chore: license

fails tests

Cargo.toml

@@ -2,6 +2,7 @@
 name = "chess_inator"
 version = "0.1.0"
 edition = "2021"
+license = "GPL-3.0-or-later"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 

LICENSE

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
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+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

src/bin/movegen_tool.rs

@@ -0,0 +1,15 @@
+//! Generates moves from the FEN in the argv.
+
+use chess_inator::fen::FromFen;
+use chess_inator::movegen::{MoveGen, MoveGenType};
+use chess_inator::Board;
+use std::env;
+
+fn main() {
+    let fen = env::args().nth(1).unwrap();
+    let mut board = Board::from_fen(&fen).unwrap();
+    let mvs = board.gen_moves(MoveGenType::Legal);
+    for mv in mvs.into_iter() {
+        println!("{mv:?}")
+    }
+}

src/bin/perft_tool.rs

@@ -0,0 +1,14 @@
+//! Runs perft at depth for a given FEN.
+
+use chess_inator::fen::FromFen;
+use chess_inator::movegen::perft;
+use chess_inator::Board;
+use std::env;
+
+fn main() {
+    let depth = env::args().nth(1).unwrap().parse::<usize>().unwrap();
+    let fen = env::args().nth(2).unwrap();
+    let mut board = Board::from_fen(&fen).unwrap();
+    let res = perft(depth, &mut board);
+    println!("{res}")
+}

src/fen.rs

@@ -1,4 +1,17 @@
-use crate::{BoardState, CastleRights, ColPiece, Color, Square, BOARD_HEIGHT, BOARD_WIDTH};
+/*
+
+This file is part of chess_inator.
+
+chess_inator is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+
+chess_inator is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with chess_inator. If not, see https://www.gnu.org/licenses/.
+
+Copyright © 2024 dogeystamp <dogeystamp@disroot.org>
+*/
+
+use crate::{Board, ColPiece, Color, Square, SquareIdx, BOARD_HEIGHT, BOARD_WIDTH};
 
 pub const START_POSITION: &str = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1";
 
@@ -34,9 +47,9 @@ pub enum FenError {
     InternalError(usize),
 }
 
-impl FromFen for BoardState {
+impl FromFen for Board {
     type Error = FenError;
-    fn from_fen(fen: &str) -> Result<BoardState, FenError> {
+    fn from_fen(fen: &str) -> Result<Board, FenError> {
         //! Parse FEN string into position.
 
         /// Parser state machine.
@@ -60,7 +73,7 @@ impl FromFen for BoardState {
             FullMove,
         }
 
-        let mut pos = BoardState::default();
+        let mut pos = Board::default();
 
         let mut parser_state = FenState::Piece(0, 0);
         let mut next_state = FenState::Space;
@@ -179,7 +192,7 @@ impl FromFen for BoardState {
                             parse_space_and_goto!(FenState::HalfMove);
                         }
                         'a'..='h' => {
-                            pos.ep_square = Some(Square(c as usize - 'a' as usize));
+                            pos.ep_square = Some(Square(c as SquareIdx - b'a'));
                             parser_state = FenState::EnPassantFile;
                         }
                         _ => return bad_char!(i, c),
@@ -188,8 +201,8 @@ impl FromFen for BoardState {
                 FenState::EnPassantFile => {
                     if let Some(digit) = c.to_digit(10) {
                         pos.ep_square = Some(Square(
-                            usize::from(pos.ep_square.unwrap_or(Square(0)))
+                            SquareIdx::from(pos.ep_square.unwrap_or(Square(0)))
-                                + (digit as usize - 1) * 8,
+                                + (digit as SquareIdx - 1) * 8,
                         ));
                     } else {
                         return bad_char!(i, c);
@@ -198,7 +211,7 @@ impl FromFen for BoardState {
                 }
                 FenState::HalfMove => {
                     if let Some(digit) = c.to_digit(10) {
-                        if pos.half_moves > BoardState::MAX_MOVES {
+                        if pos.half_moves > Board::MAX_MOVES {
                             return Err(FenError::TooManyMoves);
                         }
                         pos.half_moves *= 10;
@@ -211,7 +224,7 @@ impl FromFen for BoardState {
                 }
                 FenState::FullMove => {
                     if let Some(digit) = c.to_digit(10) {
-                        if pos.half_moves > BoardState::MAX_MOVES {
+                        if pos.half_moves > Board::MAX_MOVES {
                             return Err(FenError::TooManyMoves);
                         }
                         pos.full_moves *= 10;
@@ -233,7 +246,7 @@ impl FromFen for BoardState {
     }
 }
 
-impl ToFen for BoardState {
+impl ToFen for Board {
     fn to_fen(&self) -> String {
         let pieces_str = (0..BOARD_HEIGHT)
             .rev()
@@ -280,15 +293,14 @@ impl ToFen for BoardState {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::CastlePlayer;
+    use crate::{CastlePlayer, CastleRights, N_SQUARES};
-    use crate::N_SQUARES;
 
     #[test]
     fn test_fen_pieces() {
         let fen = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1";
-        let board = BoardState::from_fen(fen.into()).unwrap();
+        let board = Board::from_fen(fen.into()).unwrap();
         assert_eq!(
-            (0..N_SQUARES)
+            (0..SquareIdx::try_from(N_SQUARES).unwrap())
                 .map(Square)
                 .map(|i| board.get_piece(i))
                 .map(ColPiece::opt_to_char)
@@ -301,7 +313,7 @@ mod tests {
 
     macro_rules! make_board {
         ($fen_fmt: expr) => {
-            BoardState::from_fen(&format!($fen_fmt)).unwrap()
+            Board::from_fen(&format!($fen_fmt)).unwrap()
         };
     }
 
@@ -388,7 +400,7 @@ mod tests {
 
     #[test]
     fn test_fen_half_move_counter() {
-        for i in 0..=BoardState::MAX_MOVES {
+        for i in 0..=Board::MAX_MOVES {
             let board = make_board!("8/8/8/8/8/8/8/8 w - - {i} 0");
             assert_eq!(board.half_moves, i);
             assert_eq!(board.full_moves, 0);
@@ -397,7 +409,7 @@ mod tests {
 
