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Parse file and rank from move 

I realized that ambiguous moves might require the file _and_ rank.

Also, ambiguous moves are not limited to capturing moves.
This commit is contained in:
ekzyis 2024-09-26 06:25:40 +02:00
parent 87856f694d
commit e6f9c529f8
2 changed files with 193 additions and 122 deletions
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269
chess/board.go
View File

@ -271,36 +271,20 @@ func (b *Board) Parse(pgn string) error {
func (b *Board) Move(move string) error {
var (
to string
piece string
targetPosition string
// the x column from which the piece is captured.
// for example, this would be 'e' for exd4 and 'e' for Nexd4.
captureFrom int
// if the move is ambiguous, the originating square rank must be given
// see https://en.wikipedia.org/wiki/Algebraic_notation_(chess)#Disambiguating_moves
fromX int
fromY int
collisionPiece *Piece
err error
)
if captureFrom, err = parseCaptureMove(move); err != nil {
if piece, fromX, fromY, to, err = parseMove(move); err != nil {
return err
}
if captureFrom != -1 {
parts := strings.Split(move, "x")
piece := parts[0]
position := parts[1]
if strings.ToLower(piece) == piece {
// pawn capture move like exd4
move = position
} else {
// piece capture move like Nbxd4
// remove the capture column from the piece
move = piece[:1] + position
}
} else {
// even if captureFrom is not set, it might still be a capture move just unambiguous like Nxe4
move = strings.Replace(move, "x", "", 1)
}
// TODO: parse ambiguous captures for all pieces
// TODO: parse promotions
// TODO: parse checks e.g. e5+
@ -311,40 +295,32 @@ func (b *Board) Move(move string) error {
// ( this avoids moving into check and moving a piece that exposes the king to check e.g. pinned pieces )
move_ := func() error {
if len(move) == 2 {
return b.movePawn(move, captureFrom)
}
if len(move) == 3 {
piece = move[0:1]
targetPosition = move[1:3]
// collision detection
if collisionPiece, err = b.getCollision(targetPosition); err != nil {
if collisionPiece, err = b.getCollision(to); err != nil {
return fmt.Errorf("invalid move %s: %v", move, err)
} else if collisionPiece != nil {
return fmt.Errorf("invalid move %s: position %s blocked by %s", move, targetPosition, collisionPiece)
return fmt.Errorf("invalid move %s: position %s blocked by %s", move, to, collisionPiece)
}
switch strings.ToLower(piece) {
case "p":
return b.movePawn(to, fromX, fromY)
case "r":
return b.moveRook(targetPosition, false)
return b.moveRook(to, false, fromX, fromY)
case "b":
return b.moveBishop(targetPosition, false)
return b.moveBishop(to, false)
case "n":
return b.moveKnight(targetPosition, captureFrom)
return b.moveKnight(to, fromX, fromY)
case "q":
return b.moveQueen(targetPosition)
return b.moveQueen(to)
case "k":
return b.moveKing(targetPosition)
return b.moveKing(to)
default:
return fmt.Errorf("invalid move %s: %v", move, err)
}
}
return fmt.Errorf("invalid move %s: %v", move, err)
}
if err = move_(); err != nil {
return err
}
@ -360,65 +336,154 @@ func (b *Board) Move(move string) error {
return nil
}
func parseCaptureMove(move string) (int, error) {
func parseMove(move string) (string, int, int, string, error) {
var (
parts = strings.Split(move, "x")
from = parts[0]
piece string
fromX = -1
fromY = -1
to string
from string
)
toIndex := func(column string) int {
switch column {
case "a":
return 0
case "b":
return 1
case "c":
return 2
case "d":
return 3
case "e":
return 4
case "f":
return 5
case "g":
return 6
case "h":
return 7
}
return -1
if strings.Contains(move, "x") {
return parseCaptureMove(move)
}
if !strings.Contains(move, "x") {
return -1, nil
if len(move) < 2 {
return piece, fromX, fromY, to, fmt.Errorf("invalid move: %s", move)
}
if len(parts) != 2 {
return -1, fmt.Errorf("invalid move: %s", move)
if len(move) == 2 {
// pawn move
piece = "p"
to = move
return piece, fromX, fromY, to, nil
}
if len(move) == 3 {
// unambiguous piece move
piece = move[0:1]
to = move[1:]
return piece, fromX, fromY, to, nil
}
// last two characters are the target position
to = move[len(move)-2:]
// everything before is about origin
from = move[:len(move)-2]
// piece is first character
piece = from[0:1]
// we can ignore piece from here on
from = from[1:]
if len(from) == 1 {
// rank or file given
if from[0] >= 'a' && from[0] <= 'h' {
// file given
return piece, toFile(rune(from[0])), -1, to, nil
}
if from[0] >= '1' && from[0] <= '8' {
// rank given
return piece, -1, toRank(rune(from[0])), to, nil
}
return "", -1, -1, "", fmt.Errorf("invalid move: %s", move)
}
if len(from) == 2 {
// example: Nexd4
return toIndex(from[1:]), nil
// file and rank given
return piece, toFile(rune(from[0])), toRank(rune(from[1])), to, nil
}
if len(from) == 1 {
if strings.ToLower(from) == from {
// example: exd4
return toIndex(from), nil
}
// example: Nxd4
return -1, nil
}
return -1, fmt.Errorf("invalid move: %s", move)
return "", -1, -1, "", fmt.Errorf("invalid move: %s", move)
}
func (b *Board) movePawn(position string, captureFrom int) error {
func parseCaptureMove(move string) (string, int, int, string, error) {
var (
parts = strings.Split(move, "x")
piece string
fromX = -1
fromY = -1
from = parts[0]
to = parts[1]
)
if len(from) == 1 {
// pawn move with rank given (exd4) or piece move (Nxe5)
if strings.ToLower(from) == from {
piece = "p"
fromX = toFile(rune(from[0]))
return piece, fromX, fromY, to, nil
}
piece = from
return piece, fromX, fromY, to, nil
}
// piece is always first character
piece = from[0:1]
if len(from) == 2 {
