#!/usr/bin/perl -w

=head1 NAME

dh_installsystemd - install systemd unit files

=cut

use strict;
use warnings;
use Debian::Debhelper::Dh_Lib;
use File::Find;
use Cwd qw(getcwd abs_path);

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);
}

our $VERSION = DH_BUILTIN_VERSION;

=head1 SYNOPSIS

B<dh_installsystemd> [S<I<debhelper options>>] [B<--restart-after-upgrade>] [B<--no-stop-on-upgrade>] [B<--no-enable>] [B<--no-start>] [B<--name=>I<name>] [S<I<unit file> ...>]

=head1 DESCRIPTION

B<dh_installsystemd> is a debhelper program that is responsible for
installing package maintainer supplied systemd unit files.

It also finds the service files installed by a package and generates
F<preinst>, F<postinst>, and F<prerm> code blocks for enabling,
disabling, starting, stopping, and restarting the corresponding
systemd services, when the package is installed, updated, or
removed. These snippets are added to the maintainer scripts by
L<dh_installdeb(1)>.

L<deb-systemd-helper(1)> is used to enable and disable systemd units,
thus 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.

B<dh_installsystemd> operates on all unit files installed by a
package. For only generating blocks for specific unit files, pass them
as arguments, C<dh_installsystemd quota.service>. Specific unit files
can be excluded from processing using the B<-X> common L<debhelper(1)>
option.

=head1 FILES

=over 4

=item debian/I<package>.mount,
      debian/I<package>.path,
      debian/I<package>@.path,
      debian/I<package>.service,
      debian/I<package>@.service,
      debian/I<package>.socket,
      debian/I<package>@.socket,
      debian/I<package>.target,
      debian/I<package>@.target,
      debian/I<package>.timer,
      debian/I<package>@.timer

If any of those files exists, they are installed into
F<lib/systemd/system/> in the package build directory.

=item debian/I<package>.tmpfile

If this exists, it is installed into F<usr/lib/tmpfiles.d/> in the
package build directory. Note that the C<tmpfiles.d> mechanism is
currently only used by systemd.

=back

=head1 OPTIONS

=over 4

=item B<--no-enable>

Disable the service(s) on purge, but do not enable them on install.

B<Note> that this option does not affect whether the services are
started.  Please remember to also use B<--no-start> if the service
should not be started.

=item B<--name=>I<name>

This option controls several things.

It changes the name that B<dh_installsystemd> uses when it looks for
maintainer provided systemd unit files as listed in the L</FILES>
section.  As an example, B<dh_installsystemd --name foo> will look for
F<<< I<debian/package.>B<< I<foo> >>I<.service> >>> instead of
F<< I<debian/package.service> >>).  These unit files are installed as F<<
I<name.unit-extension> >> (in the example, it would be installed as
F<<< B<< I<foo> >>I<.service> >>>).

Furthermore, if no unit files are passed explicitly as command line
arguments, B<dh_installsystemd> will only act on unit files called
I<name> (rather than all unit files found in the package).

=item B<--restart-after-upgrade>

Do not stop the unit file until after the package upgrade has been completed.
This is the default behaviour in compat 10.

In earlier compat levels the default was to stop the unit file in the
F<prerm>, and start it again in the F<postinst>.

This can be useful for daemons that should not have a possibly long
downtime during upgrade. But you should make sure that the daemon will not
get confused by the package being upgraded while it's running before using
this option.

=item B<--no-restart-after-upgrade>

Undo a previous B<--restart-after-upgrade> (or the default of compat
10).  If no other options are given, this will cause the service to be
stopped in the F<prerm> script and started again in the F<postinst>
script.

=item B<-r>, B<--no-stop-on-upgrade>, B<--no-restart-on-upgrade>

Do not stop service on upgrade.

=item B<--no-start>

Do not start the unit file after upgrades and after initial installation (the
latter is only relevant for services without a corresponding init script).

B<Note> that this option does not affect whether the services are
enabled.  Please remember to also use B<--no-enable> if the services
should not be enabled.

=item S<B<unit file> ...>

Only process and generate maintscripts for the installed unit files
with the (base)name I<unit file>.

Note: B<dh_installsystemd> will still install unit files from
F<debian/> but it will not generate any maintscripts for them unless
they are explicitly listed in S<B<unit file> ...>

=back

=head1 NOTES

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.

