Implement Chess960 castling rules on the backend.
authorSteinar H. Gunderson <sgunderson@bigfoot.com>
Sat, 6 Jan 2018 17:31:37 +0000 (18:31 +0100)
committerSteinar H. Gunderson <sgunderson@bigfoot.com>
Sat, 6 Jan 2018 17:31:37 +0000 (18:31 +0100)
Board.pm
Position.pm

index cb2bc71..783aef0 100644 (file)
--- a/Board.pm
+++ b/Board.pm
@@ -42,56 +42,62 @@ sub make_move {
                die "Invalid move $move";
        }
 
-       # white short castling
-       if ($move eq 'e1g1' && $piece eq 'K') {
-               # king
-               $nb->[7][4] = '-';
-               $nb->[7][6] = $piece;
+       if ($piece eq 'K') {
+               my $dst_piece = $board->[$to_row][$to_col];
 
-               # rook
-               $nb->[7][7] = '-';
-               $nb->[7][5] = 'R';
+               # White short castling (regular or Chess960 king-takes-rook)
+               if ($move eq 'e1g1' || $dst_piece eq 'R') {
+                       # king
+                       $nb->[7][$from_col] = '-';
+                       $nb->[7][6] = $piece;
 
-               return $nb;
-       }
+                       # rook
+                       $nb->[7][$to_col] = '-';
+                       $nb->[7][5] = 'R';
 
-       # white long castling
-       if ($move eq 'e1c1' && $piece eq 'K') {
-               # king
-               $nb->[7][4] = '-';
-               $nb->[7][2] = $piece;
+                       return $nb;
+               }
 
-               # rook
-               $nb->[7][0] = '-';
-               $nb->[7][3] = 'R';
+               # White long castling (regular or Chess960 king-takes-rook)
+               if ($move eq 'e1c1' || $dst_piece eq 'R') {
+                       # king
+                       $nb->[7][$from_col] = '-';
+                       $nb->[7][2] = $piece;
 
-               return $nb;
-       }
+                       # rook
+                       $nb->[7][$to_col] = '-';
+                       $nb->[7][3] = 'R';
 
-       # black short castling
-       if ($move eq 'e8g8' && $piece eq 'k') {
-               # king
-               $nb->[0][4] = '-';
-               $nb->[0][6] = $piece;
+                       return $nb;
+               }
+       } elsif ($piece eq 'k') {
+               my $dst_piece = $board->[$to_row][$to_col];
 
-               # rook
-               $nb->[0][7] = '-';
-               $nb->[0][5] = 'r';
+               # Black short castling (regular or Chess960 king-takes-rook)
+               if ($move eq 'e8g8' || $dst_piece eq 'r') {
+                       # king
+                       $nb->[0][$from_col] = '-';
+                       $nb->[0][6] = $piece;
 
-               return $nb;
-       }
+                       # rook
+                       $nb->[0][$from_col] = '-';
+                       $nb->[0][5] = 'r';
+
+                       return $nb;
+               }
 
-       # black long castling
-       if ($move eq 'e8c8' && $piece eq 'k') {
-               # king
-               $nb->[0][4] = '-';
-               $nb->[0][2] = $piece;
+               # black long castling
+               if ($move eq 'e8c8' || $dst_piece eq 'r') {
+                       # king
+                       $nb->[0][$from_col] = '-';
+                       $nb->[0][2] = $piece;
 
-               # rook
-               $nb->[0][0] = '-';
-               $nb->[0][3] = 'r';
+                       # rook
+                       $nb->[0][$to_col] = '-';
+                       $nb->[0][3] = 'r';
 
-               return $nb;
+                       return $nb;
+               }
        }
 
        # check if the from-piece is a pawn
@@ -136,9 +142,12 @@ sub _row_letter_to_num {
         return 7 - (ord(shift) - ord('1'));
 }
 
+use Carp;
+
 sub _square_to_pos {
        my ($square) = @_;
-       $square =~ /^([a-h])([1-8])$/ or die "Invalid square $square";  
+       #$square =~ /^([a-h])([1-8])$/ or die "Invalid square $square"; 
+       $square =~ /^([a-h])([1-8])$/ or Carp::confess("Invalid square $square");
        return (_row_letter_to_num($2), _col_letter_to_num($1));
 }
 
@@ -148,25 +157,53 @@ sub move_to_uci_notation {
        return _pos_to_square($from_row, $from_col) . _pos_to_square($to_row, $to_col) . $promo;
 }
 
