refactor: abstract perft result into a structure

3 files changed, 42 insertions, 34 deletions

diff --git a/benches/perft.rs b/benches/perft.rs
index c73208f..1d82ed5 100644
--- a/benches/perft.rs
+++ b/benches/perft.rs
@@ -5,7 +5,8 @@ fn main() {
     let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
     let mut board = Board::from_FEN(fen);
 
+    let depth = 4;
     let start = Instant::now();
-    let result = board.perft(5, false);
-    println!("Perft finished in {:?}: {:?}", start.elapsed(), result);
+    let result = board.perft(depth, false);
+    println!("Perft({}) finished in {:?}: {:?}", depth, start.elapsed(), result);
 }
diff --git a/src/board/engine.rs b/src/board/engine.rs
index c8b174f..61d9fda 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -1,9 +1,21 @@
 use crate::{bitboard::pop_count, board::*};
 
+#[derive(Debug, Default, PartialEq)]
+pub struct PerftResult {
+    leaf_nodes: u64,
+    captures: u64,
+    en_passants: u64,
+    castles: u64,
+    checks: u64,
+}
+
 impl Board {
-    pub fn perft(&mut self, depth: u8, print: bool) -> (u64, u64, u64, u64, u64) {
+    pub fn perft(&mut self, depth: u8, print: bool) -> PerftResult {
+        let mut result = PerftResult::default();
+
         if depth == 0 {
-            return (1, 0, 0, 0, 0) // This a leaf, exactly one node
+            result.leaf_nodes = 1;
+            return result;
         }
         let color = self.color_to_move();
 
@@ -14,12 +26,6 @@ impl Board {
             println!("{} moves available", moves.len());
         }
 
-        let mut total = 0;
-        let mut captures = 0;
-        let mut checks = 0;
-        let mut castles = 0;
-        let mut en_passants = 0;
-
         for mov in moves {
             let ep_target_before = self.ep_target.clone();
             let castling_rights_before = self.castling_rights.clone();
@@ -29,19 +35,19 @@ impl Board {
                 if depth == 1 {
                     match mov.kind {
                         MoveKind::Capture => {
-                            captures += 1;
+                            result.captures += 1;
                         }
                         MoveKind::EnPassant => {
-                            en_passants += 1;
-                            captures += 1;
+                            result.en_passants += 1;
+                            result.captures += 1;
                         }
                         MoveKind::Castle => {
-                            castles += 1;
+                            result.castles += 1;
                         }
                         _ => {}
                     }
                     if self.is_king_in_check(color.flip()) {
-                        checks += 1;
+                        result.checks += 1;
                     }
                 }
 
@@ -49,22 +55,23 @@ impl Board {
                     println!("{:?}", mov);
                     self.print();
                 }
-                let (children_total, children_tactical, children_checks, children_castles, children_ep) = self.perft(depth - 1, print);
-                total += children_total;
-                captures += children_tactical;
-                checks += children_checks;
-                castles += children_castles;
-                en_passants += children_ep;
+                let subtree_result = self.perft(depth - 1, print);
+
+                result.leaf_nodes += subtree_result.leaf_nodes;
+                result.captures += subtree_result.captures;
+                result.checks += subtree_result.checks;
+                result.castles += subtree_result.castles;
+                result.en_passants += subtree_result.en_passants;
 
             }
             self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
         }
 
         if print {
-            println!("Found {} nodes in this subtree (depth {})", total, depth);
+            println!("Found {} leaf nodes in this subtree (depth {})", result.leaf_nodes, depth);
         }
 
-        (total, captures, checks, castles, en_passants)
+        result
     }
     pub fn evaluate(&self) -> f32 {
         let mut eval = 0f32;
@@ -116,17 +123,17 @@ impl Board {
 mod tests {
     use std::f32::INFINITY;
 
-    use crate::board::Board;
+    use crate::board::{Board, engine::PerftResult};
 
     #[test]
     fn perft() {
         let mut board = Board::new();
 
-        assert_eq!(board.perft(0, false), (1, 0, 0, 0, 0));
-        assert_eq!(board.perft(1, false), (20, 0, 0, 0, 0));
-        assert_eq!(board.perft(2, false), (400, 0, 0, 0, 0));
-        assert_eq!(board.perft(3, false), (8902, 34, 12, 0, 0));
-        assert_eq!(board.perft(4, false), (197281, 1576, 469, 0, 0));
+        assert_eq!(board.perft(0, false), PerftResult { leaf_nodes: 1, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
+        assert_eq!(board.perft(1, false), PerftResult { leaf_nodes: 20, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
+        assert_eq!(board.perft(2, false), PerftResult { leaf_nodes: 400, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
+        assert_eq!(board.perft(3, false), PerftResult { leaf_nodes: 8902, captures: 34, en_passants: 0, castles: 0 , checks: 12 });
+        assert_eq!(board.perft(4, false), PerftResult { leaf_nodes: 197281, captures: 1576, en_passants: 0, castles: 0 , checks: 469 });
         // assert_eq!(board.perft(5, false), (4865609, 82719, 27351, 0, 258));
         // assert_eq!(board.perft(6, false), (119060324, 2812008, 809099, 0, 5248));
     }
@@ -135,10 +142,10 @@ mod tests {
     fn position_perft() {
         let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
         let mut board = Board::from_FEN(fen);
-        assert_eq!(board.perft(0, false), (1, 0, 0, 0, 0));
-        assert_eq!(board.perft(1, false), (48, 8, 0, 2, 0));
-        assert_eq!(board.perft(2, false), (2039, 351, 3, 91, 1));
-        assert_eq!(board.perft(3, false), (97862, 17102, 993, 3162, 45));
+        assert_eq!(board.perft(0, false), PerftResult { leaf_nodes: 1, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
+        assert_eq!(board.perft(1, false), PerftResult { leaf_nodes: 48, captures: 8, en_passants: 0, castles: 2 , checks: 0 });
+        assert_eq!(board.perft(2, false), PerftResult { leaf_nodes: 2039, captures: 351, en_passants: 1, castles: 91 , checks: 3 });
+        assert_eq!(board.perft(3, false), PerftResult { leaf_nodes: 97862, captures: 17102, en_passants: 45, castles: 3162, checks: 993 });
     }
 
     #[test]
diff --git a/src/board/mod.rs b/src/board/mod.rs
index 10d0a73..e2d4d60 100644
--- a/src/board/mod.rs
+++ b/src/board/mod.rs
@@ -1,4 +1,4 @@
-use crate::{bitboard::{Bitboard, serialize_bitboard, bitscan, pop_count}, moves::{Move, MoveKind}, attacks::Attacks, square::Square};
+use crate::{bitboard::{Bitboard, serialize_bitboard, bitscan}, moves::{Move, MoveKind}, attacks::Attacks, square::Square};
 mod engine;
 
 pub enum CastlingSide {