talk";
   names[2] = "sms";
   names[3] = "blogger";
   names[4] = "desktop";
   names[5] = "scholar";
   names[6] = "picasa";

   var urls = new Array(n);
   urls[0]="http://services.google.com/university/cgi-bin/gmail"; 
   urls[1]="http://www.google.com/talk/"; 
   urls[2]="http://www.google.com/sms/"; 
   urls[3]="http://www.blogger.com"; 
   urls[4]="http://desktop.google.com/"; 
   urls[5]="http://scholar.google.com/"; 
   urls[6]="http://picasa.google.com"; 

   var header = document.getElementById("banner"); 
   var bannerLink = document.getElementById("bannerLink");
   //-------------

   //-- double check whichHeader;
   var foundit=0;
   for (i=0; i<n; i++) {if (names[i] == whichHeader) {foundit=1; break;}}
   if (!foundit) whichHeader = names[0];

   //-- turn off all except one
   var elements = new Array(n);
   for (i=0; i<n; i++) {
      elements[i] = document.getElementById(names[i]+"Icon");
      if (names[i] == whichHeader) {
         elements[i].src = "./images/icon_"+names[i]+"_on.gif";
         header.src = "./images/header_"+names[i]+".jpg";
         bannerLink.href = urls[i];
      }
      else {elements[i].src = "./images/icon_"+names[i]+"_off.gif";}
   }
}