     #[test]
     fn test_fen_move_counter() {
-        for i in 0..=BoardState::MAX_MOVES {
+        for i in 0..=Board::MAX_MOVES {
             let board = make_board!("8/8/8/8/8/8/8/8 w - - 0 {i}");
             assert_eq!(board.half_moves, 0);
             assert_eq!(board.full_moves, i);
@@ -437,7 +449,7 @@ mod tests {
 
         for fen1 in test_cases {
             println!("fen1: {fen1:?}");
-            let fen2 = BoardState::from_fen(fen1).unwrap().to_fen();
+            let fen2 = Board::from_fen(fen1).unwrap().to_fen();
 
             assert_eq!(fen1.to_string(), fen2, "FEN not equivalent")
         }

src/lib.rs

@@ -1,3 +1,16 @@
+/*
+
+This file is part of chess_inator.
+
+chess_inator is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+
+chess_inator is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with chess_inator. If not, see https://www.gnu.org/licenses/.
+
+Copyright © 2024 dogeystamp <dogeystamp@disroot.org>
+*/
+
 #![deny(rust_2018_idioms)]
 
 use std::fmt::Display;
@@ -6,12 +19,14 @@ use std::str::FromStr;
 pub mod fen;
 pub mod movegen;
 
+use crate::fen::{FromFen, ToFen, START_POSITION};
+
 const BOARD_WIDTH: usize = 8;
 const BOARD_HEIGHT: usize = 8;
 const N_SQUARES: usize = BOARD_WIDTH * BOARD_HEIGHT;
 
 #[derive(Debug, Copy, Clone, Default, PartialEq, Eq)]
-enum Color {
+pub enum Color {
     #[default]
     White = 0,
     Black = 1,
@@ -48,11 +63,11 @@ enum Piece {
 }
 const N_PIECES: usize = 6;
 
-struct PieceErr;
+pub struct PieceErr;
 
 /// Color and piece.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
-struct ColPiece {
+pub struct ColPiece {
     pc: Piece,
     col: Color,
 }
@@ -107,11 +122,13 @@ impl ColPiece {
     }
 }
 
+type SquareIdx = u8;
+
 /// Square index newtype.
 ///
 /// A1 is (0, 0) -> 0, A2 is (0, 1) -> 2, and H8 is (7, 7) -> 63.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-struct Square(usize);
+pub struct Square(SquareIdx);
 
 #[derive(Debug)]
 pub enum SquareError {
@@ -119,11 +136,11 @@ pub enum SquareError {
     InvalidCharacter(char),
 }
 
-impl TryFrom<usize> for Square {
+impl TryFrom<SquareIdx> for Square {
     type Error = SquareError;
 
-    fn try_from(value: usize) -> Result<Self, Self::Error> {
+    fn try_from(value: SquareIdx) -> Result<Self, Self::Error> {
-        if (0..N_SQUARES).contains(&value) {
+        if (0..N_SQUARES).contains(&value.into()) {
             Ok(Square(value))
         } else {
             Err(SquareError::OutOfBounds)
@@ -139,7 +156,7 @@ macro_rules! sq_try_from {
             fn try_from(value: $T) -> Result<Self, Self::Error> {
                 if let Ok(upper_bound) = <$T>::try_from(N_SQUARES) {
                     if (0..upper_bound).contains(&value) {
-                        return Ok(Square(value as usize));
+                        return Ok(Square(value as SquareIdx));
                     }
                 }
                 Err(SquareError::OutOfBounds)
@@ -148,13 +165,20 @@ macro_rules! sq_try_from {
     };
 }
 
+sq_try_from!(i8);
 sq_try_from!(i32);
 sq_try_from!(isize);
-sq_try_from!(i8);
+sq_try_from!(usize);
+
+impl From<Square> for SquareIdx {
+    fn from(value: Square) -> Self {
+        value.0
+    }
+}
 
 impl From<Square> for usize {
     fn from(value: Square) -> Self {
-        value.0
+        value.0.into()
     }
 }
 
@@ -179,10 +203,10 @@ impl Square {
     }
     fn to_row_col(self) -> (usize, usize) {
         //! Get row, column from index
-        let div = self.0 / BOARD_WIDTH;
+        let div = usize::from(self.0) / BOARD_WIDTH;
-        let rem = self.0 % BOARD_WIDTH;
+        let rem = usize::from(self.0) % BOARD_WIDTH;
-        assert!(div <= 7);
+        debug_assert!(div <= 7);
-        assert!(rem <= 7);
+        debug_assert!(rem <= 7);
         (div, rem)
     }
     fn to_row_col_signed(self) -> (isize, isize) {
@@ -266,7 +290,7 @@ impl From<Piece> for char {
 }
 
 #[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
-struct Bitboard(u64);
+pub struct Bitboard(u64);
 
 impl Bitboard {
     pub fn on_sq(&mut self, idx: Square) {
@@ -299,7 +323,7 @@ impl IntoIterator for Bitboard {
     }
 }
 
-struct BitboardIterator {
+pub struct BitboardIterator {
     remaining: Bitboard,
 }
 
@@ -311,7 +335,7 @@ impl Iterator for BitboardIterator {
             None
         } else {
             let next_idx = self.remaining.0.trailing_zeros() as usize;
-            let sq = Square(next_idx);
+            let sq = Square(next_idx.try_into().unwrap());
             self.remaining.off_sq(sq);
             Some(sq)
         }
@@ -401,7 +425,7 @@ impl ToString for CastleRights {
 ///
 /// Default is empty.
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
-pub struct BoardState {
+pub struct Board {
     /// Player bitboards
     players: [Player; N_COLORS],
 
@@ -426,11 +450,12 @@ pub struct BoardState {
     turn: Color,
 }
 
-/// Piece missing where there should be one.
+impl Board {
-#[derive(Debug)]
+    /// Default chess position.
-struct NoPieceError;
+    pub fn starting_pos() -> Self {
+        Board::from_fen(START_POSITION).unwrap()
+    }
 
