package Runner;

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

use Future;
use IO::Async::PID;

sub new {
    my ( $class, $loop, $max_active ) = @_;
    
    return bless {
        loop   => $loop,
        max    => $max_active,
        active => {},
        queue  => [],
    }, $class    
}

sub call {
    my ( $self, $list ) = @_;
    
    my @F = map {
        my $F = $self-> { loop }-> new_future;
        $F-> { _job_id } = $_;
        $F-> on_ready( sub {
            delete $self-> { active }{ $F };
            $self-> _run;
        })
    } @$list;

    push @{ $self-> { queue }}, @F;
    $self-> _run;
    return Future-> needs_all( @F )
}

sub _run {
    my $self = shift;
    
    if ( keys %{ $self-> { active }}) {
        say 'jobs active: ', join ',', 
            map { $_-> { _job_id }} values %{ $self-> { active }}
    }

    while( keys %{ $self-> { active }} < $self-> { max }
           and @{ $self-> { queue }}) {

        my $F = shift @{ $self-> { queue }};
        $self-> { active }{ $F } = $F;
        
        my $pid = system 1, 'echo', $F-> { _job_id };

        $self-> { loop }-> add( IO::Async::PID-> new(
            pid     => $pid,
            on_exit => sub {
                my ( $self, $exitcode ) = @_; 
                my $pid = $self-> pid;
                
                $F-> done( $F-> { _job_id });
            }
        ));
    }
}

1;