Add PGN export and a Copy PGN button for finished games

- Record moves in standard algebraic notation (GameState.SanHistory), built at move time in ChessService (captures, disambiguation, castling, promotion, en passant, and the check/mate suffix) - Add PgnExporter.ToPgn (seven-tag header + movetext + result) and a GET /api/chess/{gameId}/pgn endpoint - Show a Copy PGN button when a game ends on both the play and watch pages, prefetching the PGN so it works during the post-game cleanup window Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
2026-06-08 19:14:39 -06:00
parent d87cea572f
commit b651683e63
11 changed files with 255 additions and 0 deletions
@@ -0,0 +1,50 @@
+using JoshHeaps.Net.Models;
+using System.Text;
+
+namespace JoshHeaps.Net.Services.Implementations;
+
+public static class PgnExporter
+{
+    /// <summary>
+    /// Render a game as PGN: the standard seven-tag header plus the SAN movetext and result.
+    /// </summary>
+    public static string ToPgn(this GameState gs)
+    {
+        var result = ResultTag(gs);
+        var name = gs.IsComputerVsComputer ? "Computer" : null;
+
+        var sb = new StringBuilder();
+        sb.AppendLine("[Event \"JoshHeaps.Net Chess\"]");
+        sb.AppendLine("[Site \"joshheaps.net\"]");
+        sb.AppendLine($"[Date \"{DateTime.Now:yyyy.MM.dd}\"]");
+        sb.AppendLine($"[White \"{name ?? "White"}\"]");
+        sb.AppendLine($"[Black \"{name ?? "Black"}\"]");
+        sb.AppendLine($"[Result \"{result}\"]");
+        sb.AppendLine();
+
+        for (int i = 0; i < gs.SanHistory.Count; i++)
+        {
+            if (i % 2 == 0)
+                sb.Append(i / 2 + 1).Append(". ");
+
+            sb.Append(gs.SanHistory[i]).Append(' ');
+        }
+
+        sb.Append(result);
+        return sb.ToString();
+    }
+
+    private static string ResultTag(GameState gs)
+    {
+        if (gs.IsCheckmate)
+            return gs.CurrentPlayer == PieceColor.White ? "0-1" : "1-0";
+
+        if (gs.IsStalemate || gs.IsThreefoldRepetition)
+            return "1/2-1/2";
+
+        if (gs.IsForfeited)
+            return gs.Winner == PieceColor.White ? "1-0" : "0-1";
+
+        return "*";
+    }
+}