Wilderness Warbands calendar event generator (for RuneScape)

wbscal.py

import argparse
import sys
import time
import uuid
from datetime import datetime, timedelta, timezone

ICAL_TIME = '%Y%m%dT%H%M%SZ'


def generate(f, begin=None, alarms=None, opaque=True, duration=15):
    now = datetime.now(timezone.utc)
    unixhour = int((begin or now).timestamp()) // 3600
    if unixhour % 7 != 0:
        unixhour += 7 - unixhour % 7
    first = datetime.fromtimestamp(3600 * unixhour, tz=timezone.utc)

    def write(line, *args):
        print(line % args, file=f)

    def write_time(line, time):
        print('%s:%s' % (line, time.strftime(ICAL_TIME)), file=f)

    write('BEGIN:VCALENDAR')
    write('PRODID:-//Quantum//NONSGML Warbands Calendar//EN')
    write('VERSION:2.0')

    for i in range(24):
        start = first + timedelta(hours=7) * i
        end = start + timedelta(minutes=duration)
        write('BEGIN:VEVENT')
        write_time('CREATED', now)
        write_time('LAST-MODIFIED', now)
        write_time('DTSTAMP', now)
        write('UID:%s', uuid.uuid4())
        write('SUMMARY:Wilderness Warbands')
        write('RRULE:FREQ=WEEKLY')
        write_time('DTSTART', start)
        write_time('DTEND', end)
        write('TRANSP:%s', 'OPAQUE' if opaque else 'TRANSPARENT')
        write('SEQUENCE:1')

        for alarm in alarms or []:
            write('BEGIN:VALARM')
            write('ACTION:DISPLAY')
            write('TRIGGER;VALUE=DURATION:-PT%dM', alarm)
            write('DESCRIPTION:Wilderness Warbands starts in %d minutes!', alarm)
            write('END:VALARM')

        write('END:VEVENT')

    write('END:VCALENDAR')


def main():
    parser = argparse.ArgumentParser(description='Wilderness Warbands calendar generator.')
    parser.add_argument('output', nargs='?', type=argparse.FileType('w'), default=sys.stdout,
                        help='file to write calendar to')
    parser.add_argument('-a', '--alarm', type=int, action='append', metavar='N',
                        help='set an alarm N minutes before the event (can be repeated, default: 5 minutes)')
    parser.add_argument('-n', '--no-alarm', action='store_true',
                        help='disable alarms')
    parser.add_argument('--opaque', action='store_true', default=True,
                        help='make events opaque (marked as busy, default)')
    parser.add_argument('-t', '--transparent', action='store_false', dest='opaque',
                        help='make events transparent (not marked as busy)')
    parser.add_argument('-d', '--duration', type=int, default=15,
                        help='duration of warband event in minutes (default: 15)')
    args = parser.parse_args()

    with args.output:
        generate(args.output, alarms=[] if args.no_alarm else args.alarm or [5],
                 opaque=args.opaque, duration=args.duration)

if __name__ == '__main__':
    main()