#! /usr/bin/env python
#
#    Copyright 2014 North Dakota State University
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import datetime
import icalendar
import logging
import os
import pytz
import yaml

import const


class Meeting:
    """An OpenStack meeting."""

    def __init__(self, yaml, filename):
        """Initialize meeting from yaml file name 'filename'."""

        self.filename = filename

        # initialize using yaml
        self.project = yaml['project']
        self.chair = yaml['chair']
        self.description = yaml['description']
        self.agenda = yaml['agenda']  # this is a list of list of topics

        # create schedule objects
        self.schedules = [Schedule(schedule) for schedule in yaml['schedule']]

    def write_ical(self):
        """Write this meeting to disk using the iCal format."""
        cal = icalendar.Calendar()

        # add properties to ensure compliance
        cal.add('prodid', '-//OpenStack//Gerrit-Powered Meeting Agendas//EN')
        cal.add('version', '2.0')

        i = 1
        for schedule in self.schedules:
            # one Event per iCal file
            event = icalendar.Event()

            # NOTE(jotan): I think the summary field needs to be unique per
            # event in an ical file (at least, for it to work with
            # Google Calendar)

            event.add('summary', self.project + ' ' + str(i))

            # add ical description
            project_descript = "Project:  %s" % (self.project)
            chair_descript = "Chair:  %s" % (self.chair)
            irc_descript = "IRC:  %s" % (schedule.irc)
            agenda_yaml = yaml.dump(self.agenda, default_flow_style=False)
            agenda_descript = "Agenda:\n%s\n" % (agenda_yaml)
            descript_descript = "Description:  %s" % (self.description)
            ical_descript = "\n".join((project_descript,
                                       chair_descript,
                                       irc_descript,
                                       agenda_descript,
                                       descript_descript))
            event.add('description', ical_descript)

            # get starting date
            d = datetime.datetime.utcnow()
            next_meeting = next_weekday(d, const.WEEKDAYS[schedule.day])

            next_meeting_dt = datetime.datetime(next_meeting.year,
                                                next_meeting.month,
                                                next_meeting.day,
                                                schedule.time.hour,
                                                schedule.time.minute,
                                                tzinfo=pytz.utc)
            event.add('dtstart', next_meeting_dt)

            # add recurrence rule
            event.add('rrule', {'freq': schedule.freq})

            # add meeting length
            # TODO(jotan): determine duration to use for OpenStack meetings
            event.add('duration', datetime.timedelta(hours=1))

            # add event to calendar
            cal.add_component(event)
            i += 1

        # write ical files to disk
        ical_dir = '../icals'
        ical_filename = self.filename[:-4] + 'ics'

        if not os.path.exists(ical_dir):
            os.makedirs(ical_dir)
        os.chdir(ical_dir)

        with open(ical_filename, 'wb') as ics:
            ics.write(cal.to_ical())

        num_events = len(cal.subcomponents)
        logging.info('\'%s\' processed. [%d event(s)]' % (ical_filename,
                                                          num_events))


class Schedule:
    """A meeting schedule."""

    def __init__(self, sched_yaml):
        """Initialize schedule from yaml."""

        self.time = datetime.datetime.strptime(sched_yaml['time'], '%H%M')
        self.day = sched_yaml['day']
        self.irc = sched_yaml['irc']
        self.freq = sched_yaml['frequency']


def next_weekday(ref_date, weekday):
    """Return the date of the next weekday after ref_date."""

    days_ahead = weekday - ref_date.weekday()
    if days_ahead <= 0:  # target day already happened this week
        days_ahead += 7
    return ref_date + datetime.timedelta(days_ahead)