import datetime

import dateutil.parser as dateparser
import ics
import pytz
import requests
from rcal.db import Session
from rcal.model import Calendar, Entry


def update_event_data(db_event, ical_event):
    db_event.name = ical_event.name
    db_event.location = ical_event.location
    db_event.begin_date = ical_event.begin.datetime
    db_event.end_date = ical_event.end.datetime
    db_event.all_day = (
        (db_event.end_date - db_event.begin_date).seconds % 86400 == 0
    ) and (
        db_event.begin_date.time() == datetime.time.min)
    if db_event.all_day:
        db_event.end_date = db_event.end_date - datetime.timedelta(days=1)
    return db_event


def update_event(db_event, ical_event):
    update_event_data(db_event, ical_event)


def add_event(event, calendar, session):
    entry = Entry()
    entry.uid = event.uid
    entry.calendar = calendar
    entry = update_event_data(entry, event)
    session.add(entry)


def remove_event(event, session):
    session.delete(event)


def get_last_modification_time(event):
    for unused in event.__dict__['_unused']:
        if unused.name == 'LAST-MODIFIED':
            return dateparser.parse(unused.value)
    return None


def fetch_calendar(calendar, session):
    cal_data = requests.get(calendar.url)
    cal_object = ics.Calendar(cal_data.content.decode(cal_data.encoding))
    cal_events = {e.uid: e for e in cal_object.events}
    db_events = {e.uid: e for e in calendar.entries}
    new_events = [e for u, e in cal_events.iteritems()
                  if u not in db_events.keys()]
    old_events = [e for u, e in db_events.iteritems()
                  if u not in cal_events.keys()]
    mod_events = [{'ics': cal_events[u], 'db': e}
                  for u, e in db_events.iteritems() if u in cal_events.keys()]
    for event in mod_events:
        modified_date = get_last_modification_time(event['ics'])
        if not modified_date or \
           not calendar.last_updated or \
           modified_date > calendar.last_updated.replace(tzinfo=pytz.UTC):
            print 'Updating event %s' % event['db'].uid
            update_event(event['db'], event['ics'])
    for event in new_events:
        print 'Adding event %s' % event.uid
        add_event(event, calendar, session)
    for event in old_events:
        print 'Removing event %s' % event.uid
        remove_event(event, session)
    calendar.last_updated = datetime.datetime.now()


def main():
    session = Session.create()

    calendars = session.query(Calendar).all()
    for calendar in calendars:
        # print 'Fetching %s' % calendar.url
        fetch_calendar(calendar, session)

    session.commit()


if __name__ == '__main__':
    main()