/*

* 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,
                padding: 0
        },

        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 - this.config.padding;

                $('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 );