events.py

from collections import defaultdict
from datetime import timedelta as td
from functools import partial

from dates import (RFC_WEEKDAYS, last_workday, day_changes as CHANGE_DATES,
                   midsem_dates as MIDSEM_DATES, holidays as HOLIDAYS)
from utils import combine_dt
from enum import Flag, auto


class EventType(Flag):
    Lectures = auto()
    Midsem = auto()
    Compre = auto()
    All = Lectures | Midsem | Compre


DATE_FMT = '%Y%m%dT%H%M%S'
RFC_WDAY = tuple(RFC_WEEKDAYS.values())
COLORS = {'event': {'L': '9', 'P': '6', 'T': '10'},
          'midsem': '4', 'compre': '7'}

INCLUDE_DATES = defaultdict(list)
for change_date, day in CHANGE_DATES.items():
    INCLUDE_DATES[day].append(change_date)
LAST_DATE = (last_workday + td(days=1)).strftime('%Y%m%d')


def join_event_dt(event, date_):
    return combine_dt(date_, event['start'].time()).strftime(DATE_FMT)


def get_indates(event):
    indates = set()
    for wday in event['wdays']:
        dates = INCLUDE_DATES.get(RFC_WDAY[wday - 1], [])
        indates.update(dates)
    return indates


def get_exdates(event, indates):
    exdates = HOLIDAYS.copy()
    if MIDSEM_DATES:
        midsem_date = MIDSEM_DATES['start']
        while midsem_date <= MIDSEM_DATES['end']:
            if midsem_date.isoweekday() in event['wdays']:
                exdates.add(midsem_date)
            midsem_date = midsem_date + td(days=1)
    for change_date in CHANGE_DATES:
        if change_date.isoweekday() in event['wdays'] and change_date not in indates:
            exdates.add(change_date)
    return exdates


def make_section_events(course_name, section):
    for event in section['sched']:
        rrule = {
            'FREQ': 'WEEKLY',
            'BYDAY': ','.join(RFC_WDAY[day - 1] for day in event['wdays']),
            'UNTIL': LAST_DATE
        }
        get_dt = partial(join_event_dt, event)
        indates = get_indates(event)
        exdates = get_exdates(event, indates)

        gcal_event = {
            'summary': f"{course_name} {section['num']}",
            'description': section['instructors'],
            'location': event['room'],
            'start': {
                'dateTime': event['start'].isoformat(),
                'timeZone': 'Asia/Kolkata'
            },
            'end': {
                'dateTime': event['end'].isoformat(),
                'timeZone': 'Asia/Kolkata'
            },
            'recurrence': [
                'RRULE:' + ";".join(f"{k}={v}" for k, v in rrule.items()),
            ],
            'reminders': {
                'useDefault': False,
                'overrides': [
                    {
                        'method': 'popup',
                        'minutes': 10
                    }
                ]
            },
            'colorId': COLORS['event'][section['num'][0]]
        }
        if indates:
            gcal_event['recurrence'].append(
                'RDATE;TZID=Asia/Kolkata:' + ','.join(map(get_dt, indates)))
        if exdates:
            gcal_event['recurrence'].append(
                'EXDATE;TZID=Asia/Kolkata:' + ','.join(map(get_dt, exdates)))
        yield gcal_event


def make_event(title, start, end, color):
    return {
        'summary': title,
        'start': {
            'dateTime': start.isoformat(),
            'timeZone': 'Asia/Kolkata'
        },
        'end': {
            'dateTime': end.isoformat(),
            'timeZone': 'Asia/Kolkata'
        },
        'colorId': color
    }


def make_midsem_event(course_name, midsem):
    return make_event(course_name + ' Midsem', midsem['start'],
                      midsem['end'], COLORS['midsem'])


def make_compre_event(course_name, compre):
    return make_event(course_name + ' Compre', compre['start'],
                      compre['end'], COLORS['compre'])


def make_course_events(course, event_types=EventType.All):
    name = course['name']
    if event_types & EventType.Lectures:
        for section in course['sections']:
            yield from make_section_events(name, section)
    if event_types & EventType.Midsem:
        midsem = course.get('midsem')
        if midsem:
            yield make_midsem_event(name, midsem)
    if event_types & EventType.Compre:
        compre = course.get('compre')
        if compre:
            yield make_compre_event(name, compre)