/*
 * 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 2.1
 *
 * 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: 850,
			scrollOffset: 45,
			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;
			
			self.$nav.each(function() {
				linkHref = self.getHash($(this));
				topPos = $('#' + linkHref).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 );