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feat: added en passant movement to the game (#11)
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@sgatu
sgatu authored May 12, 2024
1 parent cd72c7c commit c73f796
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Showing 3 changed files with 130 additions and 53 deletions.
169 changes: 123 additions & 46 deletions game/gamestate.go
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Original file line number Diff line number Diff line change
Expand Up @@ -41,9 +41,10 @@ type DirectionVector struct {
y int
}
type MoveResult struct {
Move string
CheckedPlayer PLAYER
MateStatus GameStateStatus
Move string
EnPassantCapture string
CheckedPlayer PLAYER
MateStatus GameStateStatus
}

func newPiece(_type PIECE_TYPE, player PLAYER, hasBeenMoved bool) *Piece {
Expand Down Expand Up @@ -111,13 +112,14 @@ const (
)

type GameState struct {
table [64]*Piece
moves []string
outTable []Piece
playerTurn PLAYER
checkedPlayer PLAYER
gameStatus GameStateStatus
castleRights CastleRights
table [64]*Piece
moves []string
outTable []Piece
playerTurn PLAYER
checkedPlayer PLAYER
gameStatus GameStateStatus
lastMoveIsAPJump bool
castleRights CastleRights
}

type Action struct {
Expand Down Expand Up @@ -159,7 +161,7 @@ func bishopDirections() []DirectionVector {
}
}

var regexpUCI = regexp.MustCompile(`^([a-h][1-8])([a-h][1-8])([nbrqNBRQ]?)$`)
var regexpUCI = regexp.MustCompile(`^([a-h][1-8])([a-h][1-8])([nbrqNBRQ]?|(e\.p)?)$`)

func coordsToPos(letter rune, pos int) (int, error) {
p := (pos-1)*8 + strings.IndexRune("abcdefgh", letter)
Expand Down Expand Up @@ -228,6 +230,25 @@ func posInRange(pos int) bool {
return pos >= 0 && pos < 64
}

func (gs *GameState) isEnPassantMovement(startPos int, endPos int, who PLAYER) bool {
if !gs.lastMoveIsAPJump || len(gs.moves) == 0 {
return false
}
directionMultiplier := getDirection(startPos, endPos)
enPassantRightPos := startPos + (-1 * directionMultiplier)
enPassantLeftPos := startPos + (1 * directionMultiplier)
checkPos := enPassantLeftPos
moveDiff := math.Abs(float64(endPos - startPos))
if moveDiff < 8 {
checkPos = enPassantRightPos
}
lastAction, _ := gs.uci2Action(gs.moves[len(gs.moves)-1])
if lastAction.posEnd != checkPos {
return false
}
return (gs.table[checkPos] != nil && gs.table[checkPos].PieceType == PAWN && gs.table[checkPos].Player == gs.getOppositePlayer(who))
}

func (gs *GameState) getPawnMovements(pos int, who PLAYER) []int {
directionMultiplier := 1
expectedEatColor := WHITE_PLAYER
Expand Down Expand Up @@ -258,17 +279,26 @@ func (gs *GameState) getPawnMovements(pos int, who PLAYER) []int {
columnLeft := leftPos % 8
currentColumn := pos % 8
/* check for eating movements
* first: check if column left or right is 1 step away(if movement leads to jump from one side of the table to another it is invalid)
* second: check if the new position has a enemy piece
*/
if posInRange(rightPos) && math.Abs(float64(currentColumn-columnRight)) == 1 &&
gs.table[rightPos] != nil &&
gs.table[rightPos].Player == expectedEatColor {
allowedMovePositions = append(allowedMovePositions, rightPos)
* first: check if column left or right is 1 step away(if movement leads to jump from one side of the table to another it is invalid)
* second: check if the new position has a enemy piece if so, it's allowed to capture it
* else if there is an enemy pawn next to my pawn that hast just jumped, we are allowed to capture it too
* same check for both columns
*/
if posInRange(rightPos) && math.Abs(float64(currentColumn-columnRight)) == 1 {
if gs.table[rightPos] != nil && gs.table[rightPos].Player == expectedEatColor {
allowedMovePositions = append(allowedMovePositions, rightPos)
} else if gs.isEnPassantMovement(pos, rightPos, who) {
allowedMovePositions = append(allowedMovePositions, rightPos)
}
}
if posInRange(leftPos) && math.Abs(float64(currentColumn-columnLeft)) == 1 && gs.table[leftPos] != nil && gs.table[leftPos].Player == expectedEatColor {
allowedMovePositions = append(allowedMovePositions, leftPos)
if posInRange(leftPos) && math.Abs(float64(currentColumn-columnLeft)) == 1 {
if gs.table[leftPos] != nil && gs.table[leftPos].Player == expectedEatColor {
allowedMovePositions = append(allowedMovePositions, leftPos)
} else if gs.isEnPassantMovement(pos, leftPos, who) {
allowedMovePositions = append(allowedMovePositions, leftPos)
}
}

