From 4da0e165b5d6a7d9900ae4fbc55edc3b4bc617a8 Mon Sep 17 00:00:00 2001
From: Martin Ledvinka <martin.ledvinka@fel.cvut.cz>
Date: Fri, 30 Jun 2023 16:11:30 +0200
Subject: [PATCH] [Enhancement #161] Support attribute language tag extraction
 (and comparison) in SOQL.

---
 .../src/main/antlr4/cz/cvut/kbss/jopa/query/soql/Soql.g4 | 1 +
 .../java/cz/cvut/kbss/jopa/query/soql/SoqlConstants.java | 5 +++++
 .../kbss/jopa/query/soql/SoqlFunctionTranslator.java     | 1 +
 .../kbss/jopa/environment/utils/MetamodelFactory.java    | 1 +
 .../cvut/kbss/jopa/query/soql/SoqlQueryParserTest.java   | 9 +++++++++
 5 files changed, 17 insertions(+)

diff --git a/jopa-impl/src/main/antlr4/cz/cvut/kbss/jopa/query/soql/Soql.g4 b/jopa-impl/src/main/antlr4/cz/cvut/kbss/jopa/query/soql/Soql.g4
index ac9ba1fc3..880e9fc37 100644
--- a/jopa-impl/src/main/antlr4/cz/cvut/kbss/jopa/query/soql/Soql.g4
+++ b/jopa-impl/src/main/antlr4/cz/cvut/kbss/jopa/query/soql/Soql.g4
@@ -102,6 +102,7 @@ functionsReturningStrings
    | 'SUBSTRING' '(' stringExpression ',' simpleArithmeticExpression ',' simpleArithmeticExpression ')'
    | 'LOWER' '(' stringExpression ')'
    | 'UPPER' '(' stringExpression ')'
+   | 'LANG' '(' whereClauseParam ')'
    ;
 
 simpleArithmeticExpression
diff --git a/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlConstants.java b/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlConstants.java
index 337b0036e..ee2631d67 100644
--- a/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlConstants.java
+++ b/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlConstants.java
@@ -121,6 +121,11 @@ public static class Functions {
          */
         public static final String FLOOR = "FLOOR";
 
+        /**
+         * Returns language tag of a literal, if it has one. Returns an empty string if it has no language tag.
+         */
+        public static final String LANG = "LANG";
+
         private Functions() {
             throw new AssertionError();
         }
diff --git a/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlFunctionTranslator.java b/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlFunctionTranslator.java
index f48befa7e..037f8f76d 100644
--- a/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlFunctionTranslator.java
+++ b/jopa-impl/src/main/java/cz/cvut/kbss/jopa/query/soql/SoqlFunctionTranslator.java
@@ -35,6 +35,7 @@ private static Map<String, String> initFunctions() {
         map.put(SoqlConstants.Functions.ABS, "ABS");
         map.put(SoqlConstants.Functions.CEIL, "CEIL");
         map.put(SoqlConstants.Functions.FLOOR, "FLOOR");
+        map.put(SoqlConstants.Functions.LANG, "lang");
         return map;
     }
 
diff --git a/jopa-impl/src/test/java/cz/cvut/kbss/jopa/environment/utils/MetamodelFactory.java b/jopa-impl/src/test/java/cz/cvut/kbss/jopa/environment/utils/MetamodelFactory.java
index a8f58a1fb..544d544e0 100644
--- a/jopa-impl/src/test/java/cz/cvut/kbss/jopa/environment/utils/MetamodelFactory.java
+++ b/jopa-impl/src/test/java/cz/cvut/kbss/jopa/environment/utils/MetamodelFactory.java
@@ -1286,6 +1286,7 @@ static void initOwlClassUMocks(IdentifiableEntityType<OWLClassU> et, SingularAtt
         when(et.getJavaType()).thenReturn(OWLClassU.class);
         when(id.getJavaField()).thenReturn(OWLClassU.getIdField());
         when(id.getDeclaringType()).thenReturn(et);
+        when(id.getName()).thenReturn(OWLClassU.getIdField().getName());
         when(et.getIRI()).thenReturn(IRI.create(OWLClassU.getClassIri()));
         when(et.getName()).thenReturn(OWLClassU.class.getSimpleName());
         when(et.getFieldSpecifications())
diff --git a/jopa-impl/src/test/java/cz/cvut/kbss/jopa/query/soql/SoqlQueryParserTest.java b/jopa-impl/src/test/java/cz/cvut/kbss/jopa/query/soql/SoqlQueryParserTest.java
index 4581a62df..e63adf941 100644
--- a/jopa-impl/src/test/java/cz/cvut/kbss/jopa/query/soql/SoqlQueryParserTest.java
+++ b/jopa-impl/src/test/java/cz/cvut/kbss/jopa/query/soql/SoqlQueryParserTest.java
@@ -739,4 +739,13 @@ void parseQueryWithRelatedAttributeAndIdentifierIsCommutative() {
         parseAndAssertEquality(soqlIdFirst, expectedSparql);
         parseAndAssertEquality(soqlIdSecond, expectedSparql);
     }
+
+    @Test
+    void parseQuerySupportsLangExtractionAndComparison() {
+        final String soql = "SELECT u FROM OWLClassU u WHERE LANG(u.singularStringAtt) = :language";
+        final String expectedSparql = "SELECT ?x WHERE { ?x a " + strUri(Vocabulary.c_OwlClassU) + " . " +
+                "?x " + strUri(Vocabulary.P_U_SINGULAR_MULTILINGUAL_ATTRIBUTE) + " ?uSingularStringAtt . " +
+                "FILTER (lang(?uSingularStringAtt) = ?language) }";
+        parseAndAssertEquality(soql, expectedSparql);
+    }
 }