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from airflow.sensors.base_sensor_operator import BaseSensorOperator
from airflow.utils import timezone
from airflow.utils.decorators import apply_defaults


class TimeDeltaSensor(BaseSensorOperator):
    """
    Waits for a timedelta after the task's execution_date + schedule_interval.
    In Airflow, the daily task stamped with ``execution_date``
    2016-01-01 can only start running on 2016-01-02. The timedelta here
    represents the time after the execution period has closed.

    :param delta: time length to wait after execution_date before succeeding
    :type delta: datetime.timedelta
    """

    @apply_defaults
    def __init__(self, delta, *args, **kwargs):
        super(TimeDeltaSensor, self).__init__(*args, **kwargs)
        self.delta = delta

    def poke(self, context):
        dag = context['dag']
        target_dttm = dag.following_schedule(context['execution_date'])
        target_dttm += self.delta
        self.log.info('Checking if the time (%s) has come', target_dttm)
        return timezone.utcnow() > target_dttm