/**
 * 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));
                        aniTop = (pageScroll - box.initialOffsetTop + box.initialTop);
//                        $('#autoScrollContent').html("aniTop: " + aniTop +
//                        "<br>PageScroll: " + pageScroll +
//                        "<br>Val1: " + (-parentTop) +
//                        "<br>Val2: " + (pageScroll - box.initialOffsetTop + box.initialTop) +
//                        "<br>Val3: " + (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);
        }

        // 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);