fen2txt

#!/bin/bash
TXT_CHESS_PIECES=${TXT_CHESS_PIECES:-auto}   # Whether to use Unicode chess pieces
# TXT_CHESS_STYLE # If not empty, the style to use
# TXT_CHESS_OUT  # If not empty, the output file to use

# Load the textfun library from the same directory as this script
source "$(dirname "${BASH_SOURCE}")/textfun.sh"

# Try and determine the terminal capabilities
if [ -t 1 ] ; then
    have_unicode=
    check_unicode "♙" &>/dev/null && have_unicode=1 # discard warnings
    is_real_xterm=
    test -n "$XTERM_VERSION" && is_real_xterm=1
    is_apple_terminal=
    test "$TERM_PROGRAM" = "Apple_Terminal" && is_apple_terminal=1
fi

set_chess_style() {
    case $1 in
        none|gnu|stock|boxed|pixelart) ;;
        brown) TXT_CHESS_LIGHT_SQUARE=223 ; TXT_CHESS_DARK_SQUARE=137 ;;
        green) TXT_CHESS_LIGHT_SQUARE=187 ; TXT_CHESS_DARK_SQUARE=64 ;;
        gray) TXT_CHESS_LIGHT_SQUARE=254 ; TXT_CHESS_DARK_SQUARE=248 ;;
        *) echo "Invalid style: $1" >&2 ; usage >&2 ;;
    esac
    TXT_CHESS_STYLE=$1
}

auto_chess_style() {
    if [ ! -t 1 ] ; then
        set_chess_style none
    elif [ -n "$have_unicode"  ] ; then
        if [ "$TXT_CHESS_PIECES" = "auto" ] ; then
            # Don't default to using chess pieces on plain X11 xterms, as the bitmapped fonts
            # are often bad.
            if [ -n "$is_real_xterm" ] ; then
                TXT_CHESS_PIECES=
            else
                TXT_CHESS_PIECES=1
            fi
        fi
        # Letter chess-pieces look better on a boxed board. On plain X11 xterm, also default to
        # boxed representation as bitmapped fonts may not have the required half block characters.
        if [ -z "$TXT_CHESS_PIECES" -o -n "$is_real_xterm" ] ; then
            set_chess_style boxed
        else
            set_chess_style green
        fi
    else
        TXT_CHESS_PIECES=
        set_chess_style gray
    fi
}

usage() {
    echo "Usage: $0 [-o outfile] [-s style] <fen>"
    echo "  -c          Use Unicode chess pieces"
    echo "  -h          Display this help message"
    echo "  -o outfile  Output file (default: standard output)"
    echo "  -s style    Style of the squares on the chess board"
    echo "                auto: (default) Guess output style for terminals, otherwise \"none\""
    echo "                none: No styling, plain ASCII, '.' for empty squares"
    echo "                gnu:  GNU Chess style, same as above but spaced out"
    echo "                stock: Stockfish style, ASCII art with KQRBNPkqrbnp pieces"
    echo "                boxed: Unicode box drawing characters"
    echo "                brown, green, gray: Checkered grid with light and dark squares"
    echo "                pixelart: Use simple 8-bit style block graphics"
    echo "  fen         FEN piece placement (default: standard starting position)"
    exit 1
}

if [ -n "$TXT_CHESS_STYLE" ] ; then
    set_chess_style "$TXT_CHESS_STYLE"
fi

# Process the command line options
while getopts "cho:s:" opt ; do
    case $opt in
        c) TXT_CHESS_PIECES=1 ;;
        h) usage >&2 ;;
        o) TXT_CHESS_OUT="$OPTARG" ;;
        s) set_chess_style "$OPTARG" || usage &> 2 ;;
        *) echo "Invalid option: $opt" ; usage &> 2 ;;
    esac
done
shift $((OPTIND - 1))

if [ -z "$TXT_CHESS_STYLE" ] ; then
    auto_chess_style
fi

if [ "$TXT_CHESS_PIECES" = "auto" ] ; then
    TXT_CHESS_PIECES=
fi

# This script takes a chess FEN piece placement and outputs a text file that shows
# the chessboard with that setup.
if [ $# -lt 1 ] ; then
    fen="rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR"
else
    fen=$1
fi

# Sanity check the argument - maybe be more flexible?
if [[ ! ("$fen" =~ ^([rnbqkpRNBQKP1-8]{1,8}/){7}[rnbqkpRNBQKP1-8]{1,8}$) ]] ; then
    echo "Invalid FEN piece placement: $fen" >&2
    usage >&2
    exit 1
fi

fen_expand() {
        if (($# != 1)) ; then
                echo "$0 <fen>"
                exit 1
        fi
        dots=""
        exp=$1
        for i in $(seq 8) ; do
                dots=".$dots"
                exp=${exp//$i/$dots}
        done
        echo "$exp" | tr '/' '\n'
}

output_txt() {
    echo "$(fen_expand $fen)" | (
        # Choose ASCII pieces, Unicode pieces, or pixelart
        if [ $TXT_CHESS_STYLE = "pixelart" ] ; then
            chess_art $TXT_CHESS_LIGHT_SQUARE $TXT_CHESS_DARK_SQUARE
        elif [ -n "$TXT_CHESS_PIECES" ] ; then
            chess_chars
        else
            cat
        fi ) | (
    case $TXT_CHESS_STYLE in
        stock) ascii_grid -w ;;
        boxed) unicode_grid -w ;;
        gnu) sed -e "s/./& /g " -e "s/ $//" ;;
        brown|green|gray)
            if [ -n "$have_unicode" ] ; then
                chess_chars | checkered_grid -w $TXT_CHESS_LIGHT_SQUARE $TXT_CHESS_DARK_SQUARE | (
                    if [ -n "$is_apple_terminal" ] ; then large_lines ; else cat ; fi )
            else
                # Likely a plain xterm so try DECDWL sequence, ignored if not supported
                checkered_grid $TXT_CHESS_LIGHT_SQUARE $TXT_CHESS_DARK_SQUARE | wide_lines
            fi ;;
        *) cat ;;
    esac
    )
}

# Output the TXT to the standard output or to a file
if [ -n "$TXT_CHESS_OUT" ] ; then
    output_txt > "$TXT_CHESS_OUT"
else
    output_txt
fi