import { Chess } from 'chess.js';

function engine(state) {
  const game = new Chess();
  for (const move of state.moves) game.move(move);
  return game;
}

export const chess = {
  id: 'ajedrez',
  version: '1.0.0',
  minPlayers: 2,
  maxPlayers: 2,
  /** @returns {{ moves: string[], fen: string, turn: number }} */
  create() {
    return { moves: [], fen: new Chess().fen(), turn: 0 };
  },
  legal(state, seat) {
    if (seat !== state.turn) return [];
    return engine(state)
      .moves({ verbose: true })
      .map((m) => ({
        type: 'move',
        from: m.from,
        to: m.to,
        ...(m.promotion ? { promotion: m.promotion } : {}),
      }));
  },
  apply(state, action, seat) {
    if (seat !== state.turn || action.type !== 'move')
      throw new Error('No puedes hacer esa jugada.');
    const game = engine(state);
    const move = game.move({
      from: action.from,
      to: action.to,
      ...(action.promotion ? { promotion: action.promotion } : {}),
    });
    if (!move) throw new Error('Movimiento ilegal.');
    const next = {
      moves: [...state.moves, move.san],
      fen: game.fen(),
      turn: game.turn() === 'w' ? 0 : 1,
    };
    let result = null;
    if (game.isCheckmate()) result = { winner: seat, reason: 'jaque mate' };
    else if (game.isDraw())
      result = {
        winner: null,
        reason: game.isStalemate() ? 'rey ahogado' : 'tablas por las reglas',
      };
    return {
      state: next,
      label: move.san,
      result,
      sound: result
        ? 'finish'
        : game.isCheck()
          ? 'check'
          : move.promotion
            ? 'promotion'
            : move.captured
              ? 'capture'
              : 'move',
    };
  },
  view(state) {
    const game = engine(state);
    return {
      ...state,
      board: game.board(),
      check: game.isCheck(),
      pgn: game.pgn(),
    };
  },
};