FHIR Integrated Patient Module

• Decoupled, Service-Oriented Backend: 

The ASP.NET Core API is architected with a clean separation of concerns, using dependency injection to manage services for FHIR interaction, database context, auditing, and encryption. This modular design makes the system highly maintainable and scalable.

• Robust Security & Compliance Framework: 

The API is secured using a fully configured JWT Bearer authentication system that validates every request by issuer, audience, lifetime, and signing key. All critical operations are logged via a dedicated audit service to support HIPAA compliance requirements.

• The Problem: 

The HAPI FHIR server returned birthDate fields in a full xsd:dateTime format (e.g., 2017-09-05T22:00:00.000Z). However, the official FHIR R4 specification, strictly enforced by the .NET
Hl7.Fhir.R4 library used for deserialization, mandates that birthDate must be in the xsd:date format (YYYY-MM-DD). This mismatch caused the deserialization process to fail, triggering an unhandled exception and crashing the API endpoint with a 500 Internal Server Error.

• The Solution: 

Instead of treating this as a simple bug, a defensive, proactive solution was engineered within the FhirService.SearchPatientsAsync method. Before the raw JSON response from the FHIR server is passed to the Hl7.Fhir.R4 parser, a custom pre-processing step manually and reliably truncates the time component from any birthDate field in the raw string data. This cleansed, now-compliant JSON is then passed to the deserialiser, completely preventing the exception. This demonstrates an ability to anticipate and neutralise integration failures with external systems before they impact the application.