use strict;
use warnings;

my $folder_IN     = $ARGV[0];
my $finaltreefile = "./final.CSV";
my $level = 0;
my $rootfile      = `ls $folder_IN/$level*.CSV`;
chomp($rootfile);
print "rootfile: $rootfile\n";


open( my $final, '>', $finaltreefile ) or die "$finaltreefile: $!";

treebuilder($rootfile, $level+1);

close($final);

exit(0);



sub treebuilder {
    my $filename = shift;
    my $level = shift;
    my $nextlevel = $level + 1;

    print "File level $level : $filename\n";

    my $PRESENTLEVELFILE;
    unless(open($PRESENTLEVELFILE, '<', $filename)) {
        warn "$filename: $!";
        return;
    }


    my $leafline = <$PRESENTLEVELFILE>;
    if ( $filename eq $rootfile ) {
        print $final "0 $leafline";
    }

    while ( my $leafline = <$PRESENTLEVELFILE> ) {
        print "Leggo $leafline\n";
        chomp($leafline);
        print "next level=$nextlevel\n";
        my @element = split( '§', $leafline );
        print "Find $element[0]\n";
        my $NEXTLEVELFILE =
          $folder_IN . "/" . $level . "_" . $element[0] . ".CSV";
        print "Check if file exists: $NEXTLEVELFILE\n";
        print $final "$level $leafline\n";
        treebuilder($NEXTLEVELFILE, $nextlevel);
    }
    close($PRESENTLEVELFILE);
}