131 lines
4.1 KiB
C#
131 lines
4.1 KiB
C#
using JoshHeaps.Net.Models;
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using System.Text;
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namespace JoshHeaps.Net.Services.Implementations;
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public static class ChessEngineHelpers
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{
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public static MoveDto ToMoveDto(
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this string uci,
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GameState gameState,
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Guid playerId)
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{
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int fCol = uci[0] - 'a', fRow = 7 - (uci[1] - '1');
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int tCol = uci[2] - 'a', tRow = 7 - (uci[3] - '1');
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var piece = gameState.Board[fRow, fCol]
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?? throw new Exception("No piece at source square");
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PieceType? promo = uci.Length == 5 ? uci[4] switch
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{
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'q' => PieceType.Queen,
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'r' => PieceType.Rook,
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'b' => PieceType.Bishop,
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'n' => PieceType.Knight,
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_ => null
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} : null;
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return new MoveDto
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{
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GameId = gameState.GameId,
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PlayerId = playerId,
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PieceId = piece.Id,
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TargetRow = tRow,
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TargetCol = tCol,
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PromotionChoice = promo,
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SourceCol = fCol,
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SourceRow = fRow,
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};
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}
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/// <summary>
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/// Convert a 2-D board array (rank 8 = row 0, file a = col 0) to a FEN string.
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/// Only piece placement + active colour + castling are computed; the rest use
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/// safe defaults (-, 0, 1). That is all the engine needs.
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/// </summary>
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public static string ToFen(this GameState gs)
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{
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var sb = new StringBuilder(64);
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/* 1) piece placement */
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for (int row = 0; row < 8; row++)
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{
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int empty = 0;
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for (int col = 0; col < 8; col++)
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{
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var p = gs.Board[row, col];
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if (p is null)
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{
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empty++;
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}
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else
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{
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if (empty > 0) { sb.Append(empty); empty = 0; }
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sb.Append(ToFenChar(p)); // ← unchanged helper
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}
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}
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if (empty > 0) sb.Append(empty);
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if (row < 7) sb.Append('/');
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}
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/* 2) active colour */
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sb.Append(gs.CurrentPlayer == PieceColor.White ? " w " : " b ");
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/* 3) castling rights (from GameState flags) */
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sb.Append(GetCastlingFlags(gs));
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/* 4) en-passant target square */
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sb.Append(' ');
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sb.Append(gs.EnPassantTarget.HasValue
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? Alg(gs.EnPassantTarget.Value)
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: "-");
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/* 5-6) half-move clock + full-move number */
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int fullMoves = gs.MoveHistory.Count / 2 + 1;
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sb.Append(" 0 ").Append(fullMoves);
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return sb.ToString();
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}
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/* ---------- helpers ---------- */
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private static string GetCastlingFlags(GameState gs)
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{
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var flags = new StringBuilder(4);
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if (gs.WhiteCanCastleKingside) flags.Append('K');
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if (gs.WhiteCanCastleQueenside) flags.Append('Q');
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if (gs.BlackCanCastleKingside) flags.Append('k');
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if (gs.BlackCanCastleQueenside) flags.Append('q');
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return flags.Length == 0 ? "-" : flags.ToString();
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}
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private static string Alg(Position p)
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{
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char file = (char)('a' + p.Col);
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int rank = 8 - p.Row;
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return $"{file}{rank}";
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}
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private static char ToFenChar(ChessPiece p) => p switch
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{
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{ Type: PieceType.Pawn, Color: PieceColor.White } => 'P',
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{ Type: PieceType.Pawn, Color: PieceColor.Black } => 'p',
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{ Type: PieceType.Knight, Color: PieceColor.White } => 'N',
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{ Type: PieceType.Knight, Color: PieceColor.Black } => 'n',
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{ Type: PieceType.Bishop, Color: PieceColor.White } => 'B',
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{ Type: PieceType.Bishop, Color: PieceColor.Black } => 'b',
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{ Type: PieceType.Rook, Color: PieceColor.White } => 'R',
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{ Type: PieceType.Rook, Color: PieceColor.Black } => 'r',
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{ Type: PieceType.Queen, Color: PieceColor.White } => 'Q',
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{ Type: PieceType.Queen, Color: PieceColor.Black } => 'q',
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{ Type: PieceType.King, Color: PieceColor.White } => 'K',
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{ Type: PieceType.King, Color: PieceColor.Black } => 'k',
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_ => throw new ArgumentOutOfRangeException(nameof(p))
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};
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}
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