window.slideshow = {
	
	/**
	 * Number of slideshow items
	 */
	ITEMCOUNT : 19,
	
	/**
	 * Delay between images in milliseconds
	 */
	DELAY : 3000,
	
	/**
	 * Image width in pixels
	 */
	IMAGE_WIDTH : 480,
	
	/**
	 * Current slide index
	 */
	currentIndex : 0,
	
	/**
	 * Timer
	 */
	timer : null,
	
	/**
	 * Init
	 */
	init : function() {
		var i, ilen, images = [], img, slides = document.getElementById('slides');
		
		// Randomize images:
		for (i = 0, ilen = this.ITEMCOUNT; i < ilen; ++i) {
			images[images.length] = i + 1;
		}
		images = this.shuffle(images);
		
		// Add images to DOM:
		for (i = 0, ilen = this.ITEMCOUNT; i < ilen; ++i) {
			img = document.createElement('img');
			img.src = 'images/slide' + images[i] + '.jpg';
			slides.appendChild(img);
		}
		
		// Add end slide:
		img = document.createElement('img');
		img.src = 'images/slide_end.jpg';
		slides.appendChild(img);
		
		// Start the timer:
		this.resetTimer();
		
		return this;
	},
	
	/**
	 * Previous slide
	 */
	prev : function() {
		this.resetTimer();
		if (this.currentIndex > 0) {
			--this.currentIndex;
		}else{
			this.currentIndex = this.ITEMCOUNT;
		}
		this.showSlide(this.currentIndex);
		return this;
	},
	
	/**
	 * Next slide
	 */
	next : function() {
		this.resetTimer();
		if (this.currentIndex < this.ITEMCOUNT) {
			++this.currentIndex;
		}else{
			this.currentIndex = 0;
		}
		this.showSlide(this.currentIndex);
		return this;
	},
	
	/**
	 * Show specific slide
	 */
	showSlide : function(index) {
		var slides = document.getElementById('slides'),
			position = (0 - index * this.IMAGE_WIDTH) + 'px';
		slides.setAttribute('style', '-webkit-transform: translateY(' + position + '); -moz-transform: translateY(' + position + '); -ms-transform: translateY(' + position + '); -o-transform: translateY(' + position + '); transform: translateY(' + position + ');');
		return this;
	},
	
	/**
	 * Reset timer
	 */
	resetTimer : function() {
		if (this.timer !== null) {
			window.clearInterval(this.timer);
		}
		this.timer = window.setInterval(function() {
			window.slideshow.next();
		}, this.DELAY);
		return this;
	},
	
	/**
	 * Shuffle array
	 */
	shuffle : function(array) {
		var currentIndex = array.length, temporaryValue, randomIndex;
	
		// While there remain elements to shuffle...
		while (0 !== currentIndex) {
	
			// Pick a remaining element...
			randomIndex = Math.floor(Math.random() * currentIndex);
			currentIndex -= 1;
	
			// And swap it with the current element.
			temporaryValue = array[currentIndex];
			array[currentIndex] = array[randomIndex];
			array[randomIndex] = temporaryValue;
		}
	
		return array;
	}

};
window.onload = window.slideshow.init();