/**
 * jquery.scrollFollow.js
 * Copyright (c) 2008 Net Perspective (http://kitchen.net-perspective.com/)
 * Licensed under the MIT License (http://www.opensource.org/licenses/mit-license.php)
 * 
 * @author R.A. Ray
 *
 * @projectDescription	jQuery plugin for allowing an element to animate down as the user scrolls the page.
 * 
 * @version 0.4.0
 * 
 * @requires jquery.js (tested with 1.2.6)
 * @requires ui.core.js (tested with 1.5.2)
 * 
 * @optional jquery.cookie.js (http://www.stilbuero.de/2006/09/17/cookie-plugin-for-jquery/)
 * @optional jquery.easing.js (http://gsgd.co.uk/sandbox/jquery/easing/ - tested with 1.3)
 * 
 * @param speed		int - Duration of animation (in milliseconds)
 * 								default: 500
 * @param offset			int - Number of pixels box should remain from top of viewport
 * 								default: 0
 * @param easing		string - Any one of the easing options from the easing plugin - Requires jQuery Easing Plugin < http://gsgd.co.uk/sandbox/jquery/easing/ >
 * 								default: 'linear'
 * @param container	string - ID of the containing div
 * 								default: box's immediate parent
 * @param killSwitch	string - ID of the On/Off toggle element
 * 								default: 'killSwitch'
 * @param onText		string - killSwitch text to be displayed if sliding is enabled
 * 								default: 'Turn Slide Off'
 * @param offText		string - killSwitch text to be displayed if sliding is disabled
 * 								default: 'Turn Slide On'
 * @param relativeTo	string - Scroll animation can be relative to either the 'top' or 'bottom' of the viewport
 * 								default: 'top'
 * @param delay			int - Time between the end of the scroll and the beginning of the animation in milliseconds
 * 								default: 0
 */

( function( $ ) {
	
	$.scrollFollow = function ( box, options )
	{ 
		// Convert box into a jQuery object
		box = $( box );

		// 'box' is the object to be animated
		var position = box.css( 'position' );

		var before_scroll_point = 0;
		var em = 0;

		function ani()
		{		
			// The script runs on every scroll which really means many times during a scroll.
			// We don't want multiple slides to queue up.
			box.queue( [ ] );
		
			// A bunch of values we need to determine where to animate to
			var viewportHeight = parseInt( $( window ).height() );	
			var pageScroll =  parseInt( $( document ).scrollTop() );
			var parentTop =  parseInt( box.cont.offset().top );
			var parentHeight = parseInt( box.cont.outerHeight() );
			var boxHeight = parseInt( box.outerHeight() + ( parseInt( box.css( 'marginTop' ) ) || 0 ) + ( parseInt( box.css( 'marginBottom' ) ) || 0 ) );
			var aniTop;
			var cur_dp;
			var tmp_p;
			cur_dp = boxHeight + parentTop - viewportHeight;

			if ( viewportHeight > boxHeight + parentTop)
			{
				tmp_p = pageScroll;
				if ( tmp_p + boxHeight > parentHeight)
				{
					tmp_p = parentHeight - boxHeight;
				}
				if ( ( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 ) )
				{
			//		box.css( 'top', tmp_p );
					box.animate(
						{
							top: tmp_p
						}, options.speed, options.easing
					);
				}

			} else {
				if ( before_scroll_point != pageScroll)
				{
					if ( before_scroll_point < pageScroll)
					{
						// down
						em += pageScroll - before_scroll_point;
						if ( em > cur_dp )
						{
							em = cur_dp;
						}

						if ( em >= cur_dp)
						{
							tmp_p = pageScroll - ( boxHeight + parentTop - viewportHeight);
							if ( tmp_p + boxHeight > parentHeight)
							{
								tmp_p = parentHeight - boxHeight;
							}
							if ( ( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 ) )
							{
			//					box.css( 'top', tmp_p );
								box.animate(
									{
										top: tmp_p
									}, options.speed, options.easing
								);
							}
						}
					} else {
						// up
						em -= before_scroll_point - pageScroll;
						if ( em < 0 )
						{
							em = 0;
						}

						if ( em <= 0)
						{
							if ( ( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 ) )
							{
			//					box.css( 'top', pageScroll);
								box.animate(
									{
										top: pageScroll
									}, options.speed, options.easing
								);
							}
						}
					}
					before_scroll_point = pageScroll;
				}
			}

