#!/usr/bin/env perl

use strict;
use warnings;

use Time::HiRes qw(usleep);
use IO::Select;
use File::Spec::Functions qw(catfile);

use constant USLEEP_TIME => 25_000; # Microseconds
use constant RUN_TIME    => 30;     # Seconds

my $cmd = catfile((getpwnam($ENV{USER}))[7],'scripts','outputter'); # This just sets up the path to the external script. You could hard-code it or base it on FindBin if you want.

open my $r, '-|', $cmd or die $!;
my $s = IO::Select->new($r);

__PACKAGE__->run(
    {read => $r, select => $s, ping => 0},
    [
        sub {
            my $self = shift;
            $self->{select}->can_read(0)
        } =>
        sub {
            my $self = shift;
            my $ifh = $self->{'read'};
            chomp(my $i = <$ifh>);
            print "\n<$i>\n";
            $self->{ping} = 1;
        }
    ],
    [
        sub {
            my $self = shift;
            !$self->{ping};
        } =>
        sub {
            usleep USLEEP_TIME;
            print ".";
            STDOUT->flush;
        }
    ],
    [
        sub {
            my $self = shift;
            $self->{ping};
        } =>
        sub {
            my $self = shift;
            print "(pong)\n";
            $self->{ping} = 0;
        }
    ],
);

sub run {
    my ($class, $args) = (shift(), shift());
    $args ||= {};
    my $s = bless $args, $class;

    my $time = time();
    while(time() < $time + RUN_TIME) {
        foreach my $step (@_) {
            $step->[1]->($s) if $step->[0]->($s);
        }
    }
}