$(function() {
				function Pointer(x, y) {
					this.x = x;
					this.y = y;
				}

				function Position(left, top) {
					this.left = left;
					this.top = top;
				}
				$(".item_content .item").each(function(i) {
					this.init = function() { // 初始化
							this.box = $(this).parent();
							$(this).attr("index", i).css({
								position: "absolute",
								left: this.box.offset().left,
								top: this.box.offset().top
							}).appendTo(".item_content");
							this.drag();
						},
						this.move = function(callback) { // 移动
							$(this).stop(true).animate({
								left: this.box.offset().left,
								top: this.box.offset().top
							}, 200, function() {
								if(callback) {
									callback.call(this);
								}
							});
						},
						this.collisionCheck = function() {
							var currentItem = this;
							var direction = null;
							$(this).siblings(".item").each(function() {
								if(
									currentItem.pointer.x > this.box.offset().left &&
									currentItem.pointer.y > this.box.offset().top &&
									(currentItem.pointer.x < this.box.offset().left + this.box.width()) &&
									(currentItem.pointer.y < this.box.offset().top + this.box.height())
								) {
									// 返回对象和方向
									if(currentItem.box.offset().top < this.box.offset().top) {
										direction = "down";
									} else if(currentItem.box.offset().top > this.box.offset().top) {
										direction = "up";
									} else {
										direction = "normal";
									}
									this.swap(currentItem, direction);
								}
							});
						},
						this.swap = function(currentItem, direction) { // 交换位置
							if(this.moveing) return false;
							var directions = {
								normal: function() {
									var saveBox = this.box;
									this.box = currentItem.box;
									currentItem.box = saveBox;
									this.move();
									$(this).attr("index", this.box.index());
									$(currentItem).attr("index", currentItem.box.index());
								},
								down: function() {
									// 移到上方
									var box = this.box;
									var node = this;
									var startIndex = currentItem.box.index();
									var endIndex = node.box.index();;
									for(var i = endIndex; i > startIndex; i--) {
										var prevNode = $(".item_content .item[index=" + (i - 1) + "]")[0];
										node.box = prevNode.box;
										$(node).attr("index", node.box.index());
										node.move();
										node = prevNode;
									}
									currentItem.box = box;
									$(currentItem).attr("index", box.index());
								},
								up: function() {
									// 移到上方
									var box = this.box;
									var node = this;
									var startIndex = node.box.index();
									var endIndex = currentItem.box.index();;
									for(var i = startIndex; i < endIndex; i++) {
										var nextNode = $(".item_content .item[index=" + (i + 1) + "]")[0];
										node.box = nextNode.box;
										$(node).attr("index", node.box.index());
										node.move();
										node = nextNode;
									}
									currentItem.box = box;
									$(currentItem).attr("index", box.index());
								}
							}
							directions[direction].call(this);
						},
						this.drag = function() { // 拖拽
							var oldPosition = new Position();
							var oldPointer = new Pointer();
							var isDrag = false;
							var currentItem = null;
							$(this).mousedown(function(e) {
								e.preventDefault();
								oldPosition.left = $(this).position().left;
								oldPosition.top = $(this).position().top;
								oldPointer.x = e.clientX;
								oldPointer.y = e.clientY;
								isDrag = true;

								currentItem = this;

							});
							$(document).mousemove(function(e) {
								var currentPointer = new Pointer(e.clientX, e.clientY);
								if(!isDrag) return false;
								$(currentItem).css({
									"opacity": "0.8",
									"z-index": 999
								});
								var left = currentPointer.x - oldPointer.x + oldPosition.left;
								var top = currentPointer.y - oldPointer.y + oldPosition.top;
								$(currentItem).css({
									left: left,
									top: top
								});
								currentItem.pointer = currentPointer;
								// 开始交换位置

								currentItem.collisionCheck();

							});
							$(document).mouseup(function() {
								if(!isDrag) return false;
								isDrag = false;
								currentItem.move(function() {
									$(this).css({
										"opacity": "1",
										"z-index": 0
									});
								});
							});
						}
					this.init();
				});
			});