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1 | package DX::SearchState; |
2 | |
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3 | use Types::Standard qw(Maybe); |
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4 | use DX::Step::InvokeNextPredicate; |
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5 | use DX::Class; |
6 | |
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7 | has current_hypothesis => (is => 'ro', isa => Hypothesis, required => 1); |
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8 | |
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9 | has next_step => (is => 'ro', isa => Maybe[Step]); |
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10 | |
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11 | has propositions => (is => 'ro', isa => PropositionSequence, required => 1); |
12 | |
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13 | has alternatives => (is => 'ro', isa => AlternativeList, required => 1); |
14 | |
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15 | sub next_proposition { |
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16 | my ($self, $hyp) = @_; |
17 | $hyp ||= $self->current_hypothesis; |
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18 | $self->propositions->members->[ |
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19 | $hyp->resolved_propositions->resolved_count |
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20 | ]; |
21 | } |
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22 | |
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23 | sub new_for { |
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24 | my ($class, $hyp, $props) = @_; |
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25 | $class->new( |
26 | current_hypothesis => $hyp, |
27 | alternatives => [], |
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28 | next_step => DX::Step::InvokeNextPredicate->new( |
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29 | proposition => $props->members->[0], |
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30 | ), |
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31 | propositions => $props, |
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32 | ); |
33 | } |
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34 | |
35 | sub with_one_step { |
36 | my ($self) = @_; |
37 | my $hyp = $self->current_hypothesis; |
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38 | return undef unless my $step = $self->next_step; |
39 | my ($first_alt, @rest_alt) = my @alt = @{$self->alternatives}; |
40 | my ($new_hyp, $alt_step) = $step->apply_to($hyp); |
41 | if ($new_hyp) { |
42 | return $self->but( |
43 | current_hypothesis => $new_hyp, |
44 | alternatives => [ |
45 | ($alt_step |
46 | ? [ $hyp, $alt_step ] |
47 | : ()), |
48 | @alt |
49 | ], |
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50 | next_step => DX::Step::InvokeNextPredicate->new( |
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51 | proposition => $self->next_proposition($new_hyp), |
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52 | ), |
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53 | ); |
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54 | } |
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55 | if ($alt_step) { |
56 | return $self->but(next_step => $alt_step); |
57 | } |
58 | return undef unless $first_alt; |
59 | trace 'search.backtrack.rewind_to' => $first_alt->[1]; |
60 | return $self->but( |
61 | current_hypothesis => $first_alt->[0], |
62 | alternatives => \@rest_alt, |
63 | next_step => $first_alt->[1], |
64 | ); |
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65 | } |
66 | |
67 | sub find_solution { |
68 | my $state = $_[0]; |
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69 | while ($state and $state->next_proposition) { |
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70 | $state = $state->with_one_step; |
71 | } |
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72 | trace 'search.solution.hyp' => $state->current_hypothesis if $state; |
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73 | return $state; |
74 | } |
75 | |
76 | sub force_backtrack { |
77 | my ($self) = @_; |
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78 | my ($first_alt, @rest_alt) = @{$self->alternatives}; |
79 | return undef unless $first_alt; |
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80 | trace 'search.backtrack.forced' => $first_alt->[0]; |
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81 | return ref($self)->new( |
82 | current_hypothesis => $first_alt->[0], |
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83 | next_step => $first_alt->[1], |
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84 | alternatives => \@rest_alt, |
85 | propositions => $self->propositions, |
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86 | ); |
87 | } |
88 | |
89 | sub find_next_solution { |
90 | my ($self) = @_; |
91 | return undef unless my $bt = $self->force_backtrack; |
92 | return $bt->find_solution; |
93 | } |
94 | |
95 | 1; |