feature: FHIR R4 Inbound Facade

VigilCareClinicalAPI/Services/PatientService.cs

@@ -4,8 +4,13 @@ using Microsoft.EntityFrameworkCore;
 public class PatientService : IPatientService
 {
     private readonly AppDbContext _db;
+    private readonly IExternalIdentifierService _identifiers;
 
-    public PatientService(AppDbContext db) => _db = db;
+    public PatientService(AppDbContext db, IExternalIdentifierService identifiers)
+    {
+        _db = db;
+        _identifiers = identifiers;
+    }
 
     public async Task<Patient> RegisterAsync(RegisterPatientRequest req)
     {
@@ -122,6 +127,61 @@ public class PatientService : IPatientService
         return encounter;
     }
 
+    public async Task<Patient> RegisterOrUpdateByIdentifierAsync(FhirPatientUpsertRequest req)
+    {
+        var existingId = await _identifiers.ResolveInternalIdAsync(
+            ExternalResourceType.Patient, req.IdentifierSystem, req.IdentifierValue);
+
+        if (existingId.HasValue)
+        {
+            var patient = await _db.Patients.FindAsync(existingId.Value)
+                ?? throw new NotFoundException("Patient not found.", "PATIENT_NOT_FOUND");
+
+            patient.FirstName = req.FirstName;
+            patient.LastName = req.LastName;
+            patient.DateOfBirth = req.DateOfBirth;
+            patient.Gender = req.Gender;
+            patient.BloodType = req.BloodType;
+            patient.Allergies = req.Allergies;
+            patient.EmergencyContactName = req.EmergencyContactName;
+            patient.EmergencyContactPhone = req.EmergencyContactPhone;
+
+            await _db.SaveChangesAsync();
+            return patient;
+        }
+
+        // Use hospital identifier value as MRN when it fits the column constraint (max 20 chars).
+        var mrn = req.IdentifierValue.Length <= 20
+            ? req.IdentifierValue
+            : await GenerateMrnAsync();
+
+        var newPatient = new Patient
+        {
+            Id = Guid.NewGuid(),
+            Mrn = mrn,
+            FirstName = req.FirstName,
+            LastName = req.LastName,
+            DateOfBirth = req.DateOfBirth,
+            Gender = req.Gender,
+            BloodType = req.BloodType,
+            Allergies = req.Allergies,
+            EmergencyContactName = req.EmergencyContactName,
+            EmergencyContactPhone = req.EmergencyContactPhone,
+            CreatedAt = DateTimeOffset.UtcNow
+        };
+
+        _db.Patients.Add(newPatient);
+        await _db.SaveChangesAsync();
+
+        await _identifiers.LinkAsync(
+            ExternalResourceType.Patient,
+            newPatient.Id,
+            req.IdentifierSystem,
+            req.IdentifierValue);
+
+        return newPatient;
+    }
+
     private async Task<string> GenerateMrnAsync()
     {
         var count = await _db.Patients.CountAsync();