Add Piece encapsulation

56_Life_for_Two/csharp/Piece.cs

@@ -0,0 +1,50 @@
+using System.Collections.Immutable;
+
+namespace LifeforTwo;
+
+public struct Piece
+{
+    public const int None = 0x0000;
+    public const int Player1 = 0x0100;
+    public const int Player2 = 0x1000;
+    private const int PieceMask = Player1 | Player2;
+    private const int NeighbourValueOffset = 8;
+
+    private static readonly ImmutableHashSet<int> _willBePlayer1 = 
+        new[] { 0x0003, 0x0102, 0x0103, 0x0120, 0x0130, 0x0121, 0x0112, 0x0111, 0x0012 }.ToImmutableHashSet();
+    private static readonly ImmutableHashSet<int> _willBePlayer2 = 
+        new[] { 0x0021, 0x0030, 0x1020, 0x1030, 0x1011, 0x1021, 0x1003, 0x1002, 0x1012 }.ToImmutableHashSet();
+
+    private int _value;
+
+    private Piece(int value) => _value = value;
+
+    public int Value => _value;
+    public bool IsEmpty => (_value & PieceMask) == None;
+
+    public static Piece NewEmpty() => new(None);
+    public static Piece NewPlayer1() => new(Player1);
+    public static Piece NewPlayer2() => new(Player2);
+
+    public Piece AddNeighbour(Piece neighbour)
+    {
+        _value += neighbour.Value >> NeighbourValueOffset;
+        return this;
+    }
+
+    public Piece GetNext() => new(
+        _value switch
+        {
+            _ when _willBePlayer1.Contains(_value) => Player1,
+            _ when _willBePlayer2.Contains(_value) => Player2,
+            _ => None
+        });
+
+    public override string ToString() =>
+        (_value & PieceMask) switch
+        {
+            Player1 => "*",
+            Player2 => "#",
+            _ => " "
+        };
+}