/*
 * 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 3.0.0
 *
 * 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.$win = $(window);
		this.sections = {};
		this.didscroll = false;
		this.$doc = $(document);
		this.docheight = this.$doc.height();
	};

	// the plugin prototype
	onepagenav.prototype = {
		defaults: {
			navitems: 'a',
			currentclass: 'current',
			changehash: false,
			easing: 'swing',
			filter: '',
			scrollspeed: 750,
			scrollthreshold: 0.5,
			begin: false,
			end: false,
			scrollchange: false
		},

		init: function() {
			// introduce defaults that can be extended either
			// globally or using an object literal.
			this.config = $.extend({}, this.defaults, this.options, this.metadata);

			this.$nav = this.$elem.find(this.config.navitems);

			//filter any links out of the nav
			if(this.config.filter !== '') {
				this.$nav = this.$nav.filter(this.config.filter);
			}

			//handle clicks on the nav
			this.$nav.on('click.onepagenav', $.proxy(this.handleclick, this));

			//get the section positions
			this.getpositions();

			//handle scroll changes
			this.bindinterval();

			//update the positions on resize too
			this.$win.on('resize.onepagenav', $.proxy(this.getpositions, this));

			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);
				}
			});
		},

		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
				self.scrollto(newloc, 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);
					}
				}
			}
		},

		scrollto: function(target, callback) {
			var offset = $(target).offset().top;

			$('html, body').animate({
				scrolltop: offset
			}, this.config.scrollspeed, this.config.easing, callback);
		},

		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 );