#!/usr/bin/perl -w

=head1 NAME

dh_systemd_enable - enable/disable systemd unit files

=cut

use strict;
use Debian::Debhelper::Dh_Lib;
use File::Find;
use Text::ParseWords qw(shellwords); # in core since Perl 5

my $deb_host_arch_os = dpkg_architecture_value('DEB_HOST_ARCH_OS');
if ($deb_host_arch_os ne 'linux')
{
    warning("systemd is unsupported on $deb_host_arch_os, doing nothing");
    exit(0);
}

=head1 SYNOPSIS

B<dh_systemd_enable> [S<I<debhelper options>>] [B<--no-enable>] [S<I<unit file> ...>]

=head1 DESCRIPTION

B<dh_systemd_enable> is a debhelper program that is responsible for enabling
and disabling systemd unit files.

In the simple case, it finds all unit files installed by a package (e.g.
bacula-fd.service) and enables them. It is not necessary that the machine
actually runs systemd during package installation time, enabling happens on all
machines in order to be able to switch from sysvinit to systemd and back.

In the complex case, you can call B<dh_systemd_enable> and B<dh_systemd_start>
manually (by overwriting the debian/rules targets) and specify flags per unit
file. An example is colord, which ships colord.service, a dbus-activated
service without an [Install] section. This service file cannot be enabled or
disabled (a state called "static" by systemd) because it has no
[Install] section. Therefore, running dh_systemd_enable does not make sense.

=head1 FILES

=over 4

=item debian/I<package>.service

If this exists, it is installed into lib/systemd/system/I<package>.service in
the package build directory.

=item debian/I<package>.tmpfile

If this exists, it is installed into usr/lib/tmpfiles.d/I<package>.conf in the
package build directory. (The tmpfiles.d mechanism is currently only used
by systemd.)

=back

=head1 OPTIONS

=over 4

=item B<--no-enable>

Just disable the service(s) on purge, but do not enable them by default.

=back

=head1 NOTES

Note that this command is not idempotent. L<dh_prep(1)> should be called
between invocations of this command (with the same arguments). Otherwise, it
may cause multiple instances of the same text to be added to maintainer
scripts.

Note that B<dh_systemd_enable> should be run before B<dh_installinit>.
The default sequence in B<dh> does the right thing, this note is only relevant
when you are calling B<dh_systemd_enable> manually.

This command currently works for Linux only, for other Debian archs
it does nothing and returns 0;

=cut

init(options => {
	"no-enable" => \$dh{NO_ENABLE},
});

sub contains_install_section {
	my ($unit_path) = @_;
	my $fh;
	if (!open($fh, '<', $unit_path)) {
		warning("Cannot open($unit_path) for extracting the Also= line(s)");
		return;
	}
	while (my $line = <$fh>) {
		chomp($line);
		return 1 if $line =~ /^\s*\[Install\]$/i;
	}
	close($fh);
	return 0;
}

foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmpdir = tmpdir($package);
	my @installed_units;
	my @units;

	# XXX: This is duplicated in dh_installinit, which is unfortunate.
	# We do need the service files before running dh_installinit though,
	# every other solution makes things much worse for all the maintainers.

	# Figure out what filename to install it as.
	my $script;
	my $jobfile=$package;
	if (defined $dh{NAME}) {
		$jobfile=$script=$dh{NAME};
	}
	elsif ($dh{D_FLAG}) {
		# -d on the command line sets D_FLAG. We will
		# remove a trailing 'd' from the package name and
		# use that as the name.
		$script=$package;
		if ($script=~m/(.*)d$/) {
			$jobfile=$script=$1;
		}
		else {
			warning("\"$package\" has no final d' in its name, but -d was specified.");
		}
	}
	elsif ($dh{INIT_SCRIPT}) {
		$script=$dh{INIT_SCRIPT};
	}
	else {
		$script=$package;
	}

	my $service=pkgfile($package,"service");
	if ($service ne '') {
		my $path="$tmpdir/lib/systemd/system";
		if (! -d "$path") {
			doit("install","-d","$path");
		}

		doit("install","-p","-m644",$service,"$path/$script.service");
	}

	my $socket=pkgfile($package,"socket");
	if ($socket ne '') {
		my $path="$tmpdir/lib/systemd/system";
		if (! -d "$path") {
			doit("install","-d","$path");
		}

		doit("install","-p","-m644",$socket,"$path/$script.socket");
	}

	my $tmpfile=pkgfile($package,"tmpfile");
	if ($tmpfile ne '') {
		my $path="$tmpdir/usr/lib/tmpfiles.d";
		if (! -d "$path") {
			doit("install","-d","$path");
		}

		doit("install","-p","-m644",$tmpfile,"$path/$script.conf");
	}

	find({
		wanted => sub {
			my $name = $File::Find::name;
			return unless -f $name;
			# Skip symbolic links, their only legitimate use is for
			# adding an alias, e.g. linking smartmontools.service
			# -> smartd.service.
			return if -l $name;
			return unless $name =~ m,^$tmpdir/lib/systemd/system/[^/]+$,;
			push @installed_units, $name;
		},
		no_chdir => 1,
	}, $tmpdir);

	# Handle either only the unit files which were passed as arguments or
	# all unit files that are installed in this package.
	my @args = @ARGV > 0 ? @ARGV : @installed_units;

	for my $name (@args) {
		my $base = basename($name);

		# Try to make the path absolute, so that the user can call
		# dh_installsystemd bacula-fd.service
		if ($base eq $name) {
			# NB: This works because @installed_units contains
			# files from precisely one directory.
			my ($full) = grep { basename($_) eq $base } @installed_units;
			if (defined($full)) {
				$name = $full;
			} else {
				warning(qq|Could not find "$name" in the /lib/systemd/system of $package.| .
					qq|This could be a typo, or using Also= with a service file from another package.| .
					qq|Please check carefully that this message is harmless.|);
			}
		}

		# Skip template service files like e.g. getty@.service.
		# Enabling, disabling, starting or stopping those services
		# without specifying the instance (e.g. getty@ttyS0.service) is
		# not useful.
		if ($name =~ /\@/) {
			next;
		}

		# Skip unit files that don’t have an [Install] section.
		next unless contains_install_section($name);

		push @units, $name;
	}

	next if @units == 0;

	my $unitargs = join(" ", map { basename($_) } @units);
	for my $unit (@units) {
		my $base = basename($unit);
		if ($dh{NO_ENABLE}) {
			autoscript($package, "postinst", "postinst-systemd-dont-enable", "s/#UNITFILE#/$base/");
		} else {
			autoscript($package, "postinst", "postinst-systemd-enable", "s/#UNITFILE#/$base/");
		}
	}
	autoscript($package, "postrm", "postrm-systemd", "s/#UNITFILES#/$unitargs/");

	# init-system-helpers ships deb-systemd-helper which we use in our
	# autoscripts
	addsubstvar($package, "misc:Depends", "init-system-helpers (>= 1.18~)");
}

=head1 SEE ALSO

L<dh_systemd_start(1)>, L<debhelper(7)>

=head1 AUTHORS

pkg-systemd-maintainers@lists.alioth.debian.org

=cut