"""Dimension Refresh flow configuration."""

from importlib.resources import files
import logging
import os
import re

from garcon.param import StaticParam
import yaml


logger = logging.getLogger('dim_refresh_etl')

YAML_ENVVAR_RGX = re.compile(r'^ENV\[(.*)\]$')


def _parse_envvar(token):
    """Look if YAML scalar contains the "ENV[foo]".

    Args:
        token: a YAML scalar.
    """
    return YAML_ENVVAR_RGX.match(token).groups()[0]


def _yaml_envvar_constructor(loader, node):
    """Get YAML environment variables with constructor.

    Looks to see if YAML node contains ENV keyword and, if so, will replace
    it with the os environment var's value.

    Args:
        loader: a YAML Loader.
        node: a YAML Node.
    """
    token = loader.construct_scalar(node)
    env_var = _parse_envvar(token)
    if env_var in os.environ:
        return os.environ[env_var]
    return None


yaml.add_implicit_resolver('!env_var', YAML_ENVVAR_RGX)
yaml.add_constructor('!env_var', _yaml_envvar_constructor)


def getconf(config_name, ext='yml', package=None):
    """Convert a config file into a dictionary of Garcon StaticParms.

    Note will replace YAML scalars whose value is ENV[foo] with the value in
    stored by os environment var foo.

    Args:
        config_name (str): name of the YAML config file minus extension.
        ext (str): extension of the YAML config file.
        package (str): package where config file is located
            (defaults to __name__).

    Returns:
        Object: a Python object representing the YAML config.
    """
    if not package:
        package = __name__

    filename = '.'.join((config_name, ext))
    logger.debug('loading config file %s', filename)
    resource = files(package).joinpath(filename)
    with resource.open('rb') as conf_stream:
        return yaml.load(conf_stream, Loader=yaml.FullLoader)


def get_static_dict(config_name, sub_key=None):
    """Convert values in config file into a dictionary of Garcon StaticParms.

    Args:
        config_name (str): name of the YAML config file.
        sub_key (str): if passed only converts this config var in the file
            to a dictionary of Garcon StaticParms.

    Returns:
        dict: dictionary of StaticParam vars.
    """
    if sub_key:
        config_dict = getconf(config_name)[sub_key]
    else:
        config_dict = getconf(config_name)
    static_param_dict(config_dict)
    return config_dict


def static_param_dict(config_dict):
    """Convert dictionary values into Garcon StaticParams.

    Args:
        config_dict (dict): dictionary.

    Returns:
        dict: dictionary now has each value as a StaticParam.
    """
    for key, value in config_dict.items():
        config_dict[key] = StaticParam(value)