-impl BoardState {
     /// Get mutable reference to a player.
     fn pl_mut(&mut self, col: Color) -> &mut Player {
         &mut self.players[col as usize]
@@ -442,7 +467,7 @@ impl BoardState {
     }
 
     /// Get immutable reference to castling rights.
-    fn pl_castle(&self, col: Color) -> &CastlePlayer {
+    pub fn pl_castle(&self, col: Color) -> &CastlePlayer {
         &self.castle.0[col as usize]
     }
 
@@ -452,58 +477,58 @@ impl BoardState {
     }
 
     /// Get iterator over all squares.
-    fn squares() -> impl Iterator<Item = Square> {
+    pub fn squares() -> impl Iterator<Item = Square> {
         (0..N_SQUARES).map(Square::try_from).map(|x| x.unwrap())
     }
 
-    /// Create a new piece in a location.
+    /// Create a new piece in a location, and pop any existing piece in the destination.
-    fn set_piece(&mut self, idx: Square, pc: ColPiece) {
+    pub fn set_piece(&mut self, idx: Square, pc: ColPiece) -> Option<ColPiece> {
-        let _ = self.del_piece(idx);
+        let dest_pc = self.del_piece(idx);
         let pl = self.pl_mut(pc.col);
         pl.board_mut(pc.into()).on_sq(idx);
         *self.mail.sq_mut(idx) = Some(pc);
+        dest_pc
     }
 
-    /// Set the piece (or no piece) in a square.
+    /// Set the piece (or no piece) in a square, and return ("pop") the existing piece.
-    fn set_square(&mut self, idx: Square, pc: Option<ColPiece>) {
+    pub fn set_square(&mut self, idx: Square, pc: Option<ColPiece>) -> Option<ColPiece> {
         match pc {
             Some(pc) => self.set_piece(idx, pc),
-            None => {
+            None => self.del_piece(idx),
-                let _ = self.del_piece(idx);
-            }
         }
     }
 
     /// Delete the piece in a location, and return ("pop") that piece.
-    ///
+    pub fn del_piece(&mut self, idx: Square) -> Option<ColPiece> {
-    /// Returns an error if there is no piece in the location.
-    fn del_piece(&mut self, idx: Square) -> Result<ColPiece, NoPieceError> {
         if let Some(pc) = *self.mail.sq_mut(idx) {
             let pl = self.pl_mut(pc.col);
             pl.board_mut(pc.into()).off_sq(idx);
             *self.mail.sq_mut(idx) = None;
-            Ok(pc)
+            Some(pc)
         } else {
-            Err(NoPieceError)
+            None
         }
     }
 
     fn move_piece(&mut self, src: Square, dest: Square) {
-        let pc = self
+        let pc = self.del_piece(src).unwrap_or_else(|| {
-            .del_piece(src)
+            panic!(
-            .unwrap_or_else(|_| panic!("move ({src} -> {dest}) should have piece at source"));
+                "move ({src} -> {dest}) should have piece at source (pos '{}')",
+                self.to_fen()
+            )
+        });
         self.set_piece(dest, pc);
     }
 
     /// Get the piece at a location.
-    fn get_piece(&self, idx: Square) -> Option<ColPiece> {
+    pub fn get_piece(&self, idx: Square) -> Option<ColPiece> {
         *self.mail.sq(idx)
     }
 
     /// Mirrors the position so that black and white are switched.
     ///
     /// Mainly to avoid duplication in tests.
-    fn flip_colors(&self) -> Self {
+    pub fn flip_colors(&self) -> Self {
         let mut new_board = Self {
             turn: self.turn.flip(),
             half_moves: self.half_moves,
@@ -516,21 +541,70 @@ impl BoardState {
 
         new_board.castle.0.reverse();
 
-        for sq in BoardState::squares() {
+        for sq in Board::squares() {
             let opt_pc = self.get_piece(sq.mirror_vert()).map(|pc| ColPiece {
                 col: pc.col.flip(),
                 pc: pc.pc,
             });
-            new_board.set_square(sq, opt_pc)
+            new_board.set_square(sq, opt_pc);
         }
         new_board
     }
 
+    /// Is a given player in check?
+    pub fn is_check(&self, pl: Color) -> bool {
+        for src in self.pl(pl).board(Piece::King).into_iter() {
+            macro_rules! detect_checker {
+                ($dirs: ident, $pc: pat, $keep_going: expr) => {
+                    for dir in $dirs.into_iter() {
+                        let (mut r, mut c) = src.to_row_col_signed();
+                        loop {
+                            let (nr, nc) = (r + dir.0, c + dir.1);
+                            if let Ok(sq) = Square::from_row_col_signed(nr, nc) {
+                                if let Some(pc) = self.get_piece(sq) {
+                                    if matches!(pc.pc, $pc) && pc.col != pl {
+                                        return true;
+                                    } else {
+                                        break;
+                                    }
+                                }
+                            } else {
+                                break;
+                            }
+                            if (!($keep_going)) {
+                                break;
+                            }
+                            r = nr;
+                            c = nc;
+                        }
+                    }
+                };
+            }
+
+            let dirs_white_pawn = [(-1, 1), (-1, -1)];
+            let dirs_black_pawn = [(1, 1), (1, -1)];
+
+            use Piece::*;
+
+            use movegen::{DIRS_DIAG, DIRS_KNIGHT, DIRS_STAR, DIRS_STRAIGHT};
+
+            detect_checker!(DIRS_DIAG, Bishop | Queen, true);
+            detect_checker!(DIRS_STRAIGHT, Rook | Queen, true);
+            detect_checker!(DIRS_STAR, King, false);
+            detect_checker!(DIRS_KNIGHT, Knight, false);
+            match pl {
+                Color::White => detect_checker!(dirs_black_pawn, Pawn, false),
+                Color::Black => detect_checker!(dirs_white_pawn, Pawn, false),
+            }
+        }
+        false
+    }
+
     /// Maximum amount of moves in the counter to parse before giving up
     const MAX_MOVES: usize = 9_999;
 }
 
