from datetime import datetime, timedelta
from math import ceil
from dateutil.parser import parse
from workloadmgr.apscheduler.util import convert_to_datetime, timedelta_seconds


class IntervalTrigger(object):
    def __init__(self, interval, start_time, start_date=None):
        if not isinstance(interval, timedelta):
            raise TypeError('interval must be a timedelta')

        self.interval = interval
        self.start_time = start_time
        self.interval_length = timedelta_seconds(self.interval)
        if self.interval_length == 0:
            self.interval = timedelta(seconds=1)
            self.interval_length = 1

        if start_date is None:
            self.start_date = convert_to_datetime(
                parse(datetime.now().strftime("%m/%d/%Y") + " " + self.start_time))
        else:
            self.start_date = convert_to_datetime(
                parse(start_date + " " + self.start_time))

    def get_next_fire_time(self, start_date):
        if start_date < self.start_date:
            return self.start_date

        timediff_seconds = timedelta_seconds(start_date - self.start_date)
        next_interval_num = int(ceil(timediff_seconds / self.interval_length))
        return self.start_date + self.interval * next_interval_num

    def __str__(self):
        return 'interval[%s]' % str(self.interval)

    def __repr__(self):
        return "<%s (interval=%s, start_time=%s, start_date=%s)>" % (
            self.__class__.__name__, repr(
                self.interval), repr(
                self.start_time),
            repr(self.start_date))