Split Shogi into ShogiBoardState and StandardRules

Shogi.Domain/Piece.cs

@@ -0,0 +1,44 @@
+using System.Diagnostics;
+
+namespace Shogi.Domain
+{
+  [DebuggerDisplay("{WhichPiece} {Owner}")]
+  public class Piece
+  {
+    public WhichPiece WhichPiece { get; }
+    public WhichPlayer Owner { get; private set; }
+    public bool IsPromoted { get; private set; }
+    public bool IsUpsideDown => Owner == WhichPlayer.Player2;
+
+    public Piece(WhichPiece piece, WhichPlayer owner, bool isPromoted = false)
+    {
+      WhichPiece = piece;
+      Owner = owner;
+      IsPromoted = isPromoted;
+    }
+    public Piece(Piece piece) : this(piece.WhichPiece, piece.Owner, piece.IsPromoted)
+    {
+    }
+
+    public bool CanPromote => !IsPromoted
+      && WhichPiece != WhichPiece.King
+      && WhichPiece != WhichPiece.GoldGeneral;
+
+    public void ToggleOwnership()
+    {
+      Owner = Owner == WhichPlayer.Player1
+        ? WhichPlayer.Player2
+        : WhichPlayer.Player1;
+    }
+
+    public void Promote() => IsPromoted = CanPromote;
+
+    public void Demote() => IsPromoted = false;
+
+    public void Capture()
+    {
+      ToggleOwnership();
+      Demote();
+    }
+  }
+}