feat: add IChunkModificationStore and in-memory implementation

World/Persistence/InMemoryChunkModificationStore.cs

@@ -0,0 +1,33 @@
+using OpenTK.Mathematics;
+
+namespace VoxelEngine.World.Persistence;
+
+public sealed class InMemoryChunkModificationStore : IChunkModificationStore
+{
+    private readonly Dictionary<Vector3i, Dictionary<int, ushort>> _diffs = new();
+
+    public bool TryGetDiff(Vector3i chunkPos, out IReadOnlyDictionary<int, ushort>? diff)
+    {
+        if (this._diffs.TryGetValue(chunkPos, out Dictionary<int, ushort>? d))
+        {
+            diff = d;
+            return true;
+        }
+        diff = null;
+        return false;
+    }
+
+    public void RecordEdit(Vector3i chunkPos, int localIndex, ushort blockId)
+    {
+        if (!this._diffs.TryGetValue(chunkPos, out Dictionary<int, ushort>? d))
+        {
+            d = new Dictionary<int, ushort>();
+            this._diffs[chunkPos] = d;
+        }
+        d[localIndex] = blockId;
+    }
+
+    public void ClearDiff(Vector3i chunkPos) => this._diffs.Remove(chunkPos);
+
+    public bool HasDiff(Vector3i chunkPos) => this._diffs.ContainsKey(chunkPos);
+}