feature: HL7 FHIR R4 Integration

VigilCareRecordsAPI/Controllers/Fhir/FhirEncounterController.cs

@@ -0,0 +1,42 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+[ApiController]
+[Route("fhir/Encounter")]
+[Produces("application/fhir+json")]
+[Authorize]
+public class FhirEncounterController : ControllerBase
+{
+    private readonly IFhirService _fhir;
+
+    public FhirEncounterController(IFhirService fhir) => _fhir = fhir;
+
+    /// <summary>
+    /// FHIR read: GET /fhir/Encounter/{id}
+    /// </summary>
+    [HttpGet("{id}")]
+    public async Task<IActionResult> Read(string id)
+    {
+        var encounter = await _fhir.GetEncounterAsync(Guid.Parse(id));
+        if (encounter is null)
+            return NotFound(FhirErrorHelper.NotFound("Encounter", id));
+
+        return Ok(encounter);
+    }
+
+    /// <summary>
+    /// FHIR search: GET /fhir/Encounter?patient=X&status=Y&date=Z
+    /// Supports search by patient reference, status, and date range.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> Search(
+        [FromQuery] string? patient,
+        [FromQuery] string? status,
+        [FromQuery] string? date,
+        [FromQuery(Name = "_count")] int count = 20,
+        [FromQuery(Name = "_offset")] int offset = 0)
+    {
+        var bundle = await _fhir.SearchEncountersAsync(patient, status, date, count, offset);
+        return Ok(bundle);
+    }
+}

VigilCareRecordsAPI/Controllers/Fhir/FhirMetadataController.cs

@@ -0,0 +1,27 @@
+using Hl7.Fhir.Model;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+[ApiController]
+[Route("fhir")]
+[Produces("application/fhir+json")]
+public class FhirMetadataController : ControllerBase
+{
+    private readonly IFhirService _fhir;
+
+    public FhirMetadataController(IFhirService fhir) => _fhir = fhir;
+
+    /// <summary>
+    /// FHIR metadata: GET /fhir/metadata
+    /// Returns the server's CapabilityStatement describing supported
+    /// resources, interactions, and search parameters.
+    /// No authentication required (FHIR spec requirement).
+    /// </summary>
+    [HttpGet("metadata")]
+    [AllowAnonymous]
+    [ProducesResponseType(typeof(CapabilityStatement), StatusCodes.Status200OK)]
+    public IActionResult GetMetadata()
+    {
+        return Ok(_fhir.GetCapabilityStatement());
+    }
+}

VigilCareRecordsAPI/Controllers/Fhir/FhirObservationController.cs

@@ -0,0 +1,45 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+[ApiController]
+[Route("fhir/Observation")]
+[Produces("application/fhir+json")]
+[Authorize]
+public class FhirObservationController : ControllerBase
+{
+    private readonly IFhirService _fhir;
+
+    public FhirObservationController(IFhirService fhir) => _fhir = fhir;
+
+    /// <summary>
+    /// FHIR read: GET /fhir/Observation/{id}
+    /// </summary>
+    [HttpGet("{id}")]
+    public async Task<IActionResult> Read(string id)
+    {
+        var observation = await _fhir.GetObservationAsync(Guid.Parse(id));
+        if (observation is null)
+            return NotFound(FhirErrorHelper.NotFound("Observation", id));
+
+        return Ok(observation);
+    }
+
+    /// <summary>
+    /// FHIR search: GET /fhir/Observation?patient=X&code=Y&date=Z&category=W
+    /// Supports search by patient reference, LOINC code, date range, and category.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> Search(
+        [FromQuery] string? patient,
+        [FromQuery] string? code,
+        [FromQuery] string? date,
+        [FromQuery] string? category,
+        [FromQuery] string? encounter,
+        [FromQuery(Name = "_count")] int count = 50,
+        [FromQuery(Name = "_offset")] int offset = 0)
+    {
+        var bundle = await _fhir.SearchObservationsAsync(
+            patient, code, date, category, encounter, count, offset);
+        return Ok(bundle);
+    }
+}

VigilCareRecordsAPI/Controllers/Fhir/FhirPatientController.cs

@@ -0,0 +1,65 @@
+using Hl7.Fhir.Model;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+[ApiController]
+[Route("fhir/Patient")]
+[Produces("application/fhir+json")]
+[Authorize]
+public class FhirPatientController : ControllerBase
+{
+    private readonly IFhirService _fhir;
+
+    public FhirPatientController(IFhirService fhir) => _fhir = fhir;
+
+    /// <summary>
+    /// FHIR read: GET /fhir/Patient/{id}
+    /// Returns a single Patient resource by logical ID.
+    /// </summary>
+    [HttpGet("{id}")]
+    [ProducesResponseType(typeof(Hl7.Fhir.Model.Patient), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(Hl7.Fhir.Model.OperationOutcome), StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> Read(string id)
+    {
+        var patient = await _fhir.GetPatientAsync(Guid.Parse(id));
+        if (patient is null)
+            return NotFound(FhirErrorHelper.NotFound("Patient", id));
+
+        return Ok(patient);
+    }
+
+    /// <summary>
+    /// FHIR search: GET /fhir/Patient?name=X&birthdate=Y&identifier=Z
+    /// Supports search by name (contains), birthdate (exact), and MRN identifier.
+    /// Returns a FHIR Bundle of type searchset.
+    /// </summary>
+    [HttpGet]
+    [ProducesResponseType(typeof(Hl7.Fhir.Model.Bundle), StatusCodes.Status200OK)]
+    public async Task<IActionResult> Search(
+        [FromQuery] string? name,
+        [FromQuery] string? birthdate,
+        [FromQuery] string? identifier,
+        [FromQuery(Name = "_count")] int count = 20,
+        [FromQuery(Name = "_offset")] int offset = 0)
+    {
+        var bundle = await _fhir.SearchPatientsAsync(name, birthdate, identifier, count, offset);
+        return Ok(bundle);
+    }
+
+    /// <summary>
+    /// FHIR $everything: GET /fhir/Patient/{id}/$everything
+    /// Returns a Bundle containing the Patient resource, all Encounters,
+    /// and all Observations for the patient.
+    /// </summary>
+    [HttpGet("{id}/$everything")]
+    [ProducesResponseType(typeof(Bundle), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(OperationOutcome), StatusCodes.Status404NotFound)]
+    public async Task<IActionResult> Everything(string id)
+    {
+        var bundle = await _fhir.GetPatientEverythingAsync(Guid.Parse(id));
+        if (bundle is null)
+            return NotFound(FhirErrorHelper.NotFound("Patient", id));
+
+        return Ok(bundle);
+    }    
+}