[position] Move capture list to a CapturesList struct

This one has a custom Display implementation for easier integration with Positon's.

position/src/position.rs

@@ -1,5 +1,6 @@
 // Eryn Wells <eryn@erynwells.me>
 
+mod captures;
 mod make_move;
 mod position;
 

position/src/position/captures.rs

@@ -0,0 +1,42 @@
+// Eryn Wells <eryn@erynwells.me>
+
+use std::fmt::Display;
+
+use chessfriend_core::{Color, Piece};
+
+#[derive(Clone, Debug, Default, Eq, PartialEq)]
+pub(crate) struct CapturesList([Vec<Piece>; Color::NUM]);
+
+impl CapturesList {
+    pub fn push(&mut self, color: Color, piece: Piece) {
+        self.0[color as usize].push(piece);
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.0.iter().all(Vec::is_empty)
+    }
+}
+
+impl Display for CapturesList {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut is_first = true;
+        for color in Color::into_iter() {
+            if is_first {
+                is_first = false;
+            } else {
+                writeln!(f)?;
+            }
+
+            write!(f, "{color}: ")?;
+
+            let captures = &self.0[color as usize];
+            for piece in captures {
+                write!(f, "{piece}")?;
+            }
+
+            write!(f, "")?;
+        }
+
+        Ok(())
+    }
+}

position/src/position/make_move.rs

@@ -172,7 +172,7 @@ impl Position {
             .ok_or(MakeMoveError::NoCapturePiece(capture_square))?;
 
         // Register the capture
-        self.captures[piece.color as usize].push(captured_piece);
+        self.captures.push(piece.color, captured_piece);
 
         self.remove_piece(origin_square).unwrap();
 

position/src/position/position.rs

@@ -1,5 +1,6 @@
 // Eryn Wells <eryn@erynwells.me>
 
+use super::captures::CapturesList;
 use crate::move_record::MoveRecord;
 use chessfriend_bitboard::BitBoard;
 use chessfriend_board::{
@@ -13,7 +14,7 @@ use std::{cell::OnceCell, fmt};
 pub struct Position {
     pub board: Board,
     pub(crate) moves: Vec<MoveRecord>,
-    pub(crate) captures: [Vec<Piece>; Color::NUM],
+    pub(crate) captures: CapturesList,
 }
 
 impl Position {
@@ -197,7 +198,13 @@ impl PartialEq for Position {
 
 impl fmt::Display for Position {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", self.board.display())
+        write!(f, "{}", self.board.display())?;
+
+        if !self.captures.is_empty() {
+            write!(f, "\n\n{}", self.captures)?;
+        }
+
+        Ok(())
     }
 }