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use core::{
fmt::{self, Display, Write as _},
num,
};
use crate::{
castling_side::CastlingSide,
color::{ByColor, Color},
role::Role,
square::Square,
util::out_of_range_error,
};
/// A piece with [`Color`] and [`Role`].
#[allow(missing_docs)]
#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
pub struct Piece {
pub color: Color,
pub role: Role,
}
impl Piece {
pub fn char(self) -> char {
self.color.fold_wb(self.role.upper_char(), self.role.char())
}
pub fn from_char(ch: char) -> Option<Piece> {
Role::from_char(ch).map(|role| role.of(Color::from_white(32 & ch as u8 == 0)))
}
}
/// Information about a move.
///
/// # Display
///
/// `Move` implements [`Display`] using long algebraic notation. If a position
/// is available for context, it is more common to use [SAN](crate::san)
/// (for human interfaces) or [UCI](crate::uci) (for text-based protocols).
#[derive(Clone, Eq, PartialEq, Hash, Debug)]
#[repr(align(4))]
pub enum Move {
/// A normal move, e.g., `Bd3xh7`.
Normal {
role: Role,
from: Square,
capture: Option<Role>,
to: Square,
promotion: Option<Role>,
},
/// An en passant capture, e.g., `e5xd6`.
EnPassant { from: Square, to: Square },
/// A castling move, `O-O` or `O-O-O`.
Castle { king: Square, rook: Square },
/// A piece drop in Crazyhouse, e.g., `Q@g8`.
Put { role: Role, to: Square },
}
impl Move {
/// Gets the role of the moved piece.
pub const fn role(&self) -> Role {
match *self {
Move::Normal { role, .. } | Move::Put { role, .. } => role,
Move::EnPassant { .. } => Role::Pawn,
Move::Castle { .. } => Role::King,
}
}
/// Gets the origin square or `None` for drops.
pub const fn from(&self) -> Option<Square> {
match *self {
Move::Normal { from, .. } | Move::EnPassant { from, .. } => Some(from),
Move::Castle { king, .. } => Some(king),
Move::Put { .. } => None,
}
}
/// Gets the target square. For castling moves this is the corresponding
/// rook square.
pub const fn to(&self) -> Square {
match *self {
Move::Normal { to, .. } | Move::EnPassant { to, .. } | Move::Put { to, .. } => to,
Move::Castle { rook, .. } => rook,
}
}
/// Gets the role of the captured piece or `None`.
pub const fn capture(&self) -> Option<Role> {
match *self {
Move::Normal { capture, .. } => capture,
Move::EnPassant { .. } => Some(Role::Pawn),
_ => None,
}
}
/// Checks if the move is a capture.
pub const fn is_capture(&self) -> bool {
matches!(
*self,
Move::Normal {
capture: Some(_),
..
} | Move::EnPassant { .. }
)
}
/// Checks if the move is en passant.
pub const fn is_en_passant(&self) -> bool {
matches!(*self, Move::EnPassant { .. })
}
/// Checks if the move zeros the half-move clock.
pub const fn is_zeroing(&self) -> bool {
matches!(
*self,
Move::Normal {
role: Role::Pawn,
..
} | Move::Normal {
capture: Some(_),
..
} | Move::EnPassant { .. }
| Move::Put {
role: Role::Pawn,
..
}
)
}
/// Gets the castling side.
pub fn castling_side(&self) -> Option<CastlingSide> {
match *self {
Move::Castle { king, rook } => Some(CastlingSide::from_king_side(king < rook)),
_ => None,
}
}
/// Checks if the move is a castling move.
pub const fn is_castle(&self) -> bool {
matches!(*self, Move::Castle { .. })
}
/// Gets the promotion role.
pub const fn promotion(&self) -> Option<Role> {
match *self {
Move::Normal { promotion, .. } => promotion,
_ => None,
}
}
/// Checks if the move is a promotion.
pub const fn is_promotion(&self) -> bool {
matches!(
*self,
Move::Normal {
promotion: Some(_),
..
}
)
}
}
impl Display for Move {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Move::Normal {
role,
from,
capture,
to,
promotion,
} => {
if role != Role::Pawn {
f.write_char(role.upper_char())?;
}
write!(
f,
"{}{}{}",
from,
if capture.is_some() { 'x' } else { '-' },
to
)?;
if let Some(p) = promotion {
write!(f, "={}", p.upper_char())?;
}
Ok(())
}
Move::EnPassant { from, to, .. } => write!(f, "{from}x{to}"),
Move::Castle { king, rook } => f.write_str(if king < rook { "O-O" } else { "O-O-O" }),
Move::Put { role, to } => {
if role != Role::Pawn {
f.write_char(role.upper_char())?;
}
write!(f, "@{to}")
}
}
}
}
/// `Standard` or `Chess960`.
