/*
 * 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 0.9
 *
 * 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, {
          easing: o.easing,
          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) {
      var $nav = $this.find('a');
      
      if(o.filter !== '') {
        $nav = $nav.filter(o.filter);
      }
      
      /*$nav.each(function() {
        var linkhref = $(this).attr('href');
        var divpos = $(linkhref).offset();
        var toppos = divpos.top;
            
        onepagenav.sections[linkhref.substr(1)] = math.round(toppos) - o.scrolloffset;
      });*/
    };
    
    onepagenav.getsection = function(windowpos, o) {
      var returnvalue = '',
          windowheight = math.round($(window).height() * o.scrollthreshold);
      
      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, o);
          
      if(position !== '') {
        onepagenav.adjustnav($this,$this.find('a[href=#'+position+']').parent(), o.currentclass);
      }
    };
    
    onepagenav.init = function($this, o) {
      var didscroll = false,
          $nav = $this.find('a');
      
      if(o.filter !== '') {
        $nav = $nav.filter(o.filter);
      }

      $nav.bind('click', function(e) {
        onepagenav.bindnav($(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,
    easing: 'swing',
    filter: '',
    scrollspeed: 750,
    scrolloffset: 0,
    scrollthreshold: 0.5,
    begin: false,
    end: false
  };

})(jquery);