move backtracking into a stream

[scpubgit/DKit.git] / lib / DX / ResultStream.pm

package DX::ResultStream;

use Moo;

has for_state => (is => 'ro', required => 1);

has _current_state => (is => 'rw');

has is_exhausted => (is => 'rwp');

sub next {
  my ($self) = @_;
  return if $self->is_exhausted;
  my $start_state = do {
    if (my $cur = $self->_current_state) {
      $cur->backtrack;
    } else {
      $self->for_state
    }
  };
  my $state = $self->_current_state($start_state->run);
  return +{
    map +($_ => $state->scope_var($_)->bound_value), keys %{$state->scope}
  };
}

1;