-impl core::fmt::Display for BoardState {
+impl core::fmt::Display for Board {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let mut str = String::with_capacity(N_SQUARES + BOARD_HEIGHT);
         for row in (0..BOARD_HEIGHT).rev() {
@@ -568,10 +642,10 @@ mod tests {
             try_type!(i32);
             try_type!(i8);
             try_type!(isize);
-            try_type!(usize);
+            try_type!(u8);
         }
 
-        let good_cases = 0..N_SQUARES;
+        let good_cases = 0..SquareIdx::try_from(N_SQUARES).unwrap();
         for tc in good_cases {
             macro_rules! try_type {
                 ($T: ty) => {
@@ -583,7 +657,7 @@ mod tests {
             try_type!(i32);
             try_type!(i8);
             try_type!(isize);
-            try_type!(usize);
+            try_type!(u8);
         }
     }
 
@@ -601,10 +675,7 @@ mod tests {
 
     #[test]
     fn test_bitboard_iteration() {
-        let indices = [
+        let indices = [0, 5, 17, 24, 34, 39, 42, 45, 49, 50, 63];
-            0usize, 5usize, 17usize, 24usize, 34usize, 39usize, 42usize, 45usize, 49usize, 50usize,
-            63usize,
-        ];
 
         let mut bitboard = Bitboard::default();
 
@@ -619,7 +690,7 @@ mod tests {
             }
         }
 
-        let board = BoardState::from_fen("8/4p3/1q1Q1p2/4p3/1p1r4/8/8/8 w - - 0 1").unwrap();
+        let board = Board::from_fen("8/4p3/1q1Q1p2/4p3/1p1r4/8/8/8 w - - 0 1").unwrap();
         let white_queens = board
             .pl(Color::White)
             .board(Piece::Queen)
@@ -654,8 +725,8 @@ mod tests {
             ),
         ];
         for (tc, expect) in test_cases {
-            let tc = BoardState::from_fen(tc).unwrap();
+            let tc = Board::from_fen(tc).unwrap();
-            let expect = BoardState::from_fen(expect).unwrap();
+            let expect = Board::from_fen(expect).unwrap();
             assert_eq!(tc.flip_colors(), expect);
         }
     }

src/movegen.rs

@@ -1,46 +1,23 @@
+/*
+
+This file is part of chess_inator.
+
+chess_inator is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.
+
+chess_inator is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with chess_inator. If not, see https://www.gnu.org/licenses/.
+
+Copyright © 2024 dogeystamp <dogeystamp@disroot.org>
+*/
+
 //! Move generation.
 
-use crate::fen::{FromFen, ToFen, START_POSITION};
+use crate::fen::ToFen;
 use crate::{
-    BoardState, ColPiece, Color, Piece, Square, SquareError, BOARD_HEIGHT, BOARD_WIDTH, N_SQUARES,
+    Board, CastleRights, ColPiece, Color, Piece, Square, SquareError, BOARD_HEIGHT, BOARD_WIDTH,
+    N_SQUARES,
 };
-use std::rc::Rc;
-
-/// Game tree node.
-#[derive(Clone, Debug)]
-pub struct Node {
-    /// Immutable position data.
-    pos: BoardState,
-    /// Backlink to previous node.
-    prev: Option<Rc<Node>>,
-}
-
-impl Default for Node {
-    fn default() -> Self {
-        Node::new(BoardState::from_fen(START_POSITION).expect("Starting FEN should be valid"))
-    }
-}
-
-impl Node {
-    /// Undo move.
-    ///
-    /// Intended usage is to always keep an Rc to the current node, and overwrite it with the
-    /// result of unmake.
-    pub fn unmake(&self) -> Rc<Node> {
-        if let Some(prev) = &self.prev {
-            Rc::clone(prev)
-        } else {
-            panic!("unmake should not be called on root node");
-        }
-    }
-
-    pub fn new(board: BoardState) -> Self {
-        Node {
-            pos: board,
-            prev: None,
-        }
-    }
-}
 
 /// Piece enum specifically for promotions.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
@@ -62,6 +39,93 @@ impl From<PromotePiece> for Piece {
     }
 }
 
+#[derive(Debug, Clone, Copy)]
+enum AntiMoveType {
+    Normal,
+    /// En passant.
+    EnPassant {
+        cap: Square,
+    },
+    /// Pawn promotion.
+    Promotion,
+    /// King-rook castle. The king is the one considered to move.
+    Castle {
+        rook_src: Square,
+        rook_dest: Square,
+    },
+}
+
+/// Information used to reverse (unmake) a move.
+#[derive(Debug, Clone, Copy)]
+pub struct AntiMove {
+    dest: Square,
+    src: Square,
+    /// Captured piece, always assumed to be of enemy color.
+    cap: Option<Piece>,
+    move_type: AntiMoveType,
+    /// Half-move counter prior to this move
+    half_moves: usize,
+    /// Castling rights prior to this move.
+    castle: CastleRights,
+    /// En passant target square prior to this move.
+    ep_square: Option<Square>,
+}
+
+impl AntiMove {
+    /// Undo the move.
+    fn unmake(self, pos: &mut Board) {
+        pos.move_piece(self.dest, self.src);
+        pos.half_moves = self.half_moves;
+        pos.castle = self.castle;
+        pos.ep_square = self.ep_square;
+
+        /// Restore captured piece at a given square.
+        macro_rules! cap_sq {
+            ($sq: expr) => {
+                if let Some(cap_pc) = self.cap {
+                    pos.set_piece(
+                        $sq,
+                        ColPiece {
+                            pc: cap_pc,
+                            col: pos.turn.flip(),
+                        },
+                    );
+                }
+            };
+        }
+
+        pos.turn = pos.turn.flip();
+        if pos.turn == Color::Black {
+            pos.full_moves -= 1;
+        }
+
+        match self.move_type {
+            AntiMoveType::Normal => {
+                cap_sq!(self.dest)
+            }
+            AntiMoveType::EnPassant { cap } => {
+                cap_sq!(cap);
+            }
+            AntiMoveType::Promotion => {
+                cap_sq!(self.dest);
+                pos.set_piece(
+                    self.src,
+                    ColPiece {
+                        pc: Piece::Pawn,
+                        col: pos.turn,
+                    },
+                );
+            }
+            AntiMoveType::Castle {
+                rook_src,
+                rook_dest,
+            } => {
+                pos.move_piece(rook_dest, rook_src);
+            }
+        }
+    }
+}
+
 #[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone, Copy)]
 enum MoveType {
     /// Pawn promotes to another piece.
@@ -80,24 +144,30 @@ pub struct Move {
 }
 
