1 files changed, 42 insertions, 0 deletions

diff --git a/subprojects/store-query/src/main/java/tools/refinery/store/query/equality/SubstitutingLiteralHashCodeHelper.java b/subprojects/store-query/src/main/java/tools/refinery/store/query/equality/SubstitutingLiteralHashCodeHelper.java
new file mode 100644
index 00000000..754f6976
--- /dev/null
+++ b/subprojects/store-query/src/main/java/tools/refinery/store/query/equality/SubstitutingLiteralHashCodeHelper.java
@@ -0,0 +1,42 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package tools.refinery.store.query.equality;
+
+import tools.refinery.store.query.dnf.SymbolicParameter;
+import tools.refinery.store.query.term.Variable;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public class SubstitutingLiteralHashCodeHelper implements LiteralHashCodeHelper {
+        private final Map<Variable, Integer> assignedHashCodes = new LinkedHashMap<>();
+
+        // 0 is for {@code null}, so we start with 1.
+        private int next = 1;
+
+        public SubstitutingLiteralHashCodeHelper() {
+                this(List.of());
+        }
+
+        public SubstitutingLiteralHashCodeHelper(List<SymbolicParameter> parameters) {
+                for (var parameter : parameters) {
+                        getVariableHashCode(parameter.getVariable());
+                }
+        }
+
+        @Override
+        public int getVariableHashCode(Variable variable) {
+                if (variable == null) {
+                        return 0;
+                }
+                return assignedHashCodes.computeIfAbsent(variable, key -> {
+                        int sequenceNumber = next;
+                        next++;
+                        return variable.hashCodeWithSubstitution(sequenceNumber);
+                });
+        }
+}