[board] Reorganize bitboard and position modules and export some symbols from the crate

Move position.rs to the position module and create a mod.rs.
Do the same for bitboard.rs in the bitboard modules.
Export Color, Piece, Position, and Square and use crate::Thing directly instead of referring to the symbol in the nested modules.

board/src/bitboard/bitboard.rs

@@ -1,9 +1,7 @@
 // Eryn Wells <eryn@erynwells.me>
 
-mod bit_scanner;
-
-use self::bit_scanner::BitScanner;
-use crate::square::Square;
+use super::BitScanner;
+use crate::Square;
 use std::fmt;
 use std::ops::{BitAnd, BitOr, Not};
 
@@ -154,7 +152,7 @@ impl BitOr<&BitBoard> for BitBoard {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::square::Square;
+    use crate::Square;
 
     #[test]
     fn is_empty() {

board/src/bitboard/mod.rs

@@ -0,0 +1,5 @@
+mod bit_scanner;
+mod bitboard;
+
+pub(crate) use self::bit_scanner::BitScanner;
+pub(crate) use self::bitboard::BitBoard;

board/src/lib.rs

@@ -3,3 +3,7 @@ mod neighbor;
 mod piece;
 mod position;
 mod square;
+
+pub use piece::{Color, Piece};
+pub use position::Position;
+pub use square::Square;

board/src/piece.rs

@@ -1,6 +1,6 @@
 // Eryn Wells <eryn@erynwells.me>
 
-use crate::square::Square;
+use crate::Square;
 
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
 pub enum Color {

board/src/position/mod.rs

@@ -0,0 +1,5 @@
+mod pieces;
+mod position;
+
+pub use pieces::Pieces;
+pub use position::Position;

board/src/position/pieces.rs

@@ -1,10 +1,9 @@
 // Eryn Wells <eryn@erynwells.me>
 
+use super::Position;
 use crate::bitboard::BitBoard;
 use crate::piece::{Color, Piece, PlacedPiece, Shape};
-use crate::position::Position;
-use crate::square::Square;
-use std::collections::HashSet;
+use crate::Square;
 
 pub struct Pieces<'a> {
     color: Color,
@@ -89,8 +88,9 @@ impl<'a> Iterator for Pieces<'a> {
 mod tests {
     use super::*;
     use crate::piece::{Color, Piece, Shape};
-    use crate::position::Position;
-    use crate::square::Square;
+    use crate::Position;
+    use crate::Square;
+    use std::collections::HashSet;
 
     fn square_at(sq: &str) -> Square {
         Square::from_algebraic_string(sq).expect(sq)

board/src/position/position.rs

@@ -1,11 +1,9 @@
 // Eryn Wells <eryn@erynwells.me>
 
-mod pieces;
-
-use self::pieces::Pieces;
+use super::Pieces;
 use crate::bitboard::BitBoard;
-use crate::square::Square;
 use crate::piece::{Color, Piece, PiecePlacementError};
+use crate::Square;
 use std::fmt;
 use std::fmt::Write;
 
@@ -21,7 +19,7 @@ pub struct Position {
 }
 
 impl Position {
-    fn empty() -> Position {
+    pub fn empty() -> Position {
         Position {
             color_to_move: Color::White,
             pieces_per_color: [BitBoard::empty(), BitBoard::empty()],
@@ -76,7 +74,11 @@ impl Position {
         }
     }
 
-    fn place_piece(&mut self, piece: &Piece, square: &Square) -> Result<(), PiecePlacementError> {
+    pub fn place_piece(
+        &mut self,
+        piece: &Piece,
+        square: &Square,
+    ) -> Result<(), PiecePlacementError> {
         let bitboard = self.bitboard_for_piece_mut(piece);
 
         if bitboard.has_piece_at(&square) {
@@ -96,7 +98,7 @@ impl Position {
         &mut self.pieces_per_type[piece.color as usize][piece.shape as usize]
     }
 
-    fn pieces(&self, color: Color) -> Pieces {
+    pub fn pieces(&self, color: Color) -> Pieces {
         Pieces::new(&self, color)
     }
 }