🔨 rename package compute -> solver

packages/solver/outside.ts

@@ -0,0 +1,48 @@
+import {
+  createEmptyGrid,
+  getColor,
+  isEmpty,
+  isInside,
+  setColor,
+  setColorEmpty,
+} from "@snk/types/grid";
+import { around4 } from "@snk/types/point";
+import type { Color, Grid } from "@snk/types/grid";
+
+export type Outside = Grid & { __outside: true };
+
+export const createOutside = (grid: Grid, color: Color = 0 as Color) => {
+  const outside = createEmptyGrid(grid.width, grid.height) as Outside;
+  for (let x = outside.width; x--; )
+    for (let y = outside.height; y--; ) setColor(outside, x, y, 1 as Color);
+
+  fillOutside(outside, grid, color);
+
+  return outside;
+};
+
+export const fillOutside = (
+  outside: Outside,
+  grid: Grid,
+  color: Color = 0 as Color
+) => {
+  let changed = true;
+  while (changed) {
+    changed = false;
+    for (let x = outside.width; x--; )
+      for (let y = outside.height; y--; )
+        if (
+          getColor(grid, x, y) <= color &&
+          !isOutside(outside, x, y) &&
+          around4.some((a) => isOutside(outside, x + a.x, y + a.y))
+        ) {
+          changed = true;
+          setColorEmpty(outside, x, y);
+        }
+  }
+
+  return outside;
+};
+
+export const isOutside = (outside: Outside, x: number, y: number) =>
+  !isInside(outside, x, y) || isEmpty(getColor(outside, x, y));