use Algorithm::Loops qw( NestedLoops );

sub get_target_iter {
   my ($envs) = @_;
   
   my $iter = NestedLoops(
      [
               [ keys %$envs                          ]  ,
         sub { [ keys %{$envs->{$_[0]}              } ] },
         sub { [ keys %{$envs->{$_[0]}{$_[1]}       } ] },
         sub { [ keys %{$envs->{$_[0]}{$_[1]}{$_[2]}} ] },
      ],
   );
   
   return sub {
      if (my (
         $env_name,
         $platform_name,
         $host_name,
         $target_name,
      ) = $iter->()) {
         my $target = $envs->{$env_name     }
                             {$platform_name}
                             {$host_name    }
                             {$target_name  };
         my $total_capacity = $target->{total_capacity};
         my $free_capacity  = $target->{free_capacity};

         return $env_name,
                $platform_name,
                $host_name,
                $target_name,
                $total_capacity,
                $free_capacity;
      }

      return;
   };
}