move backend to subfolder

tanks-backend/TanksServer/Interactivity/PlayerScreenData.cs

@@ -0,0 +1,39 @@
+using System.Diagnostics;
+using TanksServer.GameLogic;
+using TanksServer.Graphics;
+
+namespace TanksServer.Interactivity;
+
+internal sealed class PlayerScreenData(ILogger logger)
+{
+    private readonly Memory<byte> _data = new byte[MapService.PixelsPerRow * MapService.PixelsPerColumn / 2];
+    private int _count = 0;
+
+    public void Clear()
+    {
+        _count = 0;
+        _data.Span.Clear();
+    }
+
+    public ReadOnlyMemory<byte> GetPacket()
+    {
+        var index = _count / 2 + (_count % 2 == 0 ? 0 : 1);
+        logger.LogTrace("packet length: {} (count={})", index, _count);
+        return _data[..index];
+    }
+
+    public void Add(GamePixelEntityType entityKind, bool isCurrentPlayer)
+    {
+        var result = (byte)(isCurrentPlayer ? 0x1 : 0x0);
+        var kind = (byte)entityKind;
+        Debug.Assert(kind <= 3);
+        result += (byte)(kind << 2);
+
+        var index = _count / 2;
+        if (_count % 2 != 0)
+            _data.Span[index] |= (byte)(result << 4);
+        else
+            _data.Span[index] = result;
+        _count++;
+    }
+}