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Implement castling rules in toyfish #988

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Implement castling rules in toyfish #988

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201 changes: 194 additions & 7 deletions domains/games/libs/toyfish/types.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,15 @@ const (
Black = 1
)

type CastlingRights uint8

const (
CastlingWhiteKingSide CastlingRights = 1 << 0
CastlingWhiteQueenSide CastlingRights = 1 << 1
CastlingBlackKingSide CastlingRights = 1 << 2
CastlingBlackQueenSide CastlingRights = 1 << 3
)

type Piece struct {
FenRepr int8
Glyph rune
Expand Down Expand Up @@ -52,7 +61,7 @@ func populatePieceMap() map[int8]*Piece {
Side: White,
Value: pieceInfo.S,
}
lowerCased := int8(strings.ToLower(string(pieceInfo.F))[0])
lowerCased := int8(strings.ToLower(string(rune(pieceInfo.F)))[0])
pieceMap[lowerCased] = &Piece{
FenRepr: lowerCased,
Glyph: pieceInfo.G[1],
Expand All @@ -69,6 +78,7 @@ type Game struct {
Settings *s.Settings
Board Board
Side Color
Castling CastlingRights
}

func FenToBoard(fen string, pieceMap map[int8]*Piece) (Board, error) {
Expand Down Expand Up @@ -116,6 +126,91 @@ func (g *Game) Fen() string {
return g.StartingFen
}

func (g *Game) IsAttacked(square int, attackerSide Color) bool {
// Check for attacks from sliding pieces (Rook, Queen)
for _, offset := range g.Settings.Directions["R"] {
target := square
for {
target += offset
if g.Settings.Coordinates[target] == "xx" {
break
}
p := g.Board[target]
if p != nil {
if p.Side == attackerSide && strings.Contains("rRqQ", string(rune(p.FenRepr))) {
return true
}
break
}
}
}

// Check for attacks from sliding pieces (Bishop, Queen)
for _, offset := range g.Settings.Directions["B"] {
target := square
for {
target += offset
if g.Settings.Coordinates[target] == "xx" {
break
}
p := g.Board[target]
if p != nil {
if p.Side == attackerSide && strings.Contains("bBqQ", string(rune(p.FenRepr))) {
return true
}
break
}
}
}

// Check for attacks from Knights
for _, offset := range g.Settings.Directions["N"] {
target := square + offset
if g.Settings.Coordinates[target] != "xx" {
p := g.Board[target]
if p != nil && p.Side == attackerSide && strings.Contains("nN", string(rune(p.FenRepr))) {
return true
}
}
}

// Check for attacks from Kings
for _, offset := range g.Settings.Directions["K"] {
target := square + offset
if g.Settings.Coordinates[target] != "xx" {
p := g.Board[target]
if p != nil && p.Side == attackerSide && strings.Contains("kK", string(rune(p.FenRepr))) {
return true
}
}
}

// Check for attacks from Pawns
// White pawns attack up (-9, -11). So if attacker is White, look down (+9, +11).
// Black pawns attack down (+9, +11). So if attacker is Black, look up (-9, -11).
var pawnOffsets []int
var pawnChar string
if attackerSide == White {
pawnOffsets = []int{9, 11}
pawnChar = "P"
} else {
pawnOffsets = []int{-9, -11}
pawnChar = "p"
}

for _, offset := range pawnOffsets {
target := square + offset
if g.Settings.Coordinates[target] != "xx" {
p := g.Board[target]
if p != nil && p.Side == attackerSide && string(rune(p.FenRepr)) == pawnChar {
return true
}
}
}

return false
}

type Move struct {
Source int
Target int
Expand All @@ -133,7 +228,7 @@ func (g *Game) GenerateMoves() []Move {
for idx, piece := range g.Board {
//square := g.Settings.Coordinates[idx]
if piece != nil && piece.Side == g.Side {
for _, offset := range g.Settings.Directions[s.Piece(piece.FenRepr)] {
for _, offset := range g.Settings.Directions[s.Piece(rune(piece.FenRepr))] {
//fmt.Printf("piece %c on square %s with offset %d\n", piece.Glyph, square, offset)
targetSquare := idx
for {
Expand All @@ -151,7 +246,7 @@ func (g *Game) GenerateMoves() []Move {
// ***************************************************
// ******************* PAWN LOGIC ********************
// ***************************************************
if strings.Contains("pP", string(piece.FenRepr)) {
if strings.Contains("pP", string(rune(piece.FenRepr))) {
// no en-passant on empty square
if offset%10 != 0 && capturedPiece == nil {
break
Expand Down Expand Up @@ -180,12 +275,77 @@ func (g *Game) GenerateMoves() []Move {
}
// TODO: implement es-passant capture suppoer

