import datetime


class Term:
    """A representation of a term in the CSC LDAP, e.g. 's2021'."""

    seasons = ['w', 's', 'f']

    def __init__(self, s_term: str):
        assert len(s_term) == 5 and s_term[0] in self.seasons and \
            s_term[1:].isdigit()
        self.s_term = s_term

    def __repr__(self):
        return self.s_term

    @staticmethod
    def current():
        """Get a Term object for the current date."""
        dt = datetime.datetime.now()
        c = 'w'
        if 5 <= dt.month <= 8:
            c = 's'
        elif 9 <= dt.month:
            c = 'f'
        s_term = c + str(dt.year)
        return Term(s_term)

    def __add__(self, other):
        assert type(other) is int and other >= 0
        c = self.s_term[0]
        season_idx = self.seasons.index(c)
        year = int(self.s_term[1:])
        year += other // 3
        season_idx += other % 3
        if season_idx >= 3:
            year += 1
            season_idx -= 3
        s_term = self.seasons[season_idx] + str(year)
        return Term(s_term)

    def __eq__(self, other):
        return isinstance(other, Term) and self.s_term == other.s_term

    def __lt__(self, other):
        if not isinstance(other, Term):
            return NotImplemented
        c1, c2 = self.s_term[0], other.s_term[0]
        year1, year2 = int(self.s_term[1:]), int(other.s_term[1:])
        return year1 < year2 or (
            year1 == year2 and self.seasons.index(c1) < self.seasons.index(c2)
        )

    def __gt__(self, other):
        if not isinstance(other, Term):
            return NotImplemented
        c1, c2 = self.s_term[0], other.s_term[0]
        year1, year2 = int(self.s_term[1:]), int(other.s_term[1:])
        return year1 > year2 or (
            year1 == year2 and self.seasons.index(c1) > self.seasons.index(c2)
        )

    def __ge__(self, other):
        return self > other or self == other

    def __le__(self, other):
        return self < other or self == other

    def to_datetime(self) -> datetime.datetime:
        c = self.s_term[0]
        year = int(self.s_term[1:])
        month = self.seasons.index(c) * 4 + 1
        day = 1
        return datetime.datetime(year, month, day)