lib/DX/Step/Backtrack.pm

   1 package DX::Step::Backtrack;
   2
   3 use DX::DependencyMap;
   4 use DX::Utils qw(format_deps);
   5 use DX::Class;
   6
   7 with 'DX::Role::Step';
   8
   9 has resolution_space => (is => 'ro', isa => ResolutionSpace, required => 1);
  10
  11 sub apply_to {
  12   my ($self, $ss) = @_;
  13   my $rspace = $self->resolution_space;
  14   trace backtrack => [ statement => [
  15     [ symbol => 'backtrack' ],
  16     [ statement => [
  17       [ symbol => 'because' ],
  18       format_deps($rspace->geometry_depends_on)
  19     ] ]
  20   ] ];
  21   my $dmap = DX::DependencyMap->new_empty
  22                               ->with_dependencies_for(
  23                                   backtrack => $rspace->geometry_depends_on
  24                                 );
  25
  26   foreach my $adj (@{$ss->decisions_taken}) {
  27     my ($rspace_was, $ss_was) = @$adj;
  28     $dmap = $dmap->with_dependencies_for(
  29       backtrack => $rspace_was->geometry_depends_on
  30     );
  31     next unless @{$rspace_was->remaining_resolution_space->members};
  32     trace rspace => [ statement => [
  33       [ symbol => 'remaining' ],
  34       @{$rspace_was->remaining_resolution_space->for_deparse->[1]}
  35     ] ];
  36     return $ss_was->but(
  37       next_step => $rspace_was->remaining_resolution_space->next_step
  38     );
  39   }
  40   return $ss->but(next_step => $ss->on_exhaustion_step);
  41 }
  42
  43 1;