var url = document.location,
	linkScreen = document.querySelector('link[title=screen]'),
	linkProjection = document.querySelector('link[title=projection]'),
	shower = document.querySelector('div.shower'),
	slides = document.querySelectorAll('section.slide'),
	slideList = [], hashList = {},
	fullscreen = false;

for(var i = 0, slidesLength = slides.length; i < slidesLength; i++) {
	var id = slides[i].id;
	slideList[i] = '#' + id;
	hashList['#' + id] = i;
}

function toggleFull(force) {
	fullscreen = (typeof force == 'boolean') ? force : (
		window.fullScreen || // Firefox
		document.webkitFullScreen || // Webkit
		screen.width == window.outerWidth && screen.height == window.outerHeight
	);
	updateView();
}

function turnSlide(e) {
	if(!fullscreen) return;
	var current = hashList[url.hash],
		target;
	if(e.type == 'keyup') { // Key-Based
		switch(e.which) {
			case 33 : // PgUp
			case 38 : // Up
			case 37 : // Left
				current--;
				break;
			case 34 : // PgDown
			case 40 : // Down
			case 39 : // Right
				current++;
				break;
			case 32 : // Space
				current += e.shiftKey ? -1 : 1;
				break;
			default:
				return;
		}
		target = slideList[current];
		e.preventDefault();
	}
	if(typeof e == 'number') { // Specific
		target = slideList[e];
	}
	if(typeof e == 'undefined') { // Next
		target = slideList[current++];
	}
	if(target) url.hash = target;
}

function updateView() {
	linkScreen.disabled = fullscreen;
	linkProjection.disabled = !fullscreen;
	if(!hashList[url.hash]) turnSlide(0);
}

slides[0].addEventListener('click', function(){
	toggleFull(true);
}, false);

document.addEventListener('keyup', turnSlide, false);
document.addEventListener('keyup', function(e) {
	if(e.which == 27) toggleFull(false);
}, false);

window.addEventListener('resize', toggleFull, false);
window.addEventListener('DOMContentLoaded', toggleFull, false);