=cut

$dh{RESTART_AFTER_UPGRADE} = 1;

init(options => {
	"no-enable" => \$dh{NO_ENABLE},
	"r" => \$dh{R_FLAG},
	'no-stop-on-upgrade' => \$dh{R_FLAG},
	"no-restart-on-upgrade" => \$dh{R_FLAG},
	"no-start" => \$dh{NO_START},
	"R|restart-after-upgrade!" => \$dh{RESTART_AFTER_UPGRADE},
	"no-also" => \$dh{NO_ALSO}, # undocumented option
});

sub quote {
	# Add single quotes around the argument.
	return '\'' . $_[0] . '\'';
}

sub uniq {
	my %seen;
	return grep { !$seen{$_}++ } @_;
}

sub contains_install_section {
	my ($unit_path) = @_;

	open(my $fh, '<', $unit_path) or error("Cannot open($unit_path): $!");

	while (my $line = <$fh>) {
		chomp($line);
		return 1 if $line =~ /^\s*\[Install\]$/i;
	}
	close($fh);
	return 0;
}

sub has_sysv_equivalent {
	my ($tmpdir, $unit) = @_;

	$unit =~ s/\.(?:mount|service|socket|target|path)$//g;
	return -f "$tmpdir/etc/init.d/$unit";
}

sub install_unit {
	my ($package, $script, $pkgsuffix, $path, $installsuffix) = @_;
	$installsuffix = $installsuffix || $pkgsuffix;
	my $unit = pkgfile($package, $pkgsuffix);
	return if $unit eq '';
	install_dir($path);
	install_file($unit, "${path}/${script}.${installsuffix}");
}

# Extracts the directive values from a unit file. Handles repeated
# directives in the same unit file. Assumes values can only be
# composed of lists of unit names. This is good enough for the 'Also='
# and 'Alias=' directives handled here.
sub extract_key {
	my ($unit_path, $key) = @_;
	my @values;

	open(my $fh, '<', $unit_path) or error("Cannot open($unit_path): $!");

	while (my $line = <$fh>) {
		chomp($line);

		# Since unit names can't have whitespace in systemd, simply
		# use split and strip any leading/trailing quotes. See
		# systemd-escape(1) for examples of valid unit names.
		if ($line =~ /^\s*$key=(.+)$/i) {
			for my $value (split(/\s+/, $1)) {
				$value =~ s/^(["'])(.*)\g1$/$2/;
				push @values, $value;
			}
		}
	}

	close($fh);
	return @values;
}

sub list_installed_units {
	my ($tmpdir, $aliases) = @_;

	my $lib_systemd_system = "$tmpdir/lib/systemd/system";
	my @installed;

	return unless -d $lib_systemd_system;
	opendir(my $dh, "$lib_systemd_system") or error("Cannot opendir($lib_systemd_system): $!");

	foreach my $name (readdir($dh)) {
		my $path = "$lib_systemd_system/$name";
		next unless -f $path;
		if (-l "$path") {
			my $dest = basename(readlink($path));
			$aliases->{$dest} //= [ ];
			push @{$aliases->{$dest}}, $name;
		} else {
			push @installed, $name;
		}
	}

	closedir($dh);
	return @installed;
}


# PROMISE: DH NOOP WITHOUT tmp(lib/systemd/system) tmp(usr/lib/tmpfiles.d) tmp(etc/tmpfiles.d) mount path service socket target tmpfile timer cli-options()


# Install package maintainer supplied unit files
foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmpdir = tmpdir($package);

	# Intall all unit files in the debian/ directory with names in the
	# form $package.(service|target|socket|path|timer|mount|tmpfile)
	# and their templated versison when relevant.

	# This can be modified with the --name option to look for unit
	# files with names in the form $package.$name.(service|...) and
	# $name.(service|target|socket|path|timer|mount|tmpfile) and their
	# templated version when relevant.
	my $name = $dh{NAME} // $package;

	for my $type (qw(service target socket path timer)) {
		install_unit($package, $name, $type, "$tmpdir/lib/systemd/system");
		install_unit("${package}@", "${name}@", $type, "$tmpdir/lib/systemd/system");
	}

	install_unit($package, $name, 'mount', "$tmpdir/lib/systemd/system");
	install_unit($package, $name, 'tmpfile', "$tmpdir/usr/lib/tmpfiles.d", 'conf');
}


# Add postinst code blocks to handle tmpfiles
foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmpdir = tmpdir($package);
	my @tmpfiles;

	my @dirs = grep { -d } map { "${tmpdir}/$_" } qw(usr/lib/tmpfiles.d etc/tmpfiles.d);

	find({
		wanted => sub {
			my $name = $File::Find::name;
			return unless -f $name;
			push(@tmpfiles, basename($name)); },
		no_chdir => 1,
		}, @dirs) if @dirs;

	if (@tmpfiles) {
		autoscript($package, 'postinst', 'postinst-init-tmpfiles', { 'TMPFILES' => join(' ', sort @tmpfiles) });
	}
}


