#!/bin/bash

# by Vladimir Kudrya
# https://github.com/Vladimir-csp/
#
# This script is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version. See <http://www.gnu.org/licenses/>.

# This is a replacement for original dbus.service script by Thomas Liske <thomas@fiasko-nw.net>
# Dbus dependencies are enumerated dynamically and restarted after dbus and systemd daemon reexec

# enable xtrace if we should be verbose
if [ "$NR_VERBOSE" = '1' ]; then
    set -x
fi

if [ "$(id -ru)" != "0" ]
then
	echo "Not root, exiting" >&2
	exit 1
fi

INIT_EXEC="$(readlink /proc/1/exe)"

if [ "$(basename "$INIT_EXEC")" != "systemd" ]
then
	echo "Init system is not systemd ($INIT_EXEC), doing nothing"
	exit 0
fi

get_active_deps(){
	# return all dbus dependencies, filter out dbus and DM, leave only active
	{
		systemctl list-dependencies -l --reverse --plain dbus.socket
		systemctl list-dependencies -l --reverse --plain dbus.service
	} | grep -o '[^[:space:]]\+.service' | sort -u | while read SERVICE
	do
		if [ "$SERVICE" != "dbus.service" -a "$SERVICE" != "$DISPLAY_MANAGER" ] && systemctl -q is-active "$SERVICE"
		then
			echo "$SERVICE"
		fi
	done
}

# if DM is active, return canonical ID
DISPLAY_MANAGER="$(systemctl -q is-active display-manager.service && systemctl show --value -p Id display-manager.service)"

# get dependencies
ACTIVE_DEPS="$(get_active_deps)"

# get logind sessions
SESSIONS="$(loginctl list-sessions --no-legend | grep -o '^[[:space:]]*[0-9]\+' | tr '\n' ' ')"

cat << EOF
!!! In $PAUSE seconds dbus restart will be performed !!!
User sessions to be terminated: $SESSIONS

Services to be restarted:
$ACTIVE_DEPS
$DISPLAY_MANAGER
EOF

[ -t 0 ] && read -p "Press Enter to continue > " PRESSENTER

# prepare list to be a CLI arg
ACTIVE_DEPS="$(echo "$ACTIVE_DEPS" | tr '\n' ' ')"

# run restart sequence as transient unit...
if [ -n "$DISPLAY_MANAGER" ]
then
	# terminate user sessions, stop DM, restart dbus, reexec systemd, restart dbus dependencies, start DM
	systemd-run -G --unit=restart-dbus sh -c "loginctl terminate-session $SESSIONS ; systemctl stop $DISPLAY_MANAGER ; systemctl restart dbus.service ; sleep 1 ; systemctl daemon-reexec ; sleep 1 ; systemctl restart $ACTIVE_DEPS ; systemctl start $DISPLAY_MANAGER"
else
	# terminate user sessions, restart dbus, reexec systemd, restart dbus dependencies
	systemd-run -G --unit=restart-dbus sh -c "loginctl terminate-session $SESSIONS ; systemctl restart dbus.service ; sleep 1 ; systemctl daemon-reexec ; sleep 1 ; systemctl restart $ACTIVE_DEPS"
fi

# restart sequence runs as a unit, so it is possible to view its output in the log if, any:
# journalctl -u restart-dbus