from datetime import datetime, timedelta


class DateIterator:

    def __init__(self, from_date: datetime, to_date: datetime, interval: timedelta, closed: bool = True):
        assert (from_date < to_date), 'to_date must be greater than from_date'

        self.from_date = from_date
        self.to_date = to_date
        self.interval = interval
        self.closed = closed

        self.total_times = None
        self.current_position = None
        self._init_iterator()

    def _init_iterator(self):
        self._calculate_total_times()
        self.current_position = 0

    def _calculate_total_times(self):
        self.total_times = (self.to_date - self.from_date) / self.interval
        is_exact_fit = self.total_times.is_integer()
        if not is_exact_fit and self.closed:
            self.total_times += 1
        self.total_times = int(self.total_times)

    def __iter__(self):
        self._init_iterator()
        return self

    def __next__(self):
        if self.current_position >= self.total_times:
            raise StopIteration

        interval_start_date = self.from_date + self.interval * self.current_position
        interval_end_date = interval_start_date + self.interval
        self.current_position += 1

        return interval_start_date, interval_end_date