#!/usr/bin/env python

import os
import sys
import pydbus
import datetime
from gi.repository import GLib

def main(argv):

    loop = GLib.MainLoop()

    battery = pydbus.SystemBus().get(
            'org.freedesktop.UPower',
            '/org/freedesktop/UPower/devices/battery_BAT0',
            )

    def battery_changed():
        """ screen backtick does not kill the backtick process whenever the screen terminates. """
        if os.getppid() == 1:
            loop.quit()
        """ 0: Unknown
            1: Charging
            2: Discharging
            3: Empty
            4: Fully charged
            5: Pending charge
            6: Pending discharge
            """
        if battery.State == 2:
            sys.stdout.write('%.1fW %s\n' % (
                battery.EnergyRate,
                (datetime.datetime.now() + datetime.timedelta(seconds = battery.TimeToEmpty)).strftime("%H:%M"),
                ))
        elif battery.State == 4:
            sys.stdout.write('full\n')
        else:
            sys.stdout.write('%d%% %s\n' % (
                battery.Percentage,
                (datetime.datetime.now() + datetime.timedelta(seconds = battery.TimeToFull)).strftime("%H:%M"),
                ))
        sys.stdout.flush()

    battery.onChanged = battery_changed
    battery.onPropertiesChanged = lambda interface, attr, l: battery_changed()

    loop.run()

if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))