src/util/board_vis.py

from typing import Optional
import chess

WHITE_PIECE_COLOR = "\033[97m"  # Bright white
BLACK_PIECE_COLOR = "\033[90m"  # Bright black (gray)
LIGHT_SQUARE_BG = "\033[50m"  # White background
DARK_SQUARE_BG = "\033[47m"  # Standard blue background (darker/more blue)

RESET = "\033[0m"

UNICODE_PIECES = {
    "P": "♙",
    "N": "♘",
    "B": "♗",
    "R": "♖",
    "Q": "♕",
    "K": "♔",
    "p": "♟",
    "n": "♞",
    "b": "♝",
    "r": "♜",
    "q": "♛",
    "k": "♚",
}


def colored_unicode_board(fen: Optional[str] = None) -> str:
    if fen is None:
        fen = chess.STARTING_FEN

    board = chess.Board(fen)

    board_str = ""
    white_to_move = board.turn

    # Decide ranks and files order depending on who's to move
    if white_to_move:
        ranks = range(8, 0, -1)  # 8 to 1
        files = range(1, 9)  # a to h
    else:
        ranks = range(1, 9)  # 1 to 8
        files = range(8, 0, -1)  # h to a (reverse files)

    for rank in ranks:
        board_str += f"{rank} "
        for file in files:
            square = chess.square(file - 1, rank - 1)
            piece = board.piece_at(square)

            # Correct square color for orientation
            if (rank + file) % 2 == 1:
                bg = LIGHT_SQUARE_BG
            else:
                bg = DARK_SQUARE_BG

            if piece:
                fg = (
                    WHITE_PIECE_COLOR
                    if piece.color == chess.WHITE
                    else BLACK_PIECE_COLOR
                )
                symbol = UNICODE_PIECES[piece.symbol()]
                board_str += f"{bg}{fg} {symbol} {RESET}"
            else:
                board_str += f"{bg}   {RESET}"
        board_str += "\n"

    # Files labels in proper order
    if white_to_move:
        files_label = "a  b  c  d  e  f  g  h"
    else:
        files_label = "h  g  f  e  d  c  b  a"
    board_str += "   " + files_label + "\n"

    return board_str


if __name__ == "__main__":
    # Example usage:
    board = chess.Board()
    fen = board.fen()
    print(colored_unicode_board(fen))

    # Try switching turns for demo:
    print(colored_unicode_board())