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feat: NCS-9 include en passant square in pawn legal targets

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This commit is contained in:
LQ63
2026-03-29 15:32:58 +02:00
committed by Janis
parent f63b449947
commit 008881741e
2 changed files with 50 additions and 0 deletions
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modules/core/src/main/scala/de/nowchess/chess/logic/MoveValidator.scala
+13
View File
@@ -155,8 +155,21 @@ object MoveValidator:
board.pieceAt(from) match
case Some(piece) if piece.pieceType == PieceType.King =>
legalTargets(board, from) ++ castlingTargets(board, history, piece.color)
case Some(piece) if piece.pieceType == PieceType.Pawn =>
pawnTargets(board, history, from, piece.color)
case _ =>
legalTargets(board, from)
private def pawnTargets(board: Board, history: GameHistory, from: Square, color: Color): Set[Square] =
val existing = pawnTargets(board, from, color)
val fi = from.file.ordinal
val ri = from.rank.ordinal
val dir = if color == Color.White then 1 else -1
val epCapture: Set[Square] =
EnPassantCalculator.enPassantTarget(board, history).filter: target =>
squareAt(fi - 1, ri + dir).contains(target) || squareAt(fi + 1, ri + dir).contains(target)
.toSet
existing ++ epCapture
def isLegal(board: Board, history: GameHistory, from: Square, to: Square): Boolean =
legalTargets(board, history, from).contains(to)
modules/core/src/test/scala/de/nowchess/chess/logic/MoveValidatorTest.scala
+37
View File
@@ -211,3 +211,40 @@ class MoveValidatorTest extends AnyFunSuite with Matchers:
sq(File.E, Rank.R4) -> Piece.BlackRook
)
MoveValidator.legalTargets(b, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R4))
// ──── Pawn – en passant targets ──────────────────────────────────────
test("white pawn includes ep target in legal moves after black double push"):
// Black pawn just double-pushed to d5 (ep target = d6); white pawn on e5
val b = board(
sq(File.E, Rank.R5) -> Piece.WhitePawn,
sq(File.D, Rank.R5) -> Piece.BlackPawn
)
val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should contain(sq(File.D, Rank.R6))
test("white pawn does not include ep target without a preceding double push"):
val b = board(
sq(File.E, Rank.R5) -> Piece.WhitePawn,
sq(File.D, Rank.R5) -> Piece.BlackPawn
)
val h = GameHistory.empty.addMove(sq(File.D, Rank.R6), sq(File.D, Rank.R5)) // single push
MoveValidator.legalTargets(b, h, sq(File.E, Rank.R5)) should not contain sq(File.D, Rank.R6)
test("black pawn includes ep target in legal moves after white double push"):
// White pawn just double-pushed to e4 (ep target = e3); black pawn on d4
val b = board(
sq(File.D, Rank.R4) -> Piece.BlackPawn,
sq(File.E, Rank.R4) -> Piece.WhitePawn
)
val h = GameHistory.empty.addMove(sq(File.E, Rank.R2), sq(File.E, Rank.R4))
MoveValidator.legalTargets(b, h, sq(File.D, Rank.R4)) should contain(sq(File.E, Rank.R3))
test("pawn on wrong file does not get ep target from adjacent double push"):
// White pawn on a5, black pawn double-pushed to d5 — a5 is not adjacent to d5
val b = board(
sq(File.A, Rank.R5) -> Piece.WhitePawn,
sq(File.D, Rank.R5) -> Piece.BlackPawn
)
val h = GameHistory.empty.addMove(sq(File.D, Rank.R7), sq(File.D, Rank.R5))
MoveValidator.legalTargets(b, h, sq(File.A, Rank.R5)) should not contain sq(File.D, Rank.R6)