jquery.geo.js

/*!
 * jQuery-Geo jQuery plugin v0.0.1
 *
 * Copyright 2010 by Dan Singerman <dansingerman@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

(function($){

   var publicMethods = {
     locate : function( successCallback, failureCallback ) {
          if ( navigator.geolocation ) {
            // browser supports W3C geolocation API
            navigator.geolocation.getCurrentPosition(
              function( position ){
                processLocation( position , successCallback);
              },
              function(err){
                processError( err, failureCallback );
              });
          }
          else if ( window.google && google.gears ) {
            // this provides support for Android versions < 2.0
            var geo = google.gears.factory.create( 'beta.geolocation' );
            geo.getCurrentPosition(
              function( position ){
                processLocation( position , successCallback );
              },
              function(err){
                processError( err , failureCallback );
              });
          }
          else {
            processError( {
              code: 99
            }, failureCallback );
          }
     },
     
     /* Haversine formula calculations taken from
        http://www.movable-type.co.uk/scripts/latlong.html
     */
     
     distance : function( lat1 , lon1 , lat2 , lon2) {
       var R = 6371; // km
       var dLat = (lat2-lat1) * (Math.PI / 180);
       var dLon = (lon2-lon1) * (Math.PI / 180);
       var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
               Math.cos(lat1 * (Math.PI / 180)) * Math.cos(lat2 * (Math.PI / 180)) *
               Math.sin(dLon/2) * Math.sin(dLon/2);
       var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
       var d = R * c;
       return d * 1000;
     }
     
   };

  // success!! we have a latitude and longitude
  var processLocation = function ( position , callback ) {
    callback( position );
  };

  /* we have failed to get a location
   * error has made up status code of 99 if device does not support W3C geolocation
   * otherwise error is instance of PositionError
   * http://dev.w3.org/geo/api/spec-source.html#position_error_interface */
   
  var processError = function ( error, callback ) {
    var message;
    
    switch( error.code ) {
      case error.TIMEOUT:
        message = "Geolocation Timeout";
        break;
      case error.PERMISSION_DENIED:
        message = "Permission Denied";
        break;
      case error.POSITION_UNAVAILABLE:
        message = "Position Unavailable";
        break;
      default:
        message = "Geolocation not supported by jQuery-Geo for your device";
    }

    callback( error, message );
  };

  // best practice jQuery plugin namespacing
  $.geo = function( method ) {

    if ( publicMethods[method] ) {
     return publicMethods[method].apply( this, Array.prototype.slice.call( arguments, 1 ));
    } else if ( typeof method === 'object' || ! method ) {
     return publicMethods.init.apply( this, arguments );
    } else {
     $.error( 'Method ' +  method + ' does not exist in jQuery.geo' );
    }    

  };
})(jQuery);