vypocet_lhuty_s_hlubokym_zrusenim.py

from datetime import date, datetime, timedelta


def main():
    events = [
        ZakladniInterval(dt('2020-01-01'), dt('2030-01-01')),
        Prodlouzeni(id=222, roky=3),
        Zruseni(id=333, zrusit_id=222),
        Zruseni(id=444, zrusit_id=333),
        Zruseni(id=555, zrusit_id=444),
    ]
    zacatek, konec = spocitej(events)
    print(f'{zacatek} - {konec}')


def spocitej(events):
    while True:
        old_events = events
        for event in events:
            events = event.process_events(events)
        if old_events == events:
            break
    interval = None
    for event in events:
        interval = event.process_interval(interval)
    return interval


def dt(s):
    return datetime.strptime(s, '%Y-%m-%d').date()


class BaseEvent:

    def __init__(self, id):
        self.id = id

    def process_events(self, events):
        return events

    def process_interval(self, interval):
        return interval


class ZakladniInterval (BaseEvent):

    def __init__(self, zacatek, konec):
        super().__init__(id=None)
        self.zacatek = zacatek
        self.konec = konec

    def process_interval(self, interval):
        assert interval is None
        return (self.zacatek, self.konec)


class Prodlouzeni (BaseEvent):

    def __init__(self, id, roky):
        self.id = id
        self.roky = roky

    def process_interval(self, interval):
        zacatek, konec = interval
        konec = konec.replace(year=konec.year + self.roky)
        return (zacatek, konec)


class Zruseni (BaseEvent):

    def __init__(self, id, zrusit_id):
        self.id = id
        self.zrusit_id = zrusit_id

    def process_events(self, events):
        event, = [ev for ev in events if ev.id == self.zrusit_id]
        return [Zruseno(ev, self.id) if ev is event and not isinstance(event, Zruseno) else ev for ev in events]


class Zruseno (BaseEvent):

    def __init__(self, puvodni_event, id_zruseno_kym):
        self.puvodni_event = puvodni_event
        self.id = puvodni_event.id
        self.id_zruseno_kym = id_zruseno_kym

    def __eq__(self, other):
        return isinstance(other, Zruseno) and self._get_data() == other._get_data()

    def _get_data(self):
        return (self.puvodni_event, self.id_zruseno_kym)

    def process_events(self, events):
        event_ktery_toto_zrusil, = [ev for ev in events if ev.id == self.id_zruseno_kym]
        if isinstance(event_ktery_toto_zrusil, Zruseno):
            return [self.puvodni_event if ev is self else ev for ev in events]
        else:
            return events




if __name__ == '__main__':
    main()

vypocet_lhuty_s_jednoduchym_vnorenim.py

from datetime import date, datetime, timedelta


def main():
    events = [
        ZakladniInterval(dt('2020-01-01'), dt('2030-01-01')),
        Prodlouzeni(id=123, roky=3),
        ZruseniProdlouzeni(id_prodlouzeni=123)
    ]
    zacatek, konec = spocitej(events)
    print(f'{zacatek} - {konec}')


def spocitej(events):
    for event in list(events):
        events = event.process_events(events)
    interval = None
    for event in events:
        interval = event.process_interval(interval)
    return interval


def dt(s):
    return datetime.strptime(s, '%Y-%m-%d').date()


class BaseEvent:

    def process_events(self, events):
        return events

    def process_interval(self, interval):
        return interval


class ZakladniInterval (BaseEvent):

    def __init__(self, zacatek, konec):
        self.zacatek = zacatek
        self.konec = konec

    def process_interval(self, interval):
        assert interval is None
        return (self.zacatek, self.konec)


class Prodlouzeni (BaseEvent):

    def __init__(self, id, roky):
        self.id = id
        self.roky = roky

    def process_interval(self, interval):
        zacatek, konec = predchozi
        konec = konec.replace(year=konec.year + roky)
        return (zacatek, konec)


class ZruseniProdlouzeni (BaseEvent):

    def __init__(self, id_prodlouzeni):
        self.id_prodlouzeni = id_prodlouzeni

    def process_events(self, events):
        event, = [ev for ev in events if isinstance(ev, Prodlouzeni) and ev.id == self.id_prodlouzeni]
        return [ev for ev in events if ev is not event]


if __name__ == '__main__':
    main()