3 # There are too many chess modules on CPAN already, so here's another one...
11 my ($class, @rows) = @_;
16 $board->[$row][$col] = substr($rows[$row], $col, 1);
29 $nb->[$row][$col] = $board->[$row][$col];
36 # Returns a new board.
38 my ($board, $from_row, $from_col, $to_row, $to_col, $promo) = @_;
39 my $move = _move_to_uci_notation($from_row, $from_col, $to_row, $to_col, $promo);
40 my $piece = $board->[$from_row][$from_col];
41 my $nb = $board->clone();
44 die "Invalid move $move";
47 # white short castling
48 if ($move eq 'e1g1' && $piece eq 'K') {
61 if ($move eq 'e1c1' && $piece eq 'K') {
73 # black short castling
74 if ($move eq 'e8g8' && $piece eq 'k') {
87 if ($move eq 'e8c8' && $piece eq 'k') {
99 # check if the from-piece is a pawn
100 if (lc($piece) eq 'p') {
102 if ($from_col != $to_col) {
104 if ($board->[$to_row][$to_col] eq '-') {
106 $nb->[$to_row + 1][$to_col] = '-';
108 $nb->[$to_row - 1][$to_col] = '-';
112 if (defined($promo) && $promo ne '') {
123 $nb->[$from_row][$from_col] = '-';
124 $nb->[$to_row][$to_col] = $piece;
130 my ($row, $col) = @_;
131 return sprintf("%c%d", ord('a') + $col, 8 - $row);
134 sub _col_letter_to_num {
135 return ord(shift) - ord('a');
138 sub _row_letter_to_num {
139 return 7 - (ord(shift) - ord('1'));
144 $square =~ /^([a-h])([1-8])$/ or die "Invalid square $square";
145 return (_row_letter_to_num($2), _col_letter_to_num($1));
148 sub _move_to_uci_notation {
149 my ($from_row, $from_col, $to_row, $to_col, $promo) = @_;
151 return _pos_to_square($from_row, $from_col) . _pos_to_square($to_row, $to_col) . $promo;
154 sub parse_pretty_move {
155 my ($board, $move, $toplay) = @_;
157 # Strip check or mate
160 if ($move eq '0-0' or $move eq 'O-O') {
161 if ($toplay eq 'W') {
162 return (_square_to_pos('e1'), _square_to_pos('g1'));
164 return (_square_to_pos('e8'), _square_to_pos('g8'));
166 } elsif ($move eq '0-0-0' or $move eq 'O-O-O') {
167 if ($toplay eq 'W') {
168 return (_square_to_pos('e1'), _square_to_pos('c1'));
170 return (_square_to_pos('e8'), _square_to_pos('c8'));
176 if ($move =~ s/=([QRNB])$//) {
180 $move =~ /^([KQRBN])?([a-h])?([1-8])?x?([a-h][1-8])$/ or die "Invalid move $move";
181 my $piece = $1 // 'P';
182 my $from_col = defined($2) ? _col_letter_to_num($2) : undef;
183 my $from_row = defined($3) ? _row_letter_to_num($3) : undef;
184 my ($to_row, $to_col) = _square_to_pos($4);
186 # Find all possible from-squares that could have been meant.