 impl Move {
-    /// Make move, without setting up the backlink for unmake.
+    /// Apply move to a position.
-    ///
+    fn make(self, pos: &mut Board) -> AntiMove {
-    /// Call this directly when making new positions that are dead ends (won't be used further).
+        let mut anti_move = AntiMove {
-    fn make_unlinked(self, old_pos: BoardState) -> BoardState {
+            dest: self.dest,
-        let mut new_pos = old_pos;
+            src: self.src,
+            cap: None,
+            move_type: AntiMoveType::Normal,
+            half_moves: pos.half_moves,
+            castle: pos.castle,
+            ep_square: pos.ep_square,
+        };
 
         // reset en passant
-        new_pos.ep_square = None;
+        let ep_square = pos.ep_square;
+        pos.ep_square = None;
 
-        if old_pos.turn == Color::Black {
+        if pos.turn == Color::Black {
-            new_pos.full_moves += 1;
+            pos.full_moves += 1;
         }
 
         /// Get the piece at the source square.
         macro_rules! pc_src {
             ($data: ident) => {
-                new_pos
+                pos.get_piece($data.src)
-                    .get_piece($data.src)
                     .expect("Move source should have a piece")
             };
         }
@@ -106,11 +176,11 @@ impl Move {
             ($pc_src: ident) => {
                 debug_assert_eq!(
                     $pc_src.col,
-                    new_pos.turn,
+                    pos.turn,
                     "Moving piece on wrong turn. Move {} -> {} on board '{}'",
                     self.src,
                     self.dest,
-                    old_pos.to_fen()
+                    pos.to_fen()
                 );
                 debug_assert_ne!(self.src, self.dest, "Moving piece to itself.");
             };
@@ -122,27 +192,33 @@ impl Move {
                 pc_asserts!(pc_src);
                 debug_assert_eq!(pc_src.pc, Piece::Pawn);
 
-                let _ = new_pos.del_piece(self.src);
+                pos.half_moves = 0;
-                new_pos.set_piece(
+
+                anti_move.move_type = AntiMoveType::Promotion;
+
+                pos.del_piece(self.src);
+                let cap_pc = pos.set_piece(
                     self.dest,
                     ColPiece {
                         pc: Piece::from(to_piece),
                         col: pc_src.col,
                     },
-                )
+                );
+                anti_move.cap = cap_pc.map(|pc| pc.pc);
             }
             MoveType::Normal => {
                 let pc_src = pc_src!(self);
                 pc_asserts!(pc_src);
 
-                let pc_dest: Option<ColPiece> = new_pos.get_piece(self.dest);
+                let pc_dest: Option<ColPiece> = pos.get_piece(self.dest);
+                anti_move.cap = pc_dest.map(|pc| pc.pc);
 
                 let (src_row, src_col) = self.src.to_row_col_signed();
                 let (dest_row, dest_col) = self.dest.to_row_col_signed();
 
                 if matches!(pc_src.pc, Piece::Pawn) {
                     // pawn moves are irreversible
-                    new_pos.half_moves = 0;
+                    pos.half_moves = 0;
 
                     // set en-passant target square
                     if src_row.abs_diff(dest_row) == 2 {
@@ -155,31 +231,49 @@ impl Move {
                             };
                         let ep_targ = Square::from_row_col_signed(ep_row, ep_col)
                             .expect("En-passant target should be valid.");
-                        new_pos.ep_square = Some(ep_targ)
+                        pos.ep_square = Some(ep_targ)
                     } else if pc_dest.is_none() && src_col != dest_col {
                         // we took en passant
                         debug_assert!(src_row.abs_diff(dest_row) == 1);
-                        debug_assert_eq!(self.dest, old_pos.ep_square.unwrap());
+                        assert_eq!(
+                            self.dest,
+                            ep_square.expect("ep target should exist if taking ep")
+                        );
                         // square to actually capture at
                         let ep_capture = Square::try_from(match pc_src.col {
-                            Color::White => self.dest.0 - BOARD_WIDTH,
+                            Color::White => usize::from(self.dest.0) - BOARD_WIDTH,
-                            Color::Black => self.dest.0 + BOARD_WIDTH,
+                            Color::Black => usize::from(self.dest.0) + BOARD_WIDTH,
                         })
                         .expect("En-passant capture square should be valid");
-                        new_pos.del_piece(ep_capture).unwrap_or_else(|_| {
+
-                            panic!("En-passant capture square should have piece. Position '{}', move {:?}", old_pos.to_fen(), self)
+                        anti_move.move_type = AntiMoveType::EnPassant { cap: ep_capture };
-                        });
+                        if let Some(pc_cap) = pos.del_piece(ep_capture) {
+                            debug_assert_eq!(
+                                pc_cap.col,
+                                pos.turn.flip(),
+                                "attempt to en passant wrong color, pos '{}', move {:?}",
+                                pos.to_fen(),
+                                self
+                            );
+                            anti_move.cap = Some(pc_cap.pc);
+                        } else {
+                            panic!(
+                                "En-passant capture square should have piece. Position '{}', move {:?}",
+                                pos.to_fen(),
+                                self
+                            );
+                        }
                     }
                 } else {
-                    new_pos.half_moves += 1;
+                    pos.half_moves += 1;
                 }
 
                 if pc_dest.is_some() {
                     // captures are irreversible
-                    new_pos.half_moves = 0;
+                    pos.half_moves = 0;
                 }
 
