Add some PGN hysteresis to guard against truncated PGNs.

diff --git a/remoteglot.pl b/remoteglot.pl
index d15a5282a41b52ef0e5d8237a335798c19def51d..ec26401a6cbcd296341ce616e69f32ed94738189 100755 (executable)
--- a/remoteglot.pl
+++ b/remoteglot.pl
@@ -200,6 +200,10 @@ sub fetch_pgn {
        });
 }
 
+my ($last_pgn_white, $last_pgn_black);
+my @last_pgn_uci_moves = ();
+my $pgn_hysteresis_counter = 0;
+
 sub handle_pgn {
        my ($body, $header, $url) = @_;
        my $pgn = Chess::PGN::Parse->new(undef, $body);
@@ -217,7 +221,27 @@ sub handle_pgn {
                }
                $pos->{'history'} = \@uci_moves;
                $pos->{'pretty_history'} = $moves;
-               handle_position($pos);
+
+               # Sometimes, PGNs lose a move or two for a short while,
+               # or people push out new ones non-atomically. 
+               # Thus, if we PGN doesn't change names but becomes
+               # shorter, we mistrust it for a few seconds.
+               my $trust_pgn = 1;
+               if (defined($last_pgn_white) && defined($last_pgn_black) &&
+                   $last_pgn_white eq $pgn->white &&
+                   $last_pgn_black eq $pgn->black &&
+                   scalar(@uci_moves) < scalar(@last_pgn_uci_moves)) {
+                       if (++$pgn_hysteresis_counter < 3) {
+                               $trust_pgn = 0; 
+                       }
+               }
+               if ($trust_pgn) {
+                       $last_pgn_white = $pgn->white;
+                       $last_pgn_black = $pgn->black;
+                       @last_pgn_uci_moves = @uci_moves;
+                       $pgn_hysteresis_counter = 0;
+                       handle_position($pos);
+               }
        }
        
        $http_timer = AnyEvent->timer(after => 1.0, cb => sub {