#!/usr/bin/perl

use strict;
use warnings;

# POE checking/debug levels
sub POE::Kernel::ASSERT_DEFAULT { 0 } # DATA, EVENTS, FILES, RETVALS, USAGE
sub POE::Kernel::ASSERT_EVENTS  { 1 }
sub POE::Kernel::ASSERT_USAGE   { 1 }
sub POE::Session::ASSERT_STATES { 1 }

use POE;
use POSIX;

my $num_kids = 8;
my %kid_pids;

main();


END { do_end(); }

sub do_end
{
  # FILL HERE
  exit(0);
}

sub main
{
  # catch CTRL-C interrupt to tidy up cleanly
  $SIG{QUIT} = $SIG{INT} = $SIG{HUP} = \&do_end;

  POE::Session->create
  (
    inline_states =>
    {
      _start => sub
      {
        print "Starting\n";
        $_[KERNEL]->sig('INT', 'signal_handler');
        $_[KERNEL]->delay(reaper => 1 );
        $_[KERNEL]->delay(spawner => 1 );
      },
      _stop => sub {},
      signal_handler => sub {
        my ($kernel, $sig) = @_[KERNEL, ARG0];
        print "caught SIG$sig\n";
        do_end();
      },
      reaper => sub
      {
        $_[KERNEL]->delay(reaper => 1);
        while ( (my $pid = waitpid(-1, POSIX::WNOHANG)) > -1 )
        {
          my $exit_status = $? / 256;
          delete $kid_pids{$pid};
          print "child $pid died status $exit_status\n";
        }
      },
      spawner => sub
      {
        $_[KERNEL]->delay(spawner => 1);
        # start new kid if slot free
        if (scalar keys %kid_pids < $num_kids)
        {
          my $pid = start_child();
          if ($pid > 0)
          {
            $kid_pids{$pid} = 1;
            print "child $pid started\n";
          }
        }
      },
    },
  );

  $poe_kernel->run();
}

sub start_child
{
  # FILL HERE
  return $pid;
}