@publishvue/chessground/fen.js

lichess.org chess ui

import { pos2key, invRanks } from './util';
import * as cg from './types';
export const initial = 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR';
const roles = {
    p: 'pawn',
    r: 'rook',
    n: 'knight',
    b: 'bishop',
    q: 'queen',
    k: 'king',
};
const letters = {
    pawn: 'p',
    rook: 'r',
    knight: 'n',
    bishop: 'b',
    queen: 'q',
    king: 'k',
};
export function read(fen) {
    if (fen === 'start')
        fen = initial;
    const pieces = new Map();
    let row = 7, col = 0;
    for (const c of fen) {
        switch (c) {
            case ' ':
                return pieces;
            case '/':
                --row;
                if (row < 0)
                    return pieces;
                col = 0;
                break;
            case '~': {
                const piece = pieces.get(pos2key([col, row]));
                if (piece)
                    piece.promoted = true;
                break;
            }
            default: {
                const nb = c.charCodeAt(0);
                if (nb < 57)
                    col += nb - 48;
                else {
                    const role = c.toLowerCase();
                    pieces.set(pos2key([col, row]), {
                        role: roles[role],
                        color: c === role ? 'black' : 'white',
                    });
                    ++col;
                }
            }
        }
    }
    return pieces;
}
export function write(pieces) {
    return invRanks
        .map(y => cg.files
        .map(x => {
        const piece = pieces.get((x + y));
        if (piece) {
            const letter = letters[piece.role];
            return piece.color === 'white' ? letter.toUpperCase() : letter;
        }
        else
            return '1';
    })
        .join(''))
        .join('/')
        .replace(/1{2,}/g, s => s.length.toString());
}
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