-                let castle = &mut new_pos.pl_castle_mut(pc_src.col);
+                let castle = &mut pos.pl_castle_mut(pc_src.col);
                 if matches!(pc_src.pc, Piece::King) {
                     // forfeit castling rights
                     castle.k = false;
@@ -203,8 +297,12 @@ impl Move {
                             .expect("rook castling src square should be valid");
                         let rook_dest = Square::from_row_col_signed(rook_row, rook_dest_col)
                             .expect("rook castling dest square should be valid");
-                        debug_assert!(new_pos.get_piece(rook_src).is_some(), "rook castling src square has no rook (move: {rook_src} -> {rook_dest})");
+                        debug_assert!(pos.get_piece(rook_src).is_some(), "rook castling src square has no rook (move: {rook_src} -> {rook_dest})");
-                        new_pos.move_piece(rook_src, rook_dest);
+                        anti_move.move_type = AntiMoveType::Castle {
+                            rook_src,
+                            rook_dest,
+                        };
+                        pos.move_piece(rook_src, rook_dest);
                     }
                     debug_assert!(
                         (0..=2).contains(&horiz_diff),
@@ -217,40 +315,29 @@ impl Move {
                         Color::White => {
                             if self.src == Square(0) {
                                 castle.q = false;
-                            } else if self.src == Square(BOARD_WIDTH - 1) {
+                            } else if self.src == Square::try_from(BOARD_WIDTH - 1).unwrap() {
                                 castle.k = false;
                             };
                         }
                         Color::Black => {
-                            if self.src == Square((BOARD_HEIGHT - 1) * BOARD_WIDTH) {
+                            if self.src
+                                == Square::try_from((BOARD_HEIGHT - 1) * BOARD_WIDTH).unwrap()
+                            {
                                 castle.q = false;
-                            } else if self.src == Square(N_SQUARES - 1) {
+                            } else if self.src == Square::try_from(N_SQUARES - 1).unwrap() {
                                 castle.k = false;
                             };
                         }
                     }
                 }
 
-                new_pos.move_piece(self.src, self.dest);
+                pos.move_piece(self.src, self.dest);
             }
-        }
+        };
 
-        new_pos.turn = new_pos.turn.flip();
+        pos.turn = pos.turn.flip();
 
-        new_pos
+        anti_move
-    }
-
-    /// Make move and return new position.
-    ///
-    /// Old position is saved in a backlink.
-    /// No checking is done to verify even pseudo-legality of the move.
-    pub fn make(self, old_node: &Rc<Node>) -> Rc<Node> {
-        let pos = self.make_unlinked(old_node.pos);
-        Node {
-            prev: Some(Rc::clone(old_node)),
-            pos,
-        }
-        .into()
     }
 }
 
@@ -321,18 +408,21 @@ impl FromUCIAlgebraic for Move {
     }
 }
 
-/// Pseudo-legal move generation.
+#[derive(Debug, Clone, Copy)]
-///
+pub enum MoveGenType {
-/// "Pseudo-legal" here means that moving into check (but not castling through check) is allowed,
+    /// Legal move generation.
-/// and capturing friendly pieces is allowed. These will be filtered out in the legal move
+    Legal,
-/// generation step.
+    /// Allow capturing friendly pieces, moving into check, but not castling through check.
-pub trait PseudoMoveGen {
+    Pseudo,
-    fn gen_pseudo_moves(&self) -> impl IntoIterator<Item = Move>;
 }
 
-const DIRS_STRAIGHT: [(isize, isize); 4] = [(0, 1), (1, 0), (-1, 0), (0, -1)];
+pub trait MoveGen {
-const DIRS_DIAG: [(isize, isize); 4] = [(1, 1), (1, -1), (-1, 1), (-1, -1)];
+    fn gen_moves(&mut self, gen_type: MoveGenType) -> impl IntoIterator<Item = Move>;
-const DIRS_STAR: [(isize, isize); 8] = [
+}
+
+pub const DIRS_STRAIGHT: [(isize, isize); 4] = [(0, 1), (1, 0), (-1, 0), (0, -1)];
+pub const DIRS_DIAG: [(isize, isize); 4] = [(1, 1), (1, -1), (-1, 1), (-1, -1)];
+pub const DIRS_STAR: [(isize, isize); 8] = [
     (1, 1),
     (1, -1),
     (-1, 1),
@@ -342,7 +432,7 @@ const DIRS_STAR: [(isize, isize); 8] = [
     (-1, 0),
     (0, -1),
 ];
-const DIRS_KNIGHT: [(isize, isize); 8] = [
+pub const DIRS_KNIGHT: [(isize, isize); 8] = [
     (2, 1),
     (1, 2),
     (-1, 2),
@@ -370,7 +460,7 @@ enum SliderDirection {
 /// * `slide_type`: Directions the piece is allowed to go in.
 /// * `keep_going`: Allow sliding more than one square (true for everything except king).
 fn move_slider(
-    board: &BoardState,
+    board: &Board,
     src: Square,
     move_list: &mut Vec<Move>,
     slide_type: SliderDirection,
@@ -413,9 +503,31 @@ fn move_slider(
         }
     }
 }
+fn is_legal(board: &mut Board, mv: Move) -> bool {
+    // mut required for check checking
+    // disallow friendly fire
+    let src_pc = board
+        .get_piece(mv.src)
+        .expect("move source should have piece");
+    if let Some(dest_pc) = board.get_piece(mv.dest) {
+        if dest_pc.col == src_pc.col {
+            return false;
+        }
+    }
 
