#!/usr/bin/perl
use warnings;
use strict;
use POE qw(Wheel::Run Filter::Reference);
sub MAX_CONCURRENT_TASKS () { 3 }
my @tasks = qw(one two three four five six seven eight nine ten);

POE::Session->create(
  inline_states => {
    _start      => \&start_tasks,
    next_task   => \&start_tasks,
    task_result => \&handle_task_result,
    task_done   => \&handle_task_done,
    task_debug  => \&handle_task_debug,
    sig_child   => \&sig_child,
  }
);

sub start_tasks {
  my ($kernel, $heap) = @_[KERNEL, HEAP];
  while (keys(%{$heap->{task}}) < MAX_CONCURRENT_TASKS) {
    my $next_task = shift @tasks;
    last unless defined $next_task;
    print "Starting task for $next_task...\n";
    my $task = POE::Wheel::Run->new(
      Program      => sub { do_stuff($next_task) },
      StdoutFilter => POE::Filter::Reference->new(),
      StdoutEvent  => "task_result",
      StderrEvent  => "task_debug",
      CloseEvent   => "task_done",
    );
    $heap->{task}->{$task->ID} = $task;
    $kernel->sig_child($task->PID, "sig_child");
  }
}

sub do_stuff {
  binmode(STDOUT);    # Required for this to work on MSWin32
  my $task   = shift;
  my $filter = POE::Filter::Reference->new();

  sleep(rand 5);

  my %result = (
    task   => $task,
    status => "seems ok to me",
  );

  my $output = $filter->put([\%result]);
  print @$output;
}

sub handle_task_result {
  my $result = $_[ARG0];
  print "Result for $result->{task}: $result->{status}\n";
}

sub handle_task_debug {
  my $result = $_[ARG0];
  print "Debug: $result\n";
}

sub handle_task_done {
  my ($kernel, $heap, $task_id) = @_[KERNEL, HEAP, ARG0];
  delete $heap->{task}->{$task_id};
  $kernel->yield("next_task");
}

sub sig_child {
  my ($heap, $sig, $pid, $exit_val) = @_[HEAP, ARG0, ARG1, ARG2];
  my $details = delete $heap->{$pid};

  # warn "$$: Child $pid exited";
}

$poe_kernel->run();
exit 0;