#!/usr/bin/perl -d:DProf

use Carp;
use Text::Balanced;

our $extract_section_tag  =  Text::Balanced::gen_extract_tagged( '<SECTION\[([^\]]+)\]>\n?', '</SECTION>\n?', '[\S\s]*?(?=<SECTION\[)' );

my $page;
$page .= "This is some filler.\n" x 20000;
$page .= "<SECTION[test1]>\n";
$page .= "This is some filler.\n" x 20000;
$page .= "</SECTION>\n";
$page .= "This is some filler.\n" x 20000;
$page .= "<SECTION[test2]>\n";
$page .= "This is some filler.\n" x 20000;
$page .= "</SECTION>\n";
$page .= "This is some filler.\n" x 20000;

print "Calling process_section.  Length of page=[" . length($page) ."]\n";
my $newpage = process_section($page, {test1 => 1});
print "Done.  Length of newpage=[" . length($newpage) ."]\n";

sub process_section {
    my ($page, $hashref) = @_;

    my ($tag_section, $post, $pre, $tag_open, $content, $tag_close, @info);

    my $return = '';

    while ( @info = $extract_section_tag->($page) ) {
        ($tag_section, $post, $pre, $tag_open, $content, $tag_close) = @info;

        if (! (defined $tag_section && length $tag_section) ) {
            if ($post =~ m/<SECTION\[/) {
                my $excerpt = substr($post, 0, 100);
                print STDERR "\n";
                Carp::carp("Warning: Unbalanced SECTION tags.  Fix the template! Error near: $excerpt\n");
            }
            last;
        }

        my $show = 0;
        if ($tag_open =~ m/<SECTION\[(.*?)\]>/) {
            $show = 1 if (exists $hashref->{$1});
        }

        if ($show && $content =~ m/<SECTION/) {
            $content = process_section($content, $hashref);
        }

        $return .= $pre . ($show ? $content : '');
        $page = $post;
    }

    $return .= $post;
    return $return;
}