+sub _find_piece_col {
+       my ($row, $piece) = @_;
+       for my $col (0..7) {
+               return $col if ($row->[$col] eq $piece);
+       }
+       die "Could not find piece $piece";
+}
+
 # Note: This is in general not a validation that the move is actually allowed
 # (e.g. you can castle even though you're in check).
 sub parse_pretty_move {
-       my ($board, $move, $toplay) = @_;
+       my ($board, $move, $toplay, $chess960, $white_castle_k, $white_castle_q, $black_castle_k, $black_castle_q) = @_;
 
        # Strip check or mate
        $move =~ s/[+#]$//;
 
        if ($move eq '0-0' or $move eq 'O-O') {
                if ($toplay eq 'W') {
-                       return (_square_to_pos('e1'), _square_to_pos('g1'));
+                       if ($chess960) {
+                               # King takes rook.
+                               return (7, _find_piece_col($board->[7], 'K'), _square_to_pos($white_castle_k . '1'));
+                       } else {
+                               return (_square_to_pos('e1'), _square_to_pos('g1'));
+                       }
                } else {
-                       return (_square_to_pos('e8'), _square_to_pos('g8'));
+                       if ($chess960) {
+                               # King takes rook.
+                               return (0, _find_piece_col($board->[0], 'k'), _square_to_pos($black_castle_k . '8'));
+                       } else {
+                               return (_square_to_pos('e8'), _square_to_pos('g8'));
+                       }
                }
        } elsif ($move eq '0-0-0' or $move eq 'O-O-O') {
                if ($toplay eq 'W') {
-                       return (_square_to_pos('e1'), _square_to_pos('c1'));
+                       if ($chess960) {
+                               # King takes rook.
+                               return (7, _find_piece_col($board->[7], 'K'), _square_to_pos($white_castle_q . '1'));
+                       } else {
+                               return (_square_to_pos('e1'), _square_to_pos('c1'));
+                       }
                } else {
-                       return (_square_to_pos('e8'), _square_to_pos('c8'));
+                       if ($chess960) {
+                               # King takes rook.
+                               return (0, _find_piece_col($board->[0], 'k'), _square_to_pos($black_castle_q . '8'));
+                       } else {
+                               return (_square_to_pos('e8'), _square_to_pos('c8'));
+                       }
                }
        }
 
@@ -233,7 +270,8 @@ sub fen {
 sub can_reach {
        my ($board, $piece, $from_row, $from_col, $to_row, $to_col) = @_;
        
-       # can't eat your own piece
+       # Can't eat your own piece (Chess960 uses king-takes-rook for castling,
+       # but castling is irrelevant for reachability)
        my $dest_piece = $board->[$to_row][$to_col];
        if ($dest_piece ne '-') {
                return 0 if (($piece eq lc($piece)) == ($dest_piece eq lc($dest_piece)));
@@ -473,24 +511,26 @@ sub _prettyprint_move_no_check_or_mate {
                die "Invalid move $move";
        }
 
-       # white short castling
-       if ($move eq 'e1g1' && $piece eq 'K') {
-               return 'O-O';
-       }
-
-       # white long castling
-       if ($move eq 'e1c1' && $piece eq 'K') {
-               return 'O-O-O';
-       }
+       if ($piece eq 'K') {
+               # white short/long castling
+               return 'O-O' if ($move eq 'e1g1');
+               return 'O-O-O' if ($move eq 'e1c1');
 
-       # black short castling
-       if ($move eq 'e8g8' && $piece eq 'k') {
-               return 'O-O';
-       }
-
-       # black long castling
-       if ($move eq 'e8c8' && $piece eq 'k') {
-               return 'O-O-O';
+               # white short/long chess960-style castling (king takes own rook)
+               my $dst_piece = $board->[$to_row][$to_col];
+               if ($dst_piece eq 'R') {
+                       return ($to_col > $from_col) ? 'O-O' : 'O-O-O';
+               }
+       } elsif ($piece eq 'k') {
+               # black short/long castling
+               return 'O-O' if ($move eq 'e8g8');
+               return 'O-O-O' if ($move eq 'e8c8');
+
+               # black short/long chess960-style castling (king takes own rook)
+               my $dst_piece = $board->[$to_row][$to_col];
+               if ($dst_piece eq 'r') {
+                       return ($to_col > $from_col) ? 'O-O' : 'O-O-O';
+               }
        }
 
