/*
* 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: '',
scrollOffset: 89,
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.scrollOffset, // this is the important line
}, 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 );