From 8a827b37e60639e58cd7cd2500f77528ae490fb8 Mon Sep 17 00:00:00 2001
From: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Date: Fri, 10 Mar 2023 09:03:29 +1100
Subject: [PATCH] Add enumerator for box2i edges (#3834)

Will write a test later don't @ me.
---
 Robust.Shared.Maths/Box2i.cs | 60 ++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/Robust.Shared.Maths/Box2i.cs b/Robust.Shared.Maths/Box2i.cs
index 38eff5a11..604cd4f79 100644
--- a/Robust.Shared.Maths/Box2i.cs
+++ b/Robust.Shared.Maths/Box2i.cs
@@ -167,4 +167,64 @@ namespace Robust.Shared.Maths
                 Top * scalar);
         }
     }
+
+    /// <summary>
+    /// Iterates neighbouring tiles to a box2i.
+    /// </summary>
+    public struct Box2iEdgeEnumerator
+    {
+        private readonly bool _corners;
+        private readonly Box2i _box;
+        private readonly int _offset;
+        private int _x;
+        private int _y;
+
+        public Box2iEdgeEnumerator(Box2i box, bool corners, int offset = 1)
+        {
+            _box = box;
+            _corners = corners;
+            _x = _box.Left - offset;
+            _y = _box.Bottom - offset;
+            _offset = offset;
+        }
+
+        public bool MoveNext(out Vector2i index)
+        {
+            for (var x = _x; x < _box.Right + _offset; x++)
+            {
+                for (var y = _y; y < _box.Top + _offset; y++)
+                {
+                    if (x != _box.Left - _offset &&
+                        x != _box.Right + (_offset - 1) &&
+                        y != _box.Bottom - _offset &&
+                        y != _box.Top + (_offset - 1))
+                    {
+                        continue;
+                    }
+
+                    if (!_corners &&
+                        (x == _box.Left - _offset && (y == _box.Bottom - _offset || y == _box.Top + (_offset - 1)) ||
+                        x == _box.Right && (y == _box.Bottom - _offset || y == _box.Top + (_offset - 1))))
+                    {
+                        continue;
+                    }
+
+                    _x = x;
+                    _y = y + 1;
+
+                    if (_y == _box.Top + _offset)
+                    {
+                        _x++;
+                        _y = _box.Bottom - _offset;
+                    }
+
+                    index = new Vector2i(x, y);
+                    return true;
+                }
+            }
+
+            index = default;
+            return false;
+        }
+    }
 }