#!/usr/bin/env perl6

my @insrtuctions = "advent2018-d7.txt".IO.lines;
my $re = / "Step " $<before>=(\w) " must be finished before step " $<after>=(\w) " can begin." /;
my %steps;

for @insrtuctions {
    .match: $re;
    if %steps{$<after>}:!exists {
        %steps{$<after>} = %{ depends => [], blocking => [], available => False}
    }
    %steps{$<after>}<depends>.push($<before>.Str);
}

for %steps.pairs -> $step {
    for $step.value<depends><> -> $dep {
        if %steps{$dep}:!exists {
            %steps{$dep} = %{ depends => [], blocking => [], available => False};
        }
        %steps{$dep}<blocking>.push($step.key);
    }
}

.say for %steps.sort;