execute method

@override List execute(List results, Map<String, dynamic> passed)

The iterable, nested function that evaluates the entire FHIRPath expression one object at a time

Implementation

@override
List execute(List results, Map<String, dynamic> passed) {
  // The regular .execute method on CommaParser does not implement the
  // short-circuit logic. Bespoke execution path required.
  if (value.first is! CommaParser) {
    // While this happens at eval time, it is due to incorrect syntax
    throw FhirPathInvalidExpressionException(
      'The function iif must have a criterion expression, followed by '
      ' a true-result collection, and an optional other-wise-result. '
      'Instead it has: ${value.first}',
    );
  }

  final criterionResultParser = value.first as CommaParser;
  final List<dynamic> criterionCollection = [];
  if (criterionResultParser.before.first is CommaParser) {
    criterionCollection.addAll(
        (criterionResultParser.before.first as CommaParser)
            .before
            .execute([], passed));
  } else {
    criterionCollection
        .addAll(criterionResultParser.before.execute([], passed));
  }

  final criterion = SingletonEvaluation.toBool(criterionCollection,
      name: 'criterion expression', operation: 'iif', collection: results);

  // Short-circuit: Only evaluate what matches the criterion.
  if (criterion == true) {
    final trueResultParser = criterionResultParser.before.first is CommaParser
        ? (criterionResultParser.before.first as CommaParser).after
        : (criterionResultParser.after.first is CommaParser)
            ? (criterionResultParser.after.first as CommaParser).before
            : criterionResultParser.after.first;

    final trueResult = trueResultParser.execute([], passed);

    return trueResult;
  } else {
    final otherwiseResultParser =
        (criterionResultParser.after.first is CommaParser)
            ? (criterionResultParser.after.first as CommaParser).after
            : criterionResultParser.before.first is CommaParser
                ? criterionResultParser.after
                : EmptySetParser();

    final otherwiseResult = otherwiseResultParser.execute([], passed);

    return otherwiseResult;
  }
}