Added FENString class
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194
src/dev/kske/chess/board/FENString.java
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src/dev/kske/chess/board/FENString.java
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package dev.kske.chess.board;
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import java.util.LinkedHashMap;
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import java.util.Map;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import dev.kske.chess.board.Piece.Color;
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import dev.kske.chess.exception.ChessException;
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/**
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* Project: <strong>Chess</strong><br>
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* File: <strong>FENString.java</strong><br>
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* Created: <strong>20 Oct 2019</strong><br>
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* <br>
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* Represents a FEN string and enables parsing an existing FEN string or
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* serializing a {@link Board} to one.
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*
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* @author Kai S. K. Engelbart
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* @since Chess v0.4-alpha
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*/
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public class FENString {
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private Board board;
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private Map<FENField, String> fields = new LinkedHashMap<>();
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public static enum FENField {
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PIECE_PLACEMENT, ACTIVE_COLOR, CASTLING_AVAILABILITY, EN_PASSANT_TARGET_SQUARE, HALFMOVE_CLOCK, FULLMOVE_NUMBER
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}
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/**
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* Constructs a {@link FENString} representing the starting position
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* {@code rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1}.
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*/
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public FENString() {
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board = new Board();
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fields.put(FENField.PIECE_PLACEMENT, "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR");
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fields.put(FENField.ACTIVE_COLOR, "w");
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fields.put(FENField.CASTLING_AVAILABILITY, "KQkq");
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fields.put(FENField.EN_PASSANT_TARGET_SQUARE, "-");
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fields.put(FENField.HALFMOVE_CLOCK, "0");
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fields.put(FENField.FULLMOVE_NUMBER, "1");
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}
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/**
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* Constructs a {@link FENString} by parsing an existing string.
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*
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* @param fen the FEN string to parse
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* @throws ChessException
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*/
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public FENString(String fen) throws ChessException {
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// Check fen string against regex
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Pattern fenPattern = Pattern.compile(
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"^(?<PIECE_PLACEMENT>(?:[1-8nbrqkpNBRQKP]{1,8}\\/){7}[1-8nbrqkpNBRQKP]{1,8}) (?<ACTIVE_COLOR>[wb]) (?<CASTLING_AVAILABILITY>-|[KQkq]{1,4}) (?<EN_PASSANT_TARGET_SQUARE>-|[a-h][1-8]) (?<HALFMOVE_CLOCK>\\d) (?<FULLMOVE_NUMBER>\\d)$");
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Matcher matcher = fenPattern.matcher(fen);
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if (!matcher.find()) throw new ChessException("FEN string does not match pattern " + fenPattern.pattern());
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for (FENField field : FENField.values())
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fields.put(field, matcher.group(field.toString()));
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// Initialize and clean board
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board = new Board();
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for (int i = 0; i < 8; i++)
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for (int j = 0; j < 8; j++)
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board.getBoardArr()[i][j] = null;
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// Parse individual fields
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// Piece placement
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final String[] rows = fields.get(FENField.PIECE_PLACEMENT).split("/");
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if (rows.length != 8) throw new ChessException("FEN string contains invalid piece placement");
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for (int i = 0; i < 8; i++) {
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final char[] cols = rows[i].toCharArray();
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int j = 0;
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for (char c : cols) {
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// Empty space
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if (Character.isDigit(c)) {
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j += Character.getNumericValue(c);
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} else {
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Color color = Character.isUpperCase(c) ? Color.WHITE : Color.BLACK;
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switch (Character.toUpperCase(c)) {
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case 'K':
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board.getBoardArr()[i][j] = new King(color, board);
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break;
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case 'Q':
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board.getBoardArr()[i][j] = new Queen(color, board);
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break;
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case 'R':
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board.getBoardArr()[i][j] = new Rook(color, board);
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break;
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case 'N':
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board.getBoardArr()[i][j] = new Knight(color, board);
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break;
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case 'B':
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board.getBoardArr()[i][j] = new Bishop(color, board);
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break;
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case 'P':
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board.getBoardArr()[i][j] = new Pawn(color, board);
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break;
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}
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++j;
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}
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}
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}
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// Active color
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board.getLog().setActiveColor(Color.fromFirstChar(fields.get(FENField.ACTIVE_COLOR).charAt(0)));
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// TODO: Castling availability
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// En passant square
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if (!fields.get(FENField.EN_PASSANT_TARGET_SQUARE).equals("-"))
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board.getLog().setEnPassant(Position.fromLAN(fields.get(FENField.EN_PASSANT_TARGET_SQUARE)));
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// Halfmove clock
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board.getLog().setHalfmoveClock(Integer.parseInt(fields.get(FENField.HALFMOVE_CLOCK)));
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// Fullmove number
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board.getLog().setFullmoveNumber(Integer.parseInt(fields.get(FENField.FULLMOVE_NUMBER)));
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}
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/**
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* Constructs a {@link FENString} form a {@link Board} object.
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*
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* @param board the {@link Board} object to encode in this {@link FENString}
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*/
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public FENString(Board board) {
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this.board = board;
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// Serialize individual fields
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// Piece placement
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StringBuilder sb = new StringBuilder();
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for (int i = 0; i < 8; i++) {
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int empty = 0;
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for (int j = 0; j < 8; j++) {
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final Piece piece = board.getBoardArr()[i][j];
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if (piece == null) ++empty;
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else {
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// Write empty field count
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if (empty > 0) {
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sb.append(empty);
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empty = 0;
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}
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// Write piece character
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char p = piece.getType().firstChar();
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sb.append(piece.getColor() == Color.WHITE ? Character.toUpperCase(p) : p);
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}
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}
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// Write empty field count
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if (empty > 0) {
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sb.append(empty);
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empty = 0;
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}
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if (i < 7) sb.append('/');
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}
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fields.put(FENField.PIECE_PLACEMENT, sb.toString());
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// Active color
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fields.put(FENField.ACTIVE_COLOR, String.valueOf(board.getLog().getActiveColor().firstChar()));
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// TODO: Castling availability
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// En passant availability
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final Position enPassantPosition = board.getLog().getEnPassant();
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fields.put(FENField.EN_PASSANT_TARGET_SQUARE, enPassantPosition == null ? "-" : enPassantPosition.toLAN());
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// Halfmove clock
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fields.put(FENField.HALFMOVE_CLOCK, String.valueOf(board.getLog().getHalfmoveClock()));
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// Fullmove counter
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fields.put(FENField.FULLMOVE_NUMBER, String.valueOf(board.getLog().getFullmoveNumber()));
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}
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/**
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* Exports this {@link FENString} object to a FEN string.
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*
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* @return a FEN string representing the board
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*/
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@Override
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public String toString() {
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return String.join(" ", fields.values());
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}
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/**
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* @return a {@link Board} object corresponding to this {@link FENString}
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*/
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public Board getBoard() { return board; }
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}
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