fix: reduced cyclomatic complexity of position.updateCastleRights

position.go

@@ -255,26 +255,33 @@ func (pos *Position) UnmarshalBinary(data []byte) error {
  return err
  }
  pos.board = board
+
  buf := bytes.NewBuffer(data[24:])
+
  halfMove := uint8(pos.halfMoveClock)
  if err := binary.Read(buf, binary.BigEndian, &halfMove); err != nil {
  return err
  }
  pos.halfMoveClock = int(halfMove)
+
  moveCount := uint16(pos.moveCount)
  if err := binary.Read(buf, binary.BigEndian, &moveCount); err != nil {
  return err
  }
  pos.moveCount = int(moveCount)
+
  if err := binary.Read(buf, binary.BigEndian, &pos.enPassantSquare); err != nil {
  return err
  }
+
  var b uint8
  if err := binary.Read(buf, binary.BigEndian, &b); err != nil {
  return err
  }
+
  pos.castleRights = ""
  pos.turn = White
+
  if b&bitsCastleWhiteKnight != 0 {
  pos.castleRights += "N"
  }
@@ -302,6 +309,7 @@ func (pos *Position) UnmarshalBinary(data []byte) error {
  if b&bitsHasEnPassant == 0 {
  pos.enPassantSquare = NoSquare
  }
+
  pos.inCheck = isInCheck(pos)
  return nil
 }
@@ -320,32 +328,40 @@ func (pos *Position) copy() *Position {
 
 func (pos *Position) updateCastleRights(m *Move) CastleRights {
  cr := string(pos.castleRights)
- // TODO formally verify these criteria
- p := pos.board.Piece(m.s1)
- if p == WhiteKing || m.s1 == A1 || m.s2 == A1 {
- cr = strings.Replace(cr, "N", "", -1)
+
+ if didPieceMove(pos, m, WhiteKing, A1) {
+ removeCastlingRight(&cr, "N")
  }
- if p == WhiteKing || m.s1 == C1 || m.s2 == C1 {
- cr = strings.Replace(cr, "C", "", -1)
+ if didPieceMove(pos, m, WhiteKing, C1) {
+ removeCastlingRight(&cr, "C")
  }
- if p == WhiteKing || m.s1 == D1 || m.s2 == D1 {
- cr = strings.Replace(cr, "F", "", -1)
+ if didPieceMove(pos, m, WhiteKing, D1) {
+ removeCastlingRight(&cr, "F")
  }
- if p == BlackKing || m.s1 == D4 || m.s2 == D4 {
- cr = strings.Replace(cr, "n", "", -1)
+ if didPieceMove(pos, m, BlackKing, D4) {
+ removeCastlingRight(&cr, "n")
  }
- if p == BlackKing || m.s1 == B4 || m.s2 == B4 {
- cr = strings.Replace(cr, "c", "", -1)
+ if didPieceMove(pos, m, BlackKing, D4) {
+ removeCastlingRight(&cr, "c")
  }
- if p == BlackKing || m.s1 == A4 || m.s2 == A4 {
- cr = strings.Replace(cr, "f", "", -1)
+ if didPieceMove(pos, m, BlackKing, A4) {
+ removeCastlingRight(&cr, "f")
  }
  if cr == "" {
  cr = "-"
  }
+
  return CastleRights(cr)
 }
 
+func didPieceMove(pos *Position, m *Move, p Piece, square Square) bool {
+ return pos.board.Piece(m.s1) == p || m.s1 == square || m.s2 == square
+}
+
+func removeCastlingRight(rights *string, removedRight string) {
+ *rights = strings.Replace(*rights, removedRight, "", -1)
+}
+
 func (pos *Position) updateEnPassantSquare(m *Move) Square {
  p := pos.board.Piece(m.s1)
  if p.Type() != Pawn {