feat(runtime): freeze initial placement inbound admission

src/AcDream.Runtime/Entities/RuntimeInitialCreateAdmissionFreezer.cs

@@ -0,0 +1,92 @@
+using System.Collections.Immutable;
+using AcDream.Core.Net;
+using AcDream.Core.Net.Messages;
+
+namespace AcDream.Runtime.Entities;
+
+/// <summary>
+/// Takes ownership of decoded wire collections retained beyond the inbound
+/// callback. The protocol records expose read-only views, but those views may
+/// still wrap parser-owned arrays. Initial-placement admission must therefore
+/// copy every collection before an asynchronous residence lease can retain it.
+/// </summary>
+internal static class RuntimeInitialCreateAdmissionFreezer
+{
+    internal static WorldSession.EntitySpawn Freeze(
+        in WorldSession.EntitySpawn spawn) => spawn with
+    {
+        AnimPartChanges = spawn.AnimPartChanges.ToImmutableArray(),
+        TextureChanges = spawn.TextureChanges.ToImmutableArray(),
+        SubPalettes = spawn.SubPalettes.ToImmutableArray(),
+        MotionState = Freeze(spawn.MotionState),
+        Physics = Freeze(spawn.Physics),
+    };
+
+    internal static ObjDescEvent.Parsed Freeze(
+        in ObjDescEvent.Parsed update) => update with
+    {
+        ModelData = Freeze(update.ModelData),
+    };
+
+    internal static WorldSession.EntityMotionUpdate Freeze(
+        in WorldSession.EntityMotionUpdate update) => update with
+    {
+        MotionState = Freeze(update.MotionState),
+    };
+
+    internal static RuntimeInitialCreateTailAction Freeze(
+        in RuntimeInitialCreateTailAction action) => action with
+    {
+        Description = Freeze(action.Description),
+        ObjDesc = action.ObjDesc is { } objDesc
+            ? Freeze(objDesc)
+            : null,
+        Movement = action.Movement is { } movement
+            ? Freeze(movement)
+            : null,
+        WeenieDescription = action.WeenieDescription is { } spawn
+            ? Freeze(spawn)
+            : null,
+    };
+
+    private static CreateObject.ModelData Freeze(
+        in CreateObject.ModelData model) => model with
+    {
+        SubPalettes = model.SubPalettes.ToImmutableArray(),
+        TextureChanges = model.TextureChanges.ToImmutableArray(),
+        AnimPartChanges = model.AnimPartChanges.ToImmutableArray(),
+    };
+
+    private static CreateObject.ServerMotionState Freeze(
+        in CreateObject.ServerMotionState motion) => motion with
+    {
+        Commands = motion.Commands?.ToImmutableArray(),
+    };
+
+    private static CreateObject.ServerMotionState? Freeze(
+        CreateObject.ServerMotionState? motion) => motion is { } value
+            ? Freeze(value)
+            : null;
+
+    private static PhysicsSpawnData? Freeze(PhysicsSpawnData? physics)
+    {
+        if (physics is not { } value)
+            return null;
+
+        PhysicsMovementData? movement = value.Movement is { } source
+            ? source with
+            {
+                RawData = source.RawData.ToArray(),
+                MotionState = Freeze(source.MotionState),
+            }
+            : null;
+        ReadOnlyMemory<PhysicsAttachment>? children = value.Children is { } list
+            ? list.ToArray()
+            : null;
+        return value with
+        {
+            Movement = movement,
+            Children = children,
+        };
+    }
+}