yaml2ical/yaml2ical/meeting.py

# 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 hashlib
import os

import icalendar
import pytz
import yaml

from yaml2ical import schedule


WEEKDAYS = {'Monday': 0, 'Tuesday': 1, 'Wednesday': 2, 'Thursday': 3,
            'Friday': 4, 'Saturday': 5, 'Sunday': 6}


class Yaml2IcalCalendar(icalendar.Calendar):
    """A calendar in ics format."""

    def __init__(self):
        super(Yaml2IcalCalendar, self).__init__()
        self.add('prodid', '-//yaml2ical agendas//EN')
        self.add('version', '2.0')

    def write_to_disk(self, filename):
        # write ical files to disk
        with open(filename, 'wb') as ics:
            ics.write(self.to_ical())


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

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

    def add_to_calendar(self, cal):
        """Add this meeting to an existing calendar."""

        for sch 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)
            event.add('location', '#' + sch.irc)

            # add ical description
            project_descript = "Project:  %s" % (self.project)
            chair_descript = "Chair:  %s" % (self.chair)
            descript_descript = "Description:  %s" % (self.description)
            ical_descript = "\n".join((project_descript,
                                       chair_descript,
                                       descript_descript))
            event.add('description', ical_descript)

            # get starting date
            start_date = datetime.datetime.utcnow()
            if sch.freq.startswith('biweekly'):
                meet_on_even = sch.freq.endswith('even')
                next_meeting = next_biweekly_meeting(start_date,
                                                     WEEKDAYS[sch.day],
                                                     meet_on_even=meet_on_even)
            else:
                next_meeting = next_weekday(start_date,
                                            WEEKDAYS[sch.day])

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

            # add recurrence rule
            if sch.freq.startswith('biweekly'):
                cadence = ()
                # NOTE(lbragstad): Setting the `cadence` for the schedule
                # will allow for alternating meetings. Typically there are
                # only 4 weeks in a month but adding `5` and `6` allow for
                # cases where there are 5 meetings in a month, which would
                # otherwise be unsupported if only setting `cadence` to
                # either (1, 3) or (2, 4).
                if sch.freq == 'biweekly-odd':
                    cadence = (1, 3, 5)
                elif sch.freq == 'biweekly-even':
                    cadence = (2, 4, 6)
                rule_dict = {'freq': 'monthly',
                             'byday': sch.day[0:2],
                             'bysetpos': cadence}
                event.add('rrule', rule_dict)
            else:
                event.add('rrule', {'freq': sch.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)


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

    :param ref_date: datetime object of meeting
    :param weekday: weekday the meeting is held on

    :returns: datetime object of the next meeting time
    """

    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)


def load_meetings(yaml_source):
    """Build YAML object and load meeting data

    :param yaml_source: source data to load, which can be a directory or
                        stream.
    :returns: list of meeting objects
    """
    meetings_yaml = []
    # Determine what the yaml_source is
    if os.path.isdir(yaml_source):
        # TODO(lbragstad): use os.path.walk?
        for f in os.listdir(yaml_source):
            # Build the entire file path and append to the list of yaml
            # meetings
            yaml_file = os.path.join(yaml_source, f)
            meetings_yaml.append(yaml_file)
    elif isinstance(yaml_source, str):
        return [_load_meeting(yaml_source)]
    else:
        # If we don't have a .yaml file, a directory of .yaml files, or any
        # YAML data fail out here.
        raise ValueError("YAML source isn't a .yaml file, directory "
                         "containing .yaml files, or YAML data.")

    meetings = []
    for yaml_file in meetings_yaml:
        with open(yaml_file, 'r') as f:
            meetings.append(_load_meeting(f))

    return meetings


def _load_meeting(meeting_yaml):
    yaml_obj = yaml.safe_load(meeting_yaml)
    m = Meeting()

    # Build meeting attributes from yaml
    m.chair = yaml_obj['chair']
    m.description = yaml_obj['description']
    m.project = yaml_obj['project']
    m._filename = (yaml_obj['project'] + '-' +
                   hashlib.md5(str(yaml_obj).encode('utf-8')).hexdigest()[:8])

    # TODO(lbragstad): See if there is another way we can do this instead
    # of having every Meeting object build a list of Schedule objects.
    m.schedules = []
    for sch in yaml_obj['schedule']:
        s = schedule.Schedule(sch)
        m.schedules.append(s)

    return m


def next_biweekly_meeting(current_date_time, weekday, meet_on_even=False):
    """Calculate the next biweekly meeting.

    :param current_date_time: the current datetime object
    :param weekday: scheduled day of the meeting
    :param meet_on_even: True if meeting on even weeks and False if meeting
    on odd weeks
    :returns: datetime object of next meeting

    """
    first_day_of_mo = current_date_time.replace(day=1)
    day_of_week = first_day_of_mo.strftime("%w")
    adjustment = (8 - int(day_of_week)) % (7 - weekday)
    if meet_on_even:
        adjustment += 7
    next_meeting = first_day_of_mo + datetime.timedelta(adjustment)

    if current_date_time > next_meeting:
        next_meeting = next_meeting + datetime.timedelta(14)
        if current_date_time > next_meeting:
            current_date_time = current_date_time.replace(
                month=current_date_time.month + 1, day=1)
            first_wday_next_mo = next_weekday(current_date_time, weekday)
            if meet_on_even:
                next_meeting = first_wday_next_mo + datetime.timedelta(7)
            else:
                next_meeting = first_wday_next_mo
    return next_meeting