"""
Application configuration

values can be configured in the OS environment via KEY_NAME=...
or in a toml file using 

[section]
foo = ...
bar_baz = ...

in the latter case, the section and name are uppercased and joined with `_`,
then inserted into the OS environment (in this case, resulting in 
SECTION_FOO=... and SECTION_BAR_BAZ=... ). 
The OS environment takes precedence - if a key is found in both env and config,
the config setting will be ignored.
"""
import tomllib
import logging
from os import environ
from functools import wraps

import consts

logger = logging.getLogger(consts.LOG_ROOT)


def load(file):
    """
    Load configuration from toml and add to environment
    """

    if file is None:
        logger.debug('no config file provided.')
    else:
        logger.debug('loading config')
        with open(file, 'rb') as fh:
            config = tomllib.load(fh)
            for k, v in config.items():
                for k_inner, v_inner in v.items():
                    effective_key = f'{k.upper()}_{k_inner.upper()}'
                    if effective_key in environ:
                        logger.warning(
                            '%s already exists in os environment, skipping', effective_key)
                    else:
                        environ[effective_key] = str(v_inner)
                    logger.debug('raw: %s = %s', effective_key,
                                 environ[effective_key])


def env(key, default=None):
    """
    retrieve a key from the OS environment.
    throws `KeyError` when the key is not found and no default fallback is provided.
    """
    if default is None:
        return environ[key]
    return environ.get(key, default=default)


def logged(f):
    """
    logging wrapper for resolved configuration settings
    """
    @wraps(f)
    def decorated(*args, **kwargs):
        res = f(*args, **kwargs)
        logger.debug('resolved: %s = %s', args[0], res)
        return res
    return decorated


@logged
def int_val(key, default=None):
    """
    retrieve configuration value as int
    """

    return int(env(key, default=default))


def strtobool(val):
    """Convert a string representation of truth to true (1) or false (0).
    True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
    are 'n', 'no', 'f', 'false', 'off', and '0'.  Raises ValueError if
    'val' is anything else.
    """
    val = val.lower()
    if val in ("y", "yes", "t", "true", "on", "1"):
        return True
    elif val in ("n", "no", "f", "false", "off", "0"):
        return False
    else:
        raise ValueError(f'Invalid bool string: {val}')


@logged
def bool_val(key, default=None):
    """
    retrieve configuration value as bool
    """
    return strtobool(env(key, default=default))


@logged
def str_val(key, default=None):
    """
    retrieve configuration value as bool
    """
    return env(key, default=default)