switch SearchState to using Backtrack step

[scpubgit/DX.git] / lib / DX / SearchState.pm

diff --git a/lib/DX/SearchState.pm b/lib/DX/SearchState.pm
index d97ab9b..99ac3f2 100644 (file)
--- a/lib/DX/SearchState.pm
+++ b/lib/DX/SearchState.pm
@@ -1,62 +1,63 @@
 package DX::SearchState;
 
+use Types::Standard qw(Maybe);
+use DX::Step::Backtrack;
+use DX::Step::InvokeNextPredicate;
 use DX::Class;
 
-has current_hypothesis => (is => 'ro', required => 1);
+has current_hypothesis => (is => 'ro', isa => Hypothesis, required => 1);
 
-has resume_step => (is => 'ro');
+has next_step => (is => 'ro', isa => Maybe[Step]);
 
-has alternatives => (is => 'ro', required => 1);
+has propositions => (is => 'ro', isa => PropositionSequence, required => 1);
+
+has alternatives => (is => 'ro', isa => AlternativeList, required => 1);
+
+sub next_proposition {
+  my ($self, $hyp) = @_;
+  $hyp ||= $self->current_hypothesis;
+  $self->propositions->members->[
+    $hyp->resolved_propositions->resolved_count
+  ];
+}
+
+sub new_for {
+  my ($class, $hyp, $props) = @_;
+  $class->new(
+    current_hypothesis => $hyp,
+    alternatives => [],
+    next_step => DX::Step::InvokeNextPredicate->new(
+      proposition => $props->members->[0],
+    ),
+    propositions => $props,
+  );
+}
 
 sub with_one_step {
   my ($self) = @_;
   my $hyp = $self->current_hypothesis;
-  my $step = $self->resume_step
-             || $hyp->head_proposition->resolve_for($hyp->scope);
-  my @alt = @{$self->alternatives};
-  HYP: while ($hyp) {
-    STEP: while ($step) {
-      my ($new_hyp, $alt_step) = $step->apply_to($hyp);
-      if ($new_hyp) {
-        return ref($self)->new(
-          current_hypothesis => $new_hyp,
-          ($alt_step
-             ? (alternatives => [
-                  [ $hyp, $alt_step ],
-                  @alt
-               ])
-             : ())
-        );
-      }
-      $step = $alt_step;
-    }
-    ($hyp, $step) = @{shift(@alt)||[]};
-  }
-  return undef;
-}
-
-sub find_solution {
-  my $state = $_[0];
-  while ($state and @{$state->current_hypothesis->outstanding_propositions}) {
-    $state = $state->with_one_step;
-  }
-  return $state;
+  return undef unless my $step = $self->next_step;
+  my ($new_ss) = $step->apply_to($self);
+  return $new_ss if $new_ss;
+  my ($first_alt, @rest_alt) = @{$self->alternatives};
+  return undef unless $first_alt;
+  trace 'search.backtrack.rewind_to' => $first_alt->[1];
+  return $self->but(
+    next_step => DX::Step::Backtrack->new,
+  );
 }
 
 sub force_backtrack {
   my ($self) = @_;
-  my ($first_alt, @rest_alt) = $self->alternatives;
+  my ($first_alt, @rest_alt) = @{$self->alternatives};
+  return undef unless $first_alt;
+  trace 'search.backtrack.forced' => $first_alt->[0];
   return ref($self)->new(
     current_hypothesis => $first_alt->[0],
-    resume_step => $first_alt->[1],
-    alternatives => \@rest_alt
+    next_step => $first_alt->[1],
+    alternatives => \@rest_alt,
+    propositions => $self->propositions,
   );
 }
 
-sub find_next_solution {
-  my ($self) = @_;
-  return undef unless my $bt = $self->force_backtrack;
-  return $bt->find_solution;
-}
-
 1;