188 if ($toplay eq 'B') {
192 next if (defined($from_row) && $from_row != $row);
194 next if (defined($from_col) && $from_col != $col);
195 next if ($board->[$row][$col] ne $piece);
196 next if (!$board->can_reach($piece, $row, $col, $to_row, $to_col));
197 push @squares, [ $row, $col ];
200 if (scalar @squares != 1) {
201 die "Ambigious or impossible move $move";
203 return (@{$squares[0]}, $to_row, $to_col, $promo);
210 my $str = join('', @{$board->[$row]});
211 $str =~ s/(-+)/length($1)/ge;
215 return join('/', @rows);
219 my ($board, $piece, $from_row, $from_col, $to_row, $to_col) = @_;
221 # can't eat your own piece
222 my $dest_piece = $board->[$to_row][$to_col];
223 if ($dest_piece ne '-') {
224 return 0 if (($piece eq lc($piece)) == ($dest_piece eq lc($dest_piece)));
227 if (lc($piece) eq 'k') {
228 return (abs($from_row - $to_row) <= 1 && abs($from_col - $to_col) <= 1);
230 if (lc($piece) eq 'r') {
231 return 0 unless ($from_row == $to_row || $from_col == $to_col);
233 # check that there's a clear passage
234 if ($from_row == $to_row) {
235 if ($from_col > $to_col) {
236 ($to_col, $from_col) = ($from_col, $to_col);
239 for my $c (($from_col+1)..($to_col-1)) {
240 my $middle_piece = $board->[$to_row][$c];
241 return 0 if ($middle_piece ne '-');
246 if ($from_row > $to_row) {
247 ($to_row, $from_row) = ($from_row, $to_row);
250 for my $r (($from_row+1)..($to_row-1)) {
251 my $middle_piece = $board->[$r][$to_col];
252 return 0 if ($middle_piece ne '-');
258 if (lc($piece) eq 'b') {
259 return 0 unless (abs($from_row - $to_row) == abs($from_col - $to_col));
261 my $dr = ($to_row - $from_row) / abs($to_row - $from_row);
262 my $dc = ($to_col - $from_col) / abs($to_col - $from_col);
264 my $r = $from_row + $dr;
265 my $c = $from_col + $dc;
267 while ($r != $to_row) {
268 my $middle_piece = $board->[$r][$c];
269 return 0 if ($middle_piece ne '-');
277 if (lc($piece) eq 'n') {
278 my $diff_r = abs($from_row - $to_row);
279 my $diff_c = abs($from_col - $to_col);
280 return 1 if ($diff_r == 2 && $diff_c == 1);
281 return 1 if ($diff_r == 1 && $diff_c == 2);
285 return (can_reach($board, 'r', $from_row, $from_col, $to_row, $to_col) ||
286 can_reach($board, 'b', $from_row, $from_col, $to_row, $to_col));
289 return (can_reach($board, 'R', $from_row, $from_col, $to_row, $to_col) ||
290 can_reach($board, 'B', $from_row, $from_col, $to_row, $to_col));
296 if ($to_col == $from_col && $to_row == $from_row + 1) {
297 return ($dest_piece eq '-');
299 if ($to_col == $from_col && $from_row == 1 && $to_row == 3) {
300 my $middle_piece = $board->[2][$to_col];
301 return ($dest_piece eq '-' && $middle_piece eq '-');
303 if (abs($to_col - $from_col) == 1 && $to_row == $from_row + 1) {
304 return ($dest_piece ne '-');
310 if ($to_col == $from_col && $to_row == $from_row - 1) {
311 return ($dest_piece eq '-');
313 if ($to_col == $from_col && $from_row == 6 && $to_row == 4) {
314 my $middle_piece = $board->[5][$to_col];
315 return ($dest_piece eq '-' && $middle_piece eq '-');
317 if (abs($to_col - $from_col) == 1 && $to_row == $from_row - 1) {
318 return ($dest_piece ne '-');
327 # Returns 'none', 'white', 'black' or 'both', depending on which sides are in check.
328 # The latter naturally indicates an invalid position.
331 my ($black_check, $white_check) = (0, 0);
333 my ($wkr, $wkc, $bkr, $bkc) = _find_kings($board);
335 # check all pieces for the possibility of threatening the two kings
338 my $piece = $board->[$row][$col];
339 next if ($piece eq '-');
341 if (uc($piece) eq $piece) {
343 $black_check = 1 if ($board->can_reach($piece, $row, $col, $bkr, $bkc));
346 $white_check = 1 if ($board->can_reach($piece, $row, $col, $wkr, $wkc));
351 if ($black_check && $white_check) {
353 } elsif ($black_check) {
355 } elsif ($white_check) {
364 my ($wkr, $wkc, $bkr, $bkc);
368 my $piece = $board->[$row][$col];
370 ($wkr, $wkc) = ($row, $col);
371 } elsif ($piece eq 'k') {
372 ($bkr, $bkc) = ($row, $col);
377 return ($wkr, $wkc, $bkr, $bkc);
380 # Returns if any side is in mate.