        my $pretty;
index 17c8512..cd0cc97 100644 (file)
@@ -19,10 +19,10 @@ sub new {
        $pos->{'board'} = Board->new(@x[1..8]);
        $pos->{'toplay'} = $x[9];
        $pos->{'ep_file_num'} = $x[10];
-       $pos->{'white_castle_k'} = $x[11];
-       $pos->{'white_castle_q'} = $x[12];
-       $pos->{'black_castle_k'} = $x[13];
-       $pos->{'black_castle_q'} = $x[14];
+       $pos->{'white_castle_k'} = $x[11] ? 'h' : undef;
+       $pos->{'white_castle_q'} = $x[12] ? 'a' : undef;
+       $pos->{'black_castle_k'} = $x[13] ? 'h' : undef;
+       $pos->{'black_castle_q'} = $x[14] ? 'a' : undef;
        $pos->{'time_since_100move_rule_reset'} = $x[15];
        $pos->{'player_w'} = $x[17];
        $pos->{'player_b'} = $x[18];
@@ -58,6 +58,7 @@ sub from_fen {
        my $pos = {};
        $board =~ s/(\d)/"-"x$1/ge;
        $pos->{'board'} = Board->new(split /\//, $board);
+       $board = $pos->{'board'};
        $pos->{'toplay'} = uc($toplay);
 
        if ($ep_square =~ /^([a-h])/) {
@@ -66,10 +67,37 @@ sub from_fen {
                $pos->{'ep_file_num'} = -1;
        }
 
-       $pos->{'white_castle_k'} = ($castling =~ /K/) ? 1 : 0;
-       $pos->{'white_castle_q'} = ($castling =~ /Q/) ? 1 : 0;
-       $pos->{'black_castle_k'} = ($castling =~ /k/) ? 1 : 0;
-       $pos->{'black_castle_q'} = ($castling =~ /q/) ? 1 : 0;
+       # X-FEN castling rights parsing.
+       if ($castling =~ /K/) {
+               $pos->{'white_castle_k'} = _col_num_to_letter(_find_piece_col_from_right($board->[7], 'R'));
+       }
+       if ($castling =~ /Q/) {
+               $pos->{'white_castle_q'} = _col_num_to_letter(_find_piece_col($board->[7], 'R'));
+       }
+       while ($castling =~ s/([A-H])//g) {
+               my $rook_col = lc($1);
+               my $king_col = _find_piece_col($board->[7], 'K');
+               if ($rook_col < $king_col) {
+                       $pos->{'white_castle_q'} = _col_num_to_letter($rook_col);
+               } else {
+                       $pos->{'white_castle_k'} = _col_num_to_letter($rook_col);
+               }
+       }
+       if ($castling =~ /k/) {
+               $pos->{'white_castle_k'} = _col_num_to_letter(_find_piece_col_from_right($board->[0], 'r'));
+       }
+       if ($castling =~ /q/) {
+               $pos->{'black_castle_q'} = _col_num_to_letter(_find_piece_col($board->[0], 'r'));
+       }
+       while ($castling =~ s/([a-h])//g) {
+               my $rook_col = $1;
+               my $king_col = _find_piece_col($board->[0], 'k');
+               if ($rook_col < $king_col) {
+                       $pos->{'black_castle_q'} = _col_num_to_letter($rook_col);
+               } else {
+                       $pos->{'black_castle_k'} = _col_num_to_letter($rook_col);
+               }
+       }
        $pos->{'time_since_100move_rule_reset'} = $halfmove_clock // 0;
        $pos->{'player_w'} = 'white';
        $pos->{'player_b'} = 'black';
@@ -95,12 +123,40 @@ sub fen {
        $fen .= " ";
        $fen .= lc($pos->{'toplay'});
 
-       # castling
+       # Castling (X-FEN compatible).
        my $castling = "";
-       $castling .= "K" if ($pos->{'white_castle_k'} == 1);
-       $castling .= "Q" if ($pos->{'white_castle_q'} == 1);
-       $castling .= "k" if ($pos->{'black_castle_k'} == 1);
-       $castling .= "q" if ($pos->{'black_castle_q'} == 1);
+       if (defined($pos->{'white_castle_k'})) {
+               my $outer_rook_col = _col_num_to_letter(_find_piece_col_from_right($pos->{'board'}[7], 'R'));
+               if ($outer_rook_col eq $pos->{'white_castle_k'}) {
+                       $castling .= "K";
+               } else {
+                       $castling .= uc($pos->{'white_castle_k'});
+               }
+       }
+       if (defined($pos->{'white_castle_q'})) {
+               my $outer_rook_col = _col_num_to_letter(_find_piece_col($pos->{'board'}[7], 'R'));
+               if ($outer_rook_col eq $pos->{'white_castle_q'}) {
+                       $castling .= "Q";
+               } else {
+                       $castling .= uc($pos->{'white_castle_q'});
+               }
+       }
+       if (defined($pos->{'black_castle_k'})) {
+               my $outer_rook_col = _col_num_to_letter(_find_piece_col_from_right($pos->{'board'}[0], 'r'));
+               if ($outer_rook_col eq $pos->{'black_castle_k'}) {
+                       $castling .= "k";
+               } else {
+                       $castling .= $pos->{'black_castle_k'};
+               }
+       }
+       if (defined($pos->{'black_castle_q'})) {
+               my $outer_rook_col = _col_num_to_letter(_find_piece_col($pos->{'board'}[0], 'r'));
+               if ($outer_rook_col eq $pos->{'black_castle_q'}) {
+                       $castling .= "q";
+               } else {
+                       $castling .= $pos->{'black_castle_q'};
+               }
+       }
        $castling = "-" if ($castling eq "");
        # $castling = "-"; # chess960
        $fen .= " ";
@@ -155,7 +211,7 @@ sub to_json_hash {
 