-impl PseudoMoveGen for BoardState {
+    // disallow moving into check
-    fn gen_pseudo_moves(&self) -> impl IntoIterator<Item = Move> {
+    let anti_move = mv.make(board);
+    let is_check = board.is_check(board.turn.flip());
+    anti_move.unmake(board);
+    if is_check {
+        return false;
+    }
+
+    true
+}
+
+impl MoveGen for Board {
+    fn gen_moves(&mut self, gen_type: MoveGenType) -> impl IntoIterator<Item = Move> {
         let mut ret = Vec::new();
         let pl = self.pl(self.turn);
         macro_rules! squares {
@@ -491,7 +603,7 @@ impl PseudoMoveGen for BoardState {
                     .map(|dest| {
                         let mut board = *self;
                         board.move_piece(src, dest);
-                        is_check(&board, self.turn)
+                        board.is_check(self.turn)
                     })
                     .any(|x| x);
                 if is_any_checked {
@@ -597,97 +709,26 @@ impl PseudoMoveGen for BoardState {
                 }
             }
         }
-        ret
+        ret.into_iter().filter(move |mv| match gen_type {
-    }
+            MoveGenType::Legal => is_legal(self, *mv),
-}
+            MoveGenType::Pseudo => true,
-
+        })
-/// Legal move generation.
-pub trait LegalMoveGen {
-    fn gen_moves(&self) -> impl IntoIterator<Item = Move>;
-}
-
-/// Is a given player in check?
-fn is_check(board: &BoardState, pl: Color) -> bool {
-    for src in board.pl(pl).board(Piece::King).into_iter() {
-        macro_rules! detect_checker {
-            ($dirs: ident, $pc: ident, $keep_going: expr) => {
-                for dir in $dirs.into_iter() {
-                    let (mut r, mut c) = src.to_row_col_signed();
-                    loop {
-                        let (nr, nc) = (r + dir.0, c + dir.1);
-                        if let Ok(sq) = Square::from_row_col_signed(nr, nc) {
-                            if let Some(pc) = board.get_piece(sq) {
-                                if pc.pc == Piece::$pc && pc.col != pl {
-                                    return true;
-                                } else {
-                                    break;
-                                }
-                            }
-                        } else {
-                            break;
-                        }
-                        if (!($keep_going)) {
-                            break;
-                        }
-                        r = nr;
-                        c = nc;
-                    }
-                }
-            };
-        }
-
-        let dirs_white_pawn = [(-1, 1), (-1, -1)];
-        let dirs_black_pawn = [(1, 1), (1, -1)];
-
-        detect_checker!(DIRS_STAR, Queen, true);
-        detect_checker!(DIRS_DIAG, Bishop, true);
-        detect_checker!(DIRS_STRAIGHT, Rook, true);
-        detect_checker!(DIRS_STAR, King, false);
-        detect_checker!(DIRS_KNIGHT, Knight, false);
-        match pl {
-            Color::White => detect_checker!(dirs_black_pawn, Pawn, false),
-            Color::Black => detect_checker!(dirs_white_pawn, Pawn, false),
-        }
-    }
-    false
-}
-
-impl LegalMoveGen for Node {
-    fn gen_moves(&self) -> impl IntoIterator<Item = Move> {
-        self.pos
-            .gen_pseudo_moves()
-            .into_iter()
-            .filter(|mv| {
-                // disallow friendly fire
-                let src_pc = self
-                    .pos
-                    .get_piece(mv.src)
-                    .expect("move source should have piece");
-                if let Some(dest_pc) = self.pos.get_piece(mv.dest) {
-                    return dest_pc.col != src_pc.col;
-                }
-                true
-            })
-            .filter(|mv| {
-                // disallow moving into check
-                let new_pos = mv.make_unlinked(self.pos);
-                !is_check(&new_pos, self.pos.turn)
-            })
     }
 }
 
 /// How many nodes at depth N can be reached from this position.
-pub fn perft(depth: usize, node: &Rc<Node>) -> usize {
+pub fn perft(depth: usize, pos: &mut Board) -> usize {
     if depth == 0 {
         return 1;
     };
 
     let mut ans = 0;
 
-    let moves = node.gen_moves();
+    let moves: Vec<Move> = pos.gen_moves(MoveGenType::Legal).into_iter().collect();
     for mv in moves {
-        let new_node = mv.make(node);
+        let anti_move = mv.make(pos);
-        ans += perft(depth - 1, &new_node);
+        ans += perft(depth - 1, pos);
+        anti_move.unmake(pos);
     }
 
     ans
@@ -696,21 +737,20 @@ pub fn perft(depth: usize, node: &Rc<Node>) -> usize {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::fen::{ToFen, START_POSITION};
+    use crate::fen::{FromFen, ToFen, START_POSITION};
 
     #[test]
     /// Ensure that bitboard properly reflects captures.
     fn test_bitboard_capture() {
-        let board = BoardState::from_fen("8/8/8/8/8/8/r7/R7 w - - 0 1").unwrap();
+        let mut pos = Board::from_fen("8/8/8/8/8/8/r7/R7 w - - 0 1").unwrap();
         let mv = Move::from_uci_algebraic("a1a2").unwrap();
-        // there's an assertion within make move that should
+        let _anti_move = mv.make(&mut pos);
-        let new_pos = mv.make_unlinked(board);
 
         use std::collections::hash_set::HashSet;
         use Piece::*;
         for pc in [Rook, Bishop, Knight, Queen, King, Pawn] {
-            let white: HashSet<_> = new_pos.pl(Color::White).board(pc).into_iter().collect();
+            let white: HashSet<_> = pos.pl(Color::White).board(pc).into_iter().collect();
-            let black: HashSet<_> = new_pos.pl(Color::Black).board(pc).into_iter().collect();
+            let black: HashSet<_> = pos.pl(Color::Black).board(pc).into_iter().collect();
             let intersect = white.intersection(&black).collect::<Vec<_>>();
             assert!(
                 intersect.is_empty(),
@@ -721,11 +761,9 @@ mod tests {
     }
 
