import datetime
from icalendar import Event, Calendar, Timezone, TimezoneStandard


def create_timezone():
    tz = Timezone()
    tz.add('TZID', 'Asia/Shanghai')

    tz_standard = TimezoneStandard()
    tz_standard.add('DTSTART', datetime.datetime(1970, 1, 1))
    tz_standard.add('TZOFFSETFROM', datetime.timedelta(hours=8))
    tz_standard.add('TZOFFSETTO', datetime.timedelta(hours=8))

    tz.add_component(tz_standard)
    return tz


def create_event(event_name, start, end):
    # 创建事件/日程
    event = Event()
    event.add('SUMMARY', event_name)

    event.add('DTSTART', start)
    event.add('DTEND', end)
    # 创建时间
    event.add('DTSTAMP', start)

    # UID保证唯一
    event['UID'] = f'{start}/{end}/NateScarlet/holiday-cn'

    return event


def ranger(lst):
    if len(lst) == 0:
        return []

    if len(lst) == 1:
        return [(lst[0], lst[0])]

    fr, to = lst[0], lst[0]
    for cur in lst[1:]:
        if (cur.get('date') - to.get('date')).days == 1 \
                and cur.get('isOffDay') == to.get('isOffDay'):
            to = cur
        else:
            yield fr, to
            fr, to = cur, cur
    yield fr, to


def conv_json_to_ics(data, filename):
    """
    将爬取的节假日JSON数据转换为ICS

    Args:
        filename: str
        data: from `fetch_holiday`
    """
    cal = Calendar()
    cal.add('VERSION', '2.0')
    cal.add('METHOD', 'PUBLISH')
    cal.add('CLASS', 'PUBLIC')

    cal.add_component(create_timezone())

    days = data.get('days', [])
    for day in days:
        if isinstance(day.get('date'), str):
            day['date'] = datetime.date(*map(int, day['date'].split('-')))

    for fr, to in ranger(days):
        start = fr.get('date')
        end = to.get('date') + datetime.timedelta(days=1)

        name = fr.get('name') + "假期"
        if not fr.get('isOffDay'):
            name = "上班(补" + name + ")"
        cal.add_component(create_event(name, start, end))

    with open(f'{filename}.ics', 'wb') as ics:
        ics.write(cal.to_ical())