import logging
import os

from airflow.models import Variable

logger = logging.getLogger(__name__)

DEV = 'dev'
PROD = 'prod'
QA = 'qa'

ALL_ENVIRONMENTS = (DEV, QA, PROD)


def var(name, default=None):
    """
    Returns value for given variable either from system environments or from airflow Variable

    It detects airflow context by existence of AIRFLOW_HOME environment variable.
    In Airflow UI Variables section, Airflow will automatically hide any values if the variable name contains "secret" or "password"

    :param name: airflow Variable name or os.environ key
    :return:
    """
    assert name
    # detect
    if os.environ.get('AIRFLOW_HOME'):
        value = Variable.get(name, default)
    else:
        value = os.environ.get(name, default)
    return value


def env_default(env, dev, prod, qa=None):
    """
    Returns value for given variable either from system environments or from airflow Variable

    It detects airflow context by existence of AIRFLOW_HOME environment variable.
    In Airflow UI Variables section, Airflow will automatically hide any values if the variable name contains "secret" or "password"

    :param env: name of environment (dev,qa,prod)
    :param dev: default value on DEV environment
    :param prod: default value on PROD environment
    :param qa: default value on QA environment (if omitted then prod value used)
    :return:
    """
    assert env in ALL_ENVIRONMENTS
    if env == DEV:
        return dev
    elif env == QA and qa is not None:
        return qa
    return prod