# Add postinst, prerm, and postrm code blocks to handle activation,
# deactivation, start and stopping of services when the package is
# installed, upgraded or removed.
foreach my $package (@{$dh{DOPACKAGES}}) {
	my $tmpdir = tmpdir($package);
	my (@args, @start_units, @enable_units, %aliases);

	my @installed_units = list_installed_units($tmpdir, \%aliases);

	# Handle either only the unit files which were passed as arguments
	# or all unit files that are installed in this package.
	if (@ARGV) {
	       @args = @ARGV;
	}
	elsif ($dh{NAME}) {
		# Treat --name option as if the corresponding unit names were
		# passed in the command line.
		@args = grep /(^|\/)$dh{NAME}\.(mount|path|service|socket|target|timer)$/, @installed_units;
	}
	else {
		@args = @installed_units;
	}

	# Support excluding units via the -X debhelper common option.
	foreach my $x (@{$dh{EXCLUDE}}) {
		@args = grep !/(^|\/)$x$/, @args;
	}

	# This hash prevents us from looping forever in the following
	# while loop.  An actual real-world example of such a loop is
	# systemd's systemd-readahead-drop.service, which contains
	# Also=systemd-readahead-collect.service, and that file in turn
	# contains Also=systemd-readahead-drop.service, thus forming an
	# endless loop.
	my %seen;

	# Must use while and shift because the loop alters the list.
	while (@args) {
		my $unit = shift @args;
		my $path = "${tmpdir}/lib/systemd/system/${unit}";

		error("Package '$package' does not install unit '$unit'.") unless (-f $path);

		# Skip template service files. Enabling, disabling, starting
		# or stopping those services without specifying the instance
		# is not useful.
		next if ($unit =~ /\@/);

		# Handle all unit files specified via Also= explicitly. This
		# is not necessary for enabling, but for disabling, as we
		# cannot read the unit file when disabling as it has already
		# been deleted. The undocumented --no-also option disables
		# handling of units linked via Also=. This option is provided
		# only to suport a very specific use case in network-manager.
		unless ($dh{NO_ALSO}) {
			push @args, $_ for grep { !$seen{$_}++ } extract_key($path, 'Also');
		}

		# Extract unit aliases.
		push @{$aliases{$unit}}, $_ for extract_key($path, 'Alias');

		# In compat 11 (and earlier), dh_installinit will handle services with
		# a sysv-equivalent service.  In compat 12, dh_installsystemd will
		# take care of it.
		if (not compat(11) or not grep { has_sysv_equivalent($tmpdir, $_) } ($unit, @{$aliases{$unit}})) {
			push @start_units, $unit;
		}

		if (contains_install_section($path)) {
			push @enable_units, $unit;
		}
	}

	@enable_units = map { quote($_) } uniq sort @enable_units;
	@start_units = map { quote($_) } uniq sort @start_units;

	my %options = ('snippet-order' => 'service');

	if (@enable_units) {
		for my $unit (@enable_units) {
			my $snippet = $dh{NO_ENABLE} ? 'postinst-systemd-dont-enable' : 'postinst-systemd-enable';
			autoscript($package, 'postinst', $snippet, { 'UNITFILE' => $unit }, \%options);
		}
		autoscript($package, 'postrm', 'postrm-systemd', {'UNITFILES' => join(' ', @enable_units) });
	}

	if (@start_units) {
		my $replace = { 'UNITFILES' => join(' ', @start_units) };

		if ($dh{RESTART_AFTER_UPGRADE}) {
			my $snippet;
			if ($dh{NO_START}) {
				$snippet = 'postinst-systemd-restartnostart';
				$replace->{RESTART_ACTION} = 'try-restart';
			} else {
				$snippet = 'postinst-systemd-restart';
				$replace->{RESTART_ACTION} = 'restart';
			}
			autoscript($package, 'postinst', $snippet, $replace, \%options);
		} elsif (!$dh{NO_START}) {
			# (stop|start) service (before|after) upgrade
			autoscript($package, 'postinst', 'postinst-systemd-start', $replace, \%options);
		}

		if ($dh{R_FLAG} || $dh{RESTART_AFTER_UPGRADE}) {
			# stop service only on remove
			autoscript($package, 'prerm', 'prerm-systemd-restart', $replace, \%options);
		} elsif (!$dh{NO_START}) {
			# always stop service
			autoscript($package, 'prerm', 'prerm-systemd', $replace, \%options);
		}

		# Run this with "default" order so it is always after other
		# service related autosnippets.
		autoscript($package, 'postrm', 'postrm-systemd-reload-only', $replace);
	}
}

=head1 SEE ALSO

L<debhelper(7)>, L<dh_installinit(1)>, L<deb-systemd-helper(1)>

=head1 AUTHORS

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

=cut