/**
 * Since carousel.addItem uses an HTML string to create the interface
 * for each carousel item, this method formats the HTML for an LI.
 **/
function changeImage(imgid) {
	var lrgImage = document.getElementById("lrg-image");
	lrgImage.src = imgid;
	}

var fmtItem = function(imgUrl, url, title) {

      var innerHTML = 
          '<a href="javascript:changeImage(\'' + url + '\');"' + 
          '"><img src="' + 
          imgUrl +
        '" width="' +
        75 +
        '" height="' +
        75+
        '"/>' + 
          title + 
          '<\/a>';
  
    return innerHTML;
    
};

/**
 * Custom inital load handler. Called when the carousel loads the initial
 * set of data items. Specified to the carousel as the configuration
 * parameter: loadInitHandler
 **/
var loadInitialItems = function(type, args) {
    var start = args[0];
    var last = args[1]; 
    load(this, start, last);  
};

/**
 * Custom load next handler. Called when the carousel loads the next
 * set of data items. Specified to the carousel as the configuration
 * parameter: loadNextHandler
 **/
var loadNextItems = function(type, args) {    

    var start = args[0];
    var last = args[1]; 
    var alreadyCached = args[2];
    
    if(!alreadyCached) {
        load(this, start, last);
    }
};

/**
 * Custom load previous handler. Called when the carousel loads the previous
 * set of data items. Specified to the carousel as the configuration
 * parameter: loadPrevHandler
 **/
var loadPrevItems = function(type, args) {
    var start = args[0];
    var last = args[1]; 
    var alreadyCached = args[2];
    
    if(!alreadyCached) {
        load(this, start, last);
    }
};

var load = function(carousel, start, last) {
   for(var i=1;i<=last;i++) {
        var randomIndex = getRandom(17, lastRan);
        lastRan = randomIndex;
		carousel.addItem(i, fmtItem(imageList[i], urlList[i], ""));
/*
        // Example of an alternate way to add an item (passing an element instead of html string)
        var p = document.createElement("P");
        var t = document.createTextNode("Item"+i);
        p.appendChild(t);
        carousel.addItem(i, p );
*/
    }
};

var getRandom = function(max, last) {
    var randomIndex;
    do {
        randomIndex = Math.floor(Math.random()*max);
    } while(randomIndex == last);
    
    return randomIndex;
};

/**
 * Custom button state handler for enabling/disabling button state. 
 * Called when the carousel has determined that the previous button
 * state should be changed.
 * Specified to the carousel as the configuration
 * parameter: prevButtonStateHandler
 **/
var handlePrevButtonState = function(type, args) {

    var enabling = args[0];
    var leftImage = args[1];
    if(enabling) {
        leftImage.src = "images/icn_arrow_left.gif";    
    } else {
        leftImage.src = "images/icn_arrow_left.gif";
    }
    
};