// rank or file given
fromX = toFile(rune(from[1]))
fromY = toRank(rune(from[1]))
if fromX == -1 && fromY == -1 {
return "", -1, -1, "", fmt.Errorf("invalid move: %s", move)
}
return piece, fromX, fromY, to, nil
}
if len(from) == 3 {
// both file and rank given
fromX = toFile(rune(from[1]))
fromY = toRank(rune(from[1]))
if fromX == -1 || fromY == -1 {
return "", -1, -1, "", fmt.Errorf("invalid move: %s", move)
}
return piece, fromX, fromY, to, nil
}
return "", -1, -1, "", fmt.Errorf("invalid move: %s", move)
}
func toFile(r rune) int {
if r >= 'a' && r <= 'h' {
return int(r - 'a')
}
return -1
}
func toRank(r rune) int {
if r >= '1' && r <= '8' {
return int('8' - r)
}
return -1
}
func (b *Board) validateMove(search PieceName, fromX int, fromY int) func(*Piece, int, int) bool {
return func(p *Piece, xPrev int, yPrev int) bool {
// does piece originate from given origin?
from := (fromX == -1 || xPrev == fromX) && (fromY == -1 || yPrev == fromY)
// is this the piece we're looking for?
found := p != nil && p.Name == search && p.Color == b.turn
return from && found
}
}
func (b *Board) movePawn(position string, fromX int, fromY int) error {
var (
toX int
toY int
fromX = captureFrom
fromY int
yPrev int
piece *Piece
err error
@ -428,7 +493,7 @@ func (b *Board) movePawn(position string, captureFrom int) error {
return err
}
if captureFrom != -1 {
if fromX != -1 {
if b.turn == Light {
fromY = toY + 1
} else {
@ -486,7 +551,7 @@ func (b *Board) movePawn(position string, captureFrom int) error {
return fmt.Errorf("no pawn found that can move to %s", position)
}
func (b *Board) moveRook(position string, queen bool) error {
func (b *Board) moveRook(position string, queen bool, fromX int, fromY int) error {
var (
x int
y int
@ -500,13 +565,16 @@ func (b *Board) moveRook(position string, queen bool) error {
return err
}
checkRookMove := b.validateMove(Rook, fromX, fromY)
checkQueenMove := b.validateMove(Queen, fromX, fromY)
xPrev = x
yPrev = y
for xPrev >= 0 && xPrev < 8 && yPrev >= 0 && yPrev < 8 {
xPrev++
piece = b.getPiece(xPrev, yPrev)
if piece != nil {
if ((!queen && piece.Name == Rook) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
if (!queen && checkRookMove(piece, xPrev, yPrev)) || (queen && checkQueenMove(piece, xPrev, yPrev)) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -523,7 +591,7 @@ func (b *Board) moveRook(position string, queen bool) error {
yPrev--
piece = b.getPiece(xPrev, yPrev)
if piece != nil {
if ((!queen && piece.Name == Rook) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
if (!queen && checkRookMove(piece, xPrev, yPrev)) || (queen && checkQueenMove(piece, xPrev, yPrev)) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -539,7 +607,7 @@ func (b *Board) moveRook(position string, queen bool) error {
xPrev--
piece = b.getPiece(xPrev, yPrev)
if piece != nil {
if ((!queen && piece.Name == Rook) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
if (!queen && checkRookMove(piece, xPrev, yPrev)) || (queen && checkQueenMove(piece, xPrev, yPrev)) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -555,7 +623,7 @@ func (b *Board) moveRook(position string, queen bool) error {
yPrev++
piece = b.getPiece(xPrev, yPrev)
if piece != nil {
if ((!queen && piece.Name == Rook) || (queen && piece.Name == Queen)) && piece.Color == b.turn {
if (!queen && checkRookMove(piece, xPrev, yPrev)) || (queen && checkQueenMove(piece, xPrev, yPrev)) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -654,7 +722,7 @@ func (b *Board) moveBishop(position string, queen bool) error {
return fmt.Errorf("no bishop found that can move to %s", position)
}
func (b *Board) moveKnight(position string, captureFrom int) error {
func (b *Board) moveKnight(position string, fromX int, fromY int) error {
var (
x int
y int
@ -668,17 +736,12 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
return err
}
checkMove := func(p *Piece, xPrev int) bool {
// capture condition fulfilled if capture
capture := captureFrom == -1 || xPrev == captureFrom
found := p != nil && p.Name == Knight && p.Color == b.turn
return capture && found
}
checkMove := b.validateMove(Knight, fromX, fromY)
xPrev = x + 1
yPrev = y - 2
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -687,7 +750,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x + 2
yPrev = y - 1
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -696,7 +759,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x + 2
yPrev = y + 1
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -705,7 +768,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x + 1
yPrev = y + 2
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -714,7 +777,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x - 1
yPrev = y + 2
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -723,7 +786,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x - 2
yPrev = y + 1
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -732,7 +795,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x - 2
yPrev = y - 1
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -741,7 +804,7 @@ func (b *Board) moveKnight(position string, captureFrom int) error {
xPrev = x - 1
yPrev = y - 2
piece = b.getPiece(xPrev, yPrev)
if checkMove(piece, xPrev) {
if checkMove(piece, xPrev, yPrev) {
b.tiles[xPrev][yPrev] = nil
b.tiles[x][y] = piece
return nil
@ -759,7 +822,7 @@ func (b *Board) moveQueen(position string) error {
return nil
}
if err = b.moveRook(position, true); err == nil {
if err = b.moveRook(position, true, -1, -1); err == nil {
return nil
}

