import os
import sys
import tomllib
from pathlib import Path
from collections import UserDict

from .exceptions import ConfigLoadError


NODEAGENT_CONFIG_FILE = os.getenv('NODEAGENT_CONFIG_FILE')
NODEAGENT_DEFAULT_CONFIG_FILE = '/etc/node-agent/config.toml'


class ConfigLoader(UserDict):
    def __init__(self, file: Path | None = None):
        if file is None:
            file = NODEAGENT_CONFIG_FILE or NODEAGENT_DEFAULT_CONFIG_FILE
        self.file = Path(file)
        self.data = self._load()

    def _load(self):
        try:
            with open(self.file, 'rb') as config:
                return tomllib.load(config)
                # todo: schema validation
        except (OSError, ValueError) as readerr:
            raise ConfigLoadError('Cannot read config file: %s: %s', (self.file, readerr)) from readerr
        except tomllib.TOMLDecodeError as tomlerr:
            raise ConfigLoadError('Bad TOML syntax in config file: %s: %s', (self.file, tomlerr)) from tomlerr