feat: add 3-fold repetition

4 files changed, 19 insertions, 7 deletions

diff --git a/src/board/io.rs b/src/board/io.rs
index d27b856..15d7744 100644
--- a/src/board/io.rs
+++ b/src/board/io.rs
@@ -97,6 +97,7 @@ impl IO for Board {
             castling_rights: [[true; 2]; 2], // TODO: actualy parse from FEN
             ep_target: None, // TODO: parse from FEN
             clock: Clock::default(),
+            positions: Vec::new(),
             hash: 0,
             zobrist_seed: Board::seed(),
         };
diff --git a/src/board/mod.rs b/src/board/mod.rs
index 95d470a..50aa1b9 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -15,7 +15,7 @@ pub enum CastlingSide {
 
 /// Chess board is an main interface to the internal game state.
 /// Board defines rules of the game and manages players actions.
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct Board {
     pub ply: u16,
     pub piece_sets: [Bitboard; 12],
@@ -26,12 +26,16 @@ pub struct Board {
 
     pub clock: Clock,
 
+    /// List of all positions to determine repetitions
+    pub positions: Vec<u64>,
+
     // Computed values
     pub occupancy: Bitboard,
     /// Zobrist hash of the current position
     pub hash: u64,
     zobrist_seed: ZobristSeed,
 
+
     pub attacks: Attacks,
 }
 
@@ -227,6 +231,7 @@ impl Board {
 
         self.ply += 1;
         self.zobrist_toggle_color();
+        self.positions.push(self.hash);
 
         captured_piece
     }
@@ -320,6 +325,7 @@ impl Board {
         self.castling_rights = previous_castling_rights;
         self.hash = previous_hash;
         self.ply -= 1;
+        self.positions.pop();
     }
 
     pub fn is_square_attacked(&self, square: Square, attacker_color: Color) -> bool {
@@ -388,7 +394,7 @@ mod tests {
     fn make_move() {
         let fen = String::from("q1b2k2/5p1p/4p1pb/pPPp4/3N4/3nPB2/P2QKnR1/1R6 w - - 0 25");
         let mut board = Board::from_FEN(fen);
-        let initial_board = board;
+        let initial_board = board.clone();
         board.print();
 
         let black_move = Move { source: Square::F7, target: Square::F5, kind: MoveKind::Quiet };
@@ -429,7 +435,7 @@ mod tests {
     fn unmake_move() {
         let fen = String::from("q1b2k2/5p1p/4p1pb/pPPp4/3N4/3nPB2/P2QKnR1/1R6 w - - 0 25");
         let mut board = Board::from_FEN(fen);
-        let initial_board = board;
+        let initial_board = board.clone();
 
         let mov = Move { source: Square::D2, target: Square::A5, kind: MoveKind::Capture };
 
diff --git a/src/grossmeister/UCI.rs b/src/grossmeister/UCI.rs
index 034b73b..3132e72 100644
--- a/src/grossmeister/UCI.rs
+++ b/src/grossmeister/UCI.rs
@@ -59,7 +59,7 @@ impl Grossmeister {
                                                     .find(|m| {
                                                         let promo_matches = match input_move.kind {
                                                             MoveKind::Promotion(piece) => match m.kind {
-                                                                MoveKind::Promotion(another_piece) => piece == another_piece,
+                                                                MoveKind::Promotion(another_piece) => piece.without_color() == another_piece.without_color(),
                                                                 _ => false
                                                             },
                                                             _ => true,
diff --git a/src/grossmeister/search.rs b/src/grossmeister/search.rs
index 5c03887..43423e4 100644
--- a/src/grossmeister/search.rs
+++ b/src/grossmeister/search.rs
@@ -45,6 +45,11 @@ impl Grossmeister {
             }
         }
 
+        if self.board.positions.iter().filter(|p| **p == self.board.hash).count() >= 3 {
+            // Draw by repetition
+            return (0.0, principal_variation);
+        }
+
         if depth_left == 0 {
             return (self.quiscence(alpha, beta), principal_variation);
         }
@@ -447,7 +452,7 @@ mod tests {
         let fen = String::from("2kr1b1r/pp1npppp/2p1bn2/7q/5B2/2NB1Q1P/PPP1N1P1/2KR3R w - - 0 1");
         let board = Board::from_FEN(fen);
         let mut gm = Grossmeister::new(board);
-        let (score, pv) = gm.iterative_deepening(8, Duration::from_secs(15), true);
+        let (score, pv) = gm.iterative_deepening(8);
 
         assert_eq!(score, VALUE_WIN);
         assert_eq!(pv, vec![
@@ -464,7 +469,7 @@ mod tests {
         board.ply += 1; // TODO: remove me when FEN parsing includes side to move
 
         let mut gm = Grossmeister::new(board);
-        let (_, pv) = gm.iterative_deepening(6, Duration::from_secs(60), true);
+        let (_, pv) = gm.iterative_deepening(6);
         assert_eq!(
             pv[0],
             Move { source: Square::F5, target: Square::H4, kind: MoveKind::Quiet },
@@ -478,7 +483,7 @@ mod tests {
         let board = Board::from_FEN(fen);
 
         let mut gm = Grossmeister::new(board);
-        let (_, pv) = gm.iterative_deepening(5, Duration::from_secs(60), true);
+        let (_, pv) = gm.iterative_deepening(5);
         assert_eq!(
             pv[0],
             Move { source: Square::C2, target: Square::C3, kind: MoveKind::Quiet },