// TODO: implement castling rules
// Castling Logic
if (piece.FenRepr == 'K' || piece.FenRepr == 'k') {
if piece.Side == White && idx == 95 {
// King Side (e1 -> g1)
if g.Castling&CastlingWhiteKingSide != 0 {
// Check path empty: f1(96), g1(97)
if g.Board[96] == nil && g.Board[97] == nil {
// Check safe: e1(idx), f1(96), g1(97)
if !g.IsAttacked(idx, Black) && !g.IsAttacked(96, Black) && !g.IsAttacked(97, Black) {
moveList = append(moveList, Move{
Source: idx,
Target: 97,
Piece: piece,
CapturedPiece: nil,
})
}
}
}
// Queen Side (e1 -> c1)
if g.Castling&CastlingWhiteQueenSide != 0 {
// Check path empty: d1(94), c1(93), b1(92)
if g.Board[94] == nil && g.Board[93] == nil && g.Board[92] == nil {
// Check safe: e1(idx), d1(94), c1(93)
if !g.IsAttacked(idx, Black) && !g.IsAttacked(94, Black) && !g.IsAttacked(93, Black) {
moveList = append(moveList, Move{
Source: idx,
Target: 93,
Piece: piece,
CapturedPiece: nil,
})
}
}
}
} else if piece.Side == Black && idx == 25 {
// Black King Side (e8 -> g8)
if g.Castling&CastlingBlackKingSide != 0 {
// Check path empty: f8(26), g8(27)
if g.Board[26] == nil && g.Board[27] == nil {
// Check safe: e8(idx), f8(26), g8(27)
if !g.IsAttacked(idx, White) && !g.IsAttacked(26, White) && !g.IsAttacked(27, White) {
moveList = append(moveList, Move{
Source: idx,
Target: 27,
Piece: piece,
CapturedPiece: nil,
})
}
}
}
// Black Queen Side (e8 -> c8)
if g.Castling&CastlingBlackQueenSide != 0 {
// Check path empty: d8(24), c8(23), b8(22)
if g.Board[24] == nil && g.Board[23] == nil && g.Board[22] == nil {
// Check safe: e8(idx), d8(24), c8(23)
if !g.IsAttacked(idx, White) && !g.IsAttacked(24, White) && !g.IsAttacked(23, White) {
moveList = append(moveList, Move{
Source: idx,
Target: 23,
Piece: piece,
CapturedPiece: nil,
})
}
}
}
}
}

// ***************************************************
// ******************* CHECKMATE *********************
// ***************************************************
if capturedPiece != nil && strings.Contains("kK", string(capturedPiece.FenRepr)) {
if capturedPiece != nil && strings.Contains("kK", string(rune(capturedPiece.FenRepr))) {
return nil
}

Expand All @@ -208,7 +368,7 @@ func (g *Game) GenerateMoves() []Move {
}

// pawn, knight, and king aren't sliding pieces (only one move at a time in each allowed direction)
if strings.Contains("pPnNkK", string(piece.FenRepr)) {
if strings.Contains("pPnNkK", string(rune(piece.FenRepr))) {
break
}
}
Expand All @@ -224,11 +384,38 @@ func NewGame(settings *s.Settings) (*Game, error) {
if err != nil {
return nil, err
}

parts := strings.Split(settings.Fen, " ")
var side Color = White
if len(parts) >= 2 {
if parts[1] == "b" {
side = Black
}
}

var castling CastlingRights
if len(parts) >= 3 {
c := parts[2]
if strings.Contains(c, "K") {
castling |= CastlingWhiteKingSide
}
if strings.Contains(c, "Q") {
castling |= CastlingWhiteQueenSide
}
if strings.Contains(c, "k") {
castling |= CastlingBlackKingSide
}
if strings.Contains(c, "q") {
castling |= CastlingBlackQueenSide
}
}

game := Game{
StartingFen: settings.Fen,
Settings: settings,
Board: board,
Side: White,
Side: side,
Castling: castling,
}

return &game, nil
Expand Down
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