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

use super::*;

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[repr(u8)]
#[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
pub enum CastleRights {
    None = 0,
    KingSide = 1,
    QueenSide = 2,
    Both = 3,
}

const CASTLES_PER_SQUARE: [[usize; 64]; 2] = [
    [
        2, 0, 0, 0, 3, 0, 0, 1, // 1
        0, 0, 0, 0, 0, 0, 0, 0, // 2
        0, 0, 0, 0, 0, 0, 0, 0, // 3
        0, 0, 0, 0, 0, 0, 0, 0, // 4
        0, 0, 0, 0, 0, 0, 0, 0, // 5
        0, 0, 0, 0, 0, 0, 0, 0, // 6
        0, 0, 0, 0, 0, 0, 0, 0, // 7
        0, 0, 0, 0, 0, 0, 0, 0, // 8
    ],
    [
        0, 0, 0, 0, 0, 0, 0, 0, // 1
        0, 0, 0, 0, 0, 0, 0, 0, // 2
        0, 0, 0, 0, 0, 0, 0, 0, // 3
        0, 0, 0, 0, 0, 0, 0, 0, // 4
        0, 0, 0, 0, 0, 0, 0, 0, // 5
        0, 0, 0, 0, 0, 0, 0, 0, // 6
        0, 0, 0, 0, 0, 0, 0, 0, // 7
        2, 0, 0, 0, 3, 0, 0, 1, // 8
    ],
];

impl CastleRights {
    /// Can I castle kingside?
    #[inline]
    pub const fn has_kingside(self) -> bool {
        self.to_index() & 1 == 1
    }

    /// Can I castle queenside?
    #[inline]
    pub const fn has_queenside(self) -> bool {
        self.to_index() & 2 == 2
    }

    #[inline]
    pub fn square_to_castle_rights(color: Color, square: Square) -> Self {
        Self::from_index(*get_item_unchecked!(
            CASTLES_PER_SQUARE,
            color.to_index(),
            square.to_index()
        ))
    }

    /// What squares need to be empty to castle kingside?
    #[inline]
    pub fn kingside_squares(self, color: Color) -> BitBoard {
        *get_item_unchecked!(KINGSIDE_CASTLE_SQUARES, color.to_index())
    }

    /// What squares need to be empty to castle queenside?
    #[inline]
    pub fn queenside_squares(self, color: Color) -> BitBoard {
        *get_item_unchecked!(QUEENSIDE_CASTLE_SQUARES, color.to_index())
    }

    /// Remove castle rights, and return a new `CastleRights`.
    #[inline]
    pub const fn remove(self, remove: Self) -> Self {
        Self::from_index(self.to_index() & !remove.to_index())
    }

    /// Convert `CastleRights` to `usize` for table lookups
    #[inline]
    pub const fn to_index(self) -> usize {
        self as usize
    }

    /// Convert `usize` to `CastleRights`.  Panic if invalid number.
    #[inline]
    pub const fn from_index(i: usize) -> Self {
        match i {
            0 => Self::None,
            1 => Self::KingSide,
            2 => Self::QueenSide,
            3 => Self::Both,
            _ => unreachable!(),
        }
    }

    /// Which rooks can we "guarantee" we haven't moved yet?
    #[inline]
    pub fn unmoved_rooks(self, color: Color) -> BitBoard {
        match self {
            Self::None => BB_EMPTY,
            Self::KingSide => BitBoard::from_rank_and_file(color.to_my_backrank(), File::H),
            Self::QueenSide => BitBoard::from_rank_and_file(color.to_my_backrank(), File::A),
            Self::Both => {
                BitBoard::from_rank_and_file(color.to_my_backrank(), File::A)
                    ^ BitBoard::from_rank_and_file(color.to_my_backrank(), File::H)
            }
        }
    }

    pub fn to_string(self, color: Color) -> String {
        let result = match self {
            Self::None => "",
            Self::KingSide => "k",
            Self::QueenSide => "q",
            Self::Both => "kq",
        };

        if color == White {
            result.to_uppercase()
        } else {
            result.to_string()
        }
    }

    /// Given a square of a rook, which side is it on?
    /// Note: It is invalid to pass in a non-rook square.  The code may panic.
    #[inline]
    pub fn rook_square_to_castle_rights(square: Square) -> Self {
        match square.get_file() {
            File::A => Self::QueenSide,
            File::H => Self::KingSide,
            _ => unreachable!(),
        }
    }
}

impl Add for CastleRights {
    type Output = Self;

    #[allow(clippy::suspicious_arithmetic_impl)]
    #[inline]
    fn add(self, rhs: Self) -> Self::Output {
        Self::from_index(self.to_index() | rhs.to_index())
    }
}

impl AddAssign for CastleRights {
    #[inline]
    fn add_assign(&mut self, rhs: Self) {
        *self = *self + rhs;
    }
}

impl Sub for CastleRights {
    type Output = Self;

    #[inline]
    fn sub(self, rhs: Self) -> Self::Output {
        self.remove(rhs)
    }
}

impl SubAssign for CastleRights {
    #[inline]
    fn sub_assign(&mut self, rhs: Self) {
        *self = *self - rhs;
    }
}