read static method

Implementation

static dynamic read(dynamic data, String? tag) {
  if (data == null || (data is List && data.isEmpty) || tag == null) {
    return null;
  }

  // Get Dot Notation
  DotNotation? dotNotation = DotNotation.fromString(tag);

  if (data is List<dynamic>) data = data.isNotEmpty ? data[0] : null;

  if (dotNotation != null) {
    for (NotationSegment? property in dotNotation) {
      if (property != null) {
        if (data is Map) {
          // attributes are named with an underscore
          // to make it easier for the user, we first look for the
          // property by name, then if not found, look for it by _name
          var name = property.name;
          var myName = "_$name";
          if (!data.containsKey(name) && (!data.containsKey(myName))) {
            data = null;
            break;
          }
          data = data.containsKey(name) ? data[name] : data[myName];

          if ((data is Map) && (property.offset > 0)) data = null;
          if ((data is List) && (property.offset > data.length)) data = null;
          if ((data is List) &&
              (property.offset < data.length) &&
              (property.offset >= 0)) data = data[property.offset];
        } else if (data is List) {
          if (data.length < property.offset) {
            data = null;
            break;
          }
          data = data[property.offset];
          if ((data is Map) && (data.containsKey(property.name))) {
            data = data[property.name];
          }
        } else {
          data = null;
          break;
        }
      }
    }
  }

  // this is a very odd case. if the element contains attributes, the element value will be put into a
  // map field called "value" and its attributes will be mapped to underscore (_) names _attributename
  if ((data is Map) && (data.containsKey('value'))) data = data['value'];

  // return result;
  return data;
}