#!/usr/bin/perl -w

=head1 NAME

dh_installsystemduser - install systemd unit files

=cut

use strict;
use warnings;
use Debian::Debhelper::Dh_Lib;

our $VERSION = DH_BUILTIN_VERSION;

=head1 SYNOPSIS

B<dh_installsystemduser> [S<I<debhelper options>>] [B<--no-enable>] [B<--name=>I<name>] [S<I<unit file> ...>]

=head1 DESCRIPTION

B<dh_installsystemduser> finds the systemd user instance 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 user instance 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 the systemd
units, thus it is not necessary that the machine actually runs systemd
during package installation time, enabling happens on all machines.

B<dh_installsystemduser> operates on all user instance unit files
installed by a package. For only generating blocks for specific unit
files, pass them as arguments. 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>.user.path,
      debian/I<package>@.user.path,
      debian/I<package>.user.service,
      debian/I<package>@.user.service,
      debian/I<package>.user.socket,
      debian/I<package>@.user.socket,
      debian/I<package>.user.target,
      debian/I<package>@.user.target,
      debian/I<package>.user.timer,
      debian/I<package>@.user.timer

If any of those files exists, they are installed into
F<usr/lib/systemd/user/> in the package build directory removing the
F<.user> file name part.

=back

=head1 OPTIONS

=over 4

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

Install the service file as I<name.service> instead of the default
filename I<package.service>. When this parameter is used,
B<dh_installsystemd> looks for and installs files named
F<debian/package.name.user.service> instead of the usual
F<debian/package.user.service>.  Moreover, maintainer scripts are only
generated for units that match the given I<name>.

=item B<--no-enable>

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

=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

# PROMISE: DH NOOP WITHOUT internal(bug#950723) tmp(usr/lib/systemd/user) user.service user.target user.socket user.path user.timer

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

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) to check for [Install]: $!");

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

sub install_user_unit {
	my ($package, $name, $suffix, $path) = @_;
	my $unit = pkgfile({'named' => 1}, $package, "user.$suffix");
	return if $unit eq '';

	install_dir($path);
	install_file($unit, "$path/$name.$suffix");
}

# 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_user_units {
	my ($tmpdir, $aliases) = @_;

	my $lib_systemd_user = "$tmpdir/usr/lib/systemd/user";
	my @installed;

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

	foreach my $name (readdir($dh)) {
		my $path = "$lib_systemd_user/$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;
}

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

	# unit file name
	my $name = $dh{NAME} // $package;

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

# Generate postinst and prerm code blocks to enable and disable units
foreach my $package (@{$dh{DOPACKAGES}}) {
    my (@args, @start_units, @enable_units, %aliases);

	my $tmpdir = tmpdir($package);
	my @units = list_installed_user_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 ($dh{NAME}) {
		# Treat --name flag as if the corresponding units were passed
		# in the command line.
		@args = grep /(^|\/)$dh{NAME}\.(service|target|socket|path|timer)$/, @units;
	}
	else {
		@args = @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 $name = shift @args;
		my $path = "${tmpdir}/usr/lib/systemd/user/${name}";

		error("User unit file \"$name\" not found in package \"$package\".") if ! -f $path;

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

		# 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.
		push @args, $_ for grep { !$seen{$_}++ } extract_key($path, 'Also');

		push @enable_units, $name if contains_install_section($path);
		push @start_units, $name;
	}

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

	if (@enable_units) {
		# The generated maintainer script code blocks use the --user
		# option that was added to deb-systemd-helper in version 1.52.
		addsubstvar($package, 'misc:Depends', 'init-system-helpers', ">= 1.52");

		my $postinst = $dh{NO_ENABLE} ? 'postinst-systemd-user-dont-enable' : 'postinst-systemd-user-enable';
		foreach my $unit (@enable_units) {
			autoscript($package, 'postinst', $postinst, { 'UNITFILE' => $unit });
		}
		autoscript($package, 'postrm', 'postrm-systemd-user', { 'UNITFILES' => join(' ', @enable_units) });
	}

	if (@start_units and not compat(13)) {
		# The generated maintainer script code blocks use the --user
		# option that was added to deb-systemd-invoke in version 1.61 and fixed in 1.66 to really daemon-reload.
		addsubstvar($package, 'misc:Depends', 'init-system-helpers', ">= 1.66~");

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

		# restart service after install/upgrade
		autoscript($package, 'postinst', 'postinst-systemd-user-restart', { 'UNITFILES' => join(' ', @start_units) }, \%options);

		# stop service after removal
		autoscript($package, 'prerm', 'prerm-systemd-user-stop', { 'UNITFILES' => join(' ', @start_units) }, \%options);

		# Run this with "default" order so it is always after other
		# service related autosnippets.
		autoscript($package, 'postrm', 'postrm-systemd-user-reload-only', { 'UNITFILES' => join(' ', @start_units) });
	}
}

=head1 SEE ALSO

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

=head1 AUTHORS

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

=cut