decode static method Null safety

Implementation

static CircleLayer decode(String properties) {
  var map = json.decode(properties);
  if (map["layout"] == null) {
    map["layout"] = {};
  }
  if (map["paint"] == null) {
    map["paint"] = {};
  }
  return CircleLayer(
    id: map["id"],
    sourceId: map["source"],
    sourceLayer: map["source-layer"],
    minZoom: map["minzoom"]?.toDouble(),
    maxZoom: map["maxzoom"]?.toDouble(),
    visibility: map["layout"]["visibility"] == null
        ? Visibility.VISIBLE
        : Visibility.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["layout"]["visibility"])),
    circleSortKey: map["layout"]["circle-sort-key"]?.toDouble(),
    circleBlur: map["paint"]["circle-blur"]?.toDouble(),
    circleColor: (map["paint"]["circle-color"] as List?)?.toRGBAInt(),
    circleOpacity: map["paint"]["circle-opacity"]?.toDouble(),
    circlePitchAlignment: map["paint"]["circle-pitch-alignment"] == null
        ? null
        : CirclePitchAlignment.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["paint"]["circle-pitch-alignment"])),
    circlePitchScale: map["paint"]["circle-pitch-scale"] == null
        ? null
        : CirclePitchScale.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["paint"]["circle-pitch-scale"])),
    circleRadius: map["paint"]["circle-radius"]?.toDouble(),
    circleStrokeColor:
        (map["paint"]["circle-stroke-color"] as List?)?.toRGBAInt(),
    circleStrokeOpacity: map["paint"]["circle-stroke-opacity"]?.toDouble(),
    circleStrokeWidth: map["paint"]["circle-stroke-width"]?.toDouble(),
    circleTranslate: (map["paint"]["circle-translate"] as List?)
        ?.map<double?>((e) => e.toDouble())
        .toList(),
    circleTranslateAnchor: map["paint"]["circle-translate-anchor"] == null
        ? null
        : CircleTranslateAnchor.values.firstWhere((e) => e
            .toString()
            .split('.')
            .last
            .toLowerCase()
            .contains(map["paint"]["circle-translate-anchor"])),
  );
}