#!/usr/bin/perl

no strict;

use POSIX ":sys_wait_h";

use Irssi qw/
	signal_add_first
	signal_continue
	signal_register
	command_bind
	timeout_add_once
	get_irssi_dir
/;

our $VERSION = "0.1";
our %IRSSI = (
	authors     => 'Urchlay',
	contact     => 'Urchlay on Libera',
	name        => 'yttitle',
	description => 'get titles for youtube videos using yt-dlp',
	license     => 'WTFPL',
	url         => 'none',
);

# video ID => title
our %cache;

our $tmpdir = get_irssi_dir . "/yttitle.tmp";

# pid => [server, target, video ID]
our %jobs;

# video ID keys (values meaningless; only care about key presence)
our %job_videos;

# attempts to spawn more jobs than this are just ignored.
our $maxjobs = 10;

# milliseconds: how often to check %jobs to see if any jobs are done.
our $queue_time = 1000;

# command to execute, 1st %s replaced with video ID, 2nd with tmp filename.
# --socket-timeout arg is seconds, should be longer that $timeout.
our $command_fmt =
	"yt-dlp -q --print '%%(title)s' --socket-timeout 10 -- %s >%s 2>/dev/null";

our $DEBUG = 1;

sub debug {
	Irssi::print(join "", @_) if $DEBUG;
}

sub debugf {
	Irssi::print(sprintf(@_)) if $DEBUG;
}

sub start_timer {
	timeout_add_once($queue_time, "check_jobs", undef);
}

sub get_tmp_filename {
	my $id = shift;
	return $tmpdir . "/" . $id;
}

sub read_tmp_file {
	my $file = shift;

	open my $fh, "<:encoding(UTF-8)", $file;

	if(!$fh) {
		debug("read_tmp_file() failed to open $file: $!");
		return;
	}

	my $result = <$fh>;
	close $fh;

	chomp $result if defined $result;
	return length($result) ? $result : undef;
}

sub spawn_job {
	my ($server, $target, $video_id) = @_;
	my $jobcount = keys %jobs;

	debug("spawn_job() called, video_id $video_id");

	if($jobcount > $maxjobs) {
		debug("spawn_job(): jobcount $jobcount > maxjobs $maxjobs, ignoring request");
		return;
	}

	if($job_videos{$video_id}) {
		debug("spawn_job(): video_id $video_id already in queue");
		return;
	}

	my $cmd = sprintf($command_fmt, $video_id, get_tmp_filename($video_id));
	debug("spawn_job() command is: $cmd");

	my $pid = fork();

	if($pid) {
		# parent
		debug("spawn_job() forked, kid pid is $pid");
		start_timer unless keys %jobs;
		$jobs{$pid} = [ $server, $target, $video_id ];
		$job_videos{$video_id} = 1;
		debug("spawn_job(): job pids: " . join(",", keys %jobs));
	} else {
		# child, debug() and Irssi::print don't work, here.
		exec $cmd;
	}
}

sub job_done {
	my $pid = shift;

	my ($server, $target, $video_id) = @{$jobs{$pid}};

	debug("job_done() pid $pid, target $target, video_id $video_id");

	my $file = get_tmp_filename($video_id);
	my $title = read_tmp_file($file);

	unlink $file;

	$cache{$video_id} = $title;
	delete $job_videos{$video_id};

	if(!defined($title)) {
		debug("job_done(): video_id $video_id failed to get title");
		return;
	}

	say_title($server, $target, $video_id, $title);
}

sub check_jobs {
	my @k = keys %jobs;

	debug("check_jobs(): " . @k . " jobs");
	return unless @k;

	for my $jobpid (@k) {
		debug("check_jobs(): about to waitpid($jobpid, WNOHANG)");
		$pid = waitpid($jobpid, WNOHANG);

		debug("check_jobs(): jobpid $jobpid, pid $pid");

		next if $pid == 0; # still running, let it run
		job_done($jobpid) if $pid > 0; # -1 is "no such pid"
		delete $jobs{$jobpid};
	}

	start_timer if keys %jobs;
}

sub say_title {
	my ($server, $target, $video_id, $title) = @_;
	my $tag = "YouTube" . ($DEBUG ? "($video_id)" : "");
	$server->command("msg $target $tag: $title");
}

sub on_public_msg {
	my ($server, $msg, $nick, $address, $target) = @_;
	my $mynick = $server->{nick};

	unless(length $target) {
		$target = $nick;
		$nick = $mynick;
	}

	if($target eq $mynick) {
		# private message... send response to sender
		$target = $nick;
	}

	for my $video_id ($msg =~ /(?:youtube\.com\S+(?:embed\/|v=)|youtu.be\/)([-0-9a-zA-Z_]{11})/g) {
		if($cache{$video_id}) {
			debug("video_id $video_id found in cache");
			say_title($server, $target, $video_id, $cache{$video_id});
		} else {
			debug("video_id $video_id NOT found in cache, queuing job");
			spawn_job($server, $target, $video_id);
		}
	}
}

### main()
mkdir $tmpdir;
signal_add_first("message public", "on_public_msg");