18
chess/board_test.go
View File

@ -197,7 +197,6 @@ func TestBoardMoveKnightCapture(t *testing.T) {
b := chess.NewBoard()
assertParse(t, b, "e4 Nf6 d4 Nxe4")
assertPiece(t, b, "e4", chess.Knight, chess.Dark)
assertPiece(t, b, "d4", chess.Pawn, chess.Light)
assertNoPiece(t, b, "g8")
@ -296,10 +295,7 @@ func TestBoardMoveRook(t *testing.T) {
assertMoveError(t, b, "Ra3", "no rook found that can move to a3")
assertParse(t, b, "a4")
assertParse(t, b, "a5")
assertParse(t, b, "Ra3")
assertParse(t, b, "a4 a5 Ra3")
assertPiece(t, b, "a3", chess.Rook, chess.Light)
assertNoPiece(t, b, "a1")
@ -310,6 +306,18 @@ func TestBoardMoveRook(t *testing.T) {
assertNoPiece(t, b, "a8")
}
func TestBoardMoveRookCapture(t *testing.T) {
t.Parallel()
b := chess.NewBoard()
assertParse(t, b, "a4 e6 h4 e5 Ra3 e4 Rhh3 e3 Raxe3")
assertPiece(t, b, "e3", chess.Rook, chess.Light)
assertPiece(t, b, "h3", chess.Rook, chess.Light)
assertNoPiece(t, b, "a3")
}
func TestBoardMoveRookInvalid(t *testing.T) {
t.Parallel()