#!/usr/bin/env python3

import sys
import dbus
import re
import datetime
# import pprint


class AutoSuspender(object):

    def __init__(self):
        self.__bus = dbus.SystemBus()
        self.__timer_re = re.compile('^syncoid-pull-.*\.timer$')
        # self.__pp = pprint.PrettyPrinter(indent=2)

    def _get_interface(self, dest, object, interface):
        try:
            obj = self.__bus.get_object(dest, object)
            return dbus.Interface(obj, interface)
        except dbus.exceptions.DBusException as error:
            print("ERR: %s" % error)
            sys.exit(1)

    def _get_logind_manager_interface(self):
        return self._get_interface("org.freedesktop.login1", "/org/freedesktop/login1", "org.freedesktop.login1.Manager")

    def _get_systemd_manager_interface(self):
        return self._get_interface("org.freedesktop.systemd1", "/org/freedesktop/systemd1", "org.freedesktop.systemd1.Manager")

    def _get_systemd_timer_properties(self, path):
        return self._get_interface("org.freedesktop.systemd1", path, "org.freedesktop.DBus.Properties").GetAll("org.freedesktop.systemd1.Timer")

    def _get_users_logged_in(self):
        manager = self._get_logind_manager_interface()
        users = []
        for user in manager.ListUsers():
            uid = int(user[0])
            name = str(user[1])
            users.append((name, uid))
        return users

    def _get_syncoid_timers(self):
        manager = self._get_systemd_manager_interface()
        timers = []
        for unit in manager.ListUnits():
            name = str(unit[0])
            path = str(unit[6])
            if not self.__timer_re.match(name):
                continue
            timers.append((name, path))
        return timers

    def _get_timer_next_elapse(self, path):
        props = self._get_systemd_timer_properties(path)
        try:
            return datetime.datetime.fromtimestamp(int(props['NextElapseUSecRealtime']) / 1000000)
        except ValueError:
            return None

    def check(self):
        result = True

        users = self._get_users_logged_in()
        if(len(users) > 0):
            print(" [NO]  %d users logged in: %s" % (len(users), ", ".join([user[0] for user in users])))
            result = False
        else:
            print(" [ok]  no users logged in.")

        timers = self._get_syncoid_timers()
        for timer in timers:
            next = self._get_timer_next_elapse(timer[1])
            if next == None:
                print(" [NO]  the next elapse time of '%s' is invalid, assuming the unit is currently active" % (timer[0]))
                result = False
                continue

            until = next - datetime.datetime.now()
            if(until < datetime.timedelta(minutes=10)):
                print(" [NO]  timer '%s' elapses in less than 10 minutes -> %s (%s)" % (timer[0], next, until))
                result = False
            else:
                print(" [ok]  timer '%s' elapses in %s (%s)" % (timer[0], until, next))

        return result

    def suspend(self):
        manager = self._get_logind_manager_interface()
        if not manager.CanSuspend():
            print("ERR: system can not be suspended")
            return
        try:
            manager.Suspend(False)
        except dbus.exceptions.DBusException as error:
            print("ERR: %s" % error)


if __name__ == "__main__":
    s = AutoSuspender()
    print("checking if the system can be suspended:")
    if s.check():
        print("trying to suspend system")
        s.suspend()
    else:
        print("not suspending system because at least one check failed.")