Oaf merge and get strategy added

dhp-workflows/dhp-actionmanager/src/main/java/eu/dnetlib/dhp/actionmanager/OafMergeAndGet.java

@@ -0,0 +1,37 @@
+package eu.dnetlib.dhp.actionmanager;
+
+import eu.dnetlib.dhp.schema.oaf.Oaf;
+import eu.dnetlib.dhp.schema.oaf.OafEntity;
+import eu.dnetlib.dhp.schema.oaf.Relation;
+
+import java.util.function.BiFunction;
+
+public class OafMergeAndGet {
+
+    public enum Strategy {
+        MERGE_FROM_AND_GET, SELECT_NEWER_AND_GET
+    }
+
+    public static <T extends Oaf> SerializableSupplier<BiFunction<T, T, T>> functionFor(Strategy strategy) {
+        switch (strategy) {
+            case MERGE_FROM_AND_GET:
+                return () -> (x, y) -> {
+                    if (x instanceof Relation) {
+                        ((Relation) x).mergeFrom((Relation) y);
+                        return x;
+                    }
+                    ((OafEntity) x).mergeFrom((OafEntity) y);
+                    return x;
+                };
+            case SELECT_NEWER_AND_GET:
+                return () -> (x, y) -> {
+                    if (x.getLastupdatetimestamp() > y.getLastupdatetimestamp()) {
+                        return x;
+                    }
+                    return y;
+                };
+        }
+        throw new RuntimeException();
+    }
+
+}