//			// Make sure the user wants the animation to happen
//			if ( isActive )
//			{
//				// If the box should animate relative to the top of the window
//				if ( options.relativeTo == 'top' )
//				{
//					// Don't animate until the top of the window is close enough to the top of the box
//					if ( box.initialOffsetTop >= ( pageScroll + options.offset ) )
//					{
//						aniTop = box.initialTop;
//					}
//					else
//					{
//						aniTop = Math.min( ( Math.max( ( -parentTop ), ( pageScroll - box.initialOffsetTop + box.initialTop ) ) + options.offset ), ( parentHeight - boxHeight - box.paddingAdjustment ) );
//					}
//				}
//				// If the box should animate relative to the bottom of the window
//				else if ( options.relativeTo == 'bottom' )
//				{
//					// Don't animate until the bottom of the window is close enough to the bottom of the box
//					if ( ( box.initialOffsetTop + boxHeight ) >= ( pageScroll + options.offset + viewportHeight ) )
//					{
//						aniTop = box.initialTop;
//					}
//					else
//					{
//						aniTop = Math.min( ( pageScroll + viewportHeight - boxHeight - options.offset ), ( parentHeight - boxHeight ) );
//					}
//				}
//				
//				// Checks to see if the relevant scroll was the last one
//				// "-20" is to account for inaccuracy in the timeout
//				if ( ( new Date().getTime() - box.lastScroll ) >= ( options.delay - 20 ) )
//				{
//					box.animate(
//						{
//							top: aniTop
//						}, options.speed, options.easing
//					);
//				}
//			}
		};
		
		// If no parent ID was specified, and the immediate parent does not have an ID
		// options.container will be undefined. So we need to figure out the parent element.
		if ( options.container == '')
		{
			box.cont = box.parent();
		}
		else
		{
			box.cont = $( '#' + options.container );
		}
		
		// Finds the default positioning of the box.
		box.initialOffsetTop =  parseInt( box.offset().top );
		box.initialTop = parseInt( box.css( 'top' ) ) || 0;
		
		// Hack to fix different treatment of boxes positioned 'absolute' and 'relative'
		if ( box.css( 'position' ) == 'relative' )
		{
			box.paddingAdjustment = parseInt( box.cont.css( 'paddingTop' ) ) + parseInt( box.cont.css( 'paddingBottom' ) );
		}
		else
		{
			box.paddingAdjustment = 0;
		}
		
		// Animate the box when the page is scrolled
		$( window ).scroll( function ()
			{
				// Sets up the delay of the animation
				$.fn.scrollFollow.interval = setTimeout( function(){ ani();} , options.delay );
				
				// To check against right before setting the animation
				box.lastScroll = new Date().getTime();
			}
		);
		
		// Animate the box when the page is resized
		$( window ).resize( function ()
			{
				// Sets up the delay of the animation
				$.fn.scrollFollow.interval = setTimeout( function(){ ani();} , options.delay );
				
				// To check against right before setting the animation
				box.lastScroll = new Date().getTime();
			}
		);

		// Run an initial animation on page load
		box.lastScroll = 0;
		
		ani();
	};
	
	$.fn.scrollFollow = function ( options )
	{
		options = options || {};
		options.relativeTo = options.relativeTo || 'top';
		options.speed = options.speed || 500;
		options.offset = options.offset || 0;
		options.easing = options.easing || 'swing';
		options.container = options.container || this.parent().attr( 'id' );
		options.killSwitch = options.killSwitch || 'killSwitch';
		options.onText = options.onText || 'Turn Slide Off';
		options.offText = options.offText || 'Turn Slide On';
		options.delay = options.delay || 0;
		
		this.each( function() 
			{
				new $.scrollFollow( this, options );
			}
		);
		
		return this;
	};
})( jQuery );