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from airflow.exceptions import AirflowException
from airflow.ti_deps.deps.base_ti_dep import BaseTIDep
from airflow.utils.session import provide_session


class ValidStateDep(BaseTIDep):
    """
    Ensures that the task instance's state is in a given set of valid states.

    :param valid_states: A list of valid states that a task instance can have to meet
        this dependency.
    :return: whether or not the task instance's state is valid
    """

    NAME = "Task Instance State"
    IGNORABLE = True

    def __init__(self, valid_states):
        super().__init__()

        if not valid_states:
            raise AirflowException('ValidStatesDep received an empty set of valid states.')
        self._valid_states = valid_states

    def __eq__(self, other):
        return isinstance(self, type(other)) and self._valid_states == other._valid_states

    def __hash__(self):
        return hash((type(self), tuple(self._valid_states)))

    @provide_session
    def _get_dep_statuses(self, ti, session, dep_context):
        if dep_context.ignore_ti_state:
            yield self._passing_status(reason="Context specified that state should be ignored.")
            return

        if ti.state in self._valid_states:
            yield self._passing_status(reason=f"Task state {ti.state} was valid.")
            return

        yield self._failing_status(reason=f"Task is in the '{ti.state}' state.")
