golo — Go board logic for Dart

Lightweight, well‑tested Go (Igo/Weiqi/Baduk) rules and SGF utilities in pure Dart 3.

Install

dart pub add golo

Requires Dart SDK >= 3.0.0.

Quick start

import 'package:golo/golo.dart';

void main() {
  final game = Game(width: 9); // 9x9

  // Play a few moves
  game.play((x: 2, y: 2));
  game.play((x: 6, y: 6));
  game.pass();

  // Print a snapshot and export to SGF
  print(game.board);       // ASCII board
  print(game.toSgf());     // SGF with size, moves, metadata
}

SGF: read and write

High‑level (recommended):

import 'package:golo/golo.dart';

// From SGF main line (applies AB/AW/AE setup, reads SZ)
final game = Game.fromSgf('( ;SZ[9] ;B[cc] ;W[gg] ;B[] )');
print(game.board);

// To SGF (pretty parentheses + indentation)
final sgf = game.toSgf();

Low‑level tokenizer/parser:

import 'package:golo/sgf.dart' as sgf;

final tree = sgf.Parser().parse('(;B[hh](;W[ii])(;W[hi]C[h]))');
final root = tree.id < 0 && tree.children.isNotEmpty ? tree.children.first : tree;

// Walk main line
sgf.RecursiveNode? cur = root;
while (cur != null) {
  print(cur.data); // Map<String, List<String>> of SGF props for this node
  cur = cur.children.isNotEmpty ? cur.children.first : null;
}

Notes:

• Property identifiers are normalized to upper‑case in the parser.
• Bracket values are unescaped per SGF rules (e.g., \\] -> ]).

Board API cheatsheet

final board = Board.fromDimension(19);

// Safe play with rule checks (throws IllegalMoveException on violations)
final after = board.makeMove((x: 3, y: 3), Stone.black,
  preventOutOfBoard: true,
  preventOverwrite: true,
  preventSuicide: true,
  preventKo: true,
);

// Coordinates
board.parseVertex('D16');                 // -> (x: 3, y: 3)
board.stringifyVertex((x: 3, y: 3));      // -> 'D16' (I omitted)

// Analysis helpers
board.getLiberties((x: 3, y: 3));
board.getChain((x: 3, y: 3));
board.getRelatedChains((x: 3, y: 3));
board.isValid();

// Handicap suggestions (star points, Tygem order supported)
board.getHandicapPlacement(4, tygem: true);

Examples

REPL

Interactive REPL for quick testing and demos.

Run:

dart run example/golo_repl.dart --help

Common options:

• --width N and --height M (default both 19)
• --to-play b|w
• --handicap N and --tygem ordering

Inside the REPL (type help):

• play D4, b D4, w Q16
• pass, undo, captures, show
• new 19 or new 9x13

SGF Player

Console SGF player that steps through the main line.

Run with the bundled Lee Sedol vs AlphaGo SGF:

dart run example/sgf_player.dart

Or provide your own SGF path:

dart run example/sgf_player.dart path/to/game.sgf

Controls:

• Up/Down arrows: step back/forward (TTY environments)
• j/k + Enter: forward/back (non‑TTY fallback)
• q: quit

Details:

• Follows only the first variation (main line); ignores branches.
• Prints Node.data under the board for quick inspection.
• Honors SZ and root setup AB/AW/AE.

License

MIT License. Portions adapted from SabakiHQ/go-board (MIT) and SabakiHQ/sgf (MIT). See LICENSE for third‑party notices.