/**
 * 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');

		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.attr('offsetHeight'));
			var boxHeight = parseInt(box.attr('offsetHeight') + (parseInt(box.css('marginTop')) || 0) + (parseInt(box.css('marginBottom')) || 0));
			var aniTop;

			// 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
					);
				}
			}
		};

		// For user-initiated stopping of the slide
		var isActive = true;

		if ($.cookie != undefined) {
			if ($.cookie('scrollFollowSetting' + box.attr('id')) == 'false') {
				var isActive = false;

				$('#' + options.killSwitch).text(options.offText)
					.toggle(
						function () {
							isActive = true;

							$(this).text(options.onText);

							$.cookie('scrollFollowSetting' + box.attr('id'), true, { expires: 365, path: '/' });

							ani();
						},
						function () {
							isActive = false;

							$(this).text(options.offText);

							box.animate(
								{
									top: box.initialTop
								}, options.speed, options.easing
							);

							$.cookie('scrollFollowSetting' + box.attr('id'), false, { expires: 365, path: '/' });
						}
					);
			}
			else {
				$('#' + options.killSwitch).text(options.onText)
					.toggle(
						function () {
							isActive = false;

							$(this).text(options.offText);

							box.animate(
								{
									top: box.initialTop
								}, 0
							);

							$.cookie('scrollFollowSetting' + box.attr('id'), false, { expires: 365, path: '/' });
						},
						function () {
							isActive = true;

							$(this).text(options.onText);

							$.cookie('scrollFollowSetting' + box.attr('id'), true, { expires: 365, path: '/' });

							ani();
						}
					);
			}
		}

		// 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);
		}

//MOCO TODO - Forced '0' as default value as box was not scrolling down when triggered out of site
		// Finds the default positioning of the box.
		box.initialOffsetTop = 0;// parseInt(box.offset().top);
		box.initialTop = 0; //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);