/*

 * 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 0.7

 *

 * Example usage:

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

 *   currentClass: 'current',

 *   changeHash: false,

 *   scrollSpeed: 750

 * });

 */

;(function($) {

  $.fn.onePageNav = function(options) {

    var opts = $.extend({}, $.fn.onePageNav.defaults, options),

        onePageNav = {};

    onePageNav.sections = {};

    onePageNav.bindNav = function($el, $this, o) {

      var $par = $el.parent(),

          newLoc = $el.attr('href'),

          $win = $(window);

      if(!$par.hasClass(o.currentClass)) {

        if(o.begin) {

          o.begin();

        }

        onePageNav.adjustNav($this, $par, o.currentClass);

        $win.unbind('.onePageNav');

        $.scrollTo(newLoc, o.scrollSpeed, {

          offset: {

            top: -o.scrollOffset

          },

          onAfter: function() {

            if(o.changeHash) {

              window.location.hash = newLoc;

            }

            $win.bind('scroll.onePageNav', function() {

              onePageNav.scrollChange($this, o);

            });

            if(o.end) {

              o.end();

            }

          }

        });

      }

    };

    onePageNav.adjustNav = function($this, $el, curClass) {

      $this.find('.'+curClass).removeClass(curClass);

      $el.addClass(curClass);

    };

    onePageNav.getPositions = function($this, o) {

      $this.find('a').each(function() {

        var linkHref = $(this).attr('href'),

            divPos = $(linkHref).offset(),

            topPos = divPos.top;

        onePageNav.sections[linkHref.substr(1)] = Math.round(topPos) - o.scrollOffset;

      });

    };

    onePageNav.getSection = function(windowPos) {

      var returnValue = '',

          windowHeight = Math.round($(window).height() / 2);

      for(var section in onePageNav.sections) {

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

          returnValue = section;

        }

      }

      return returnValue;

    };

    onePageNav.scrollChange = function($this, o) {

      onePageNav.getPositions($this, o);

      var windowTop = $(window).scrollTop(),

          position = onePageNav.getSection(windowTop);

      if(position !== '') {

        onePageNav.adjustNav($this,$this.find('a[href=#'+position+']').parent(), o.currentClass);

      }

    };

    onePageNav.init = function($this, o) {

      var didScroll = false;

      $this.find('a').bind('click', function(e) {

        onePageNav.bindNav($(this), $this, o);

        e.preventDefault();

      });

      onePageNav.getPositions($this, o);

      $(window).bind('scroll.onePageNav', function() {

        didScroll = true;

      });

      setInterval(function() {

        if(didScroll) {

          didScroll = false;

          onePageNav.scrollChange($this, o);

        }

      }, 250);

    };

    return this.each(function() {

      var $this = $(this),

          o = $.meta ? $.extend({}, opts, $this.data()) : opts;

      onePageNav.init($this, o);

    });

  };

  // default options

  $.fn.onePageNav.defaults = {

    currentClass: 'current',

    changeHash: false,

    scrollSpeed: 0,

    scrollOffset: 0,

    begin: false,

    end: false

  };

})(jQuery);