var selected_frame = 'main_banner1';

function banner_frame(frame) {
	
	if ('main_banner'+frame == selected_frame) {
		return true;
	}
	
	$('main_banner'+frame).set('opacity',0);
	$('main_banner'+frame).inject($(selected_frame), 'after');

	selected_frame = 'main_banner'+frame;
	
	var myImages = new Asset.images(['img/books_index/book_banner_back' + frame + '.jpg'],  {
		onComplete: function(){
			$('main_banner'+frame).setStyle('background-image','url(img/books_index/book_banner_back' + frame + '.jpg)');
			var myEffect = new Fx.Tween($('main_banner'+frame), {duration: 300, transition: Fx.Transitions.Sine.easeOut});
			myEffect.start('opacity',1);
			set_banner_timer();
		}
	});
	
	return false;

}

var banner_timer;
var is_banner_over = false;

function set_banner_timer() {
	if (!is_banner_over) {
		clearTimeout(banner_timer);
		banner_timer = setTimeout( "next_banner_frame()", 4000);
	}
}

function next_banner_frame() {
	var next_frame = parseInt(selected_frame.replace("main_banner", ""));
	next_frame = next_frame + 1;
	if (next_frame == 5) { next_frame = 1; }
	banner_frame(next_frame);
}

function clear_timer() {
	clearTimeout(banner_timer);
}

function banner_over() {
	is_banner_over = true;
	clear_timer();
}

function banner_out() {
	is_banner_over = false;
	set_banner_timer();
}

set_banner_timer();