chore: add constants and basic outline of the engine

server/src/chess/engine.ts

@@ -0,0 +1,184 @@
+export const DEFAULT_POSITION =
+  "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
+
+export const PIECE = Object.freeze({
+  PAWN: "p",
+  KNIGHT: "n",
+  BISHOP: "b",
+  ROOK: "r",
+  QUEEN: "q",
+  KING: "k"
+} as const);
+
+export type PiecePromotionType =
+  | typeof PIECE.KNIGHT
+  | typeof PIECE.BISHOP
+  | typeof PIECE.ROOK
+  | typeof PIECE.QUEEN;
+
+export type PieceType = typeof PIECE[keyof typeof PIECE];
+
+export const COLOR = Object.freeze({
+  WHITE: "w",
+  BLACK: "b"
+} as const);
+
+export type Color = typeof COLOR[keyof typeof COLOR];
+
+export type Piece = {
+  type: PieceType;
+  color: Color;
+};
+
+// prettier-ignore
+export const SQUARES = Object.freeze([
+  'a1', 'b1', 'c1', 'd1', 'e1', 'f1', 'g1', 'h1',
+  'a2', 'b2', 'c2', 'd2', 'e2', 'f2', 'g2', 'h2',
+  'a3', 'b3', 'c3', 'd3', 'e3', 'f3', 'g3', 'h3',
+  'a4', 'b4', 'c4', 'd4', 'e4', 'f4', 'g4', 'h4',
+  'a5', 'b5', 'c5', 'd5', 'e5', 'f5', 'g5', 'h5',
+  'a6', 'b6', 'c6', 'd6', 'e6', 'f6', 'g6', 'h6',
+  'a7', 'b7', 'c7', 'd7', 'e7', 'f7', 'g7', 'h7',
+  'a8', 'b8', 'c8', 'd8', 'e8', 'f8', 'g8', 'h8'
+] as const);
+
+export const EMPTY_SQUARE = "-";
+export type Square = typeof SQUARES[number] | typeof EMPTY_SQUARE;
+
+export const MOVE_FLAGS = Object.freeze({
+  NORMAL: "n",
+  CAPTURE: "c",
+  BIG_PAWN: "p",
+  K_CASTLE: "k",
+  Q_CASTLE: "q",
+  EN_PASSANT: "e"
+} as const);
+
+export type MoveFlag = typeof MOVE_FLAGS[keyof typeof MOVE_FLAGS];
+
+export type Move = {
+  from: Square;
+  to: Square;
+  flag: MoveFlag;
+  promotion?: PiecePromotionType;
+};
+
+type InternalMove = Move & {
+  beforeFEN: string;
+};
+
+// prettier-ignore
+export const PIECE_MASKS: Record<keyof typeof PIECE, number> = Object.freeze({
+  PAWN:   0b000001,
+  KNIGHT: 0b000010,
+  BISHOP: 0b000100,
+  ROOK:   0b001000,
+  QUEEN:  0b010000,
+  KING:   0b100000
+} as const);
+
+export const COLOR_MASKS: Record<keyof typeof COLOR, number> = Object.freeze({
+  WHITE: 0b01,
+  BLACK: 0b10
+} as const);
+
+// prettier-ignore
+export const MOVE_FLAG_MASKS: Record<keyof typeof MOVE_FLAGS, number> = Object.freeze({
+  NORMAL:     0b000001,
+  CAPTURE:    0b000010,
+  BIG_PAWN:   0b000100,
+  K_CASTLE:   0b001000,
+  Q_CASTLE:   0b010000,
+  EN_PASSANT: 0b100000
+} as const);
+
+const PAWN_OFFSETS = Object.freeze({
+  b: [16, 32, 17, 15],
+  w: [-16, -32, -17, -15]
+});
+
+const PIECE_OFFSETS = Object.freeze({
+  n: [-18, -33, -31, -14, 18, 33, 31, 14],
+  b: [-17, -15, 17, 15],
+  r: [-16, 1, 16, -1],
+  q: [-17, -16, -15, 1, 17, 16, 15, -1],
+  k: [-17, -16, -15, 1, 17, 16, 15, -1]
+});
+
+export function rank(squareIdx: number): number {
+  return squareIdx >> 3;
+}
+
+export function file(squareIdx: number): number {
+  return squareIdx & 0b111;
+}
+
+export function isDigit(c: string): boolean {
+  return /^d$/.test(c);
+}
+
+export function algebraic(square: number): Square {
+  const f = file(square);
+  const r = rank(square);
+  return ("abcdefgh"[f] + "12345678"[r]) as Square;
+}
+
+export function swapColor(color: Color): Color {
+  return color === COLOR.WHITE ? COLOR.BLACK : COLOR.WHITE;
+}
+
+export function validateFEN(fen: string) {}
+
+export class Chess {
+  private _board: (Piece | null)[] = [];
+  private _turn: Color = COLOR.WHITE;
+  private _castling: Record<Color, number> = { w: 0, b: 0 };
+  private _enPassant: Square = "-";
+  private _halfMoves = 0;
+  private _fullMoves = 1;
+
+  constructor(fen = DEFAULT_POSITION) {
+    this.load(fen);
+  }
+
+  reset() {
+    this.load(DEFAULT_POSITION);
+  }
+
+  load(fen: string) {}
+
+  getMoves() {}
+
+  getMovesForSquare(square: Square) {}
+
+  getFEN() {}
+
+  makeMove() {}
+
+  isSquareAttacked() {}
+
+  isCheck() {}
+
+  isCheckMate() {}
+
+  isStalemate() {}
+
+  isInsufficientMaterial() {}
+
+  isThreefoldRepetition() {}
+
+  isDraw() {}
+
+  isGameOver() {}
+
+  private _addToHistory() {}
+
+  // and a way to track how many moves were undo'ed
+  undo() {}
+
+  turn() {}
+
+  squareColor() {}
+
+  history() {}
+}