package PoeSubs;
use strict;
use warnings; 
use Data::Dumper;

use POE qw(Wheel::Run Filter::Reference);

# sub run_tasks
#{{{
sub run_tasks {
    my( %ARGS )            = @_;
    my( $debug )           = $ARGS{debug};
    my( $handle_task_sub ) = delete $ARGS{handle_task_sub};
    my( $start_tasks )     = get_start_tasks( %ARGS );

    no warnings 'redefine';
    local *POE::Kernel::_warn = sub {} if not $debug;
   
    POE::Session->create (
        inline_states => {
            _start      => $start_tasks,
            next_task   => $start_tasks,
            task_result => sub { $handle_task_sub->( $_[ARG0] ); },
            task_done   => \&PoeSubs::handle_task_done,
            task_debug  => \&PoeSubs::handle_task_stderr,
        }
    );
    
    # Run until there are no more tasks.
    POE::Kernel->run();

    my( $reduce_sub ) = delete $ARGS{reduce_sub};
    if( 'CODE' eq ref $reduce_sub ) {
        &$reduce_sub;
    }

}
#}}}


# sub get_start_tasks
#{{{
sub get_start_tasks {
    my( %ARGS ) = @_;

    my( $debug )                = $ARGS{debug};
    my( @tasks )                = @{ $ARGS{tasks} };
    my( $max_concurrent_tasks ) = $ARGS{max_concurrent_tasks} || 1;
    my( $run_task_sub )         = $ARGS{run_task_sub};

    return sub {
        my $heap = $_[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" if $debug;
            
            my $task = POE::Wheel::Run->new (
#               Program => sub { $run_task_sub->( $next_task ) },
                Program => sub { get_program_sub( $run_task_sub )->( $next_task ) },
                StdoutFilter => POE::Filter::Reference->new(),
                StdoutEvent  => "task_result",
                StderrEvent  => "task_debug",
                CloseEvent   => "task_done",
            );
            
            $heap->{task}->{ $task->ID } = $task;
        }
    };
}
#}}}

# sub get_program_sub
#{{{
sub get_program_sub {
    my( $run_task_sub ) = @_;
    return sub {
        my( $task )   = @_;
# warn '$task = ', $task;
        my( $filter ) = POE::Filter::Reference->new();
        my( $task_output ) = $run_task_sub->( $task );
# warn Dumper( $task_output );
        my $output = $filter->put( [ $task_output ] );
        print @$output;
    };
}
#}}}


# sub handle_task_stderr
#{{{
# Catch and display information from the child's STDERR.  This was
# useful for debugging since the child's warnings and errors were not
# being displayed otherwise.

sub handle_task_stderr {
    my $stderr = $_[ARG0];
#   print "Debug: $stderr\n";
    warn "handle_task_stderr: $stderr\n";
}

#}}}


# sub handle_task_done
#{{{
# The task is done.  Delete the child wheel, and try to start a new
# task to take its place.

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

1;

__END__


##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;
use PoeSubs;

use constant MAX_CONCURRENT_TASKS => 100;
# use constant TASKS                => qw( 4 10 3 7 );

my( $run_task_sub, $handle_task_sub, $reduce_sub ) = get_subs();

# for( 1..20 ) {

    PoeSubs::run_tasks(
#       debug                => 1,
        tasks                => [ 1..100 ],
        max_concurrent_tasks => MAX_CONCURRENT_TASKS,
        run_task_sub         => $run_task_sub,
        handle_task_sub      => $handle_task_sub,
        reduce_sub           => $reduce_sub,
    );
# }

exit 0;

sub get_subs {
# Gets the task as the first argument
# Should return a reference of some type
    my( $run_task_sub ) = sub {
        my( $task )   = @_;
        my( $sleep ) = int( rand 4 ) + 1;
        sleep( $sleep );
        return { task => $task, sleep => $sleep, message => sprintf( '[Task %s: slept %s seconds]', $task, $sleep ) };
    };

# Gets the reference returned by run_task as the first argument
    my( $totals ) = 0;
    my( $handle_task_sub ) = sub {
        my( $result ) = @_;
        $totals += $result->{sleep};
        printf( "{Task: %s, Got message: %s}\n", $result->{task}, $result->{message} );
    };

# Prints out the totals
    my( $reduce_sub ) = sub {
        print '$totals = ', $totals, "\n";
    };
    return( $run_task_sub, $handle_task_sub, $reduce_sub );
}