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fen.go
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fen.go
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package chessongo
import (
"fmt"
"log"
"strconv"
"strings"
)
const STARTING_POSITION_FEN = "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
const E_INVALID_FEN = "e:invalid:fen"
var RUNE_TO_PIECE = map[rune]Piece{
'P': W_PAWN, 'N': W_KNIGHT, 'B': W_BISHOP, 'R': W_ROOK, 'Q': W_QUEEN, 'K': W_KING,
'p': B_PAWN, 'n': B_KNIGHT, 'b': B_BISHOP, 'r': B_ROOK, 'q': B_QUEEN, 'k': B_KING,
}
var PIECE_TO_RUNE = map[Piece]rune{
W_PAWN: 'P', W_KNIGHT: 'N', W_BISHOP: 'B', W_ROOK: 'R', W_QUEEN: 'Q', W_KING: 'K',
B_PAWN: 'p', B_KNIGHT: 'n', B_BISHOP: 'b', B_ROOK: 'r', B_QUEEN: 'q', B_KING: 'k',
}
var STRING_TO_KIND = map[string]uint{
"P": PAWN, "N": KNIGHT, "B": BISHOP, "R": ROOK, "Q": QUEEN, "K": KING,
"p": PAWN, "n": KNIGHT, "b": BISHOP, "r": ROOK, "q": QUEEN, "k": KING,
}
var RUNE_TO_FILE = map[rune]int{'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'g': 6, 'h': 7}
var RUNE_TO_RANK = map[rune]int{'1': 7, '2': 6, '3': 5, '4': 4, '5': 3, '6': 2, '7': 1, '8': 0}
var FILE_TO_STRING = map[int]string{0: "a", 1: "b", 2: "c", 3: "d", 4: "e", 5: "f", 6: "g", 7: "h"}
var RANK_TO_STRING = map[int]string{0: "8", 1: "7", 2: "6", 3: "5", 4: "4", 5: "3", 6: "2", 7: "1"}
//initialize board from Fen string
func (b *Board) InitFromFen(fen string) error {
b.Reset()
b.Fen = fen
fen = strings.Trim(fen, " ")
parts := strings.Split(fen, " ")
if len(parts) != 6 {
return fmt.Errorf(E_INVALID_FEN)
}
pieces := parts[0]
turn := parts[1]
castling := parts[2]
enPassant := parts[3]
halfMoves := parts[4]
fullMoves := parts[5]
index := 0
for _, r := range pieces {
if index > 63 {
return fmt.Errorf(E_INVALID_FEN)
}
switch r {
case 'p', 'n', 'b', 'r', 'q', 'k', 'P', 'N', 'B', 'R', 'Q', 'K':
b.addPiece(RUNE_TO_PIECE[r], index)
index++
case '1', '2', '3', '4', '5', '6', '7', '8':
emptySquares, _ := strconv.Atoi(string(r))
for i := 0; i < emptySquares; i++ {
b.addPiece(EMPTY, index)
index++
}
}
}
if turn == "w" {
b.Turn = WHITE
} else {
b.Turn = BLACK
}
b.Castling = 0
for _, r := range castling {
switch r {
case 'K':
b.Castling |= CASTLE_WKS
case 'Q':
b.Castling |= CASTLE_WQS
case 'k':
b.Castling |= CASTLE_BKS
case 'q':
b.Castling |= CASTLE_BQS
}
}
b.HalfMoves, _ = strconv.Atoi(string(halfMoves))
b.FullMoves, _ = strconv.Atoi(string(fullMoves))
if enPassant != "-" {
enPassant = strings.ToLower(enPassant)
file := RUNE_TO_FILE[rune(enPassant[0])]
rank := RUNE_TO_RANK[rune(enPassant[1])]
log.Println("SETTING EP TO")
b.EnPassant = CoordsToSquare(rank, file)
} else {
b.EnPassant = 0
}
return nil
}
//return FEN representation of board
func (b *Board) ToFen() string {
var pieces, turn, castling, enPassant string
pieces = ""
var i, emptyCount int = 0, 0
for rank := 0; rank < 8; rank++ {
for file := 0; file < 8; file++ {
if b.Squares[i] != EMPTY {
pieces += string(PIECE_TO_RUNE[b.Squares[i]])
i++
continue
}
for emptyCount = 0; file < 8 && b.Squares[i] == EMPTY; {
emptyCount++
i++
file++
}
if emptyCount > 0 {
pieces += strconv.Itoa(emptyCount)
file--
}
}
if rank < 7 {
pieces += "/"
}
}
if b.Turn == WHITE {
turn = "w"
} else {
turn = "b"
}
castling = ""
if (b.Castling & CASTLE_WKS) > 0 {
castling += "K"
}
if (b.Castling & CASTLE_WQS) > 0 {
castling += "Q"
}
if (b.Castling & CASTLE_BKS) > 0 {
castling += "k"
}
if (b.Castling & CASTLE_BQS) > 0 {
castling += "q"
}
if len(castling) == 0 {
castling = "-"
}
if b.EnPassant == 0 {
enPassant = "-"
} else {
rank, file := squareCoords(b.EnPassant)
enPassant = FILE_TO_STRING[file] + RANK_TO_STRING[rank]
}
return fmt.Sprintf("%s %s %s %s %d %d", pieces, turn, castling, enPassant, b.HalfMoves, b.FullMoves)
}