1 files changed, 82 insertions, 0 deletions

diff --git a/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/basicdeferred/LeftJoinConstraint.java b/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/basicdeferred/LeftJoinConstraint.java
new file mode 100644
index 00000000..1c1a895e
--- /dev/null
+++ b/subprojects/interpreter/src/main/java/tools/refinery/interpreter/matchers/psystem/basicdeferred/LeftJoinConstraint.java
@@ -0,0 +1,82 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2016, Tamas Szabo, Istvan Rath and Daniel Varro
+ * Copyright (c) 2024 The Refinery Authors <https://refinery.tools/>
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.interpreter.matchers.psystem.basicdeferred;
+
+import tools.refinery.interpreter.matchers.context.IQueryMetaContext;
+import tools.refinery.interpreter.matchers.psystem.ITypeInfoProviderConstraint;
+import tools.refinery.interpreter.matchers.psystem.PBody;
+import tools.refinery.interpreter.matchers.psystem.PVariable;
+import tools.refinery.interpreter.matchers.psystem.TypeJudgement;
+import tools.refinery.interpreter.matchers.psystem.queries.PQuery;
+import tools.refinery.interpreter.matchers.tuple.Tuple;
+import tools.refinery.interpreter.matchers.tuple.Tuples;
+
+import java.util.Collections;
+import java.util.Set;
+
+public class LeftJoinConstraint extends PatternCallBasedDeferred implements ITypeInfoProviderConstraint {
+        protected PVariable resultVariable;
+        protected int optionalColumn;
+        protected Object defaultValue;
+
+        public LeftJoinConstraint(PBody pBody, Tuple actualParametersTuple, PQuery query, PVariable resultVariable,
+                                                          int optionalColumn, Object defaultValue) {
+                super(pBody, actualParametersTuple, query, Collections.singleton(resultVariable));
+                this.resultVariable = resultVariable;
+                this.optionalColumn = optionalColumn;
+                this.defaultValue = defaultValue;
+        }
+
+        public PVariable getResultVariable() {
+                return resultVariable;
+        }
+
+        public int getOptionalColumn() {
+                return optionalColumn;
+        }
+
+        public Object getDefaultValue() {
+                return defaultValue;
+        }
+
+        @Override
+        public Set<PVariable> getDeducedVariables() {
+                return Collections.singleton(resultVariable);
+        }
+
+        @Override
+        protected void doDoReplaceVariables(PVariable obsolete, PVariable replacement) {
+                if (resultVariable.equals(obsolete)) {
+                        resultVariable = replacement;
+                }
+        }
+
+        @Override
+        protected Set<PVariable> getCandidateQuantifiedVariables() {
+                return actualParametersTuple.getDistinctElements();
+        }
+
+        @Override
+        protected String toStringRest() {
+                return query.getFullyQualifiedName() + "@" + actualParametersTuple.toString() + "->"
+                                + resultVariable.toString();
+        }
+
+        @Override
+        public Set<TypeJudgement> getImpliedJudgements(IQueryMetaContext context) {
+                var optionalParameter = getReferredQuery().getParameters().get(optionalColumn);
+                var unaryType = optionalParameter.getDeclaredUnaryType();
+                if (unaryType != null && !context.isEnumerable(unaryType)) {
+                        // The outer join makes the result variable non-enumerable, since the default value might not be present in
+                        // the model.
+                        return Set.of(new TypeJudgement(unaryType, Tuples.staticArityFlatTupleOf(resultVariable)));
+                }
+                return Set.of();
+        }
+}