fix detection of potential witness loops

diff --git a/lib/Text/Tradition/Collation/RelationshipStore.pm b/lib/Text/Tradition/Collation/RelationshipStore.pm
index 981fded..e9749ad 100644 (file)
--- a/lib/Text/Tradition/Collation/RelationshipStore.pm
+++ b/lib/Text/Tradition/Collation/RelationshipStore.pm
@@ -4,6 +4,7 @@ use strict;
 use warnings;
 use Text::Tradition::Error;
 use Text::Tradition::Collation::Relationship;
+use TryCatch;
 
 use Moose;
 
@@ -79,6 +80,11 @@ sub _set_relationship {
        $self->graph->add_edge( @vector );
        $self->graph->set_edge_attribute( @vector, 'object', $relationship );
 }
+
+sub _remove_relationship {
+       my( $self, @vector ) = @_;
+       $self->graph->delete_edge( @vector );
+}
        
 =head2 create
 
@@ -251,7 +257,11 @@ sub relationship_valid {
                }
        } else {
                # Check that linking the source and target in a relationship won't lead
-               # to a path loop for any witness.  First make a lookup table of all the
+               # to a path loop for any witness.  If they have the same rank then fine.
+               return( 1, "ok" ) 
+                       if $c->reading( $source )->rank == $c->reading( $target )->rank;
+               
+               # Otherwise, first make a lookup table of all the
                # readings related to either the source or the target.
                my @proposed_related = ( $source, $target );
                push( @proposed_related, $self->related_readings( $source, 'colocated' ) );
@@ -259,14 +269,22 @@ sub relationship_valid {
                my %pr_ids;
                map { $pr_ids{ $_ } = 1 } @proposed_related;
        
-               # None of these proposed related readings should have a neighbor that
-               # is also in proposed_related.
+               # The cumulative predecessors and successors of the proposed-related readings
+               # should not overlap.
+               my %all_pred;
+               my %all_succ;
                foreach my $pr ( keys %pr_ids ) {
-                       foreach my $neighbor( $c->sequence->neighbors( $pr ) ) {
-                               return( 0, "Would relate neighboring readings $pr and $neighbor" )
-                                       if exists $pr_ids{$neighbor};
-                       }
-               }               
+                       map { $all_pred{$_} = 1 } $c->sequence->all_predecessors( $pr );
+                       map { $all_succ{$_} = 1 } $c->sequence->all_successors( $pr );
+               }
+               foreach my $k ( keys %all_pred ) {
+                       return( 0, "Relationship would create witness loop" )
+                               if exists $all_succ{$k};
+               }
+               foreach my $k ( keys %pr_ids ) {
+                       return( 0, "Relationship would create witness loop" )
+                               if exists $all_pred{$k} || exists $all_succ{$k};
+               }
                return ( 1, "ok" );
        }
 }