/*

 * jQuery One Page Nav Plugin

 * http://github.com/davist11/jQuery-One-Page-Nav

 *

 * Copyright (c) 2010 Trevor Davis (http://trevordavis.net)

 * Dual licensed under the MIT and GPL licenses.

 * Uses the same license as jQuery, see:

 * http://jquery.org/license

 *

 * @version 2.2

 *

 * Example usage:

 * $('#nav').onePageNav({

 *   currentClass: 'current',

 *   changeHash: false,

 *   scrollSpeed: 750

 * });

 */



;(function($, window, document, undefined){



	// our plugin constructor

	var OnePageNav = function(elem, options){

		this.elem = elem;

		this.$elem = $(elem);

		this.options = options;

		this.metadata = this.$elem.data('plugin-options');

		this.$nav = this.$elem.find('a');

		this.$win = $(window);

		this.sections = {};

		this.didScroll = false;

		this.$doc = $(document);

		this.docHeight = this.$doc.height();

	};



	// the plugin prototype

	OnePageNav.prototype = {

		defaults: {

			currentClass: 'current',

			changeHash: false,

			easing: 'swing',

			filter: '',

			scrollSpeed: 750,

			scrollOffset: 0,

			scrollThreshold: 0.5,

			begin: false,

			end: false,

			scrollChange: false

		},



		init: function() {

			var self = this;

			

			// Introduce defaults that can be extended either

			// globally or using an object literal.

			self.config = $.extend({}, self.defaults, self.options, self.metadata);

			

			//Filter any links out of the nav

			if(self.config.filter !== '') {

				self.$nav = self.$nav.filter(self.config.filter);

			}

			

			//Handle clicks on the nav

			self.$nav.on('click.onePageNav', $.proxy(self.handleClick, self));



			//Get the section positions

			self.getPositions();

			

			//Handle scroll changes

			self.bindInterval();

			

			//Update the positions on resize too

			self.$win.on('resize.onePageNav', $.proxy(self.getPositions, self));



			return this;

		},

		

		adjustNav: function(self, $parent) {

			self.$elem.find('.' + self.config.currentClass).removeClass(self.config.currentClass);

			$parent.addClass(self.config.currentClass);

		},

		

		bindInterval: function() {

			var self = this;

			var docHeight;

			

			self.$win.on('scroll.onePageNav', function() {

				self.didScroll = true;

			});

			

			self.t = setInterval(function() {

				docHeight = self.$doc.height();

				

				//If it was scrolled

				if(self.didScroll) {

					self.didScroll = false;

					self.scrollChange();

				}

				

				//If the document height changes

				if(docHeight !== self.docHeight) {

					self.docHeight = docHeight;

					self.getPositions();

				}

			}, 250);

		},

		

		getHash: function($link) {

			return $link.attr('href').split('#')[1];

		},

		

		getPositions: function() {

			var self = this;

			var linkHref;

			var topPos;

			var $target;

			

			self.$nav.each(function() {

				linkHref = self.getHash($(this));

				$target = $('#' + linkHref);



				if($target.length) {

					topPos = $target.offset().top;

					self.sections[linkHref] = Math.round(topPos) - self.config.scrollOffset;

				}

			});

		},

		

		getSection: function(windowPos) {

			var returnValue = null;

			var windowHeight = Math.round(this.$win.height() * this.config.scrollThreshold);



			for(var section in this.sections) {

				if((this.sections[section] - windowHeight) < windowPos) {

					returnValue = section;

				}

			}

			

			return returnValue;

		},

		

		handleClick: function(e) {

			var self = this;

			var $link = $(e.currentTarget);

			var $parent = $link.parent();

			var newLoc = '#' + self.getHash($link);

			

			if(!$parent.hasClass(self.config.currentClass)) {

				//Start callback

				if(self.config.begin) {

					self.config.begin();

				}

				

				//Change the highlighted nav item

				self.adjustNav(self, $parent);

				

				//Removing the auto-adjust on scroll

				self.unbindInterval();

				

				//Scroll to the correct position

				$.scrollTo(newLoc, self.config.scrollSpeed, {

					axis: 'y',

					easing: self.config.easing,

					offset: {

						top: -self.config.scrollOffset

					},

					onAfter: function() {

						//Do we need to change the hash?

						if(self.config.changeHash) {

							window.location.hash = newLoc;

						}

						

						//Add the auto-adjust on scroll back in

						self.bindInterval();

						

						//End callback

						if(self.config.end) {

							self.config.end();

						}

					}

				});

			}



			e.preventDefault();

		},

		

		scrollChange: function() {

			var windowTop = this.$win.scrollTop();

			var position = this.getSection(windowTop);

			var $parent;

			

			//If the position is set

			if(position !== null) {

				$parent = this.$elem.find('a[href$="#' + position + '"]').parent();

				

				//If it's not already the current section

				if(!$parent.hasClass(this.config.currentClass)) {

					//Change the highlighted nav item

					this.adjustNav(this, $parent);

					

					//If there is a scrollChange callback

					if(this.config.scrollChange) {

						this.config.scrollChange($parent);

					}

				}

			}

		},

		

		unbindInterval: function() {

			clearInterval(this.t);

			this.$win.unbind('scroll.onePageNav');

		}

	};



	OnePageNav.defaults = OnePageNav.prototype.defaults;



	$.fn.onePageNav = function(options) {

		return this.each(function() {

			new OnePageNav(this, options).init();

		});

	};

	

})( jQuery, window , document );