algebraic to index func

src/lib/chess/utils.ts

@@ -50,4 +50,20 @@ export class Board {
       });
     });
   }
+}
+
+function algebraicToIndex(algebraic: string): number {
+  const FILE_TO_INDEX: Record<string, number> = {
+    a: 0, b: 1, c: 2, d: 3, e: 4, f: 5, g: 6, h: 7,
+  }
+  try {
+    if (algebraic.length !== 2) return -1;
+    const [file, rank] = algebraic.split("");
+    const rankIndex = parseInt(rank) - 1;
+    const fileIndex = FILE_TO_INDEX[file];
+
+    return rankIndex * 8 + fileIndex;
+  } catch { 
+    return -1;
+  }
 }