From ef4dfdc14c1cfb578c806c65300d298ea4a00ca2 Mon Sep 17 00:00:00 2001
From: Grahame Grieve <grahameg@gmail.ccom>
Date: Wed, 26 Feb 2025 15:35:44 +1100
Subject: [PATCH] Add _datatype slice when converting extensions to R4

---
 .../misc/ProfileVersionAdaptor.java           | 32 ++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/misc/ProfileVersionAdaptor.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/misc/ProfileVersionAdaptor.java
index 90b38d548c..08a50b1ca1 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/misc/ProfileVersionAdaptor.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/misc/ProfileVersionAdaptor.java
@@ -20,6 +20,7 @@
 import org.hl7.fhir.r5.model.ElementDefinition.DiscriminatorType;
 import org.hl7.fhir.r5.model.ElementDefinition.SlicingRules;
 import org.hl7.fhir.r5.model.ElementDefinition.TypeRefComponent;
+import org.hl7.fhir.r5.model.StringType;
 import org.hl7.fhir.r5.model.StructureDefinition.StructureDefinitionContextComponent;
 import org.hl7.fhir.r5.model.StructureDefinition.StructureDefinitionKind;
 import org.hl7.fhir.r5.model.StructureDefinition.TypeDerivationRule;
@@ -132,9 +133,12 @@ public StructureDefinition convert(StructureDefinition sd, List<ConversionMessag
             if (type == null) {
               throw new DefinitionException("unable to find definition for "+tr.getCode());
             }
-            log.add(new ConversionMessage("Replace the type "+tr.getCode()+" with a set of extensions for the content of the type", false));
+            log.add(new ConversionMessage("Replace the type "+tr.getCode()+" with a set of extensions for the content of the type along with the _datatype extension", false));
             int insPoint = sd.getDifferential().getElement().indexOf(lastExt);
             int offset = 1;
+            
+            // a slice extension for _datatype
+            offset = addDatatypeSlice(sd, offset, insPoint, lastExt, tr.getCode());
 
             // now, a slice extension for each thing in the data type differential
             for (ElementDefinition ted : type.getDifferential().getElement()) {
@@ -209,6 +213,32 @@ public StructureDefinition convert(StructureDefinition sd, List<ConversionMessag
     return sd;
   }
 
+  private int addDatatypeSlice(StructureDefinition sd, int offset, int insPoint, ElementDefinition base, String type) {
+    ElementDefinition ned = new ElementDefinition(base.getPath());
+    ned.setSliceName("_datatype");
+    ned.setShort("DataType name '"+type+"' from "+VersionUtilities.getNameForVersion(sCtxt.getVersion()));
+    ned.setDefinition(ned.getShort());
+    ned.setMin(1);
+    ned.setMax("1");
+    ned.addType().setCode("Extension").addProfile("http://hl7.org/fhir/StructureDefinition/_datatype");
+    offset = addDiffElement(sd, insPoint, offset, ned);
+//    // set the extensions to 0
+//    ElementDefinition need = new ElementDefinition(base.getPath()+".extension");
+//    need.setMax("0");
+//    offset = addDiffElement(sd, insPoint, offset, need);
+//    // fix the url 
+//    ned = new ElementDefinition(base.getPath()+".url");
+//    ned.setFixed(new UriType("http://hl7.org/fhir/StructureDefinition/_datatype"));
+//    offset = addDiffElement(sd, insPoint, offset, ned);
+    // set the value 
+    ned = new ElementDefinition(base.getPath()+".value[x]");
+    ned.setMin(1);
+    offset = addDiffElement(sd, insPoint, offset, ned);
+    ned.addType().setCode("string");
+    ned.setFixed(new StringType(type));
+    return offset;
+  }
+
   private int addDiffElement(StructureDefinition sd, int insPoint, int offset, ElementDefinition ned) {
     sd.getDifferential().getElement().add(insPoint+offset, ned);
     offset++;