"""
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.

Author(s): anatol.ulrich@basebox.io

Copyright (c) 2023 basebox GmbH. All rights reserved.
"""


# stdlib imports
from os import environ
from functools import wraps

# dependencies imports
try:
    import tomllib
except ImportError:
    import tomli as tomllib
import logging

# app imports
import consts

logger = logging.getLogger(consts.LOG_ROOT)


def load(file):
    """
    Load configuration from toml and add to environment.
    Skip anything already present there.
    Configuration key names are converted according to the module documentation.
    """

    if file is None:
        logger.debug('no config file provided.')
    else:
        logger.debug('loading config')
        with open(file, 'rb') as handle:
            config = tomllib.load(handle)
        for section, vals in config.items():
            for key, val in vals.items():
                effective_key = f'{section.upper()}_{key.upper()}'
                if effective_key in environ:
                    logger.warning(
                        '%s already exists in os environment, skipping', effective_key)
                else:
                    environ[effective_key] = str(val)
                logger.debug('config/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 values
    """
    @wraps(f)
    def decorated(*args, **kwargs):
        res = f(*args, **kwargs)
        logger.debug('config/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` or `False`.
    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)