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fix: threefold repetition (#82)
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* Implemented threefold repetition

---------

Signed-off-by: Thomas Mauran <thomasmauran@yahoo.com>
Co-authored-by: TomaDumitrescu <ti.dumtirescu@gmail.com>
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@TomaDumitrescu
TomaDumitrescu and TomaDumitrescu authored Nov 13, 2024
1 parent 11178a9 commit fb7b738
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Showing 2 changed files with 86 additions and 61 deletions.
143 changes: 84 additions & 59 deletions src/board.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ impl std::ops::IndexMut<&Coord> for GameBoard {
/// . a b c d e f g h .
pub struct Board {
pub board: GameBoard,
pub board_history: Vec<GameBoard>,
pub cursor_coordinates: Coord,
pub selected_coordinates: Coord,
pub selected_piece_cursor: i8,
Expand All @@ -120,55 +121,60 @@ pub struct Board {
pub black_taken_pieces: Vec<PieceType>,
}

fn init_board() -> GameBoard {
[
[
Some((PieceType::Rook, PieceColor::Black)),
Some((PieceType::Knight, PieceColor::Black)),
Some((PieceType::Bishop, PieceColor::Black)),
Some((PieceType::Queen, PieceColor::Black)),
Some((PieceType::King, PieceColor::Black)),
Some((PieceType::Bishop, PieceColor::Black)),
Some((PieceType::Knight, PieceColor::Black)),
Some((PieceType::Rook, PieceColor::Black)),
],
[
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
],
[
Some((PieceType::Rook, PieceColor::White)),
Some((PieceType::Knight, PieceColor::White)),
Some((PieceType::Bishop, PieceColor::White)),
Some((PieceType::Queen, PieceColor::White)),
Some((PieceType::King, PieceColor::White)),
Some((PieceType::Bishop, PieceColor::White)),
Some((PieceType::Knight, PieceColor::White)),
Some((PieceType::Rook, PieceColor::White)),
],
]
}

impl Default for Board {
fn default() -> Self {
Self {
board: [
[
Some((PieceType::Rook, PieceColor::Black)),
Some((PieceType::Knight, PieceColor::Black)),
Some((PieceType::Bishop, PieceColor::Black)),
Some((PieceType::Queen, PieceColor::Black)),
Some((PieceType::King, PieceColor::Black)),
Some((PieceType::Bishop, PieceColor::Black)),
Some((PieceType::Knight, PieceColor::Black)),
Some((PieceType::Rook, PieceColor::Black)),
],
[
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
Some((PieceType::Pawn, PieceColor::Black)),
],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
[
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
Some((PieceType::Pawn, PieceColor::White)),
],
[
Some((PieceType::Rook, PieceColor::White)),
Some((PieceType::Knight, PieceColor::White)),
Some((PieceType::Bishop, PieceColor::White)),
Some((PieceType::Queen, PieceColor::White)),
Some((PieceType::King, PieceColor::White)),
Some((PieceType::Bishop, PieceColor::White)),
Some((PieceType::Knight, PieceColor::White)),
Some((PieceType::Rook, PieceColor::White)),
],
],
board: init_board(),
board_history: vec![init_board()],
cursor_coordinates: Coord::new(4, 4),
selected_coordinates: Coord::undefined(),
selected_piece_cursor: 0,
Expand All @@ -193,6 +199,7 @@ impl Board {
pub fn new(board: GameBoard, player_turn: PieceColor, move_history: Vec<PieceMove>) -> Self {
Self {
board,
board_history: Vec::new(),
cursor_coordinates: Coord::new(4, 4),
selected_coordinates: Coord::undefined(),
selected_piece_cursor: 0,
Expand Down Expand Up @@ -777,23 +784,33 @@ impl Board {
}

// Check if the game is a draw
pub fn draw_by_repetition(&self) -> bool {
if self.move_history.len() >= 9 {
let last_ten: Vec<PieceMove> =
self.move_history.iter().rev().take(9).copied().collect();

if (last_ten[0], last_ten[1]) == (last_ten[4], last_ten[5])
&& last_ten[4] == last_ten[8]
&& (last_ten[2], last_ten[3]) == (last_ten[6], last_ten[7])
{
pub fn draw_by_repetition(&mut self) -> bool {
// A new game has started
if self.move_history.is_empty() {
self.board_history.clear();
self.board_history.push(self.board);
return false;
}

// Add the new move
self.board_history.push(self.board);

// Index mapping
let mut position_counts = std::collections::HashMap::new();
for board in self.board_history.iter() {
let count = position_counts.entry(board).or_insert(0);
*count += 1;

if *count >= 3 {
return true;
}
}

false
}

// Check if the game is a draw
pub fn is_draw(&self) -> bool {
pub fn is_draw(&mut self) -> bool {
self.number_of_authorized_positions() == 0
|| self.consecutive_non_pawn_or_capture == 50
|| self.draw_by_repetition()
Expand Down Expand Up @@ -1441,7 +1458,7 @@ mod tests {
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
];
let board = Board::new(custom_board, PieceColor::White, vec![]);
let mut board = Board::new(custom_board, PieceColor::White, vec![]);

assert!(board.is_draw());
}
Expand Down Expand Up @@ -1485,7 +1502,7 @@ mod tests {
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
];
let board = Board::new(custom_board, PieceColor::White, vec![]);
let mut board = Board::new(custom_board, PieceColor::White, vec![]);

assert!(!board.is_draw());
}
Expand Down Expand Up @@ -1828,6 +1845,7 @@ mod tests {
[None, None, None, None, None, None, None, None],
[None, None, None, None, None, None, None, None],
];

// We setup the board
let mut board = Board::new(
custom_board,
Expand Down Expand Up @@ -1876,7 +1894,14 @@ mod tests {
],
);

assert!(!board.is_draw());
let mut copy_move_history = board.move_history.clone();

for piece_move in copy_move_history.iter_mut() {
board.move_piece_on_the_board(&piece_move.from, &piece_move.to);

// In a chess game, board.is_draw() is called after every move
assert!(!board.is_draw());
}

// Move the king to replicate a third time the same position
board.move_piece_on_the_board(&Coord::new(0, 2), &Coord::new(0, 1));
Expand Down
4 changes: 2 additions & 2 deletions src/pieces/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,7 @@ pub mod knight;
pub mod pawn;
pub mod queen;
pub mod rook;
#[derive(Debug, Copy, Clone, PartialEq)]
#[derive(Debug, Copy, Clone, PartialEq, Hash)]
pub enum PieceType {
Pawn,
Rook,
Expand Down Expand Up @@ -189,7 +189,7 @@ pub struct PieceMove {
pub to: Coord,
}

#[derive(Debug, Copy, Clone, PartialEq)]
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
pub enum PieceColor {
White = 0,
Black = 1,
Expand Down

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