[moves] Knight move generator and tests

moves/src/generators.rs

@@ -1,10 +1,12 @@
 // Eryn Wells <eryn@erynwells.me>
 
+mod knight;
 mod pawn;
 
 #[cfg(test)]
 mod testing;
 
+pub use knight::KnightMoveGenerator;
 pub use pawn::PawnMoveGenerator;
 
 use crate::Move;

moves/src/generators/knight.rs

@@ -0,0 +1,164 @@
+// Eryn Wells <eryn@erynwells.me>
+
+use crate::Move;
+
+use super::GeneratedMove;
+use chessfriend_bitboard::{bit_scanner::TrailingBitScanner, BitBoard};
+use chessfriend_board::Board;
+use chessfriend_core::{Color, Square};
+
+#[must_use]
+pub struct KnightMoveGenerator {
+    origin_iterator: TrailingBitScanner,
+    target_iterator: Option<TrailingBitScanner>,
+    current_origin: Option<Square>,
+    friends: BitBoard,
+    enemies: BitBoard,
+}
+
+impl KnightMoveGenerator {
+    pub fn new(board: &Board, color: Option<Color>) -> Self {
+        let color = board.unwrap_color(color);
+
+        let knights = board.knights(color);
+        let friends = board.friendly_occupancy(color);
+        let enemies = board.enemies(color);
+
+        Self {
+            origin_iterator: knights.occupied_squares_trailing(),
+            target_iterator: None,
+            current_origin: None,
+            friends,
+            enemies,
+        }
+    }
+}
+
+impl Iterator for KnightMoveGenerator {
+    type Item = GeneratedMove;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_origin.is_none() {
+            self.current_origin = self.origin_iterator.next();
+        }
+
+        let origin = self.current_origin?;
+
+        let target_iterator = self.target_iterator.get_or_insert_with(|| {
+            let knight_moves = BitBoard::knight_moves(origin);
+            knight_moves.occupied_squares_trailing()
+        });
+
+        if let Some(target) = target_iterator.next() {
+            let target_bitboard: BitBoard = target.into();
+            if (target_bitboard & self.friends).is_populated() {
+                self.next()
+            } else if (target_bitboard & self.enemies).is_populated() {
+                Some(Move::capture(origin, target).into())
+            } else {
+                Some(Move::quiet(origin, target).into())
+            }
+        } else {
+            self.current_origin = None;
+            self.target_iterator = None;
+            self.next()
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{assert_move_list, ply};
+    use chessfriend_board::test_board;
+    use chessfriend_core::Color;
+
+    #[test]
+    fn white_f5_moves() {
+        let board = test_board!(White Knight on F5);
+        assert_move_list!(
+            KnightMoveGenerator::new(&board, Some(Color::White)),
+            [
+                ply!(F5 - G7),
+                ply!(F5 - H6),
+                ply!(F5 - H4),
+                ply!(F5 - G3),
+                ply!(F5 - E3),
+                ply!(F5 - D4),
+                ply!(F5 - D6),
+                ply!(F5 - E7),
+            ]
+        );
+    }
+
+    #[test]
+    fn white_f5_and_c6_moves() {
+        let board = test_board!(
+            White Knight on C6,
+            White Knight on F5,
+        );
+        assert_move_list!(
+            KnightMoveGenerator::new(&board, Some(Color::White)),
+            [
+                ply!(C6 - D8),
+                ply!(C6 - D8),
+                ply!(C6 - E7),
+                ply!(C6 - E5),
+                ply!(C6 - D4),
+                ply!(C6 - B4),
+                ply!(C6 - A5),
+                ply!(C6 - A7),
+                ply!(C6 - B8),
+                ply!(F5 - G7),
+                ply!(F5 - H6),
+                ply!(F5 - H4),
+                ply!(F5 - G3),
+                ply!(F5 - E3),
+                ply!(F5 - D4),
+                ply!(F5 - D6),
+                ply!(F5 - E7),
+            ]
+        );
+    }
+
+    #[test]
+    fn white_f5_moves_with_blockers() {
+        let board = test_board!(
+            White Knight on F5,
+            White Queen on G3,
+            White Bishop on D6,
+        );
+        assert_move_list!(
+            KnightMoveGenerator::new(&board, Some(Color::White)),
+            [
+                ply!(F5 - G7),
+                ply!(F5 - H6),
+                ply!(F5 - H4),
+                ply!(F5 - E3),
+                ply!(F5 - D4),
+                ply!(F5 - E7),
+            ]
+        );
+    }
+
+    #[test]
+    fn white_f5_moves_with_captures() {
+        let board = test_board!(
+            White Knight on F5,
+            White Queen on G3,
+            White Bishop on D6,
+            Black Queen on D4,
+        );
+        assert_move_list!(
+            KnightMoveGenerator::new(&board, Some(Color::White)),
+            [
+                ply!(F5 - G7),
+                ply!(F5 - H6),
+                ply!(F5 - H4),
+                ply!(F5 - E3),
+                ply!(F5 - E7),
+                ply!(F5 x D4),
+            ]
+        );
+    }
+}