var ScrollBar = new Class({

	Implements: [Events, Options],

	options: {
		maxThumbSize: 15,
		wheel: 8,
		arrows: true,
		hScroll: true // horizontal scrollbars
	},

	initialize: function(main, content, options){
		this.setOptions(options);
		
		this.main = $(main);
		this.content = $(content);
		
		if (this.options.arrows == true){
			this.arrowOffset = 30;
		} else {
			this.arrowOffset = 0;
		}
		
		if (this.options.hScroll == true){
			this.hScrollOffset = 15;
		} else {
			this.hScrollOffset = 0;
		}				

		this.vScrollbar = new Element('div', {
				'class': 'vScrollbar'
			}).injectAfter(this.content);				

		if (this.options.arrows == true){				
			this.arrowUp = new Element('div', {
					'class': 'arrowUp'
				}).injectInside(this.vScrollbar);
		}	

		this.vTrack = new Element('div', {
				'class': 'vTrack'
			}).injectInside(this.vScrollbar);
			
		this.vThumb = new Element('div', {
				'class': 'vThumb'
			}).injectInside(this.vTrack);

		if (this.options.arrows == true){				
			this.arrowDown = new Element('div', {
					'class': 'arrowDown'
				}).injectInside(this.vScrollbar);
		}		
		
		this.hScrollbar = new Element('div', {
				'class': 'hScrollbar'
			}).injectAfter(this.vScrollbar);

		if (this.options.arrows == true){							
			this.arrowLeft = new Element('div', {
					'class': 'arrowLeft'
				}).injectInside(this.hScrollbar);
		}		

		this.hTrack = new Element('div', {
				'class': 'hTrack'
			}).injectInside(this.hScrollbar);
			
		this.hThumb = new Element('div', {
				'class': 'hThumb'
			}).injectInside(this.hTrack);							

		if (this.options.arrows == true){
			this.arrowRight = new Element('div', {
					'class': 'arrowRight'
				}).injectInside(this.hScrollbar);
		}											

		this.corner = new Element('div', {
				'class': 'corner'
			}).injectAfter(this.hScrollbar);
		
		this.bound = {
			'vStart': this.vStart.bind(this),
			'hStart': this.hStart.bind(this),				
			'end': this.end.bind(this),
			'vDrag': this.vDrag.bind(this),
			'hDrag': this.hDrag.bind(this),				
			'wheel': this.wheel.bind(this),
			'vPage': this.vPage.bind(this),
			'hPage': this.hPage.bind(this)				
		};

		this.vPosition = {};
		this.hPosition = {};			
		this.vMouse = {};
		this.hMouse = {};			
		this.update();
		this.attach();
	},

	update: function(){
		
		this.main.setStyle('height', this.content.offsetHeight + this.hScrollOffset);
		this.vTrack.setStyle('height', this.content.offsetHeight - this.arrowOffset);
					
		this.main.setStyle('width', this.content.offsetWidth + 15);
		this.hTrack.setStyle('width', this.content.offsetWidth - this.arrowOffset);
		
		// Remove and replace vertical scrollbar			
		if (this.content.scrollHeight <= this.main.offsetHeight) {
			this.vScrollbar.setStyle('display', 'none');
			if (this.options.hScroll == true){				
				this.hTrack.setStyle('width', this.hTrack.offsetWidth + 15);
			}	
			this.content.setStyle('width', this.content.offsetWidth + 15);	
		} else {
			this.vScrollbar.setStyle('display', 'block');			
		}
		
		if (this.options.hScroll == true){			
		
			// Remove and replace horizontal scrollbar
			if (this.content.scrollWidth <= this.main.offsetWidth) {
				this.hScrollbar.setStyle('display', 'none');
				this.vTrack.setStyle('height', this.vTrack.offsetHeight + this.hScrollOffset);				
				this.content.setStyle('height', this.content.offsetHeight + this.hScrollOffset);	
			} else {
				this.hScrollbar.setStyle('display', 'block');			
			}
		
			// Remove and replace bottom right corner spacer			
			if (this.content.scrollHeight <= this.main.offsetHeight || this.content.scrollWidth <= this.main.offsetWidth) {
				this.corner.setStyle('display', 'none');				
			} else {
				this.corner.setStyle('display', 'block');			
			}		
		
			// Horizontal

			this.hContentSize = this.content.offsetWidth;
			this.hContentScrollSize = this.content.scrollWidth;
			this.hTrackSize = this.hTrack.offsetWidth;

			this.hContentRatio = this.hContentSize / this.hContentScrollSize;

			this.hThumbSize = (this.hTrackSize * this.hContentRatio).limit(this.options.maxThumbSize, this.hTrackSize);

			this.hScrollRatio = this.hContentScrollSize / this.hTrackSize;

			this.hThumb.setStyle('width', this.hThumbSize);

			this.hUpdateThumbFromContentScroll();
			this.hUpdateContentFromThumbPosition();			

		} else {
				this.hScrollbar.setStyle('display', 'none');
				this.corner.setStyle('display', 'none');										
		}
		

		// Vertical
		
		this.vContentSize = this.content.offsetHeight;
		this.vContentScrollSize = this.content.scrollHeight;
		this.vTrackSize = this.vTrack.offsetHeight;

		this.vContentRatio = this.vContentSize / this.vContentScrollSize;

		this.vThumbSize = (this.vTrackSize * this.vContentRatio).limit(this.options.maxThumbSize, this.vTrackSize);

		this.vScrollRatio = this.vContentScrollSize / this.vTrackSize;

		this.vThumb.setStyle('height', this.vThumbSize);

		this.vUpdateThumbFromContentScroll();
		this.vUpdateContentFromThumbPosition();
		
