fix: Adds Created, LastSerialized, and BeforeSerialize for all entities. (#775)

* Adds `BeforeSerialized` for entities to handle cleanup.
* Adds `Created` and `LastSerialized` fields to all entities. While this is a big bloat, this will be necessary for identifying dangling references to other invalid entities.
* Changes formula for determining a valid reference to be _not null, not deleted, and reference's created date must be at or before the entities last serialized date_.
* Adds versioning to idx file and serializes `Created` and `LastSerialized`.
* Fixes Save Stats and also disables it by default.

Projects/Server/Serialization/BinaryFileReader.cs

@@ -30,6 +30,8 @@ namespace Server
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Close() => _reader.Close();
 
+        public DateTime LastSerialized { get; init; }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public string ReadString(bool intern = false)
         {

Projects/Server/Serialization/BinaryFileWriter.cs

@@ -35,7 +35,6 @@ namespace Server
 
         public override long Position => _position + Index;
 
-
         protected override int BufferSize => 81920;
 
         public override void Flush()

Projects/Server/Serialization/BufferReader.cs

@@ -37,6 +37,8 @@ namespace Server
             _encoding = encoding ?? TextEncoding.UTF8;
         }
 
+        public BufferReader(byte[] buffer, DateTime LastSerialized) : this(buffer) => LastSerialized = LastSerialized;
+
         public void Reset(byte[] newBuffer, out byte[] oldBuffer)
         {
             oldBuffer = _buffer;
@@ -45,6 +47,8 @@ namespace Server
         }
 
         // Compatible with BinaryReader.ReadString()
+        public DateTime LastSerialized { get; init; } = DateTime.MinValue;
+
         public string ReadString(bool intern = false)
         {
             if (!ReadBool())

Projects/Server/Serialization/IGenericReader.cs

@@ -21,6 +21,9 @@ namespace Server
 {
     public interface IGenericReader
     {
+        // Used to determine valid Entity deserialization
+        DateTime LastSerialized { get; init; }
+
         string ReadString(bool intern = false);
         long ReadLong();
         ulong ReadULong();

Projects/Server/Serialization/IGenericWriter.cs

@@ -39,14 +39,13 @@ namespace Server
 
         void Write(DateTime value)
         {
-            var ticks = (value.Kind switch
+            // If DateTimeKind is Unspecified, we can't assume it needs to be converted.
+            if (value.Kind == DateTimeKind.Local)
             {
-                DateTimeKind.Local       => value.ToUniversalTime(),
-                DateTimeKind.Unspecified  => value.ToLocalTime().ToUniversalTime(),
-                _                        => value
-            }).Ticks;
+                value = value.ToUniversalTime();
+            }
 
-            Write(ticks);
+            Write(value.Ticks);
         }
         void WriteDeltaTime(DateTime value)
         {
@@ -59,17 +58,16 @@ namespace Server
             if (value == DateTime.MaxValue)
             {
                 Write(long.MaxValue);
+                return;
             }
 
-            var ticks = (value.Kind switch
+            if (value.Kind == DateTimeKind.Local)
             {
-                DateTimeKind.Local       => value.ToUniversalTime(),
-                DateTimeKind.Unspecified  => value.ToLocalTime().ToUniversalTime(),
-                _                        => value
-            }).Ticks;
+                value = value.ToUniversalTime();
+            }
 
             // Technically supports negative deltas for times in the past
-            Write(ticks - DateTime.UtcNow.Ticks);
+            Write(value.Ticks - DateTime.UtcNow.Ticks);
         }
         void Write(IPAddress value)
         {

Projects/Server/Serialization/ISerializable.cs

@@ -20,10 +20,20 @@ namespace Server
 {
     public interface ISerializable
     {
+        // Should be serialized/deserialized with the index so it can be referenced by IGenericReader
+        DateTime Created { get; set; }
+
+        // Should be serialized/deserialized with the index so it can be referenced by IGenericReader
+        DateTime LastSerialized { get; protected internal set; }
         long SavePosition { get; protected internal set; }
         BufferWriter SaveBuffer { get; protected internal set; }
+
         int TypeRef { get; }
         Serial Serial { get; }
+
+        // Executed on every entity, before it's serialized.
+        // For example, this is used to clean up weak references and mark them dirty.
+        void BeforeSerialize();
         void Deserialize(IGenericReader reader);
         void Serialize(IGenericWriter writer);
         void Delete();
@@ -48,6 +58,8 @@ namespace Server
         {
             SaveBuffer ??= new BufferWriter(true);
 
+            BeforeSerialize();
+
             // Clean, don't bother serializing
             if (SavePosition > -1)
             {
@@ -55,6 +67,7 @@ namespace Server
                 return;
             }
 
+            LastSerialized = Core.Now;
             SaveBuffer.Seek(0, SeekOrigin.Begin);
             Serialize(SaveBuffer);
 
@@ -64,7 +77,7 @@ namespace Server
             }
             else
             {
-                SavePosition = -1;
+                this.MarkDirty();
             }
         }
     }