return allowedMovePositions
}

Expand Down Expand Up @@ -444,7 +474,6 @@ func (gs *GameState) processKnightMovement(action *Action) error {
}

func (gs *GameState) processPawnMovement(action *Action) error {
fmt.Printf("Processing pawn movement %+v\n", action)
allowedMovePositions := gs.getPawnMovements(action.posStart, action.who)
if !slices.Contains(allowedMovePositions, action.posEnd) {
return &errors.InvalidMoveError{
Expand All @@ -460,7 +489,6 @@ func (gs *GameState) processPawnMovement(action *Action) error {
ErrCode: "MOVE_MISSING_PROMOTION",
}
}
fmt.Printf("Promoting pawn to %+v\n", action.promotion)
gs.table[action.posEnd] = newPiece(action.promotion, action.who, true)
gs.table[action.posStart] = nil
return nil
Expand Down Expand Up @@ -494,7 +522,6 @@ func (gs *GameState) isCastlingMovement(action *Action) (bool, int, int) {
if direction < 0 {
rookStart -= 1
}
fmt.Printf("It's castling timeee, RookStart %+v, RookEnd: %+v, KingStart: %+v, KingEnd: %+v\n", rookStart, rookEnd, action.posStart, action.posEnd)
return isCastling, rookStart, rookEnd
}
return false, 0, 0
Expand Down Expand Up @@ -528,6 +555,18 @@ func (gs *GameState) updateCastleRights(action *Action) {
}
}

func boolToInt(b bool) int {
if b {
return 1
}
return 0
}

func getDirection(startPos int, endPos int) int {
sign := boolToInt(math.Signbit(float64(startPos - endPos)))
return int(2*sign - 1)
}

func (gs *GameState) applyAction(action *Action, allowedMovePositions []int) error {
if !slices.Contains(allowedMovePositions, action.posEnd) {
return &errors.InvalidMoveError{
Expand All @@ -543,6 +582,11 @@ func (gs *GameState) applyAction(action *Action, allowedMovePositions []int) err
gs.table[rookEnd].HasBeenMoved = true
gs.table[rookStart] = nil
}
if gs.isEnPassantMovement(action.posStart, action.posEnd, action.who) {
direction := getDirection(action.posStart, action.posEnd)
gs.outTable = append(gs.outTable, *gs.table[action.posEnd-(direction*8)])
gs.table[action.posEnd-(direction*8)] = nil
}
gs.table[action.posEnd] = gs.table[action.posStart]
gs.table[action.posStart] = nil
gs.table[action.posEnd].HasBeenMoved = true
Expand Down Expand Up @@ -609,12 +653,13 @@ func NewGameState() *GameState {
}

return &GameState{
playerTurn: WHITE_PLAYER,
table: table,
outTable: []Piece{},
gameStatus: STATUS_PLAYING,
checkedPlayer: UNKNOWN_PLAYER,
moves: []string{},
playerTurn: WHITE_PLAYER,
table: table,
outTable: []Piece{},
gameStatus: STATUS_PLAYING,
checkedPlayer: UNKNOWN_PLAYER,
moves: []string{},
lastMoveIsAPJump: false,
castleRights: CastleRights{
whiteQueenSide: true,
blackQueenSide: true,
Expand Down Expand Up @@ -655,6 +700,8 @@ func FromSerialized(serializedData []byte) (*GameState, error) {
return "B"
case 4:
return "R"
case 5:
return "e.p"
default:
return ""
}
Expand All @@ -678,12 +725,17 @@ func FromSerialized(serializedData []byte) (*GameState, error) {
return "", fmt.Errorf("could not convert bytes")
}
var castleRights CastleRights
lastMoveIsAPJump := false
// used to recover moves
historyMovement := [3]byte{}
idx := 0

for i, b := range serializedData {
if i == 0 {
if b&4 == 4 {
lastMoveIsAPJump = true
b &= 3
}
playerTurn = PLAYER(b)
continue
}
Expand Down Expand Up @@ -730,13 +782,14 @@ func FromSerialized(serializedData []byte) (*GameState, error) {
}
}
return &GameState{
playerTurn: playerTurn,
table: table,
outTable: outPieces,
moves: moves,
checkedPlayer: checkedPlayer,
gameStatus: gameStatus,
castleRights: castleRights,
playerTurn: playerTurn,
table: table,
outTable: outPieces,
moves: moves,
checkedPlayer: checkedPlayer,
gameStatus: gameStatus,
castleRights: castleRights,
lastMoveIsAPJump: lastMoveIsAPJump,
}, nil
}

