"""Get feature flags on backend."""

from oto import status as response_code
from owsfeatures import features
from owsrequest import request

from masters_registry import config
from masters_registry.constant import api_const
from masters_registry.constant import field_const


class OwsFeaturesError(Exception):
    """Raised when we failed to get features."""

    def __str__(self):
        return 'Failed to load features from ows-features.'


def _is_feature_enabled(
        feature_name, orchard_user_id=None, daemon=False, correlation_id=None):
    """Wrapper to handle both flask and daemon modes.

    Currently ows-features support only Flask apps. If we want to check
        for feature from something like Celery process, we need to send
        request directly to ows-features API.

    Args:
        feature_name (str): Name of feature to check
        orchard_user_id (str): Id of user to check features for
        daemon (bool): Whether feature requested from daemon process
        correlation_id (str): correlation id for logs, optional

    Returns:
        bool: Whether feature flag enabled
    """

    if not daemon:
        return features.is_feature_enabled(feature_name)
    if orchard_user_id:
        prefix = orchard_user_id.split(':')[0]
        if prefix not in field_const.USER_ID_PREFIXES:
            orchard_user_id = '{prefix}{user_id}'.format(
                prefix=field_const.OA_USER_ID_PREFIX, user_id=orchard_user_id)

    user_features_dict = _get_user_features(orchard_user_id, correlation_id)
    return user_features_dict.get(feature_name) == 'enabled'


def _get_user_features(orchard_user_id=None, correlation_id=None):
    """Fallback function for processes that don't use Flask, i.e. Celery.

    Args:
        orchard_user_id (str): identifier for user, e.g. alw:1234
        correlation_id (str): correlation id for logs, optional

    Returns:
        dict: features for given user
    """

    if orchard_user_id:
        url = '/features/user/{user_id}'.format(user_id=orchard_user_id)
    else:
        url = '/features'
    request_args = {
        'application': config.SERVICE_NAME,
        'environment': config.ENVIRONMENT,
        'method': 'GET',
        'service_name': api_const.OWS_FEATURES,
        'path': url,
        'correlation_id': correlation_id
    }

    features_response = request.process(**request_args)
    error_message = (
        "Can't fetch features for user {0}. Response content: {1}"
        "Headers: {2}")
    if features_response.status_code != response_code.OK:
        error_message = error_message.format(
            orchard_user_id, features_response.content,
            features_response.headers)
        raise OwsFeaturesError(error_message)

    features_dict = features_response.json()
    return features_dict