private IReadOnlyList <ISearchValue> ExtractSearchValues(
string searchParameterDefinitionUrl,
SearchParamType?searchParameterType,
IReadOnlyList <string> allowedReferenceResourceTypes,
ITypedElement element,
string fhirPathExpression,
EvaluationContext context)
{
Debug.Assert(searchParameterType != SearchParamType.Composite, "The search parameter must be non-composite.");
var results = new List <ISearchValue>();
// For simple value type, we can parse the expression directly.
IEnumerable <ITypedElement> extractedValues = Enumerable.Empty <ITypedElement>();
try
{
extractedValues = element.Select(fhirPathExpression, context);
}
catch (Exception ex)
{
_logger.LogWarning(
ex,
"Failed to extract the values using '{FhirPathExpression}' against '{ElementType}'.",
fhirPathExpression,
element.GetType());
}
Debug.Assert(extractedValues != null, "The extracted values should not be null.");
// If there is target set, then filter the extracted values to only those types.
if (searchParameterType == SearchParamType.Reference &&
allowedReferenceResourceTypes?.Count > 0)
{
List <string> targetResourceTypes = _targetTypesLookup.GetOrAdd(searchParameterDefinitionUrl, _ =>
{
return(allowedReferenceResourceTypes.Select(t => t.ToString()).ToList());
});
// TODO: The expression for reference search parameters in STU3 has issues.
// The reference search parameter could be pointing to an element that can be multiple types. For example,
// the Appointment.participant.actor can be type of Patient, Practitioner, Related Person, Location, and so on.
// Some search parameter could refer to this property but restrict to certain types. For example,
// Appointment's location search parameter is returned only when Appointment.participant.actor is Location element.
// The STU3 expressions don't have this restriction so everything is being returned. This is addressed in R4 release (see
// http://community.fhir.org/t/expression-seems-incorrect-for-reference-search-parameter-thats-only-applicable-to-certain-types/916/2).
// Therefore, for now, we will need to compare the reference value itself (which can be internal or external references), and restrict
// the values ourselves.
extractedValues = extractedValues.Where(ev =>
{
if (ev.InstanceType.Equals("ResourceReference", StringComparison.OrdinalIgnoreCase))
{
return(ev.Scalar("reference") is string rr && targetResourceTypes.Any(trt => rr.Contains(trt, StringComparison.Ordinal)));
}
return(true);
});
}
foreach (var extractedValue in extractedValues)
{
if (!_fhirElementTypeConverterManager.TryGetConverter(extractedValue.InstanceType, GetSearchValueTypeForSearchParamType(searchParameterType), out ITypedElementToSearchValueConverter converter))
{
_logger.LogWarning(
"The FHIR element '{ElementType}' is not supported.",
extractedValue.InstanceType);
continue;
}
IEnumerable <ISearchValue> searchValues = converter.ConvertTo(extractedValue);
if (searchValues != null)
{
if (searchParameterType == SearchParamType.Reference && allowedReferenceResourceTypes?.Count == 1)
{
// For references, if the type is not specified in the reference string, we can set the type on the search value because
// in this case it can only be of one type.
string singleAllowedResourceType = allowedReferenceResourceTypes[0];
foreach (ISearchValue searchValue in searchValues)
{
if (searchValue is ReferenceSearchValue rsr && string.IsNullOrEmpty(rsr.ResourceType))
{
results.Add(new ReferenceSearchValue(rsr.Kind, rsr.BaseUri, singleAllowedResourceType, rsr.ResourceId));
}
else
{
results.Add(searchValue);
}
}
}
