"""Util functions for context values."""
from enum import auto, Enum


def get_context_values(values_from_context, possible_values):
    """Transform values from context into string and check them.

    Args:
        values_from_context (str or None): string with comma separator.
        possible_values (list): Return this if values_from_context is None.

    Returns:
        list: A list with values from context.
    Raises:
        ValueError: If values are inappropriate.
    """
    if not values_from_context:
        return possible_values
    values_list = [
        value.strip() for value in values_from_context.split(',')]
    if not set(values_list).issubset(possible_values):
        raise ValueError(
            'This is incorrect format! Please provide '
            'comma-separated list.\n'
            '{} was provided.\n'
            '{} are available.'.format(values_from_context, possible_values)
        )
    return values_list


class Reload(Enum):
    """Enum for values of reload argument."""

    FALSE = auto()
    SOFT = auto()
    TRUE = auto()

    @classmethod
    def possible_values(cls):
        """Return possible values for reload argument."""
        return ['false', 'soft', 'true', 'full', 'none']

    @classmethod
    def from_value(cls, value):
        """Convert str value to Reload.

        Acceptable values are (case-insensitive):
        - 'True', 'Full', -> Reload.FULL
        - 'Soft', -> Reload.SOFT
        - 'None', 'False', '' -> Reload.NONE

        For Reload.SOFT, check if soft_reload is allowed in config_module.
        """
        value = str(value).lower()
        if value in {'true', 'full'}:
            return Reload.TRUE
        elif value == 'soft':
            return Reload.SOFT
        elif value in {'none', 'false', ''}:
            return Reload.FALSE
        else:
            raise ValueError(f'Invalid reload value: {value}')


def strtobool(val):
    """Convert a string representation of truth to bool."""
    if not isinstance(val, str):
        raise ValueError(f'invalid truth value {val!r}')
    val = val.lower()
    if val in ('y', 'yes', 'true', 'on', '1'):
        return True
    elif val in ('n', 'no', 'false', 'off', '0', ''):
        return False
    else:
        raise ValueError(f'invalid truth value {val!r}')