// JavaScript Document

/**
 * 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);    
    var status = + start + " / " + this.getProperty("size");
    YAHOO.util.Dom.get("indicator").innerHTML = status;
};

var animComplete = function(type, args) {
    var direction = args[0]; // string either: 'next' or 'prev'
    
    var status = + this.getFirstVisible() + " / " + this.getProperty("size");
    YAHOO.util.Dom.get("indicator").innerHTML = status ;

};

/**
 * 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=start; i<= last+1; i++) {
        carousel.addItem(i, fmtItem(imageList[i-1]));
    }
}

/**
 * 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/interface/gpx_arrowLeftOn.gif";    
    } else {
        leftImage.src = "/images/interface/gpx_arrowLeftOff.gif";    
    }
    
};

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

    var enabling = args[0];
    var rightImage = args[1];
    
    if(enabling) {
        rightImage.src = "/images/interface/gpx_arrowRightOn.gif";
    } else {
        rightImage.src = "/images/interface/gpx_arrowRightOff.gif";
    }
    
};


/**
 * You must create the carousel after the page is loaded since it is
 * dependent on an HTML element (in this case 'mycarousel'.) See the
 * HTML code below.
 **/
var carousel; // for ease of debugging; globals generally not a good idea

var pageLoad = function() 
{
    carousel = new YAHOO.extension.Carousel("mycarousel", 
        {
            numVisible:        3,
            animationSpeed:    0.15,
            scrollInc:         3,
            navMargin:         0,
            prevElement:     "prev-arrow",
            nextElement:     "next-arrow",
            size:              6,
            loadInitHandler:   loadInitialItems,
            loadNextHandler:   loadNextItems,
            loadPrevHandler:   loadPrevItems,
            animationCompleteHandler: animComplete,
            prevButtonStateHandler:   handlePrevButtonState,
            nextButtonStateHandler:   handleNextButtonState
        }
    );

};

/**
 * Since carousel.addItem uses an HTML string to create the interface
 * for each carousel item, this method formats the HTML for an LI.
 **/
var fmtItem = function(imgUrl) {
        
      var innerHTML = 
          '<a href="#"><img src="' + 
          imgUrl +
        '"/><\/a>';
  
    return innerHTML;
    
};

YAHOO.util.Event.addListener(window, 'load', pageLoad);