Fix return value when hitting FPE limitation (#109)

* Fixed bug in setting metrics and metadata
* When hitting FPE limitation return either null or the original value according to MapFailureStrategy

src/main/java/no/ssb/dlp/pseudo/service/pseudo/RecordMapProcessorFactory.java

@@ -7,6 +7,7 @@
 import no.ssb.dapla.dlp.pseudo.func.PseudoFuncOutput;
 import no.ssb.dapla.dlp.pseudo.func.TransformDirection;
 import no.ssb.dapla.dlp.pseudo.func.fpe.FpeFunc;
+import no.ssb.dapla.dlp.pseudo.func.map.MapFailureStrategy;
 import no.ssb.dapla.dlp.pseudo.func.map.MapFunc;
 import no.ssb.dapla.dlp.pseudo.func.map.MapFuncConfig;
 import no.ssb.dapla.dlp.pseudo.func.tink.fpe.TinkFpeFunc;
@@ -28,6 +29,8 @@
 
 import java.util.Collection;
 import java.util.List;
+import java.util.Map;
+import java.util.Optional;
 
 import static no.ssb.dlp.pseudo.core.PseudoOperation.DEPSEUDONYMIZE;
 import static no.ssb.dlp.pseudo.core.PseudoOperation.PSEUDONYMIZE;
@@ -123,7 +126,7 @@ private String process(PseudoOperation operation,
                             funcDeclaration.getFuncName().equals(PseudoFuncNames.MAP_SID_FF31)
             )) {
                 metadataProcessor.addMetric(FieldMetric.FPE_LIMITATION);
-                return varValue;
+                return getMapFailureStrategy(funcDeclaration.getArgs()) == MapFailureStrategy.RETURN_ORIGINAL ? varValue : null;
             }
 
             final boolean isSidMapping = funcDeclaration.getFuncName().equals(PseudoFuncNames.MAP_SID)
@@ -184,4 +187,10 @@ protected static List<PseudoKeyset> pseudoKeysetsOf(List<EncryptedKeysetWrapper>
                 .toList();
     }
 
+    private MapFailureStrategy getMapFailureStrategy(Map<String, String> config) {
+        return Optional.ofNullable(
+                config.getOrDefault(MapFuncConfig.Param.MAP_FAILURE_STRATEGY, null)
+        ).map(String::valueOf).map(MapFailureStrategy::valueOf).orElse(MapFailureStrategy.RETURN_ORIGINAL);
+    }
+
 }