add source-generated typescript types

Author: mourner

.gitignore

@@ -1 +1,2 @@
 node_modules
+index.d.ts

LICENSE

@@ -1,6 +1,6 @@
 ISC License
 
-Copyright (c) 2022, Mapbox
+Copyright (c) 2025, Mapbox
 
 Permission to use, copy, modify, and/or distribute this software for any purpose
 with or without fee is hereby granted, provided that the above copyright notice

index.d.ts

@@ -1,4 +1,27 @@
-
+/**
+ * @typedef {Object} PotpackBox
+ * @property {number} w Box width.
+ * @property {number} h Box height.
+ * @property {number} [x] X coordinate in the resulting container.
+ * @property {number} [y] Y coordinate in the resulting container.
+ */
+
+/**
+ * @typedef {Object} PotpackStats
+ * @property {number} w Width of the resulting container.
+ * @property {number} h Height of the resulting container.
+ * @property {number} fill The space utilization value (0 to 1). Higher is better.
+ */
+
+/**
+ * Packs 2D rectangles into a near-square container.
+ *
+ * Mutates the {@link boxes} array: it's sorted (by height/width),
+ * and box objects are augmented with `x`, `y` coordinates.
+ *
+ * @param {PotpackBox[]} boxes
+ * @return {PotpackStats}
+ */
 export default function potpack(boxes) {
 
     // calculate total box area and maximum box width
@@ -46,7 +69,7 @@ export default function potpack(boxes) {
             if (box.w === space.w && box.h === space.h) {
                 // space matches the box exactly; remove it
                 const last = spaces.pop();
-                if (i < spaces.length) spaces[i] = last;
+                if (last && i < spaces.length) spaces[i] = last;
 
             } else if (box.h === space.h) {
                 // space matches the box height; update it accordingly