+# 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) = @_;
+
+ # 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'));
+ } 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'));
+ } else {
+ return (_square_to_pos('e8'), _square_to_pos('c8'));
+ }
+ }
+
+ # Parse promo
+ my $promo;
+ if ($move =~ s/=?([QRNB])$//) {
+ $promo = $1;
+ }
+
+ $move =~ /^([KQRBN])?([a-h])?([1-8])?x?([a-h][1-8])$/ or die "Invalid move $move";
+ my $piece = $1 // 'P';
+ my $from_col = defined($2) ? _col_letter_to_num($2) : undef;
+ my $from_row = defined($3) ? _row_letter_to_num($3) : undef;
+ my ($to_row, $to_col) = _square_to_pos($4);
+
+ # Find all possible from-squares that could have been meant.
+ my @squares = ();
+ my $side = 'K';
+ if ($toplay eq 'B') {
+ $piece = lc($piece);
+ $side = 'k';
+ }
+ for my $row (0..7) {
+ next if (defined($from_row) && $from_row != $row);
+ for my $col (0..7) {
+ next if (defined($from_col) && $from_col != $col);
+ next if ($board->[$row][$col] ne $piece);
+ push @squares, [ $row, $col ];
+ }
+ }
+ if (scalar @squares > 1) {
+ # Filter out pieces which cannot reach this square.
+ @squares = grep { $board->can_reach($piece, $_->[0], $_->[1], $to_row, $to_col) } @squares;
+ }
+ if (scalar @squares > 1) {
+ # See if doing this move would put us in check
+ # (yes, there are clients that expect us to do this).
+ @squares = grep { !$board->make_move($_->[0], $_->[1], $to_row, $to_col, $promo)->in_check($side) } @squares;
+ }
+ if (scalar @squares == 0) {
+ die "Impossible move $move";
+ }
+ if (scalar @squares != 1) {
+ die "Ambigious move $move";
+ }
+ return (@{$squares[0]}, $to_row, $to_col, $promo);
+}
+