poirebot 0.1.6

A chess bot engine written in Rust
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167

use anyhow::Context;

use crate::bitboard::BitBoard;
use crate::game::pieces::{Color, Pieces};
use crate::game::position::Position;
use crate::game::{Board, BoardSide};

/// The default starting position in FEN.
pub const DEFAULT_FEN: &str = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";

impl Board {
    /// Convert a Forsyth–Edwards Notation (FEN) string to `Board`
    pub fn from_fen(fen: &str) -> anyhow::Result<Self> {
        if fen == "startpos" {
            return Self::from_fen(DEFAULT_FEN);
        }

        let mut fen_split = fen.split_whitespace();

        let piece_placement = fen_split.next().with_context(|| "no piece placement")?;
        let ranks: Vec<&str> = piece_placement.split('/').collect();
        if ranks.len() != 8 {
            return Err(anyhow::Error::msg("piece placement does not have 8 ranks"));
        }

        let mut pieces = Vec::with_capacity(64);

        for (rank, rank_pieces) in ranks.into_iter().enumerate() {
            let rank = (7 - rank) as u8; // FEN starts with rank 8 (top to bottom from White's perspective)
            let mut file: u8 = 0;

            for piece in rank_pieces.chars() {
                if let Some(skip) = piece.to_digit(10) {
                    file += skip as u8;
                } else {
                    let color = if piece.is_uppercase() {
                        Color::White
                    } else {
                        Color::Black
                    };
                    let piece = match piece.to_lowercase().next() {
                        Some('p') => Pieces::Pawn(color, (file, rank).into()),
                        Some('r') => Pieces::Rook(color, (file, rank).into()),
                        Some('n') => Pieces::Knight(color, (file, rank).into()),
                        Some('b') => Pieces::Bishop(color, (file, rank).into()),
                        Some('q') => Pieces::Queen(color, (file, rank).into()),
                        Some('k') => Pieces::King(color, (file, rank).into()),
                        _ => return Err(anyhow::Error::msg("invalid piece descriptor")),
                    };
                    pieces.push(piece);
                    file += 1;
                }
            }
            if file != 8 {
                return Err(anyhow::Error::msg("incomplete rank pieces"));
            }
        }

        // TODO
        let _active_color = if fen_split.next().with_context(|| "no active color")? == "w" {
            Color::White
        } else {
            Color::Black
        };

        let castling_availability = fen_split
            .next()
            .with_context(|| "no castling availability")?;
        let white_queenside_castle = castling_availability.contains('Q');
        let white_kingside_castle = castling_availability.contains('K');
        let black_queenside_castle = castling_availability.contains('q');
        let black_kingside_castle = castling_availability.contains('k');

        let en_passant_target = fen_split
            .next()
            .with_context(|| "no en passant target square")?;
        let en_passant_target: Option<(Position, Color)> = match en_passant_target {
            "-" => None,
            p => {
                let pos =
                    Position::from_notation(p).with_context(|| "invalid en passant target")?;
                let color = if pos.rank_y == 2 {
                    // 3rd rank
                    Color::White
                } else if pos.rank_y == 5 {
                    // 6th rank
                    Color::Black
                } else {
                    return Err(anyhow::Error::msg("impossible en passant target"));
                };
                Some((pos, color))
            }
        };

        // TODO
        let _half_move_clock = fen_split.next().with_context(|| "no half-move clock")?;

        // TODO
        let _full_move_clock = fen_split.next().with_context(|| "no full-move clock")?;

        // Construct board
        let white = BoardSide::new(Color::White, |side| {
            for piece in pieces.iter().filter(|p| p.is_white()) {
                match piece {
                    Pieces::Pawn(_, position) => side.pawns |= BitBoard::from(*position),
                    Pieces::Rook(_, position) => side.rooks |= BitBoard::from(*position),
                    Pieces::Knight(_, position) => side.knights |= BitBoard::from(*position),
                    Pieces::Bishop(_, position) => side.bishops |= BitBoard::from(*position),
                    Pieces::Queen(_, position) => side.queens |= BitBoard::from(*position),
                    Pieces::King(_, position) => side.king |= BitBoard::from(*position),
                }
            }
            if white_queenside_castle {
                side.unmoved_rooks |= BitBoard::from_position("a1");
            }
            if white_kingside_castle {
                side.unmoved_rooks |= BitBoard::from_position("h1");
            }
            if let Some((pos, color)) = en_passant_target {
                if color == Color::White {
                    side.en_passant_target |= BitBoard::from(pos);
                }
            }
        });
        let black = BoardSide::new(Color::Black, |side| {
            for piece in pieces.iter().filter(|p| p.is_black()) {
                match piece {
                    Pieces::Pawn(_, position) => side.pawns |= BitBoard::from(*position),
                    Pieces::Rook(_, position) => side.rooks |= BitBoard::from(*position),
                    Pieces::Knight(_, position) => side.knights |= BitBoard::from(*position),
                    Pieces::Bishop(_, position) => side.bishops |= BitBoard::from(*position),
                    Pieces::Queen(_, position) => side.queens |= BitBoard::from(*position),
                    Pieces::King(_, position) => side.king |= BitBoard::from(*position),
                }
            }
            if black_queenside_castle {
                side.unmoved_rooks |= BitBoard::from_position("a8");
            }
            if black_kingside_castle {
                side.unmoved_rooks |= BitBoard::from_position("h8");
            }
            if let Some((pos, color)) = en_passant_target {
                if color == Color::Black {
                    side.en_passant_target |= BitBoard::from(pos);
                }
            }
        });

        Ok(Self { white, black })
    }

    /// Convert a `Board` to Forsyth–Edwards Notation (FEN) string
    pub fn to_fen(&self) -> String {
        unimplemented!()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_default_fen() {
        let parsed = Board::from_fen(DEFAULT_FEN).expect("failed to parse FEN");
        assert_eq!(parsed, Board::default());
    }
}