Expand Down Expand Up @@ -773,8 +826,11 @@ func (gs *GameState) Serialize() ([]byte, error) {
for _, p := range gs.table {
pieceBytes = append(pieceBytes, pieceToByte(p))
}

returnBytes = append(returnBytes, byte(gs.playerTurn))
encodedPlayerTurn := byte(gs.playerTurn)
if gs.lastMoveIsAPJump {
encodedPlayerTurn |= 4
}
returnBytes = append(returnBytes, encodedPlayerTurn)
returnBytes = append(returnBytes, byte(gs.checkedPlayer))
returnBytes = append(returnBytes, byte(gs.gameStatus))
returnBytes = append(returnBytes, gs.castleRights.Serialize())
Expand All @@ -786,16 +842,20 @@ func (gs *GameState) Serialize() ([]byte, error) {
for _, move := range gs.moves {
start, errStart := coordsToPos(rune(move[0]), int(move[1]-'0'))
end, errEnd := coordsToPos(rune(move[2]), int(move[3]-'0'))
promotion := byte(0)
tag := byte(0)
if len(move) == 5 {
promotion = promotionCharToByte(rune(move[4]))
tag = promotionCharToByte(rune(move[4]))
end |= 128
}
if len(move) == 7 && strings.HasSuffix(move, "e.p") {
tag = 5
end |= 128
}
if errStart == nil && errEnd == nil {
returnBytes = append(returnBytes, byte(start), byte(end))
}
if promotion > 0 {
returnBytes = append(returnBytes, promotion)
if tag > 0 {
returnBytes = append(returnBytes, tag)
}
}
return returnBytes, nil
Expand Down Expand Up @@ -884,6 +944,11 @@ func (gs *GameState) UpdateGameState(uciAction string) (*MoveResult, error) {
ErrCode: "NO_MOVE",
}
}

isPawnJump := int32(math.Abs(float64(action.posStart-action.posEnd))) == 16 &&
!gs.table[action.posStart].HasBeenMoved &&
gs.table[action.posStart].PieceType == PAWN
enPassantMovement := gs.isEnPassantMovement(action.posStart, action.posEnd, action.who)
beforeState := gs.table
var processErr error
switch gs.table[action.posStart].PieceType {
Expand Down Expand Up @@ -911,7 +976,11 @@ func (gs *GameState) UpdateGameState(uciAction string) (*MoveResult, error) {
ErrCode: "MOVE_IN_CHECK",
}
}
gs.moves = append(gs.moves, action.uci)
uciMovement := action.uci
if enPassantMovement {
uciMovement += "e.p"
}
gs.moves = append(gs.moves, uciMovement)
gs.checkedPlayer = UNKNOWN_PLAYER
if whiteCheck {
gs.checkedPlayer = WHITE_PLAYER
Expand All @@ -920,9 +989,17 @@ func (gs *GameState) UpdateGameState(uciAction string) (*MoveResult, error) {
}
gs.playerTurn = gs.getOppositePlayer(gs.playerTurn)
gs.gameStatus = gs.checkIfMate()
gs.lastMoveIsAPJump = isPawnJump
enPassantCapture := ""
if enPassantMovement {
direction := getDirection(action.posStart, action.posEnd)
letter, number, _ := posToCoords(action.posEnd - (direction * 8))
enPassantCapture = fmt.Sprintf("%c%d", letter, number)
}
return &MoveResult{
Move: uciAction,
CheckedPlayer: gs.checkedPlayer,
MateStatus: gs.gameStatus,
Move: uciAction,
CheckedPlayer: gs.checkedPlayer,
MateStatus: gs.gameStatus,
EnPassantCapture: enPassantCapture,
}, nil
}
13 changes: 7 additions & 6 deletions handlers/playHandler.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -133,18 +133,19 @@ func (ph *PlayHandler) Play(c *gin.Context) {
mateStatusStr = "-"
}
outputMessage, err := json.Marshal(struct {
Type string `json:"type"`
Move string `json:"uci"`
MateStatus string `json:"mateStatus"`
CheckedPlayer int `json:"checkedPlayer"`
}{Type: "move", Move: move.Move, CheckedPlayer: int(move.CheckedPlayer), MateStatus: mateStatusStr})
Type string `json:"type"`
Move string `json:"uci"`
MateStatus string `json:"mateStatus"`
EnPassantCapture string `json:"enPassantCapture"`
CheckedPlayer int `json:"checkedPlayer"`
}{Type: "move", Move: move.Move, CheckedPlayer: int(move.CheckedPlayer), MateStatus: mateStatusStr, EnPassantCapture: move.EnPassantCapture})
if err != nil {
fmt.Println("Could not serialize movement")
return
}
err = wsutil.WriteServerMessage(conn, ws.OpText, []byte(outputMessage))
if err == nil {
fmt.Println("Got movement, sent to player", move)
fmt.Printf("Got movement, sent to player %+v\n", move)
}
case error := <-errorCh:
if ferr, ok := error.(*errors.InvalidMoveError); ok {
Expand Down
1 change: 0 additions & 1 deletion services/gameManagerService.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -89,7 +89,6 @@ func (lgs *LiveGameState) RemoveObserver(observerCh chan *game.MoveResult) {
}
if len(lgs.observers) == 0 {
close(lgs.chCommandsChannel)
fmt.Printf("before removing the livestate %+v, %+v\n", lgs.gameManager, lgs.game.Id())
lgs.gameManager.removeLiveGameState(lgs.game.Id())
}
}
Expand Down

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