#!/usr/bin/perl

use strict;
use warnings;
use threads;
use threads::shared;
use Data::Dumper;

my %state :shared;
my $workercount = 10;
my $run = 1;

$SIG{TERM} = sub { $run = 0; };
$SIG{INT} = sub { $run = 0; };

my @workerqueue;
for my $i (1..$workercount) {
    my $thr = threads->create(\&mysub, $i);
    my $id = $thr->tid();
    print "--> enqueue $id\n";
    $state{$id} = 'running';
    push @workerqueue, $thr;
}

while ($run) {
    sleep(1);
    my @unfinished;
    while (my $thr = shift @workerqueue) {
        my $id = $thr->tid();
        if ($thr and $state{$id} eq 'finished') {
            print "--> $id is ready\n";
            my $x = $thr->join();
            delete $state{$id};
            print Dumper $x; # do something useful with the data
        } else {
            push @unfinished, $thr;
        }
    }
    push @workerqueue, @unfinished;
    ## START refill queue block ##
    my $free = $workercount - @workerqueue;
    for my $i (1..$free) {
        my $thr = threads->create(\&mysub, $i);
        my $id = $thr->tid();
        print "--> enqueue $id\n";
        $state{$id} = 'running';
        push @workerqueue, $thr;
    }
    ## END refill queue block ##
    print "mainloop\n";
}

my @threads = threads->list();
foreach my $thr (@threads) {
    $thr->join();
}


sub mysub {
    my $i = shift;
    $i *= 3;
    sleep $i;
    my $id = threads->tid();
    print "$id : slept for $i sec\n";
    my $x = {
        'ID' => $id,
        'a' => [1,2,3],
        'B' => { 'a' => 'A', },
    };
    $state{$id} = 'finished';
    return $x;
}