private static Location InferSource(
string partialSource,
State ctx,
Location destination,
PieceKind sourceKind,
bool isCapture)
{
Debug.Assert(partialSource.Length >= 0 && partialSource.Length <= 2);
bool realIsCapture = ctx[destination].HasPiece || (sourceKind == PieceKind.Pawn && destination == ctx.EnPassantTarget);
if (isCapture != realIsCapture)
{
throw new InvalidMoveException(InvalidMoveReason.BadCaptureNotation);
}
var possibleSources = ctx.ActivePlayer.GetOccupiedTiles();
char?fileChar = (partialSource.Length == 1 && partialSource[0] >= 'a' && partialSource[0] <= 'h') ? partialSource[0] : (char?)null;
char?rankChar = (partialSource.Length == 1 && partialSource[0] >= '1' && partialSource[0] <= '8') ? partialSource[0] : (char?)null;
if (partialSource.Length == 2)
{
var sourceLocation = Location.Parse(partialSource);
possibleSources = new[] { ctx[sourceLocation] };
}
else if (fileChar != null)
{
var sourceFile = FileHelpers.FromChar(fileChar.Value);
possibleSources = possibleSources.Where(t => t.Location.File == sourceFile);
}
else if (rankChar != null)
{
var sourceRank = RankHelpers.FromChar(rankChar.Value);
possibleSources = possibleSources.Where(t => t.Location.Rank == sourceRank);
}
try
{
var sourceTile = possibleSources.Single(t => t.Piece.Kind == sourceKind
// Castling should be denoted with the special notation O-O / O-O-O, we don't want to accept Kg1 / Kc1
&& ctx.Inner.IsMovePseudoLegal(t.Location, destination, allowCastling: false));
return(sourceTile.Location);
}
catch (InvalidOperationException e)
{
throw new InvalidMoveException(InvalidMoveReason.CouldNotInferSource, e);
}
}
private Location?ReadLocation()
{
if (!CanRead(2))
{
return(null);
}
var(fileChar, rankChar) = (Peek(), Peek(1));
if (fileChar < 'a' || fileChar > 'h')
{
return(null);
}
if (rankChar < '1' || rankChar > '8')
{
return(null);
}
return(FileHelpers.FromChar(Pop()), RankHelpers.FromChar(Pop()));
}