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::Themes ();

=head1 Trog::Bundle

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

A route names the scripts of its page in its definition: C<scripts> for every
reader, and C<authenticated_scripts> for a reader who is logged in as well.
finish_render() in Trog::Routes::HTML links the bundle of them at the href that
scripts() returns, and the route C</bundle/{version}/{names}.js> serves it.

The lists are the routes', and never the request's.  The route serves no list
that a route did not declare, so a URL cannot make tCMS build anything.

=cut

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

# The names of each list that a route declared, as its href carries them.
our %declared;

# The names as an href carries them.
my sub key_of (@names) {
    return join( '+', map { s/[.]js\z//r } @names );
}

=head2 declare(@lists)

Declare each list, an ARRAY reference of names as scripts() takes them, so that
the route serves its bundle.  TCMS::build_routes() declares the lists of every
route at startup, so that a worker serves a bundle before it renders a page that
links it.

=cut

sub declare (@lists) {
    $declared{ key_of( List::Util::uniq(@$_) ) } = 1 for grep { @$_ } @lists;
    return;
}

=head2 scripts(@names) = HASHREF or undef

The bundle of the scripts that @names names.  Each name is 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 for an empty list, and dies if a name is not a script.  The list
is declared, as declare() does, since only a route can have named it.

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) {
    @names = List::Util::uniq(@names);
    return undef unless @names;

    my @files = map {
        my $file = m/\A\w[\w.-]*[.]js\z/ ? Trog::Themes::themed_script($_) : undef;
        $file && -f $file ? $file : undef;    ## no critic (ProhibitFiletest_f) -- a name that is not a file is not a script
    } @names;
    my @missing = map { $names[$_] } grep { !defined $files[$_] } 0 .. $#names;
    die "There is no script to bundle named @missing\n" if @missing;

    my $key       = key_of(@names);
    my $signature = join( "\0", map { join( ':', $_, ( stat $_ )[ 7, 9 ] ) } @files );
    $declared{$key} = 1;
    return $bundles{$key} if $bundles{$key} && $bundles{$key}{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 );
    return $bundles{$key} = {
        href      => "/bundle/$version/$key.js",
        version   => $version,
        body      => $body,
        signature => $signature,
    };
}

=head2 served(@names) = HASHREF or undef

The bundle that the route serves for @names, as scripts() returns it, or undef
if a route did not declare the list.

=cut

sub served (@names) {
    @names = List::Util::uniq(@names);
    return undef unless @names && $declared{ key_of(@names) };
    return scripts(@names);
}

=head2 save($tpsgi, $bundle)

Have tPSGI save $bundle as a static render after the response, so that the
webserver serves it from then on.  A process saves a given bundle once.

finish_render() calls this for the bundle that a page links.

It also has tPSGI watch the directories of the scripts.  When a script changes,
the saved pages and bundles are thrown away: the pages are rendered again and
link the new bundle, and a page that still links an old one is redirected by
the route.  The route also serves a bundle whose static is gone, so a worker
that still counts it as saved is slower, not wrong.

=cut

# The hrefs of the bundles that this process saved.
our %saved;

sub save ( $tpsgi, $bundle ) {
    return 0 if !$tpsgi || $saved{ $bundle->{href} };

    if ( $tpsgi->can('add_watch') ) {
        my $theme = Trog::Themes::get_dir();
        foreach my $dir ( grep { -d } ( 'www/scripts', $theme ? "$theme/scripts" : () ) ) {
            $tpsgi->add_watch(
                $dir,
                sub {
                    my ( $watcher, $change ) = @_;
                    $watcher->invalidate_renders($_) for qw{html js};
                    return 1;
                },
                key => "Trog::Bundle:$dir",
            );
        }
    }

    $tpsgi->add_post_close_callback(
        sub {
            $tpsgi->save_render( $bundle->{href}, 'js', $bundle->{body} );
            $saved{ $bundle->{href} } = 1;
        }
    );
    return 1;
}