Allow protected grids to be repaired (#36989)

* Allow protected grids to be repaired

* Probably implement it

---------

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Shared/Tiles/ProtectedGridSystem.cs

@@ -0,0 +1,70 @@
+using System.Linq;
+using Robust.Shared.Map.Components;
+using Robust.Shared.Map.Enumerators;
+
+namespace Content.Shared.Tiles;
+
+public sealed class ProtectedGridSystem : EntitySystem
+{
+    [Dependency] private readonly SharedMapSystem _map = default!;
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        SubscribeLocalEvent<ProtectedGridComponent, MapInitEvent>(OnMapInit);
+        SubscribeLocalEvent<ProtectedGridComponent, FloorTileAttemptEvent>(OnFloorTileAttempt);
+    }
+
+    private void OnMapInit(Entity<ProtectedGridComponent> ent, ref MapInitEvent args)
+    {
+        if (!TryComp<MapGridComponent>(ent, out var grid))
+            return;
+
+        // Engine default is currently 16x size chunks which means we can't just easily have 64bit flags.
+        var chunkEnumerator = new ChunkIndicesEnumerator(grid.LocalAABB, 8);
+
+        while (chunkEnumerator.MoveNext(out var chunk))
+        {
+            ulong flag = 0;
+
+            for (var x = 0; x < 8; x++)
+            {
+                for (var y = 0; y < 8; y++)
+                {
+                    var index = new Vector2i(x + chunk.Value.X * 8, y + chunk.Value.Y * 8);
+                    var tile = _map.GetTileRef(ent.Owner, grid, index);
+
+                    if (tile.Tile.IsEmpty)
+                        continue;
+
+                    var data = SharedMapSystem.ToBitmask(new Vector2i(x, y));
+
+                    flag |= data;
+                }
+            }
+
+            if (flag == 0)
+                continue;
+
+            ent.Comp.BaseIndices[chunk.Value] = flag;
+        }
+
+        Dirty(ent);
+    }
+
+    private void OnFloorTileAttempt(Entity<ProtectedGridComponent> ent, ref FloorTileAttemptEvent args)
+    {
+        var chunkOrigin = SharedMapSystem.GetChunkIndices(args.GridIndices, 8);
+
+        if (!ent.Comp.BaseIndices.TryGetValue(chunkOrigin, out var data))
+        {
+            args.Cancelled = true;
+            return;
+        }
+
+        if (SharedMapSystem.FromBitmask(args.GridIndices, data))
+        {
+            args.Cancelled = true;
+        }
+    }
+}