perl handlebar primer

hb.pl

use strict;
use warnings;
use JSON::XS;
use JavaScript::V8;
use utf8;
use open ":encoding(UTF-8)";

my $page_name = 'statuses/lenta';
my $context = JavaScript::V8::Context->new();

#slurp_and_eval_js('../handlebars.runtime-v1.3.0.js');
slurp_and_eval_js('../handlebars-v1.3.0.js');
slurp_and_eval_js('tests/render_page.js');
slurp_and_eval_js("helpers/extending.js");
slurp_and_eval_js("helpers/date.js");

#put_together_page_template
#$context->eval(
my $components = _put_together_page_template($page_name);
#use Data::Dumper; print Dumper($components);

my $template = $components->{partials}{ $components->{template} };
delete $components->{partials}{ $components->{template} };

my $hb_template = $context->eval("(function(partials, template) {
    for(var partial in partials) { if ( partials.hasOwnProperty( partial ) ) {
    	Handlebars.registerPartial( partial, partials[partial] );
    } }
    return Handlebars.compile(template);
})")->($components->{partials}, $template);

my $json_file = './tests/statuses_lenta_test_data.json';
my $r = $hb_template->(_read_json_file($json_file));
print $r;
exit;

sub _put_together_page_template {
    my $p_name = shift;
    my $file_prefix = "pages/$p_name";
    unless (-f "$file_prefix.hbs") {
        die "Page template doesn't exists: $p_name";
    }

    return _put_together_template($file_prefix);
}

sub _put_together_template {
    my ($file_prefix, $seen) = @_;
    $seen = {} unless $seen;

    my $res = { template => $file_prefix, partials => {} };
    my $hbs_data_ref = slurp_file("$file_prefix.hbs");
    $res->{partials}{$file_prefix} = $$hbs_data_ref;

    my $desc_path = "$file_prefix.desc.json";
    unless (-f $desc_path) {
        return $res;
    }
    my $desc = _read_json_file($desc_path);
#print Dumper($desc);

    for my $name (qw(blocks layouts)) {
        my $value = $desc->{$name};
        next unless $value;

	for my $element (@{ ref $value ? $value : [$value] }) {
            my $sub_template_name = "$name/$element";
            next if $seen->{$sub_template_name};

            $seen->{$sub_template_name} = 1;

            my $sub_template = _put_together_template($sub_template_name, $seen);
            for my $partial (keys %{ $sub_template->{partials} }) {
                $res->{partials}{$partial} = $sub_template->{partials}{$partial};
                $seen->{$partial} = 1;
            }
        }
    }

    return $res;
}

sub _read_json_file {
    my $json_data_ref = slurp_file(shift);
#print $$json_data_ref;
    return JSON::XS->new->utf8(0)->decode($$json_data_ref);
}

sub slurp_and_eval_js {
    my $file = shift;
    my $content_ref = slurp_file($file);
    return $context->eval($$content_ref);
}

sub slurp_file {
    my $file = shift;
    $/ = undef;
    open my $fh, '<', $file or die "Can't open file $file: $!";
    my $raw = readline $fh;
    return \$raw;
}