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from airflow.exceptions import AirflowException
from airflow.providers.amazon.aws.hooks.sagemaker import SageMakerHook
from airflow.sensors.base_sensor_operator import BaseSensorOperator
from airflow.utils.decorators import apply_defaults


class SageMakerBaseSensor(BaseSensorOperator):
    """
    Contains general sensor behavior for SageMaker.
    Subclasses should implement get_sagemaker_response()
    and state_from_response() methods.
    Subclasses should also implement NON_TERMINAL_STATES and FAILED_STATE methods.
    """
    ui_color = '#ededed'

    @apply_defaults
    def __init__(
            self,
            aws_conn_id='aws_default',
            *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.aws_conn_id = aws_conn_id
        self.hook = None

    def get_hook(self):
        """Get SageMakerHook"""
        if not self.hook:
            self.hook = SageMakerHook(aws_conn_id=self.aws_conn_id)
        return self.hook

    def poke(self, context):
        response = self.get_sagemaker_response()

        if not response['ResponseMetadata']['HTTPStatusCode'] == 200:
            self.log.info('Bad HTTP response: %s', response)
            return False

        state = self.state_from_response(response)

        self.log.info('Job currently %s', state)

        if state in self.non_terminal_states():
            return False

        if state in self.failed_states():
            failed_reason = self.get_failed_reason_from_response(response)
            raise AirflowException('Sagemaker job failed for the following reason: %s'
                                   % failed_reason)
        return True

    def non_terminal_states(self):
        """Placeholder for returning states with should not terminate."""
        raise NotImplementedError('Please implement non_terminal_states() in subclass')

    def failed_states(self):
        """Placeholder for returning states with are considered failed."""
        raise NotImplementedError('Please implement failed_states() in subclass')

    def get_sagemaker_response(self):
        """Placeholder for checking status of a SageMaker task."""
        raise NotImplementedError('Please implement get_sagemaker_response() in subclass')

    def get_failed_reason_from_response(self, response):  # pylint: disable=unused-argument
        """Placeholder for extracting the reason for failure from an AWS response."""
        return 'Unknown'

    def state_from_response(self, response):
        """Placeholder for extracting the state from an AWS response."""
        raise NotImplementedError('Please implement state_from_response() in subclass')
