public override async Task WriteResponseBodyAsync()

in src/Microsoft.Health.Fhir.Shared.Api/Features/Formatters/FhirJsonOutputFormatter.cs [70:167]
87 lines of code
16 McCabe index (conditional complexity)

        public override async Task WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
        {
            EnsureArg.IsNotNull(context, nameof(context));
            EnsureArg.IsNotNull(selectedEncoding, nameof(selectedEncoding));

            context.HttpContext.AllowSynchronousIO();

            HttpResponse response = context.HttpContext.Response;

            var elementsSearchParameter = context.HttpContext.GetElementsOrDefault();
            var summarySearchParameter = context.HttpContext.GetSummaryTypeOrDefault();
            var pretty = context.HttpContext.GetPrettyOrDefault();
            var hasElements = elementsSearchParameter?.Any() == true;
            Resource resource = null;
            var summaryProvider = _modelInfoProvider.StructureDefinitionSummaryProvider;
            var additionalElements = new HashSet<string>();

            if (context.Object is Hl7.Fhir.Model.Bundle)
            {
                var bundle = context.Object as Hl7.Fhir.Model.Bundle;
                resource = bundle;

                if (hasElements ||
                    summarySearchParameter != Hl7.Fhir.Rest.SummaryType.False ||
                    !bundle.Entry.All(x => x is RawBundleEntryComponent))
                {
                    // _elements is not supported for a raw resource, revert to using FhirJsonSerializer
                    foreach (var rawBundleEntryComponent in bundle.Entry)
                    {
                        if (rawBundleEntryComponent is RawBundleEntryComponent)
                        {
                            rawBundleEntryComponent.Resource = ((RawBundleEntryComponent)rawBundleEntryComponent).ResourceElement.ToPoco<Resource>(_deserializer);
                            if (hasElements)
                            {
                                var typeinfo = summaryProvider.Provide(rawBundleEntryComponent.Resource.TypeName);
                                var required = typeinfo.GetElements().Where(e => e.IsRequired).ToList();
                                additionalElements.UnionWith(required.Select(x => x.ElementName));
                            }
                        }
                    }
                }
                else
                {
                    await _bundleSerializer.Serialize(context.Object as Hl7.Fhir.Model.Bundle, context.HttpContext.Response.Body, pretty);
                    return;
                }
            }
            else if (context.Object is RawResourceElement)
            {
                if (hasElements ||
                    summarySearchParameter != Hl7.Fhir.Rest.SummaryType.False)
                {
                    // _elements is not supported for a raw resource, revert to using FhirJsonSerializer
                    resource = (context.Object as RawResourceElement).ToPoco<Resource>(_deserializer);
                    if (hasElements)
                    {
                        var typeinfo = summaryProvider.Provide(resource.TypeName);
                        var required = typeinfo.GetElements().Where(e => e.IsRequired).ToList();
                        additionalElements.UnionWith(required.Select(x => x.ElementName));
                    }
                }
                else
                {
                    await (context.Object as RawResourceElement).SerializeToStreamAsUtf8Json(context.HttpContext.Response.Body);
                    return;
                }
            }
            else
            {
                resource = (Resource)context.Object;
                if (hasElements)
                {
                    var typeinfo = summaryProvider.Provide(resource.TypeName);
                    var required = typeinfo.GetElements().Where(e => e.IsRequired).ToList();
                    additionalElements.UnionWith(required.Select(x => x.ElementName));
                }
            }

            if (hasElements)
            {
                additionalElements.UnionWith(elementsSearchParameter);
                additionalElements.Add("meta");
            }

            using (TextWriter textWriter = context.WriterFactory(response.Body, selectedEncoding))
            using (var jsonWriter = new JsonTextWriter(textWriter))
            {
                jsonWriter.ArrayPool = _charPool;

                if (pretty)
                {
                    jsonWriter.Formatting = Formatting.Indented;
                }

                _fhirJsonSerializer.Serialize(resource, jsonWriter, summarySearchParameter, hasElements ? additionalElements.ToArray() : null);
                await jsonWriter.FlushAsync();
            }
        }