/*
* Swipe 2.0
*
* Brad Birdsall
* Copyright 2013, MIT License
*
*/

function Swipe(container, options) {

"use strict";

// utilities
var noop = function() {}; // simple no operation function
var offloadFn = function(fn) { setTimeout(fn || noop, 0) }; // offload a functions execution

// check browser capabilities
var browser = {
addEventListener: !!window.addEventListener,
touch: ('ontouchstart' in window) || window.DocumentTouch && document instanceof DocumentTouch,
transitions: (function(temp) {
var props = ['transitionProperty', 'WebkitTransition', 'MozTransition', 'OTransition', 'msTransition'];
for ( var i in props ) if (temp.style[ props[i] ] !== undefined) return true;
return false;
})(document.createElement('swipe'))
};

// quit if no root element
if (!container) return;
var element = container.children[0];
var slides, slidePos, width, length;
options = options || {};
var index = parseInt(options.startSlide, 10) || 0;
var speed = options.speed || 300;
options.continuous = options.continuous !== undefined ? options.continuous : true;

function setup() {

// cache slides
slides = element.children;
length = slides.length;

// set continuous to false if only one slide
if (slides.length < 2) options.continuous = false;

//special case if two slides
if (browser.transitions && options.continuous && slides.length < 3) {
element.appendChild(slides[0].cloneNode(true));
element.appendChild(element.children[1].cloneNode(true));
slides = element.children;
}

// create an array to store current positions of each slide
slidePos = new Array(slides.length);

// determine width of each slide
width = container.getBoundingClientRect().width || container.offsetWidth;

element.style.width = (slides.length * width) + 'px';

// stack elements
var pos = slides.length;
while(pos--) {

var slide = slides[pos];

slide.style.width = width + 'px';
slide.setAttribute('data-index', pos);

if (browser.transitions) {
slide.style.left = (pos * -width) + 'px';
move(pos, index > pos ? -width : (index < pos ? width : 0), 0);
}

}

// reposition elements before and after index
if (options.continuous && browser.transitions) {
move(circle(index-1), -width, 0);
move(circle(index+1), width, 0);
}

if (!browser.transitions) element.style.left = (index * -width) + 'px';

container.style.visibility = 'visible';

}

function prev() {

if (options.continuous) slide(index-1);
else if (index) slide(index-1);

}

function next() {

if (options.continuous) slide(index+1);
else if (index < slides.length - 1) slide(index+1);

}

function circle(index) {

// a simple positive modulo using slides.length
return (slides.length + (index % slides.length)) % slides.length;

}

function slide(to, slideSpeed) {

// do nothing if already on requested slide
if (index == to) return;

if (browser.transitions) {

var direction = Math.abs(index-to) / (index-to); // 1: backward, -1: forward

// get the actual position of the slide
if (options.continuous) {
var natural_direction = direction;
direction = -slidePos[circle(to)] / width;

// if going forward but to < index, use to = slides.length + to
// if going backward but to > index, use to = -slides.length + to
if (direction !== natural_direction) to = -direction * slides.length + to;

}

var diff = Math.abs(index-to) - 1;

// move all the slides between index and to in the right direction
while (diff--) move( circle((to > index ? to : index) - diff - 1), width * direction, 0);

to = circle(to);

move(index, width * direction, slideSpeed || speed);
move(to, 0, slideSpeed || speed);

if (options.continuous) move(circle(to - direction), -(width * direction), 0); // we need to get the next in place

} else {

to = circle(to);
animate(index * -width, to * -width, slideSpeed || speed);
//no fallback for a circular continuous if the browser does not accept transitions
}

index = to;
offloadFn(options.callback && options.callback(index, slides[index]));
}

function move(index, dist, speed) {

translate(index, dist, speed);
slidePos[index] = dist;

}

function translate(index, dist, speed) {

var slide = slides[index];
var style = slide && slide.style;

if (!style) return;

style.webkitTransitionDuration =
style.MozTransitionDuration =
style.msTransitionDuration =
style.OTransitionDuration =
style.transitionDuration = speed + 'ms';

style.webkitTransform = 'translate(' + dist + 'px,0)' + 'translateZ(0)';
style.msTransform =
style.MozTransform =
style.OTransform = 'translateX(' + dist + 'px)';

}

function animate(from, to, speed) {

// if not an animation, just reposition
if (!speed) {

element.style.left = to + 'px';
return;

}

var start = +new Date;

var timer = setInterval(function() {

var timeElap = +new Date - start;

if (timeElap > speed) {

element.style.left = to + 'px';

if (delay) begin();

options.transitionEnd && options.transitionEnd.call(event, index, slides[index]);

clearInterval(timer);
return;

}

element.style.left = (( (to - from) * (Math.floor((timeElap / speed) * 100) / 100) ) + from) + 'px';

}, 4);

}

// setup auto slideshow
var delay = options.auto || 0;
var interval;

function begin() {

interval = setTimeout(next, delay);

}

function stop() {

/* delay = 0;*/
delay = options.auto > 0 ? options.auto : 0;
clearTimeout(interval);