toSingleton static method

List toSingleton(List input, { String? name, String? operation, List? collection, })

Returns a singleton, based on the input.

Throws if input is not empty, or has single entry. Creates ValidatedQuantity from map inputs.

Anything else is merely returned unmodified.

Implementation

static List<dynamic> toSingleton(
  List<dynamic> input, {
  String? name,
  String? operation,
  List<dynamic>? collection,
}) {
  if (input.isEmpty) {
    return [];
  }

  if (input.length > 1) {
    throw FhirPathEvaluationException(
      'The $name is required to be '
      'either an empty value, or a single value. Instead it evaluated to: $input.',
      operation: operation,
      collection: collection,
    );
  }

  final item = input.first;
  if (item is Map) {
    if (item['value'] != null && item['unit'] != null) {
      return [
        ValidatedQuantity(
          value: UcumDecimal.fromString(
            ((item['value']).value ?? double.nan).toString(),
          ),
          unit: item['unit'] as String,
        ),
      ];
    }
  }

  return input;
}