1 files changed, 60 insertions, 0 deletions

diff --git a/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/StatefulMultisetAggregator.java b/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/StatefulMultisetAggregator.java
new file mode 100644
index 00000000..2798a252
--- /dev/null
+++ b/subprojects/store-query-viatra/src/main/java/tools/refinery/store/query/viatra/internal/pquery/StatefulMultisetAggregator.java
@@ -0,0 +1,60 @@
+package tools.refinery.store.query.viatra.internal.pquery;
+
+import org.eclipse.viatra.query.runtime.matchers.psystem.aggregations.IMultisetAggregationOperator;
+import tools.refinery.store.query.term.StatefulAggregate;
+import tools.refinery.store.query.term.StatefulAggregator;
+
+import java.util.stream.Stream;
+
+record StatefulMultisetAggregator<R, T>(StatefulAggregator<R, T> aggregator)
+        implements IMultisetAggregationOperator<T, StatefulAggregate<R, T>, R> {
+        @Override
+        public String getShortDescription() {
+                return getName();
+        }
+
+        @Override
+        public String getName() {
+                return aggregator.toString();
+        }
+
+        @Override
+        public StatefulAggregate<R, T> createNeutral() {
+                return aggregator.createEmptyAggregate();
+        }
+
+        @Override
+        public boolean isNeutral(StatefulAggregate<R, T> result) {
+                return result.isEmpty();
+        }
+
+        @Override
+        public StatefulAggregate<R, T> update(StatefulAggregate<R, T> oldResult, T updateValue, boolean isInsertion) {
+                if (isInsertion) {
+                        oldResult.add(updateValue);
+                } else {
+                        oldResult.remove(updateValue);
+                }
+                return oldResult;
+        }
+
+        @Override
+        public R getAggregate(StatefulAggregate<R, T> result) {
+                return result.getResult();
+        }
+
+        @Override
+        public R aggregateStream(Stream<T> stream) {
+                return aggregator.aggregateStream(stream);
+        }
+
+        @Override
+        public StatefulAggregate<R, T> clone(StatefulAggregate<R, T> original) {
+                return original.deepCopy();
+        }
+
+        @Override
+        public boolean contains(T value, StatefulAggregate<R, T> accumulator) {
+                return accumulator.contains(value);
+        }
+}