var StickerAnimation = function(){};
StickerAnimation.prototype = {
	duration : null,
	obj : null,
	from : null,
	to : null,
	timer : 0,
	step : 0,
	start : function(obj, from, to, duration, type){
		var self = this;
		this.obj = obj;
		this.from = from;
		this.to = to;
		this.now = new Date;
		this.duration = duration || 1000;
		this._delta = this['_delta' +(type || 'Elastic')];

		if(this.timer)
			this.stop();

		this.timer = setInterval(function(){self.run();}, 10);
	},
	run : function(){

		var time = ((new Date) - this.now) / this.duration;
		var delta = this._delta(time);

		var step = Math.pow(2, this.step);
		var dep_x = (this.to.x - this.from.x) * delta;
		var dep_y = (this.to.y - this.from.y) * delta;

		if(time > 1){
			this.stop();
			this.end();
		}else{

			this.obj.style.marginLeft = this.from.x + dep_x + "px";
			this.obj.style.marginTop = this.from.y + dep_y + "px";
		}
	},
	end : function(){
		this.obj.style.marginLeft = (this.to.x) + "px";
		this.obj.style.marginTop = (this.to.y) + "px";
	},
	stop : function(){
		clearInterval(this.timer);
		this.timer = 0;
	},

	_deltaBounce : function(pos){
		var p = 1 - pos;

		var value;
		for (var a = 0, b = 1; 1; a += b, b /= 2){
			if (p >= (7 - 4 * a) / 11){
				value = - Math.pow((11 - 6 * a - 11 * p) / 4, 2) + b * b;
				break;
			}
		}
		return 1 - value;
	},

	_deltaExpo : function(pos){
		var p = 1 - pos;
		return 1 - Math.pow(2, 8 * (p - 1));
	},

	_deltaElastic : function(pos){
		var p = 1 - pos;
		return 1 - Math.pow(2, 10 * --p) * Math.cos(20 * p * Math.PI * 1 / 3);
	},

	_deltaStatic : function(pos){
		return 1;
	}

}

var StickerManager = {
	init : false,
	stickers : [],
	opts : [],
	add : function(id, duration, type){

		if(!this.init){
			var self = this;
			var init_event = function(){self.oninit();};
			var scroll_event = function(){self.onscroll();};

			if(window.attachEvent){
				window.attachEvent('onload', init_event);
				window.attachEvent('onscroll', scroll_event);
			}else{
				window.addEventListener('load', init_event, false);
				document.addEventListener('scroll', scroll_event, false);
			}

			this.init = true;
		}

		this.stickers.push(id);
		this.opts.push({duration:duration,type:type});
	},

	oninit : function(){
		var sticker;
		for(var x = 0, len = this.stickers.length; x < len; x++){
			sticker = document.getElementById(this.stickers[x]);
			if(!sticker){
				alert(this.stickers[x] + ' is bad id.');
				this.stickers[x] = null;
				continue;
			}
			this.stickers[x] = sticker;
			sticker.style.marginLeft = sticker.style.marginTop = "0px";
		}
	},

	onscroll : function(){
		var left = parseInt(document.body.scrollLeft);
		var top = parseInt(document.body.scrollTop);
		var sticker;
		for(var x = 0, len = this.stickers.length; x < len; x++){
			sticker = this.stickers[x];

			if(!sticker)
				continue;

			if(!sticker.animation){
				sticker.animation = new StickerAnimation();
			}else{
				sticker.animation.stop();
			}

			if(sticker.animation==null){
				//alert(this.stickers[x] + ' is bad id.');
				continue;
			}else{
				sticker.animation.start(
					sticker, 
					{x:parseInt(sticker.style.marginLeft), y:parseInt(sticker.style.marginTop)},
					{x:left, y:top},
					this.opts[x].duration,
					this.opts[x].type
				);
			}

		}
	}
}