Add naive rook move generation

src/movegen/mod.rs

@@ -2,3 +2,4 @@
 mod bishop;
 mod king;
 mod knight;
+mod rook;

src/movegen/rook.rs

@@ -0,0 +1,55 @@
+use crate::board::{Bitboard, Direction, Square};
+
+/// Compute a rook's movement given a set of blockers that cannot be moved past.
+#[allow(unused)]
+pub fn rook_moves(square: Square, blockers: Bitboard) -> Bitboard {
+    Direction::iter_rook()
+        .map(|dir| dir.slide_board_with_blockers(square.into_bitboard(), blockers))
+        .fold(Bitboard::EMPTY, |lhs, rhs| lhs | rhs)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::board::{File, Rank};
+
+    #[test]
+    fn moves_lower_left_square() {
+        assert_eq!(
+            rook_moves(Square::A1, Bitboard::EMPTY),
+            (File::A.into_bitboard() | Rank::First.into_bitboard()) - Square::A1
+        );
+        assert_eq!(
+            rook_moves(Square::A1, Bitboard::ALL),
+            Square::A2 | Square::B1
+        );
+        assert_eq!(
+            rook_moves(Square::A1, Rank::First.into_bitboard()),
+            (File::A.into_bitboard() | Square::B1) - Square::A1
+        );
+        assert_eq!(
+            rook_moves(Square::A1, File::A.into_bitboard()),
+            (Rank::First.into_bitboard() | Square::A2) - Square::A1
+        );
+    }
+
+    #[test]
+    fn moves_middle() {
+        assert_eq!(
+            rook_moves(Square::D4, Bitboard::EMPTY),
+            (File::D.into_bitboard() | Rank::Fourth.into_bitboard()) - Square::D4
+        );
+        assert_eq!(
+            rook_moves(Square::D4, Bitboard::ALL),
+            Square::C4 | Square::D3 | Square::D5 | Square::E4
+        );
+        assert_eq!(
+            rook_moves(Square::D4, Rank::Fourth.into_bitboard()),
+            (File::D.into_bitboard() | Square::C4 | Square::E4) - Square::D4
+        );
+        assert_eq!(
+            rook_moves(Square::D4, File::D.into_bitboard()),
+            (Rank::Fourth.into_bitboard() | Square::D3 | Square::D5) - Square::D4
+        );
+    }
+}