     /// Helper to produce test cases.
-    fn decondense_moves(
+    fn decondense_moves(test_case: (&str, Vec<(&str, Vec<&str>, MoveType)>)) -> (Board, Vec<Move>) {
-        test_case: (&str, Vec<(&str, Vec<&str>, MoveType)>),
-    ) -> (BoardState, Vec<Move>) {
         let (fen, expected) = test_case;
-        let board = BoardState::from_fen(fen).unwrap();
+        let board = Board::from_fen(fen).unwrap();
 
         let mut expected_moves = expected
             .iter()
@@ -749,7 +787,7 @@ mod tests {
     }
 
     /// Generate new test cases by flipping colors on existing ones.
-    fn flip_test_case(board: BoardState, moves: &Vec<Move>) -> (BoardState, Vec<Move>) {
+    fn flip_test_case(board: Board, moves: &Vec<Move>) -> (Board, Vec<Move>) {
         let mut move_vec = moves
             .iter()
             .map(|mv| Move {
@@ -1007,8 +1045,8 @@ mod tests {
         let augmented_test_cases = test_cases.clone().map(|tc| flip_test_case(tc.0, &tc.1));
         let all_cases = [augmented_test_cases, test_cases].concat();
 
-        for (board, expected_moves) in all_cases {
+        for (mut board, expected_moves) in all_cases {
-            let mut moves: Vec<Move> = board.gen_pseudo_moves().into_iter().collect();
+            let mut moves: Vec<Move> = board.gen_moves(MoveGenType::Pseudo).into_iter().collect();
             moves.sort_unstable();
             let moves = moves;
 
@@ -1044,17 +1082,12 @@ mod tests {
 
         let all_cases = check_cases.iter().chain(&not_check_cases);
         for (fen, expected) in all_cases {
-            let board = BoardState::from_fen(fen).unwrap();
+            let board = Board::from_fen(fen).unwrap();
-            assert_eq!(
+            assert_eq!(board.is_check(Color::White), *expected, "failed on {}", fen);
-                is_check(&board, Color::White),
-                *expected,
-                "failed on {}",
-                fen
-            );
 
             let board_anti = board.flip_colors();
             assert_eq!(
-                is_check(&board_anti, Color::Black),
+                board_anti.is_check(Color::Black),
                 *expected,
                 "failed on anti-version of {} ({})",
                 fen,
@@ -1163,14 +1196,12 @@ mod tests {
 
         let all_cases = [augmented_test_cases, test_cases].concat();
 
-        for (board, mut expected_moves) in all_cases {
+        for (mut board, mut expected_moves) in all_cases {
             eprintln!("on test '{}'", board.to_fen());
             expected_moves.sort_unstable();
             let expected_moves = expected_moves;
 
-            let node = Node::new(board);
+            let mut moves: Vec<Move> = board.gen_moves(MoveGenType::Legal).into_iter().collect();
-
-            let mut moves: Vec<Move> = node.gen_moves().into_iter().collect();
             moves.sort_unstable();
             let moves = moves;
 
@@ -1236,6 +1267,14 @@ mod tests {
                     ),
                 ],
             ),
+            // promotion unmake regression test
+            (
+                "r3k2r/Pppp1ppp/1b3nbN/nP6/BBPPP3/q4N2/Pp4PP/R2Q1RK1 b kq - 0 1",
+                vec![(
+                    "b2a1q",
+                    "r3k2r/Pppp1ppp/1b3nbN/nP6/BBPPP3/q4N2/P5PP/q2Q1RK1 w kq - 0 2",
+                )],
+            ),
             // castling rights test (kings)
             (
                 "rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2",
@@ -1290,24 +1329,23 @@ mod tests {
         for (i, test_case) in test_cases.iter().enumerate() {
             let (start_pos, moves) = test_case;
 
-            // make move
             eprintln!("Starting test case {i}, make move.");
-            let mut node = Rc::new(Node::new(BoardState::from_fen(start_pos).unwrap()));
+            let mut pos = Board::from_fen(start_pos).unwrap();
             for (move_str, expect_fen) in moves {
+                let prior_fen = pos.to_fen();
                 let mv = Move::from_uci_algebraic(move_str).unwrap();
-                eprintln!("Moving {move_str}.");
+                eprintln!("Moving {move_str} on {}", prior_fen);
-                node = mv.make(&node);
+                let anti_move = mv.make(&mut pos);
-                assert_eq!(node.pos.to_fen(), expect_fen.to_string())
+                eprintln!("Unmaking {move_str} on {}.", pos.to_fen());
-            }
+                anti_move.unmake(&mut pos);
-
+                assert_eq!(
-            // unmake move
+                    pos.to_fen(),
-            eprintln!("Starting test case {i}, unmake move.");
+                    prior_fen.to_string(),
-            for (_, expect_fen) in moves.iter().rev().chain([("", *start_pos)].iter()) {
+                    "failed unmake with {anti_move:?}"
-                eprintln!("{}", expect_fen);
+                );
-                assert_eq!(*node.pos.to_fen(), expect_fen.to_string());
+                eprintln!("Remaking {move_str}.");
-                if *expect_fen != *start_pos {
+                let _anti_move = mv.make(&mut pos);
-                    node = node.unmake();
+                assert_eq!(pos.to_fen(), expect_fen.to_string());
-                }
             }
         }
     }
@@ -1353,18 +1391,18 @@ mod tests {
                 3,
             ),
         ];
-        for (fen, expected_values, debug_limit_depth) in test_cases {
+        for (fen, expected_values, _debug_limit_depth) in test_cases {
-            let root_node = Rc::new(Node::new(BoardState::from_fen(fen).unwrap()));
+            let mut pos = Board::from_fen(fen).unwrap();
 
             for (depth, expected) in expected_values.iter().enumerate() {
                 eprintln!("running perft depth {depth} on position '{fen}'");
                 #[cfg(debug_assertions)]
                 {
-                    if depth > debug_limit_depth {
+                    if depth > _debug_limit_depth {
                         break;
                     }
                 }
-                assert_eq!(perft(depth, &root_node), *expected,);
+                assert_eq!(perft(depth, &mut pos), *expected,);
             }
         }
     }