From 2da31065e9201d8aaa16a81713b935e5d6343b39 Mon Sep 17 00:00:00 2001
From: halgari <tbaldridge@gmail.com>
Date: Wed, 12 Jun 2024 15:07:12 -0600
Subject: [PATCH] Fix a bug with retractions when used with Hashed blobs

---
 src/NexusMods.MnemonicDB.Abstractions/Datom.cs    | 15 +++++++++++++++
 .../ITransaction.cs                               |  6 ++++++
 .../TxFunctions/ExtensionMethods.cs               |  6 ++----
 .../InternalTransaction.cs                        |  6 ++++++
 src/NexusMods.MnemonicDB/Transaction.cs           |  7 +++++++
 .../ABackendTest.cs                               |  1 +
 6 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/src/NexusMods.MnemonicDB.Abstractions/Datom.cs b/src/NexusMods.MnemonicDB.Abstractions/Datom.cs
index c45140f3..86643dcc 100644
--- a/src/NexusMods.MnemonicDB.Abstractions/Datom.cs
+++ b/src/NexusMods.MnemonicDB.Abstractions/Datom.cs
@@ -109,4 +109,19 @@ public int Compare(Datom other, IndexType indexType)
                 throw new ArgumentOutOfRangeException(nameof(indexType), indexType, "Unknown index type");
         }
     }
+
+    /// <summary>
+    /// Clone this datom and return it as a retraction datom
+    /// </summary>
+    /// <returns></returns>
+    public Datom Retract()
+    {
+        var data = GC.AllocateUninitializedArray<byte>(RawSpan.Length);
+        var dataSpan = data.AsSpan();
+        RawSpan.CopyTo(dataSpan);
+        var prefix = MemoryMarshal.Read<KeyPrefix>(dataSpan);
+        var newPrefix = new KeyPrefix().Set(prefix.E, prefix.A, TxId.Tmp, true);
+        MemoryMarshal.Write(dataSpan, newPrefix);
+        return new Datom(data, registry);
+    }
 }
diff --git a/src/NexusMods.MnemonicDB.Abstractions/ITransaction.cs b/src/NexusMods.MnemonicDB.Abstractions/ITransaction.cs
index 6b0898f5..28b9fdcb 100644
--- a/src/NexusMods.MnemonicDB.Abstractions/ITransaction.cs
+++ b/src/NexusMods.MnemonicDB.Abstractions/ITransaction.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Threading.Tasks;
 using NexusMods.MnemonicDB.Abstractions.Attributes;
+using NexusMods.MnemonicDB.Abstractions.DatomIterators;
 using NexusMods.MnemonicDB.Abstractions.Models;
 using NexusMods.MnemonicDB.Abstractions.TxFunctions;
 
@@ -59,6 +60,11 @@ public interface ITransaction : IDisposable
     void Retract<TVal, TLowLevel>(EntityId entityId, Attribute<TVal, TLowLevel> attribute, TVal val)
         => Add(entityId, attribute, val, isRetract: true);
 
+    /// <summary>
+    /// Retract a specific datom
+    /// </summary>
+    void Add(Datom datom);
+
     /// <summary>
     ///     Commits the transaction
     /// </summary>
diff --git a/src/NexusMods.MnemonicDB.Abstractions/TxFunctions/ExtensionMethods.cs b/src/NexusMods.MnemonicDB.Abstractions/TxFunctions/ExtensionMethods.cs
index f2d480a7..b28f2f4a 100644
--- a/src/NexusMods.MnemonicDB.Abstractions/TxFunctions/ExtensionMethods.cs
+++ b/src/NexusMods.MnemonicDB.Abstractions/TxFunctions/ExtensionMethods.cs
@@ -92,11 +92,9 @@ private static bool ShouldRecursiveDelete(IDb db, IReadDatom referenceDatom)
 
     private static void DeleteThisOnly(ITransaction tx, IDb db, EntityId eid)
     {
-        var segment = db.Get(eid);
-        foreach (var datom in segment)
+        foreach (var datom in db.Get(eid))
         {
-            var resolved = datom.Resolved;
-            resolved.Retract(tx);
+            tx.Add(datom.Retract());
         }
     }
 }
diff --git a/src/NexusMods.MnemonicDB.Storage/InternalTransaction.cs b/src/NexusMods.MnemonicDB.Storage/InternalTransaction.cs
index 141f692e..f8e4f77f 100644
--- a/src/NexusMods.MnemonicDB.Storage/InternalTransaction.cs
+++ b/src/NexusMods.MnemonicDB.Storage/InternalTransaction.cs
@@ -4,6 +4,7 @@
 using System.Threading.Tasks;
 using NexusMods.MnemonicDB.Abstractions;
 using NexusMods.MnemonicDB.Abstractions.Attributes;
+using NexusMods.MnemonicDB.Abstractions.DatomIterators;
 using NexusMods.MnemonicDB.Abstractions.IndexSegments;
 using NexusMods.MnemonicDB.Abstractions.Models;
 using NexusMods.MnemonicDB.Abstractions.TxFunctions;
@@ -57,6 +58,11 @@ public void Attach(ITemporaryEntity entity)
         _temporaryEntities.Add(entity);
     }
 
+    public void Add(Datom datom)
+    {
+        datoms.Add(datom.RawSpan);
+    }
+
     /// <inheritdoc />
     public Task<ICommitResult> Commit()
     {
diff --git a/src/NexusMods.MnemonicDB/Transaction.cs b/src/NexusMods.MnemonicDB/Transaction.cs
index 9c4e0f58..f2a0fded 100644
--- a/src/NexusMods.MnemonicDB/Transaction.cs
+++ b/src/NexusMods.MnemonicDB/Transaction.cs
@@ -4,6 +4,7 @@
 using System.Threading.Tasks;
 using NexusMods.MnemonicDB.Abstractions;
 using NexusMods.MnemonicDB.Abstractions.Attributes;
+using NexusMods.MnemonicDB.Abstractions.DatomIterators;
 using NexusMods.MnemonicDB.Abstractions.IndexSegments;
 using NexusMods.MnemonicDB.Abstractions.Internals;
 using NexusMods.MnemonicDB.Abstractions.Models;
@@ -52,6 +53,12 @@ public void Add(EntityId entityId, ReferencesAttribute attribute, IEnumerable<En
         }
     }
 
+    /// <inheritdoc />
+    public void Add(Datom datom)
+    {
+        _datoms.Add(datom.RawSpan);
+    }
+
     public void Add(ITxFunction fn)
     {
         if (_committed)
diff --git a/tests/NexusMods.MnemonicDB.Storage.Tests/ABackendTest.cs b/tests/NexusMods.MnemonicDB.Storage.Tests/ABackendTest.cs
index ea19ddc2..a5dd723a 100644
--- a/tests/NexusMods.MnemonicDB.Storage.Tests/ABackendTest.cs
+++ b/tests/NexusMods.MnemonicDB.Storage.Tests/ABackendTest.cs
@@ -107,6 +107,7 @@ public async Task CanStoreDataInBlobs(IndexType type)
         await Verify(datoms.ToTable(Registry))
             .UseDirectory("BackendTestVerifyData")
             .UseParameters(type);
+
     }