feat: add block model with IBlock flyweight and registry

World/BlockRegistry.cs

@@ -0,0 +1,26 @@
+using VoxelEngine.World.Blocks;
+
+namespace VoxelEngine.World;
+
+public sealed class BlockRegistry
+{
+    private readonly IBlock[] _byId;
+
+    public AirBlock Air { get; } = new();
+    public StoneBlock Stone { get; } = new();
+    public DirtBlock Dirt { get; } = new();
+    public GrassBlock Grass { get; } = new();
+
+    public BlockRegistry()
+    {
+        // Index by id. Order does not matter; slot = block.Id.
+        var blocks = new IBlock[] { Air, Stone, Dirt, Grass };
+        _byId = new IBlock[blocks.Length];
+        foreach (IBlock block in blocks)
+        {
+            _byId[block.Id] = block;
+        }
+    }
+
+    public IBlock Get(ushort id) => _byId[id];
+}