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from airflow.sensors.base import BaseSensorOperator
from airflow.utils import timezone
from airflow.utils.context import Context
from airflow.utils.weekday import WeekDay


class DayOfWeekSensor(BaseSensorOperator):
    """
    Waits until the first specified day of the week. For example, if the execution
    day of the task is '2018-12-22' (Saturday) and you pass 'FRIDAY', the task will wait
    until next Friday.

    **Example** (with single day): ::

        weekend_check = DayOfWeekSensor(
            task_id='weekend_check',
            week_day='Saturday',
            use_task_execution_day=True,
            dag=dag)

    **Example** (with multiple day using set): ::

        weekend_check = DayOfWeekSensor(
            task_id='weekend_check',
            week_day={'Saturday', 'Sunday'},
            use_task_execution_day=True,
            dag=dag)

    **Example** (with :class:`~airflow.utils.weekday.WeekDay` enum): ::

        # import WeekDay Enum
        from airflow.utils.weekday import WeekDay

        weekend_check = DayOfWeekSensor(
            task_id='weekend_check',
            week_day={WeekDay.SATURDAY, WeekDay.SUNDAY},
            use_task_execution_day=True,
            dag=dag)

    :param week_day: Day of the week to check (full name). Optionally, a set
        of days can also be provided using a set.
        Example values:

            * ``"MONDAY"``,
            * ``{"Saturday", "Sunday"}``
            * ``{WeekDay.TUESDAY}``
            * ``{WeekDay.SATURDAY, WeekDay.SUNDAY}``

    :param use_task_execution_day: If ``True``, uses task's execution day to compare
        with week_day. Execution Date is Useful for backfilling.
        If ``False``, uses system's day of the week. Useful when you
        don't want to run anything on weekdays on the system.
    """

    def __init__(self, *, week_day, use_task_execution_day=False, **kwargs):
        super().__init__(**kwargs)
        self.week_day = week_day
        self.use_task_execution_day = use_task_execution_day
        self._week_day_num = WeekDay.validate_week_day(week_day)

    def poke(self, context: Context):
        self.log.info(
            'Poking until weekday is in %s, Today is %s',
            self.week_day,
            WeekDay(timezone.utcnow().isoweekday()).name,
        )
        if self.use_task_execution_day:
            return context['logical_date'].isoweekday() in self._week_day_num
        else:
            return timezone.utcnow().isoweekday() in self._week_day_num
