Refactor ZeroaryFunction and Binding classes to fix now() function

The Binding class has been updated to store and retrieve the current time value, allowing the now() function to return the same value during processing. This improves the consistency and reliability of the now() function. Fix #168.

sparql/src/main/java/fr/inria/corese/sparql/triple/function/core/ZeroaryFunction.java

@@ -1,35 +1,62 @@
 package fr.inria.corese.sparql.triple.function.core;
 
+import java.util.Optional;
+
+import fr.inria.corese.kgram.api.core.ExprType;
+import fr.inria.corese.kgram.api.query.Environment;
+import fr.inria.corese.kgram.api.query.Producer;
 import fr.inria.corese.sparql.api.Computer;
 import fr.inria.corese.sparql.api.IDatatype;
 import fr.inria.corese.sparql.datatype.CoreseDouble;
 import fr.inria.corese.sparql.datatype.DatatypeMap;
+import fr.inria.corese.sparql.exceptions.EngineException;
 import fr.inria.corese.sparql.triple.function.term.Binding;
 import fr.inria.corese.sparql.triple.function.term.TermEval;
-import fr.inria.corese.kgram.api.core.ExprType;
-import fr.inria.corese.kgram.api.query.Environment;
-import fr.inria.corese.sparql.exceptions.EngineException;
-import fr.inria.corese.kgram.api.query.Producer;
 
 /**
  *
  * @author Olivier Corby, Wimmics INRIA I3S, 2017
  *
  */
 public class ZeroaryFunction extends TermEval {
-
-    public ZeroaryFunction(){}
-
-    public ZeroaryFunction(String name){
+
+    public ZeroaryFunction() {
+    }
+
+    public ZeroaryFunction(String name) {
         super(name);
     }
-    
+
     @Override
     public IDatatype eval(Computer eval, Binding b, Environment env, Producer p) throws EngineException {
-        switch (oper()){
-            case ExprType.RANDOM:   return CoreseDouble.create(Math.random());
-            case ExprType.NOW:      return DatatypeMap.newDate();
-        } 
+        switch (oper()) {
+            case ExprType.RANDOM:
+                return CoreseDouble.create(Math.random());
+            case ExprType.NOW:
+                return this.getOrSetCurrentTime(b);
+
+        }
         return null;
     }
+
+    /**
+     * Returns the current time, or sets it if it is not already set.
+     * 
+     * @param binding The Binding to get or set the current time in
+     * @return The current time
+     */
+    private IDatatype getOrSetCurrentTime(Binding binding) {
+
+        // Check if current time is already set in the Binding
+        Optional<IDatatype> savedNowTime = binding.getNowValue();
+
+        if (savedNowTime.isPresent()) {
+            return savedNowTime.get();
+        } else {
+            // If not set, create a new time, save it, and return it
+            IDatatype nowValue = DatatypeMap.newDate();
+            binding.setNowValue(nowValue);
+            return nowValue;
+        }
+    }
 }

sparql/src/main/java/fr/inria/corese/sparql/triple/function/term/Binding.java

@@ -20,6 +20,8 @@
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Optional;
+
 import org.slf4j.LoggerFactory;
 import org.slf4j.Logger;
 
@@ -112,6 +114,9 @@ public class Share {
         // transformer also records its Binding and hence its Visitor
         private Object transformerVisitor;
 
+        // Enables function now() to return the same value during processing
+        private Optional<IDatatype> savNowValue = Optional.empty();
+
         public Object getTransformerVisitor() {
             return transformerVisitor;
         }
@@ -120,6 +125,14 @@ public void setTransformerVisitor(Object transformerVisitor) {
             this.transformerVisitor = transformerVisitor;
         }
 
+        public Optional<IDatatype> getSavNowValue() {
+            return savNowValue;
+        }
+
+        public void setNowValue(IDatatype nowValue) {
+            this.savNowValue = Optional.ofNullable(nowValue);
+        }
+
     }
 
     public static Binding create() {
@@ -662,6 +675,14 @@ void shareGlobalVariable(Binding b) {
         setGlobalVariableNames(b.getGlobalVariableNames());
         setGlobalVariableValues(b.getGlobalVariableValues());
     }
+
+    public Optional<IDatatype> getNowValue() {
+        return getShare().getSavNowValue();
+    }
+
+    public void setNowValue(IDatatype nowValue) {
+        getShare().setNowValue(nowValue);
+    }
 
     public HashMap<String, Variable> getGlobalVariableNames() {
         return globalVariable;