Support starting from a nonstandard position.

[remoteglot] / Board.pm

diff --git a/Board.pm b/Board.pm
index 91d1a15f7f42b29d5057c2cb9205ae4874a52361..6df8ecae1326b4bb083f66598c3e5b59a1455b3b 100644 (file)
--- a/Board.pm
+++ b/Board.pm
@@ -233,42 +233,6 @@ sub fen {
 # Returns a compact bit string describing the same data as fen().
 # This is encoded using a Huffman-like encoding, and should be
 # typically about 1/3 the number of bytes.
-sub bitpacked_fen {
-       my ($board) = @_;
-       my $bits = "";
-
-       for my $row (0..7) {
-               for my $col (0..7) {
-                       my $piece = $board->[$row][$col];
-                       if ($piece eq '-') {
-                               $bits .= "0";
-                               next;
-                       }
-
-                       my $color = (lc($piece) eq $piece) ? 0 : 1;
-                       $bits .= "1" . $color;
-
-                       if (lc($piece) eq 'p') {
-                               $bits .= "0";
-                       } elsif (lc($piece) eq 'n') {
-                               $bits .= "100";
-                       } elsif (lc($piece) eq 'b') {
-                               $bits .= "101";
-                       } elsif (lc($piece) eq 'r') {
-                               $bits .= "1110";
-                       } elsif (lc($piece) eq 'q') {
-                               $bits .= "11110";
-                       } elsif (lc($piece) eq 'k') {
-                               $bits .= "11111";
-                       } else {
-                               die "Unknown piece $piece";
-                       }
-               }
-       }
-
-       return pack('b*', $bits);
-}
-
 sub can_reach {
        my ($board, $piece, $from_row, $from_col, $to_row, $to_col) = @_;
        
@@ -387,6 +351,20 @@ sub can_reach {
        return 0;
 }
 
+# Like can_reach, but also checks the move doesn't put the side in check.
+# We use this in prettyprint_move to reduce the disambiguation, because Chess.js
+# needs moves to be in minimally disambiguated form.
+sub can_legally_reach {
+       my ($board, $piece, $from_row, $from_col, $to_row, $to_col) = @_;
+
+       return 0 if (!can_reach($board, $piece, $from_row, $from_col, $to_row, $to_col));
+
+       my $nb = $board->make_move($from_row, $from_col, $to_row, $to_col);
+       my $side = ($piece eq lc($piece)) ? 'k' : 'K';
+
+       return !in_check($nb, $side);
+}
+
 my %pieces_against_side = (
        k => { K => 1, Q => 1, R => 1, N => 1, B => 1, P => 1 },
        K => { k => 1, q => 1, r => 1, n => 1, b => 1, p => 1 },
@@ -500,22 +478,22 @@ sub _prettyprint_move_no_check_or_mate {
 
        # white short castling
        if ($move eq 'e1g1' && $piece eq 'K') {
-               return '0-0';
+               return 'O-O';
        }
 
        # white long castling
        if ($move eq 'e1c1' && $piece eq 'K') {
-               return '0-0-0';
+               return 'O-O-O';
        }
 
        # black short castling
        if ($move eq 'e8g8' && $piece eq 'k') {
-               return '0-0';
+               return 'O-O';
        }
 
        # black long castling
        if ($move eq 'e8c8' && $piece eq 'k') {
-               return '0-0-0';
+               return 'O-O-O';
        }
 
        my $pretty;
@@ -527,12 +505,12 @@ sub _prettyprint_move_no_check_or_mate {
                        $pretty = substr($move, 0, 1) . 'x' . _pos_to_square($to_row, $to_col);
                } else {
                        $pretty = _pos_to_square($to_row, $to_col);
+               }
 
-                       if (defined($promo) && $promo ne '') {
-                               # promotion
-                               $pretty .= "=";
-                               $pretty .= uc($promo);
-                       }
+               if (defined($promo) && $promo ne '') {
+                       # promotion
+                       $pretty .= "=";
+                       $pretty .= uc($promo);
                }
                return $pretty;
        }
@@ -544,7 +522,7 @@ sub _prettyprint_move_no_check_or_mate {
        for my $col (0..7) {
                for my $row (0..7) {
                        next unless ($board->[$row][$col] eq $piece);
-                       ++$num_total if ($board->can_reach($piece, $row, $col, $to_row, $to_col));
+                       ++$num_total if ($board->can_legally_reach($piece, $row, $col, $to_row, $to_col));
                }
        }
 
@@ -552,14 +530,14 @@ sub _prettyprint_move_no_check_or_mate {
        my $num_row = 0;
        for my $col (0..7) {
                next unless ($board->[$from_row][$col] eq $piece);
-               ++$num_row if ($board->can_reach($piece, $from_row, $col, $to_row, $to_col));
+               ++$num_row if ($board->can_legally_reach($piece, $from_row, $col, $to_row, $to_col));
        }
 
        # and same for columns
        my $num_col = 0;
        for my $row (0..7) {
                next unless ($board->[$row][$from_col] eq $piece);
-               ++$num_col if ($board->can_reach($piece, $row, $from_col, $to_row, $to_col));
+               ++$num_col if ($board->can_legally_reach($piece, $row, $from_col, $to_row, $to_col));
        }
 
        # see if we need to disambiguate