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Chess: Added ability to copy board state as FEN

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You can now copy the board state as Forsyth-Edwards Notation. You can
then paste this into other chess programs/games, or into ours when
it gets implemented.
This commit is contained in:
AnicJov 2020-12-10 16:44:38 +01:00 • committed by Andreas Kling
parent b000a884c8
commit cf8fce368a
5 changed files with 85 additions and 0 deletions
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71
Libraries/LibChess/Chess.cpp
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@ -205,6 +205,73 @@ Board::Board()
set_piece(Square("h8"), { Colour::Black, Type::Rook });
}
String Board::to_fen() const
{
StringBuilder builder;
// 1. Piece placement
int empty = 0;
for (unsigned rank = 0; rank < 8; rank++) {
for (unsigned file = 0; file < 8; file++) {
const Piece p(get_piece({ 7 - rank, file }));
if (p.type == Type::None) {
empty++;
continue;
}
if (empty > 0) {
builder.append(String::number(empty));
empty = 0;
}
String piece = char_for_piece(p.type);
if (piece == "")
piece = "P";
builder.append(p.colour == Colour::Black ? piece.to_lowercase() : piece);
}
if (empty > 0) {
builder.append(String::number(empty));
empty = 0;
}
if (rank < 7)
builder.append("/");
}
// 2. Active color
ASSERT(m_turn != Colour::None);
builder.append(m_turn == Colour::White ? " w " : " b ");
// 3. Castling availability
builder.append(m_white_can_castle_kingside ? "K" : "");
builder.append(m_white_can_castle_queenside ? "Q" : "");
builder.append(m_black_can_castle_kingside ? "k" : "");
builder.append(m_black_can_castle_queenside ? "q" : "");
builder.append(" ");
// 4. En passant target square
if (!m_last_move.has_value())
builder.append("-");
else if (m_last_move.value().piece.type == Type::Pawn) {
if (m_last_move.value().from.rank == 1 && m_last_move.value().to.rank == 3)
builder.append(Square(m_last_move.value().to.rank - 1, m_last_move.value().to.file).to_algebraic());
else if (m_last_move.value().from.rank == 6 && m_last_move.value().to.rank == 4)
builder.append(Square(m_last_move.value().to.rank + 1, m_last_move.value().to.file).to_algebraic());
else
builder.append("-");
} else {
builder.append("-");
}
builder.append(" ");
// 5. Halfmove clock
builder.append(String::number(min(m_moves_since_capture, m_moves_since_pawn_advance)));
builder.append(" ");
// 6. Fullmove number
builder.append(String::number(1 + m_moves.size() / 2));
return builder.to_string();
}
Piece Board::get_piece(const Square& square) const
{
ASSERT(square.rank < 8);
@ -474,6 +541,7 @@ bool Board::apply_illegal_move(const Move& move, Colour colour)
m_last_move = move;
m_moves_since_capture++;
m_moves_since_pawn_advance++;
if (move.from == Square("a1") || move.to == Square("a1") || move.from == Square("e1"))
m_white_can_castle_queenside = false;
@ -514,6 +582,9 @@ bool Board::apply_illegal_move(const Move& move, Colour colour)
}
}
if (move.piece.type == Type::Pawn)
m_moves_since_pawn_advance = 0;
if (get_piece(move.to).colour != Colour::None) {
const_cast<Move&>(move).is_capture = true;
m_moves_since_capture = 0;