	},

	vUpdateContentFromThumbPosition: function(){
		this.content.scrollTop = this.vPosition.now * this.vScrollRatio;
	},
	
	hUpdateContentFromThumbPosition: function(){
		this.content.scrollLeft = this.hPosition.now * this.hScrollRatio;
	},		

	vUpdateThumbFromContentScroll: function(){
		this.vPosition.now = (this.content.scrollTop / this.vScrollRatio).limit(0, (this.vTrackSize - this.vThumbSize));
		this.vThumb.setStyle('top', this.vPosition.now);
	},
	
	hUpdateThumbFromContentScroll: function(){
		this.hPosition.now = (this.content.scrollLeft / this.hScrollRatio).limit(0, (this.hTrackSize - this.hThumbSize));
		this.hThumb.setStyle('left', this.hPosition.now);
	},		

	attach: function(){
		this.vThumb.addEvent('mousedown', this.bound.vStart);
		if (this.options.wheel) this.content.addEvent('mousewheel', this.bound.wheel);
		this.vTrack.addEvent('mouseup', this.bound.vPage);
		
		this.hThumb.addEvent('mousedown', this.bound.hStart);
		this.hTrack.addEvent('mouseup', this.bound.hPage);			
		
		if (this.options.arrows == true){
			this.arrowUp.addEvent('mousedown', function(event){
					this.interval = (function(event){
					this.content.scrollTop -= this.options.wheel;
					this.vUpdateThumbFromContentScroll();
				}.bind(this).periodical(40))
			}.bind(this));
		
			this.arrowUp.addEvent('mouseup', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowUp.addEvent('mouseout', function(event){
				$clear(this.interval);
			}.bind(this));
					
			this.arrowDown.addEvent('mousedown', function(event){
					this.interval = (function(event){
					this.content.scrollTop += this.options.wheel;
					this.vUpdateThumbFromContentScroll();
				}.bind(this).periodical(40))
			}.bind(this));
		
			this.arrowDown.addEvent('mouseup', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowDown.addEvent('mouseout', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowLeft.addEvent('mousedown', function(event){
					this.interval = (function(event){
					this.content.scrollLeft -= this.options.wheel;
					this.hUpdateThumbFromContentScroll();
				}.bind(this).periodical(40))
			}.bind(this));
		
			this.arrowLeft.addEvent('mouseup', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowLeft.addEvent('mouseout', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowRight.addEvent('mousedown', function(event){
					this.interval = (function(event){
					this.content.scrollLeft += this.options.wheel;
					this.hUpdateThumbFromContentScroll();
				}.bind(this).periodical(40))
			}.bind(this));
		
			this.arrowRight.addEvent('mouseup', function(event){
				$clear(this.interval);
			}.bind(this));
		
			this.arrowRight.addEvent('mouseout', function(event){
				$clear(this.interval);
			}.bind(this));
		}			
					
	},
	
	wheel: function(event){
		this.content.scrollTop -= event.wheel * this.options.wheel;
		this.vUpdateThumbFromContentScroll();
		event.stop();
	},

	vPage: function(event){
		if (event.page.y > this.vThumb.getPosition().y) this.content.scrollTop += this.content.offsetHeight;
		else this.content.scrollTop -= this.content.offsetHeight;
		this.vUpdateThumbFromContentScroll();
		event.stop();
	},
	
	hPage: function(event){
		if (event.page.x > this.hThumb.getPosition().x) this.content.scrollLeft += this.content.offsetWidth;
		else this.content.scrollLeft -= this.content.offsetWidth;
		this.hUpdateThumbFromContentScroll();
		event.stop();
	},		

	vStart: function(event){
		this.vMouse.start = event.page.y;
		this.vPosition.start = this.vThumb.getStyle('top').toInt();
		document.addEvent('mousemove', this.bound.vDrag);
		document.addEvent('mouseup', this.bound.end);
		this.vThumb.addEvent('mouseup', this.bound.end);
		event.stop();
	},
	
	hStart: function(event){
		this.hMouse.start = event.page.x;		
		this.hPosition.start = this.hThumb.getStyle('left').toInt();
		document.addEvent('mousemove', this.bound.hDrag);
		document.addEvent('mouseup', this.bound.end);
		this.hThumb.addEvent('mouseup', this.bound.end);
		event.stop();
	},		

	end: function(event){
		document.removeEvent('mousemove', this.bound.vDrag);
		document.removeEvent('mousemove', this.bound.hDrag);			
		document.removeEvent('mouseup', this.bound.end);
		this.vThumb.removeEvent('mouseup', this.bound.end);
		this.hThumb.removeEvent('mouseup', this.bound.end);			
		event.stop();
	},

	vDrag: function(event){
		this.vMouse.now = event.page.y;
		this.vPosition.now = (this.vPosition.start + (this.vMouse.now - this.vMouse.start)).limit(0, (this.vTrackSize - this.vThumbSize));
		this.vUpdateContentFromThumbPosition();
		this.vUpdateThumbFromContentScroll();
		event.stop();
	},
	
	hDrag: function(event){
		this.hMouse.now = event.page.x;
		this.hPosition.now = (this.hPosition.start + (this.hMouse.now - this.hMouse.start)).limit(0, (this.hTrackSize - this.hThumbSize));
		this.hUpdateContentFromThumbPosition();
		this.hUpdateThumbFromContentScroll();
		event.stop();
	}		

});