use strict;
use warnings;

use Imager;
use MCE;

processPics("./images");

sub processPics {
    my $dir = './images';
    my $newDat = '';

    # build list of jpg files to process
    opendir my $dh, $dir or die "Could not open '$dir' for reading '$!'\n";
    my @pics = grep(/\.jpg$/, readdir $dh);
    closedir $dh;

    # check for subdirs and make if missing
    mkdir "${dir}/medium"  unless (-d "${dir}/medium");
    mkdir "${dir}/thumbs"  unless (-d "${dir}/thumbs");
    mkdir "${dir}/upright" unless (-d "${dir}/upright");

    # construct MCE object
    my $mce = MCE->new(
        max_workers => MCE::Util::get_ncpu(),
        chunk_size  => 1,
        gather      => sub { $newDat .= $_[0]; }, # called inside parent
        user_func   => sub {
            my $p = $_;

            my $img = Imager->new(file=>"${dir}/${p}", type=>'jpeg')
                or die Imager->errstr();

            my $med   = $img->copy();
            my $thumb = $img->copy();
            my $rot90;

            # sets width to 750px, write out image
            $med = $img->scale(xpixels=>750);
            $med->write(file=>"${dir}/medium/${p}") or die $med->errstr;

            # sets the height to 150px, write out image
            $thumb = $img->scale(ypixels=>150);
            $thumb->write(file=>"${dir}/thumbs/${p}") or die $thumb->errstr;

            # rotate image, write out image
            $rot90 = $img->rotate(degrees=>-90);
            $rot90->write(file=>"${dir}/upright/${p}") or die $rot90->errstr;

            # append filename without the extension
            MCE->gather( (split(/\./, $p))[0] . '|' );
        },
    );

    # process image dir in parallel
    $mce->process(\@pics);
    $mce->shutdown();

    # display $newDat line after removing trailing |
    chop $newDat if $newDat;
    print "completed: ${newDat}\n";
}