define(function(require, exports, module) {
"use strict";
var Util = require('../util'),
	Base = require('../base');
/**
 * A image lazyload plugin for xscroll.
 * @constructor
 * @param {object} cfg
 * @extends {Base}
 */
var LazyLoad = function(cfg) {
	LazyLoad.superclass.constructor.call(this, cfg);
	this.userConfig = Util.mix({
		imgsSelector: "img",
		delay: 200,
		imgSetter: function(img) {
			var src = img.getAttribute("data-src");
			src && img.setAttribute("src", src);
		}
	}, cfg);
}

Util.extend(LazyLoad, Base, {
	/**
	 * a pluginId
	 * @memberOf LazyLoad
	 * @type {string}
	 */
	pluginId: "lazyload",
	/**
	 * plugin initializer
	 * @memberOf LazyLoad
	 * @override Base
	 * @return {LazyLoad}
	 */
	pluginInitializer: function(xscroll) {
		var self = this;
		self.xscroll = xscroll;
		self.reset();
		self._bindEvt();
		return self;
	},
	pluginDestructor: function() {
		var self = this;
		if (self.xscroll) {
			self.xscroll.off("scroll scrollend afterrender", self._filterItem, self);
		}
		self._isEvtBinded = false;
	},
	_filterItem: function() {
		var self = this;
		if (self.xscroll.getPlugin("infinite")) {
			self._filterItemByInfinite.call(self);
		} else {
			self._filterItemByNormal.call(self);
		}
	},
	_filterItemByNormal: function() {
		var self = this,
			pos;
		var e = self.xscroll.getScrollPos();
		var __scrollTop = self.zoomType == "x" ? e.scrollLeft : e.scrollTop;
		var __offsetHeight = self.zoomType == "x" ? "offsetWidth" : "offsetHeight";
		var __top = self.zoomType == "x" ? "left" : "top";
		var __bottom = self.zoomType == "x" ? "right" : "bottom";
		for (var i = 0, l = self.positions.length; i < l; i++) {
			pos = self.positions[i];
			if ((pos[__top] >= __scrollTop && pos[__top] <= __scrollTop + self.xscroll.renderTo[__offsetHeight]) || (pos[__bottom] >= __scrollTop && pos[__bottom] <= __scrollTop + self.xscroll.renderTo[__offsetHeight])) {
				self.userConfig.imgSetter.call(self, self.imgs[i]);
			}
		}
	},
	_filterItemByInfinite: function() {
		var self = this,
			infinite = self.xscroll.getPlugin("infinite");
		clearTimeout(self._timeout);
		self._timeout = setTimeout(function() {
			if (self.xscroll['isScrolling' + self.zoomType.toUpperCase()]) return;
			for (var i = 0; i < infinite.infiniteLength; i++) {
				if (infinite.infiniteElementsCache[i]._visible && infinite.infiniteElements[i]) {
					var imgs = infinite.infiniteElements[i].querySelectorAll(self.userConfig.imgsSelector);
					for (var j = 0, l = imgs.length; j < l; j++) {
						self.userConfig.imgSetter.call(self, imgs[j]);
					}
				}
			}
			self._filterItemByNormal();
		}, self.userConfig.delay);
	},
	/**
	 * reset the images
	 * @memberOf LazyLoad
	 * @override Base
	 * @return {LazyLoad}
	 */
	reset: function() {
		var self = this,
			img, rect;
		self.zoomType = self.xscroll.userConfig.zoomType;
		self.imgs = self.xscroll.renderTo.querySelectorAll(self.userConfig.imgsSelector);
		var e = self.xscroll.getScrollPos();
		var __top = self.zoomType == "x" ? "left" : "top";
		var __bottom = self.zoomType == "x" ? "right" : "bottom";
		var __getOffsetTop = self.zoomType == "x" ? Util.getOffsetLeft : Util.getOffsetTop;
		var __offsetHeight = self.zoomType == "x" ? "offsetWidth" : "offsetHeight";
		var __height = self.zoomType == "x" ? "width" : "height";
		self.positions = [];
		for (var i = 0, l = self.imgs.length; i < l; i++) {
			img = self.imgs[i];
			rect = {};
			rect[__top] = __getOffsetTop(img);
			rect[__height] = img[__offsetHeight];
			rect[__bottom] = rect[__top] + rect[__height];
			self.positions.push(rect);
		}
		return self;
	},
	_bindEvt: function() {
		var self = this;
		if (self._isEvtBinded) return;
		self._isEvtBinded = true;
		var eventType = self.xscroll.userConfig.useOriginScroll ? "scroll" : "scrollend";
		self.xscroll.on("afterrender", self._filterItem, self);
		self.xscroll.on(eventType, self._filterItem, self);
	}
});

if (typeof module == 'object' && module.exports) {
	module.exports = LazyLoad;
}
/** ignored by jsdoc **/
else if (window.XScroll && window.XScroll.Plugins) {
	return XScroll.Plugins.LazyLoad = LazyLoad;
}
});