From 68f711f70d56badde50cb8cb3f817fde06ffe55d Mon Sep 17 00:00:00 2001
From: mdesalvo <floating_point_9@msn.com>
Date: Sat, 5 Oct 2024 11:39:45 +0200
Subject: [PATCH] Reapply old code for collection

---
 RDFSharp.Test/Model/RDFCollectionTest.cs | 26 ++++--------------------
 RDFSharp/Model/RDFCollection.cs          | 26 ++++++++++++++++--------
 2 files changed, 22 insertions(+), 30 deletions(-)

diff --git a/RDFSharp.Test/Model/RDFCollectionTest.cs b/RDFSharp.Test/Model/RDFCollectionTest.cs
index 17784e52..ce6b8691 100644
--- a/RDFSharp.Test/Model/RDFCollectionTest.cs
+++ b/RDFSharp.Test/Model/RDFCollectionTest.cs
@@ -37,6 +37,7 @@ public void ShouldCreateEmptyCollection(RDFModelEnums.RDFItemTypes itemType)
             Assert.IsTrue(coll.ItemsCount == 0);
             Assert.IsTrue(coll.ReificationSubject.Equals(RDFVocabulary.RDF.NIL));
             Assert.IsTrue(coll.InternalReificationSubject.IsBlank);
+            Assert.IsFalse(coll.AcceptDuplicates);
 
             int i = 0;
             foreach (RDFPatternMember item in coll) i++;
@@ -86,7 +87,7 @@ public void ShouldAddItemsToCollection(RDFModelEnums.RDFItemTypes itemType)
                 coll.AddItem(new RDFResource("http://item/"));
             }
 
-            Assert.IsTrue(coll.ItemsCount == 2);
+            Assert.IsTrue(coll.ItemsCount == 1);
             Assert.IsFalse(coll.ReificationSubject.Equals(RDFVocabulary.RDF.NIL));
         }
 
@@ -162,7 +163,7 @@ public void ShouldNotRemoveItemsFromCollectionBecauseWrongType(RDFModelEnums.RDF
                 coll.RemoveItem(new RDFPlainLiteral("lit"));
             }
 
-            Assert.IsTrue(coll.ItemsCount == 2);
+            Assert.IsTrue(coll.ItemsCount == 1);
             Assert.IsFalse(coll.ReificationSubject.Equals(RDFVocabulary.RDF.NIL));
         }
 
@@ -185,7 +186,7 @@ public void ShouldNotRemoveItemsFromCollectionBecauseNull(RDFModelEnums.RDFItemT
                 coll.RemoveItem(null as RDFResource);
             }
 
-            Assert.IsTrue(coll.ItemsCount == 2);
+            Assert.IsTrue(coll.ItemsCount == 1);
             Assert.IsFalse(coll.ReificationSubject.Equals(RDFVocabulary.RDF.NIL));
         }
 
@@ -279,25 +280,6 @@ public void ShouldReifyCollectionWithTwoItems(RDFModelEnums.RDFItemTypes itemTyp
             Assert.IsTrue(graph.SelectTriplesByPredicate(RDFVocabulary.RDF.REST)
                                .TriplesCount == 2);
         }
-
-        [TestMethod]
-        public void ShouldReifyCollectionWithInternallyMixedItems()
-        {
-            RDFCollection coll = new RDFCollection(RDFModelEnums.RDFItemTypes.Resource);
-            coll.AddItemInternal(new RDFPlainLiteral("lit1"));
-            coll.AddItemInternal(new RDFResource("http://item1/"));
-            RDFGraph graph = coll.ReifyCollection();
-
-            Assert.IsNotNull(graph);
-            Assert.IsTrue(graph.TriplesCount == 6);
-            Assert.IsTrue(graph.SelectTriplesByPredicate(RDFVocabulary.RDF.TYPE)
-                               .SelectTriplesByObject(RDFVocabulary.RDF.LIST)
-                               .TriplesCount == 2);
-            Assert.IsTrue(graph.SelectTriplesByPredicate(RDFVocabulary.RDF.FIRST)
-                               .TriplesCount == 2);
-            Assert.IsTrue(graph.SelectTriplesByPredicate(RDFVocabulary.RDF.REST)
-                               .TriplesCount == 2);
-        }
         #endregion
     }
 }
\ No newline at end of file
diff --git a/RDFSharp/Model/RDFCollection.cs b/RDFSharp/Model/RDFCollection.cs
index 51590061..3d6d92ce 100644
--- a/RDFSharp/Model/RDFCollection.cs
+++ b/RDFSharp/Model/RDFCollection.cs
@@ -53,6 +53,11 @@ public int ItemsCount
         public IEnumerator<RDFPatternMember> ItemsEnumerator
             => Items.GetEnumerator();
 
+        /// <summary>
+        /// Flag indicating that this collection exceptionally accepts duplicates
+        /// </summary>
+        internal bool AcceptDuplicates { get; set; }
+
         /// <summary>
         /// List of the items collected by the collection
         /// </summary>
@@ -64,11 +69,13 @@ public IEnumerator<RDFPatternMember> ItemsEnumerator
         /// Default ctor to build an empty collection of the given type
         /// (initial configuration of the collection is "rdf:Nil")
         /// </summary>
-        public RDFCollection(RDFModelEnums.RDFItemTypes itemType) 
+        public RDFCollection(RDFModelEnums.RDFItemTypes itemType) : this(itemType, false) { }
+        internal RDFCollection(RDFModelEnums.RDFItemTypes itemType, bool acceptDuplicates)
         {
             ItemType = itemType;
             ReificationSubject = RDFVocabulary.RDF.NIL;
             InternalReificationSubject = new RDFResource();
+            AcceptDuplicates = acceptDuplicates;
             Items = new List<RDFPatternMember>();
         }
         #endregion
@@ -115,11 +122,14 @@ public RDFCollection AddItem(RDFLiteral item)
         /// </summary>
         internal void AddItemInternal(RDFPatternMember item)
         {
-            //Add item to collection
-            Items.Add(item);
-            //Update ReificationSubject (if collection has left "rdf:nil" configuration)
-            if (ItemsCount == 1)
-                ReificationSubject = InternalReificationSubject;
+            if (AcceptDuplicates || Items.Find(x => x.Equals(item)) == null)
+            {
+                //Add item to collection
+                Items.Add(item);
+                //Update ReificationSubject (if collection has left "rdf:nil" configuration)
+                if (ItemsCount == 1)
+                    ReificationSubject = InternalReificationSubject;
+            }
         }
         #endregion
 
@@ -188,8 +198,8 @@ public RDFGraph ReifyCollection()
                 reifColl.AddTriple(new RDFTriple(reifSubj, RDFVocabulary.RDF.TYPE, RDFVocabulary.RDF.LIST));
 
                 //  Subject -> rdf:first -> RDFCollection.ITEM[i]
-                if (collectionItem is RDFResource collectionItemResource)
-                    reifColl.AddTriple(new RDFTriple(reifSubj, RDFVocabulary.RDF.FIRST, collectionItemResource));
+                if (ItemType == RDFModelEnums.RDFItemTypes.Resource)
+                    reifColl.AddTriple(new RDFTriple(reifSubj, RDFVocabulary.RDF.FIRST, (RDFResource)collectionItem));
                 else
                     reifColl.AddTriple(new RDFTriple(reifSubj, RDFVocabulary.RDF.FIRST, (RDFLiteral)collectionItem));