// JavaScript Document

// Homepage message cycling function
// currentMessageNumber is currently displayed mesage
// rotateDirection is 1 for nest and -1 for previous

function messageUpdate(rotateDirection){


	var imageURL = new Array(   "images/home/imageMessage1.png" 
							  , "images/home/imageMessage2.png"
							  , "images/home/imageMessage3.png"
							  );

	var maxMessage = imageURL.length; // number of messages in rotation.
	
	// update the message pointer
	currentMessage += rotateDirection;
	if (currentMessage < 1){ currentMessage = maxMessage };  // rotate to last message
	if (currentMessage > maxMessage ){ currentMessage = 1 };  // rotate to first message
	
	// remove current image and load new image code
	new Effect.Opacity('imgmsg', { 
					  duration: 1.0, 
					  from: 1.0,
					  to: 0.0,
					  queue: 'front', 
					  afterFinish: function(){setNewMessageImageCode(imageURL[currentMessage-1]);
					  }}); 
	// Display new image
	new Effect.Opacity('imgmsg', {
					   duration: 1.0, 
					   from: 0.0,
					   to: 1.0,
					   queue: 'end' });
	// Set Prev/Next display status
	if (maxMessage == 1 ){ 
		$('imgNextButton').hide()
		$('imgPrevButton').hide()
	}
	else if (currentMessage == maxMessage ){ 
		$('imgNextButton').hide()
		$('imgPrevButton').show()
	}
	else if (currentMessage == 1 ){
		$('imgNextButton').show();
		$('imgPrevButton').hide();
	}
	else {
		$('imgNextButton').show();
		$('imgPrevButton').show();
	}

}
 
// set image to new image source
function setNewMessageImageCode(imageString){
	imageCode = '<img src="'+imageString+'" height="570" />'
	$('imgmsg').update(imageCode);
}