feat(bot): legalCandidates for vanilla and blind modes

2026-04-28 13:42:37 -04:00
parent bc954f4748
commit f48e0a9cdf
2 changed files with 168 additions and 0 deletions
@@ -0,0 +1,68 @@
+import {
+  geometricMoves,
+  type Color,
+  type Piece,
+  type PieceType,
+  type PromotionType,
+  type Square,
+} from '@blind-chess/shared';
+import type { Game } from '../state.js';
+import { ownSquares } from '../view.js';
+import type { CandidateMove } from './brain.js';
+
+const PROMOTION_TYPES: PromotionType[] = ['q', 'r', 'b', 'n'];
+
+export function legalCandidates(game: Game, color: Color): CandidateMove[] {
+  if (game.mode === 'vanilla') return vanillaCandidates(game, color);
+  return blindCandidates(game, color);
+}
+
+function vanillaCandidates(game: Game, color: Color): CandidateMove[] {
+  // chess.js only returns moves for the side to move via `.moves()`. To get a
+  // hypothetical move list for the other color we'd need to rotate — but the
+  // bot driver only invokes legalCandidates when it's the bot's turn, so this
+  // is fine in practice. Tests for "wrong color" use blind mode.
+  if (game.chess.turn() !== color) return [];
+
+  const moves = game.chess.moves({ verbose: true }) as Array<{
+    from: Square; to: Square; promotion?: PromotionType;
+  }>;
+  const out: CandidateMove[] = [];
+  for (const m of moves) {
+    out.push({ from: m.from, to: m.to, promotion: m.promotion });
+  }
+  return out;
+}
+
+function blindCandidates(game: Game, color: Color): CandidateMove[] {
+  const own = ownSquares(game, color);
+  const board = game.chess.board();
+  const out: CandidateMove[] = [];
+
+  for (const row of board) {
+    if (!row) continue;
+    for (const cell of row) {
+      if (!cell) continue;
+      if (cell.color !== color) continue;
+      const piece: Piece = { color: cell.color, type: cell.type as PieceType };
+      const from = cell.square as Square;
+      const tos = geometricMoves(piece, from, own);
+      for (const to of tos) {
+        if (isPromotionSquare(piece, to)) {
+          for (const promo of PROMOTION_TYPES) {
+            out.push({ from, to, promotion: promo });
+          }
+        } else {
+          out.push({ from, to });
+        }
+      }
+    }
+  }
+  return out;
+}
+
+function isPromotionSquare(piece: Piece, to: Square): boolean {
+  if (piece.type !== 'p') return false;
+  const rank = to[1];
+  return (piece.color === 'w' && rank === '8') || (piece.color === 'b' && rank === '1');
+}