import os
from pathlib import Path
from typing import IO, Optional, Union

import pydantic
from ruamel import yaml


class DatabaseConfiguration(pydantic.BaseModel):
    '''Database configuration'''

    url: str = 'sqlite:///lycodon.db'
    '''Database connection URL'''


class Configuration(pydantic.BaseModel):
    '''Application configuration'''

    database: DatabaseConfiguration = DatabaseConfiguration()
    '''Database configuration'''

    @classmethod
    def load(cls, path: Optional[Union[Path, str]] = None) -> 'Configuration':
        '''Load configuration from the specified file

        :param path: Path to the configuration file
        '''

        if path is None:
            path = Path(os.environ.get('LYCODON_CONFIG', 'config.yml'))
        elif not isinstance(path, Path):
            path = Path(path)
        with path.open('r', encoding='utf-8') as f:
            return cls.from_file(f)

    @classmethod
    def from_file(cls, f: IO[str]) -> 'Configuration':
        '''Load configuration from an open file buffer

        :param f: Open readable file object
        '''

        values = yaml.safe_load(f) or {}
        return cls.parse_obj(values)