#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
pub enum CastlingMode {
/// Castling notation and validity requirements for standard chess.
///
/// UCI notation describes the king movement, e.g., `e1g1`.
///
/// Castling rights are only valid for kings and rooks on their own
/// backrank. Kings must be on the e-file. Rooks must be on the a-file or
/// h-file.
Standard,
/// Castling notation for Chess960 and basic validity requirements.
///
/// UCI notation describes a king move to the corresponding rook, e.g.,
/// `e1h1`.
///
/// Castling rights are only valid for kings and rooks on their own
/// backrank. Each player can have only one king-side and queen-side
/// castling right respectively.
///
/// Beyond the castling rights possible in Chess960 starting positions,
/// the white and black rook files need not be the same. The king can be
/// on any backrank square, including the a/h-file.
Chess960,
}
impl CastlingMode {
pub const fn from_standard(standard: bool) -> CastlingMode {
if standard {
CastlingMode::Standard
} else {
CastlingMode::Chess960
}
}
pub const fn from_chess960(chess960: bool) -> CastlingMode {
if chess960 {
CastlingMode::Chess960
} else {
CastlingMode::Standard
}
}
pub const fn is_standard(self) -> bool {
matches!(self, CastlingMode::Standard)
}
pub const fn is_chess960(self) -> bool {
matches!(self, CastlingMode::Chess960)
}
}
/// When to include the en passant square.
#[derive(Copy, Clone, Eq, PartialEq, Debug, Hash)]
pub enum EnPassantMode {
/// Only if there is a fully legal en passant move.
Legal,
/// Only when a pawn has been advanced by two steps and there is an
/// enemy pawn next to it.
///
/// Follows the X-FEN specification.
PseudoLegal,
/// Whenever a pawn has been advanced by two steps.
///
/// Follows the FEN specification.
Always,
}
#[cfg(test)]
mod tests {
use core::mem;
use super::*;
#[test]
fn test_role_order() {
assert!(Role::Pawn < Role::Knight);
assert!(Role::Knight < Role::Bishop);
assert!(Role::Bishop < Role::Rook);
assert!(Role::Rook < Role::Queen);
assert!(Role::Queen < Role::King);
}
#[test]
fn test_move_size() {
assert!(mem::size_of::<Move>() <= 8);
}
}
/// The number of checks the respective side needs to give in order to win
/// (in a game of Three-Check).
///
/// # Examples
///
/// ```
/// use shakmaty::{ByColor, RemainingChecks};
///
/// let mut remaining_checks = ByColor::<RemainingChecks>::default();
/// assert_eq!(remaining_checks.white, RemainingChecks::new(3));
/// assert_eq!(remaining_checks.black, RemainingChecks::new(3));
///
/// for _ in 0..5 {
/// remaining_checks.white = remaining_checks.white.saturating_sub(1);
/// }
///
/// assert!(remaining_checks.white.is_zero());
/// ```
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
pub struct RemainingChecks(u32);
impl Default for RemainingChecks {
fn default() -> RemainingChecks {
RemainingChecks(3)
}
}
impl RemainingChecks {
/// Constructs a new [`RemainingChecks`] value.
///
/// # Panics
///
/// Panics if `n > 3`.
#[track_caller]
pub const fn new(n: u32) -> RemainingChecks {
assert!(n <= 3);
RemainingChecks(n)
}
pub const fn is_zero(self) -> bool {
self.0 == 0
}
#[must_use]
pub const fn saturating_sub(self, n: u32) -> RemainingChecks {
RemainingChecks(self.0.saturating_sub(n))
}
}
macro_rules! int_from_remaining_checks_impl {
($($t:ty)+) => {
$(impl From<RemainingChecks> for $t {
#[inline]
fn from(RemainingChecks(checks): RemainingChecks) -> $t {
checks as $t
}
})+
}
}
int_from_remaining_checks_impl! { u8 i8 u16 i16 u32 i32 u64 i64 u128 i128 usize isize }
macro_rules! try_remaining_checks_from_int_impl {
($($t:ty)+) => {
$(impl core::convert::TryFrom<$t> for RemainingChecks {
type Error = num::TryFromIntError;
#[inline]
fn try_from(value: $t) -> Result<RemainingChecks, Self::Error> {
let n = u32::try_from(value)?;
if n <= 3 {
Ok(RemainingChecks::new(n))
} else {
Err(out_of_range_error())
}
}
})+
}
}
try_remaining_checks_from_int_impl! { u8 i8 u16 i16 u32 i32 u64 i64 u128 i128 usize isize }
impl Display for ByColor<RemainingChecks> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}+{}", self.white.0, self.black.0)
}
}