1 files changed, 24 insertions, 0 deletions
diff --git a/src/engine/liberty.js b/src/engine/liberty.js
new file mode 100644
index 0000000..372057e
--- /dev/null
+++ b/src/engine/liberty.js
@@ -0,0 +1,24 @@
+import { board } from "../board.js"
+import { Vector2 } from "../engine/vector2.js"
+
+const SURROUNDING = [
+    new Vector2(-1, 0),
+    new Vector2(0, 1),
+    new Vector2(0, -1),
+    new Vector2(1, 0),
+]
+
+export function hasLiberties({
+    position,
+    team
+}) {
+    return Array.from(SURROUNDING)
+	.map(v => Vector2.sum(v, position))
+	.filter(z => 0 <= z.x && z.x < board.size &&
+	    0 <= z.y && z.y < board.size
+	)
+	.some(z => board.stones[z.x][z.y] == undefined ?
+	    true :
+	    board.stones[z.x][z.y].team == team
+	)
+}