128 lines
3 KiB
Rust
128 lines
3 KiB
Rust
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// Eryn Wells <eryn@erynwells.me>
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use crate::castle::Castle;
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use chessfriend_core::{PlacedPiece, Shape, Square};
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use std::fmt;
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#[repr(u16)]
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#[derive(Copy, Clone, Debug, Eq, PartialEq)]
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pub enum PromotableShape {
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Knight = 0b00,
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Bishop = 0b01,
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Rook = 0b10,
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Queen = 0b11,
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}
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#[repr(u16)]
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#[derive(Copy, Clone, Debug, Eq, PartialEq)]
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enum Kind {
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Quiet = 0b00,
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DoublePush = 0b01,
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Castle(Castle),
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Capture(PlacedPiece) = 0b0100,
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EnPassantCapture(PlacedPiece) = 0b0101,
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Promotion(PromotableShape) = 0b1000,
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CapturePromotion(PlacedPiece, PromotableShape) = 0b1100,
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}
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impl Kind {
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fn bits(&self) -> u16 {
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match self {
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Self::Promotion(shape) => self.discriminant() | *shape as u16,
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Self::CapturePromotion(_, shape) => self.discriminant() | *shape as u16,
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Self::Castle(castle) => *castle as u16,
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_ => self.discriminant(),
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}
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}
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/// Return the discriminant value. This implementation is copied from the Rust docs.
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/// See https://doc.rust-lang.org/std/mem/fn.discriminant.html
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fn discriminant(&self) -> u16 {
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unsafe { *<*const _>::from(self).cast::<u16>() }
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}
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}
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impl Default for Kind {
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fn default() -> Self {
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Self::Quiet
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}
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}
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/// A single player's move. In chess parlance, this is a "ply".
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#[derive(Clone, Copy, Eq, Hash, PartialEq)]
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pub struct Move(pub(crate) u16);
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impl Move {
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pub fn from_square(&self) -> Square {
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((self.0 >> 4) & 0b111111).try_into().unwrap()
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}
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pub fn to_square(&self) -> Square {
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(self.0 >> 10).try_into().unwrap()
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}
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pub fn is_quiet(&self) -> bool {
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self.flags() == Kind::Quiet.discriminant()
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}
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pub fn is_double_push(&self) -> bool {
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self.flags() == Kind::DoublePush.discriminant()
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}
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pub fn is_castle(&self) -> bool {
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self.castle().is_some()
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}
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pub fn castle(&self) -> Option<Castle> {
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match self.flags() {
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0b0010 => Some(Castle::KingSide),
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0b0011 => Some(Castle::QueenSide),
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_ => None,
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}
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}
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pub fn is_capture(&self) -> bool {
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(self.0 & 0b0100) != 0
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}
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pub fn is_en_passant(&self) -> bool {
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self.flags() == 0b0101
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}
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pub fn is_promotion(&self) -> bool {
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(self.0 & 0b1000) != 0
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}
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pub fn promotion(&self) -> Option<Shape> {
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if !self.is_promotion() {
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return None;
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}
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Some(match self.special() {
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0b00 => Shape::Knight,
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0b01 => Shape::Bishop,
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0b10 => Shape::Rook,
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0b11 => Shape::Queen,
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_ => unreachable!(),
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})
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}
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#[inline]
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fn flags(&self) -> u16 {
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self.0 & 0b1111
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}
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#[inline]
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fn special(&self) -> u16 {
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self.0 & 0b11
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}
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}
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impl fmt::Debug for Move {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_tuple("Move")
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.field(&format_args!("{:08b}", &self.0))
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.finish()
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}
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}
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