board updating subscriber and listener

src/lib/chess/types.ts

@@ -1,3 +1,6 @@
+import { Game } from "./utils";
+export type GameListener = (board: Game) => void;
+
 export enum Piece {
   EMPTY = 0,
   KING = 1,

src/lib/chess/utils.ts

@@ -1,8 +1,8 @@
-import { CHAR_TO_PIECE, Piece } from "./types";
+import { CHAR_TO_PIECE, Piece, type GameListener } from "./types";
 
 export const startFEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0";
 
-export class Board {
+export class Game {
   public board = new Int8Array(8 ** 2);
   public details = {
     whiteTurn: true,
@@ -15,10 +15,21 @@ export class Board {
     fullMove: 0,
   };
 
+  private listeners = new Set<GameListener>();
+  
   constructor() {
     this.loadFEN();
   }
 
+  private notify() {
+    for (const listener of this.listeners) listener(this);
+  }
+
+  subscribe(listener: GameListener): () => void {
+    this.listeners.add(listener);
+    return () => this.listeners.delete(listener);
+  }
+  
   loadFEN(fen = startFEN) {
     const [position, turn, castling, enPassant, halfMove, fullMove] = fen.split(" ");
     
@@ -43,6 +54,8 @@ export class Board {
 
     this.details.halfMove = parseInt(halfMove);
     this.details.fullMove = parseInt(fullMove);
+
+    this.notify();
   }
 }
 

src/routes/+page.svelte

@@ -1,20 +1,21 @@
 <script lang="ts">
   import { PIECE_TO_CHAR } from "$lib/chess/types";
-  import { Board, startFEN } from "$lib/chess/utils";
+  import { Game, startFEN } from "$lib/chess/utils";
 
-  const board = new Board();
-
-  let boardView = $state(Array.from(board.board));
   let showIndex = $state(false);
   let fen = $state(startFEN);
 
+  const game = new Game();
+  let board = $state(Array.from(game.board));
+
+  game.subscribe(updateView);
   function updateView() {
-    boardView = Array.from(board.board);
+    board = Array.from(game.board);
   }
 </script>
 
 <div class="grid grid-cols-8 gap-0 border-2">
-  {#each boardView as square, index}
+  {#each board as square, index}
     <div class="h-20 aspect-square relative flex justify-center items-center
       {index % 2 === Math.floor(index / 8) % 2 ? 'bg-orange-200 text-stone-800' : 'bg-amber-800 text-stone-200'}
     ">
@@ -31,10 +32,9 @@
   <label class="block">
     fen (enter to set):
     <input type="text" onkeypress={(e) => e.key === 'Enter' && (() => {
-      board.loadFEN(fen)
-      updateView()
+      game.loadFEN(fen);
     })()} bind:value={fen} />
   </label>
   <button onclick={updateView}>update view</button>
-  <button onclick={() => console.log(board)}>dump game to console</button>
+  <button onclick={() => console.log(game)}>dump game to console</button>
 </div>