use strict;
use warnings;
use Data::Dumper;
use File::Path;
use File::Spec;
use Storable qw(freeze thaw);
use POSIX ":sys_wait_h";
 
my $slow_matches_b = sub { sleep 1;
                           return unless $_[0];
                           return 1 if $_[0] =~ /b/;
                         };
my $test_strings = [ ('blee','blah','bloo', 'qoo', 'fwee' ) ];

my @results = forked_map( 'c:\\testdir', 2, $slow_matches_b, @$test_strings );

print Dumper \@results;

sub forked_map
{
	my $tempdir = shift;
	my $worker_count = shift;
	my $function = shift;

	#
	#	ensure tempdir is not some file
	#
	if ( -f $tempdir )
	{
		die "$tempdir exists!";
	}
	
	#
	#	delete dir, then recreate ( destroy any previous results )
	#
	unlink $tempdir;
	File::Path::mkpath( $tempdir );    

	#
    #    assign keys to each data element
    #
    my $id = 0;
    my %hash_input = map { ( $id++, $_ )} @_;
	my %workers;

	#
    #    loop block for assigning work to workers
    #
    {

        #
        #    assign work to available workers
        #
		while ( keys %hash_input and keys %workers < $worker_count )
		{

            $id = (keys %hash_input)[0];
            my $data = $hash_input{$id};
			delete $hash_input{$id};
			
			#
			#	fork the child process
			#
			my $pid = fork;
			if ( ! defined $pid )
			{
				die "cannot fork: $!";
			}
			if ( $pid )
			{
				#
				#	track the pid in the parent process
				#
				$workers{$pid} = 'ACTIVE';
			}
			else
			{
				#
				#	work in the child process	
				#
				my $result = $function->($data);
				my $frozen_result = freeze(\$result);
				
				#
				#	save the results
				#
				my $tempfile = File::Spec->catfile($tempdir,$id);
				open(my $fh, "> $tempfile") or die $!;
				print $fh $frozen_result;

				#
				#	bye bye baby
				#
				exit 0;
			}
		}
		
		#
		#	wait for any child to complete
		#
		my $pid = wait();

		if ($pid == -1) 
		{
			%workers = ();
		} 
		else 
		{
			delete $workers{$pid};
		}
		
        #
        #    loop if there is any work remaining
        #
        redo if ( ( keys %hash_input ) or ( keys %workers ) )
    }
	
	#
	#	read results from file
	#
	my %results;
	opendir(my $dh,$tempdir);
	for ( readdir($dh) )
	{
		my $filepath = File::Spec->catfile($tempdir,$_);
		if ( -f $filepath )
		{
			open(my $fh, $filepath ) or die $!;
			my $frozen_result = do {local $/; <$fh> };
			$results{$_} = ${thaw($frozen_result)};
		}
	}
	
	#
	#	clean up after ourselves
	#
	unlink $tempdir;
	

	#
	#	return results in order
	#
    return map { $results{$_} } sort keys %results;
}