//extend-geojson-properties
(function() {
  var extendGeoJSON = function(featColl,jsonDataSet,jsonMap) {
    // check the valid input parameters
    var collection;
    if (Array.isArray(jsonDataSet)) {
      if (Array.isArray(featColl) ) {
        collection = featColl; 
      } else if ((featColl.hasOwnProperty('type') 
        & featColl.type == 'FeatureCollection')) {
        collection = featColl.features;
      }else {
        return false;
      }
    }else {
      return false;
    }
    var geoFeatIndex = {};
    collection.forEach(function(f) {
      geoFeatIndex[valueAt(f,jsonMap.geoKey)] = f;
    });
    jsonDataSet.forEach(function(data) {
      var key = valueAt(data,jsonMap.dataKey);
      var feat = geoFeatIndex[key];
      if (feat) {
        if(jsonMap.propertyMap) {
          jsonMap.propertyMap.forEach(function(pair) {
            feat.properties[pair.geoProperty] = valueAt(data,pair.dataProperty);
          });
        } else {
          // extend all properties of data to feature excepts dataKey
          Object.keys(data).filter(function(key) {
            return key !== jsonMap.dataKey;
          })
          .forEach(function(key) {
            feat.properties[key] = data[key];
          });
        }
      }
    });
  };
  function valueAt(obj,path) {
    //taken from http://stackoverflow.com/a/6394168/713573
    function index(obj,i) { return obj[i]; }
    return path.split('.').reduce(index, obj);
  }

  if(typeof module !== 'undefined' && module.exports) {
    module.exports = extendGeoJSON;
  } 
  if(typeof window !== 'undefined') {
    window.extendGeoJSON = extendGeoJSON;
  }
})();