var box = document.querySelector('.rotationChart');
var arr = document.querySelector('.arr');
var left = document.querySelector('.left');
var right = document.querySelector('.right');
var screen = box.children[0];
var ul = screen.children[0];
var ol = screen.children[1];
var lis = ul.children;
for (var i = 0; i < lis.length; i++) {
	var li = document.createElement('li');
	li.index = i;
	li.onclick = liclick;
	if (i == 0) {
		li.className = 'current';
	}
	ol.appendChild(li);
}
var liwidth = screen.offsetWidth;
function liclick() {
	for (var i = 0; i < ol.children.length; i++) {
		ol.children[i].className = '';
	}
	this.className = 'current';
	index = this.index;
	animate(ul, -index * liwidth);
}
var index = 0;
left.onclick = function() {
	if (index === 0) {
		index = lis.length - 1;
		ul.style.left = -index * liwidth + 'px';
	}
	index--;
	ol.children[index].click();
}
right.onclick = function() {
	if (index === lis.length - 1) {
		ul.style.left = '0px';
		index = 0;
	}
	index++;
	if (index < lis.length - 1) {
		ol.children[index].click();
	} else {
		animate(ul, -index * liwidth);
		for (var i = 0; i < ol.children.length; i++) {
			var li = ol.children[i];
			li.className = '';
		}
		ol.children[0].className = 'current';
	}
}
var first = ul.children[0];
var cloneli = first.cloneNode(true);
ul.appendChild(cloneli);

//自动轮播
var move = setInterval(function() {
	right.click();
}, 3000)

function animate(element, target) {
	if (element.timerId) {
		clearInterval(element.timerId);
		element.timerId = null;
	}

	element.timerId = setInterval(function() {
		var step = 10;
		var current = element.offsetLeft;
		if (current > target) {
			step = -Math.abs(step);
		}
		if (Math.abs(current - target) <= Math.abs(step)) {
			clearInterval(element.timerId);
			element.style.left = target + 'px';
			return;
		}
		current += step;
		element.style.left = current + 'px';
	}, 10);
}