use warnings;
use strict;
use feature 'say';

use DateTime;

# this is a prototype of a light timer

my $on_at = '18:00'; # lights on
my $on_time = 12;    # hours on for
my $off_time;

my $on = 0; # light is on bool 

my $t = time;
my $count = 0;    # iter count
my $done = 20000; # num iterations

# dt objects

my ($t1, $on_at_dt, $off_at_dt) 
  = init_time($on_at, $on_time);

while (1){

    # on

    if ($t1 > $on_at_dt && ! $on){
        # light is not on, and it's time
        $on = 1;
        say "\non:  $t1";
    }

    # off

    if ($t1 > $off_at_dt && $on){
        # light's out time
        $on = 0;
        say "off: $t1";

        $on_at_dt = set_on_timer(
            $t1, 
            $on_at_dt, 
            $on_at
        );

        $off_at_dt = set_off_timer(
            $on_at_dt, 
            $off_at_dt, 
            $on_time
        );
    }

    # expedite the current time for testing

    $t1->add(seconds => 30);

    $count++;
    last if $count == $done;
}

sub init_time {
    my ($on_at, $on_time) = @_;

    my $t1 = DateTime->now;
    $t1->set_time_zone('local');

    my $on_at_dt = $t1->clone;

    $on_at_dt->set_hour(
        (split(/:/, $on_at))[0]
    );

    $on_at_dt->set_minute(
        (split(/:/, $on_at))[1]
    );

    my $off_at_dt = $on_at_dt->clone;
    $off_at_dt->add(hours => $on_time);

    return ($t1, $on_at_dt, $off_at_dt);
}
sub set_off_timer {
    my ($on_dt, $off_dt, $on_time) = @_;
    
    $off_dt = $on_dt->clone;
    $off_dt->add(hours => $on_time);

    return $off_dt;
}
sub set_on_timer {
    my ($t1, $dt, $on_at) = @_;

    $dt = $t1->clone;
    $dt->set_second(0);
    $dt->set_hour((split(/:/, $on_at))[0]);
    $dt->set_minute((split(/:/, $on_at))[1]);

    return $dt;
}