#!/usr/bin/perl
# vim:ts=4:sw=4:expandtab
# © 2013 Michael Stapelberg <stapelberg@debian.org>
#
# All rights reserved.
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# modification, are permitted provided that the following conditions are met:
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#       notice, this list of conditions and the following disclaimer.
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#       names of contributors may be used to endorse or promote products
#       derived from this software without specific prior written permission.
# .
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=head1 NAME

deb-systemd-invoke - wrapper around systemctl, respecting policy-rc.d

=head1 SYNOPSIS

B<deb-systemd-invoke> [B<--user>] start|stop|restart S<I<unit file> ...>

=head1 DESCRIPTION

B<deb-systemd-invoke> is a Debian-specific helper script which asks
/usr/sbin/policy-rc.d before performing a systemctl call.

B<deb-systemd-invoke> is intended to be used from maintscripts to start
systemd unit files. It is specifically NOT intended to be used interactively by
users. Instead, users should run systemd and use systemctl, or not bother about
the systemd enabled state in case they are not running systemd.

=cut

use strict;
use warnings;
use Getopt::Long; # in core since Perl 5

if (@ARGV < 2) {
    print STDERR "Syntax: $0 <action> <unit file> [<unit file> ...]\n";
    exit 1;
}

my $is_system = 1;
my @instances = ();
my $result = GetOptions(
    "user" => sub { $is_system = 0; },
    "system" => sub { $is_system = 1; }, # default
);

my $policyhelper = '/usr/sbin/policy-rc.d';
my @units = @ARGV;
my $action = shift @units;
if (-x $policyhelper) {
    for my $unit (@units) {
        system(qq|$policyhelper $unit "$action"|);

        # 0 or 104 means run
        # 101 means do not run
        my $exitcode = ($? >> 8);
        if ($exitcode == 101) {
            print STDERR "$policyhelper returned 101, not running '" . join(' ', @ARGV) . "'\n";
            exit 0;
        } elsif ($exitcode != 104 && $exitcode != 0) {
            print STDERR "deb-systemd-invoke only supports $policyhelper return codes 0, 101, and 104!\n";
            print STDERR "Got return code $exitcode, ignoring.\n";
        }
    }
}

if (!$is_system) {
    # '--machine <ID>@' was added in v250 and v249.10, before that we can't talk to arbitrary user instances
    my $systemctl_version = `systemctl --version --quiet | sed -n -r "s/systemd ([0-9]+) \\(.*/\\1/p"`;
    chomp ($systemctl_version);
    if (system('dpkg', '--compare-versions', $systemctl_version, 'ge', '249') != 0) {
            print STDERR "systemctl version $systemctl_version does not support acting on user instance, skipping\n";
            exit 0;
    }

    # Each user instance of the manager has a corresponding user@<id<.service unit.
    # Get the full list of IDs, so that we can talk to each user instance to start/stop
    # user units.
    @instances = `systemctl --no-legend --quiet list-units 'user@*' | sed -n -r 's/.*user@([0-9]+).service.*/\\1/p'`;
} else {
    push @instances, 'system';
}

# If the job is disabled and is not currently running, the job is not started or restarted.
# However, if the job is disabled but has been forced into the running state, we *do* stop
# and restart it since this is expected behaviour for the admin who forced the start.
# We don't autostart static units either.
if ($action eq "start" || $action eq "restart") {
    my $global_exit_code = 0;
    my @start_units = ();

    for my $instance (@instances) {
        my @instance_args = ();

        if ($instance eq 'system') {
            push @instance_args, '--system';
        } else {
            chomp ($instance);
            push @instance_args, '--user', '--machine', "$instance@";
        }

        for my $unit (@units) {
            my $unit_installed = 0;
            my $enabled_output = `systemctl @instance_args is-enabled -- '$unit'`;
            # matching enabled and enabled-runtime as an installed non static unit
            if ($enabled_output =~ /enabled/) {
                $unit_installed = 1;
            }
            system('systemctl', @instance_args, '--quiet', 'is-active', '--', $unit);
            my $unit_active = $?>>8 == 0 ? 1 : 0;
            if (!$unit_installed && $action eq "start") {
                print STDERR "$unit is a disabled or a static unit, not starting it.\n";
            } elsif (!$unit_installed && !$unit_active && $action eq "restart") {
                print STDERR "$unit is a disabled or a static unit not running, not starting it.\n";
            }
            else {
                push @start_units, $unit;
            }
        }
        if (@start_units) {
            system('systemctl', '--quiet', @instance_args, $action, @start_units) == 0 or die("Could not execute systemctl: $!");
        }
    }
    exit(0);
} elsif ($action eq "stop" && !$is_system) {
    my $global_exit_code = 0;

    for my $instance (@instances) {
        chomp ($instance);
        system('systemctl', '--quiet', '--user', '--machine', "$instance@", $action, @units);
    }
    exit(0);
} else {
    exec('systemctl', @ARGV);
}
