package Trog::Bundle;

use 5.040;
use re '/aasx';
use warnings FATAL => 'all';

use Digest::SHA              ();
use File::Slurper            ();
use JavaScript::Minifier::XS ();
use List::Util               ();

use Trog::Log    qw{:all};
use Trog::Themes ();

=head1 Trog::Bundle

The scripts that a page names, served as one response.

A route names its scripts in a list, and finish_render() in Trog::Routes::HTML
links the bundle of them at the href that scripts() returns.  The route
C</bundle/{version}/{names}.js> serves that bundle.

=cut

# The names of a bundle, as its href carries them, to the bundle.
my %bundles;

# The number of bundles kept.  A site has a few lists of scripts, and anyone can
# ask for another one, so the cache is emptied when it grows past this.
my $max_bundles = 16;

=head2 scripts(@names) = HASHREF or undef

The bundle of the scripts that @names names, each of them a file name under
F<www/scripts>, such as C<post.js>.  The theme's copy of a script is used in
place of the stock one.  The order is the order of @names, and a name that is
given twice is used once.

Returns undef if no name is a script.  A name that is not a script is left out,
with a warning.

The hash has these keys:

    href     where the bundle is served, which changes when its body does
    version  a digest of the body, which is in the href
    body     the scripts, each one minified unless its name ends in .min.js

A process builds each bundle once, and builds it again when a file in it
changes.

=cut

sub scripts (@names) {
    my ( @kept, @files );
    foreach my $name ( List::Util::uniq(@names) ) {
        my $file = $name =~ m/\A\w[\w.-]*[.]js\z/ ? Trog::Themes::themed_script($name) =~ s{\A/}{www/}r : undef;
        if ( !$file || !-f $file ) {    ## no critic (ProhibitFiletest_f) -- a name that is not a file is left out
            WARN("There is no script $name to bundle");
            next;
        }
        push( @kept,  $name );
        push( @files, $file );
    }
    return undef unless @files;

    my $names     = join( '+',  map { s/[.]js\z//r } @kept );
    my $signature = join( "\0", map { join( ':', $_, ( stat $_ )[ 7, 9 ] ) } @files );
    return $bundles{$names} if $bundles{$names} && $bundles{$names}{signature} eq $signature;

    # A newline before the semicolon, because a file can end in a line comment.
    my $body = join(
        "\n;\n",
        map {
            my $js = File::Slurper::read_binary($_);
            m/[.]min[.]js\z/ ? $js : JavaScript::Minifier::XS::minify($js)
        } @files
    );
    my $version = substr( Digest::SHA::sha256_hex($body), 0, 16 );

    %bundles = () if keys %bundles >= $max_bundles;
    return $bundles{$names} = {
        href      => "/bundle/$version/$names.js",
        version   => $version,
        body      => $body,
        signature => $signature,
    };
}