#!/usr/bin/env perl
use strict;
use warnings;
use 5.014;

use JSON::PP;

my ($sig) = @ARGV;
my $pid = get_pid();
my $pgrp = get_pgrp($pid);
kill $sig, -$pgrp;

sub get_pid {
    my $window_id = get_window_id();
    die "couldn't find window" unless defined $window_id;
    my $prop = `xprop -id $window_id _NET_WM_PID`;
    die "couldn't get pid from focused window"
        if $prop =~ /not found/;
    chomp($prop);
    $prop =~ s/^_NET_WM_PID\(CARDINAL\) = //;
    return $prop;
}

sub get_pgrp {
    my ($pid) = @_;
    open my $stat_fh, '<', "/proc/$pid/stat"
        or die "couldn't open /proc/$pid/stat";
    my $stat = do { local $/; <$stat_fh> };
    my @f = ($stat =~ /\([^)]*\)|[^ ]+/g);
    return $f[4];
}

sub get_window_id {
    return find(decode_json(`i3-msg -t get_tree`))->{window};
}

sub find {
    my ($t) = @_;
    if ($t->{focused}) {
        return $t;
    }

    for my $subtree (@{ $t->{nodes} }, @{ $t->{floating_nodes} }) {
        my $found = find($subtree);
        return $found if $found;
    }

    return;
}