383 my $check = $board->in_check();
384 return 0 if ($check eq 'none');
386 # try all possible moves for the side in check
389 my $piece = $board->[$row][$col];
390 next if ($piece eq '-');
392 if ($check eq 'white') {
393 next if ($piece eq lc($piece));
395 next if ($piece eq uc($piece));
398 for my $dest_row (0..7) {
399 for my $dest_col (0..7) {
400 next if ($row == $dest_row && $col == $dest_col);
401 next unless ($board->can_reach($piece, $row, $col, $dest_row, $dest_col));
403 my $nb = $board->clone();
404 $nb->[$row][$col] = '-';
405 $nb->[$dest_row][$dest_col] = $piece;
406 my $new_check = $nb->in_check();
407 return 0 if ($new_check ne $check && $new_check ne 'both');
413 # nothing to do; mate
417 # Returns the short algebraic form of the move, as well as the new position.
418 sub prettyprint_move {
419 my ($board, $from_row, $from_col, $to_row, $to_col, $promo) = @_;
420 my $pretty = $board->_prettyprint_move_no_check_or_mate($from_row, $from_col, $to_row, $to_col, $promo);
422 my $nb = $board->make_move($from_row, $from_col, $to_row, $to_col, $promo);
423 if ($nb->in_mate()) {
425 } elsif ($nb->in_check() ne 'none') {
428 return ($pretty, $nb);
431 sub _prettyprint_move_no_check_or_mate {
432 my ($board, $from_row, $from_col, $to_row, $to_col, $promo) = @_;
433 my $piece = $board->[$from_row][$from_col];
434 my $move = _move_to_uci_notation($from_row, $from_col, $to_row, $to_col, $promo);
437 die "Invalid move $move";
440 # white short castling
441 if ($move eq 'e1g1' && $piece eq 'K') {
445 # white long castling
446 if ($move eq 'e1c1' && $piece eq 'K') {
450 # black short castling
451 if ($move eq 'e8g8' && $piece eq 'k') {
455 # black long castling
456 if ($move eq 'e8c8' && $piece eq 'k') {
462 # check if the from-piece is a pawn
463 if (lc($piece) eq 'p') {
465 if ($from_col != $to_col) {
466 $pretty = substr($move, 0, 1) . 'x' . _pos_to_square($to_row, $to_col);
468 $pretty = _pos_to_square($to_row, $to_col);
470 if (defined($promo) && $promo ne '') {
479 $pretty = uc($piece);
481 # see how many of these pieces could go here, in all
485 next unless ($board->[$row][$col] eq $piece);
486 ++$num_total if ($board->can_reach($piece, $row, $col, $to_row, $to_col));
490 # see how many of these pieces from the given row could go here
493 next unless ($board->[$from_row][$col] eq $piece);
494 ++$num_row if ($board->can_reach($piece, $from_row, $col, $to_row, $to_col));
497 # and same for columns
500 next unless ($board->[$row][$from_col] eq $piece);
501 ++$num_col if ($board->can_reach($piece, $row, $from_col, $to_row, $to_col));
504 # see if we need to disambiguate
505 if ($num_total > 1) {
507 $pretty .= substr($move, 0, 1);
508 } elsif ($num_row == 1) {
509 $pretty .= substr($move, 1, 1);
511 $pretty .= substr($move, 0, 2);
516 if ($board->[$to_row][$to_col] ne '-') {
520 $pretty .= _pos_to_square($to_row, $to_col);