/*
---
description: StaticScroller

license:
  MIT-style

authors:
  - Luke Ehresman (http://luke.ehresman.org)
  - Ryan Florence <rpforence@gmail.com>

requires:
  core/1.2.1: '*'

provides: [StaticScroller]

...
*/
var StaticScroller = new Class({
	
	Implements: Options,
	
		options: {
			offset: 20,
			scrollElement: document
		},

	initialize: function(element, options) {
		this.setOptions(options);
		this.element = document.id(element);
		this.scrollElement = document.id(this.options.scrollElement);
		this.originalPosition = this.element.getPosition();
		this.bound = {
			scroll: this.scroll.bind(this),
			resize: this.resize.bind(this)
		};
		this.attachWindow();
		this.checkHeight();
	},
	
	attachScroll: function(){
		this.scrollElement.addEvent('scroll', this.bound.scroll);
		return this;
	},
	
	attachWindow: function(){
		window.addEvent('resize', this.bound.resize);
		return this;
	},
			
	detachScroll: function(){
		this.scrollElement.removeEvent('scroll', this.bound.scroll);
		return this;
	},
	
	detachWindow: function(){
		window.removeEvent('resize', this.bound.resize);
		return this;
	},
	
	checkHeight: function(){
		if(document.getSize().y < this.element.getSize().y) {
			this.detachScroll().reset();
		} else {
			this.attachScroll().scroll();
		}
		return this;
	},
	
	isPinned: function(){
		return (this.element.retrieve('pinned'));
	},
	
	scroll: function(){
		var collision = (this.scrollElement.getScroll().y >= this.originalPosition.y - this.options.offset);
		var isPinned = this.isPinned();
		if(collision) {
			if(!isPinned) {
				this.element.pin().setStyle('top', this.options.offset.toInt());
			};
		} else {
			if(isPinned) this.reset();
		};
		return this;
	},
	
	resize: function(){
		if(this.isPinned()) this.reset();
		this.checkHeight();
		return this;
	},
	
	reset: function(){
		if(this.isPinned()) this.element.unpin().setStyle('position','');
	}
});