conveyal/modeify

module.exports.decode = function(polyline) {

  var currentPosition = 0;

  var currentLat = 0;
  var currentLng = 0;

  var dataLength = polyline.length;

  var polylineLatLngs = [];

  while (currentPosition < dataLength) {

    var shift = 0;
    var result = 0;

    var byte;

    do {
      byte = polyline.charCodeAt(currentPosition++) - 63;
      result |= (byte & 0x1f) << shift;
      shift += 5;
    } while (byte >= 0x20);

    var deltaLat = ((result & 1) ? ~(result >> 1) : (result >> 1));
    currentLat += deltaLat;

    shift = 0;
    result = 0;

    do {
      byte = polyline.charCodeAt(currentPosition++) - 63;
      result |= (byte & 0x1f) << shift;
      shift += 5;
    } while (byte >= 0x20);

    var deltLng = ((result & 1) ? ~(result >> 1) : (result >> 1));

    currentLng += deltLng;

    polylineLatLngs.push([currentLat * 0.00001, currentLng * 0.00001]);
  }
  return polylineLatLngs;
};