 sub parse_pretty_move {
         my ($pos, $move) = @_;
-       return $pos->{'board'}->parse_pretty_move($move, $pos->{'toplay'});
+       return $pos->{'board'}->parse_pretty_move($move, $pos->{'toplay'}, $pos->{'chess960'}, $pos->{'white_castle_k'}, $pos->{'white_castle_q'}, $pos->{'black_castle_k'}, $pos->{'black_castle_q'});
 }
 
 sub num_pieces {
@@ -196,19 +252,27 @@ sub make_move {
        $np->{'black_castle_k'} = $pos->{'black_castle_k'};
        $np->{'black_castle_q'} = $pos->{'black_castle_q'};
        if ($piece eq 'K') {
-               $np->{'white_castle_k'} = 0;
-               $np->{'white_castle_q'} = 0;
+               $np->{'white_castle_k'} = undef;
+               $np->{'white_castle_q'} = undef;
        } elsif ($piece eq 'k') {
-               $np->{'black_castle_k'} = 0;
-               $np->{'black_castle_q'} = 0;
-       } elsif ($from_square eq 'a1' || $to_square eq 'a1') {
-               $np->{'white_castle_q'} = 0;
-       } elsif ($from_square eq 'h1' || $to_square eq 'h1') {
-               $np->{'white_castle_k'} = 0;
-       } elsif ($from_square eq 'a8' || $to_square eq 'a8') {
-               $np->{'black_castle_q'} = 0;
-       } elsif ($from_square eq 'h8' || $to_square eq 'h8') {
-               $np->{'black_castle_k'} = 0;
+               $np->{'black_castle_k'} = undef;
+               $np->{'black_castle_q'} = undef;
+       } elsif (defined($np->{'white_castle_q'}) &&
+                ($from_square eq ($np->{'white_castle_q'} . '1') ||
+                 $to_square   eq ($np->{'white_castle_q'} . '1'))) {
+               $np->{'white_castle_q'} = undef;
+       } elsif (defined($np->{'white_castle_k'}) &&
+                ($from_square eq ($np->{'white_castle_k'} . '1') ||
+                 $to_square   eq ($np->{'white_castle_k'} . '1'))) {
+               $np->{'white_castle_k'} = undef;
+       } elsif (defined($np->{'black_castle_q'}) &&
+                ($from_square eq ($np->{'black_castle_q'} . '8') ||
+                 $to_square   eq ($np->{'black_castle_q'} . '8'))) {
+               $np->{'black_castle_q'} = undef;
+       } elsif (defined($np->{'black_castle_k'}) &&
+                ($from_square eq ($np->{'black_castle_k'} . '8') ||
+                 $to_square   eq ($np->{'black_castle_k'} . '8'))) {
+               $np->{'black_castle_k'} = undef;
        }
 
        # 50-move rule.
@@ -261,6 +325,11 @@ sub apply_uci_pv {
        return $pvpos;
 }
 
+sub _col_num_to_letter {
+       my $col = shift;
+       return sprintf("%c", ord('a') + $col);
+}
+
 sub _col_letter_to_num {
        return ord(shift) - ord('a');
 }
@@ -269,6 +338,22 @@ sub _row_letter_to_num {
        return 7 - (ord(shift) - ord('1'));
 }
 
+sub _find_piece_col {
+       my ($row, $piece) = @_;
+       for my $col (0..7) {
+               return $col if ($row->[$col] eq $piece);
+       }
+       die "Could not find piece $piece";
+}
+
+sub _find_piece_col_from_right {
+       my ($row, $piece) = @_;
+       for my $col (reverse 0..7) {
+               return $col if ($row->[$col] eq $piece);
+       }
+       die "Could not find piece $piece";
+}
+
 sub _parse_uci_move {
         my $move = shift;
         my $from_col = _col_letter_to_num(substr($move, 0, 1));