[board] Replace Moves' separate properties with a Vec of Iterators

This makes iteration easier. Move to the next iterator if the current one returns None.
No tests for Moves yet though.

board/src/moves/mod.rs

@@ -4,5 +4,5 @@ mod r#move;
 mod move_generator;
 mod pawn;
 
-pub use move_generator::MoveGenerator;
+pub use move_generator::Moves;
 pub use r#move::Move;

board/src/moves/move_generator.rs

@@ -1,20 +1,48 @@
 // Eryn Wells <eryn@erynwells.me>
 
+use super::pawn::PawnMoveGenerator;
+use super::Move;
+use crate::piece::Color;
 use crate::Position;
 
-use super::pawn::PawnMoveGenerator;
-
-pub struct MoveGenerator<'a> {
-    pub(super) position: &'a Position,
-
-    pawn_move_generator: PawnMoveGenerator<'a>,
+pub struct Moves<'pos> {
+    position: &'pos Position,
+    color: Color,
+    iterators: Vec<Box<dyn Iterator<Item = Move> + 'pos>>,
+    index: usize,
 }
 
-impl<'a> MoveGenerator<'a> {
-    pub fn new(position: &Position) -> MoveGenerator {
-        MoveGenerator {
+impl<'a> Moves<'a> {
+    pub fn new(position: &Position, color: Color) -> Moves {
+        Moves {
             position,
-            pawn_move_generator: PawnMoveGenerator::new(position),
+            color,
+            iterators: vec![
+                Box::new(PawnMoveGenerator::new(position, color)),
+            ],
+            index: 0,
         }
     }
+
+    fn current_iterator(&mut self) -> &mut Box<dyn Iterator<Item = Move> + 'a> {
+        &mut self.iterators[self.index]
+    }
+}
+
+impl<'a> std::iter::Iterator for Moves<'a> {
+    type Item = Move;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index >= self.iterators.len() {
+            return None;
+        }
+
+        let next_move = self.current_iterator().next();
+
+        if next_move.is_none() && self.index < self.iterators.len() {
+            self.index += 1;
+        }
+
+        next_move
+    }
 }

board/src/position/position.rs

@@ -2,7 +2,7 @@
 
 use super::Pieces;
 use crate::bitboard::BitBoard;
-use crate::moves::MoveGenerator;
+use crate::moves::Moves;
 use crate::piece::{Color, Piece, PiecePlacementError, PlacedPiece, Shape};
 use crate::Square;
 use std::fmt;
@@ -94,8 +94,8 @@ impl Position {
         Ok(())
     }
 
-    pub fn move_generator(&self) -> MoveGenerator {
-        MoveGenerator::new(self)
+    pub fn move_generator(&self, color: Color) -> Moves {
+        Moves::new(self, color)
     }
 
     /// Return a BitBoard representing the set of squares containing a piece.
@@ -103,7 +103,8 @@ impl Position {
         self.pieces_per_color[Color::White as usize] | self.pieces_per_color[Color::Black as usize]
     }
 
-    /// Return a BitBoard representing the set of squares containing a piece. This set is the inverse of `occupied_squares`.
+    /// Return a BitBoard representing the set of squares containing a piece.
+    /// This set is the inverse of `occupied_squares`.
     pub(crate) fn empty_squares(&self) -> BitBoard {
         !(self.pieces_per_color[Color::White as usize]
             | self.pieces_per_color[Color::Black as usize])