#!/usr/bin/env perl

use v5.36.0;

use strict;
use warnings;
use utf8;
use GnuPG;

use Path::Tiny;
use Mojo::UserAgent;

my $target_dir = shift @ARGV or die 'No target dir passed.';

my $gpg_temp_dir = Path::Tiny::tempdir;
my $gpg_bin      = 'gpg';
my @args         = ( '--command-fd', '0', '--homedir', $gpg_temp_dir );

my $gentoo_pk_id = '13EBBDBEDE7A12775DFDB1BABB572E0E2D182910';
my $stage_destination = path('stage.tar.xz');
my $stage_destination_asc = path($stage_destination . '.asc');

_doNothingIfTargetDirExists($target_dir);
_fetchKey($gentoo_pk_id);
_trustKey($gentoo_pk_id);
_downloadGentooStage($stage_destination, $stage_destination_asc);
_verifyStage($stage_destination_asc);
_extractStageIntoTarget($target_dir, $stage_destination);

sub _extractStageIntoTarget($target, $stage) {
    system 'mkdir', $target;
    system 'sudo', 'tar', '-xpvf', $stage, '-C', $target, '--numeric-owner', q/--xattrs-include='*.*'/;
}

sub _doNothingIfTargetDirExists($target) {
    if (-e $target) {
        die "$target exists, doing nothing.";
    }
}

sub _verifyStage($stage_asc) {
    my $return_code = system $gpg_bin, @args, '--verify', $stage_asc;
    if ($return_code != 0) {
        die 'Signature is not valid, maybe someone is trying to eavesdrop your connection?';
    }
}

sub _downloadGentooStage($stage, $stage_asc) {
    if (-e $stage && -e $stage_asc) {
        return;
    }
    my $ua = Mojo::UserAgent->new;
    my $dom = $ua->get('https://www.gentoo.org/downloads/')->result->dom;
    for my $h4 ($dom->find('h4')->each) {
        next if $h4->text !~ /Stage/;
        my @next_list_groups = $h4->following('div.list-group')->each;
        my $url = $next_list_groups[0]->at('a')->attr('href');
        $stage->spew_raw($ua->get($url)->result->body); 
        $stage_asc->spew_raw($ua->get($url . '.asc')->result->body); 
        last;
    }
}

sub _fetchKey ($key) {
    my $return_code = system $gpg_bin, @args, '--recv-keys', $key;
    if ( $return_code != 0 ) {
        die 'Unable to fetch gentoo gpg key.';
    }
}

sub _trustKey ($key) {
    open( my $fh, '|-', $gpg_bin, @args, '--edit-key', $key, 'trust' );
    say $fh 5;
    say $fh 'y';
    close $fh;
    my $return_code = $?;
    if ( $return_code != 0 ) {
        die 'Unable to trust gentoo gpg key.';
    }
}