import yaml


class ConfigLoader:
    """
    default_vars = {"var1": "default1", "var2": "default2"}
    required_vars = ["var1", "var3"]
    config_loader = ConfigLoader("config.yaml", default_vars, required_vars)
    config = config_loader.load_config()
    """

    def __init__(self, config_file, default_vars=None, required_vars=None):
        self.config_file = config_file
        self.default_vars = default_vars if default_vars else {}
        self.required_vars = required_vars if required_vars else []
        self.config = {}

    def load_config(self) -> (bool, str | None, str | None):
        with open(self.config_file, 'r') as stream:
            try:
                self.config = yaml.safe_load(stream)
            except yaml.YAMLError as exc:
                return False, None, exc

        if self.config is None:
            # Handle empty file
            self.config = {}

        # Set default variables if they are not present in the config file
        for var, default_value in self.default_vars.items():
            if var not in self.config:
                self.config[var] = default_value

        # Check if required variables are present in the config file
        for var in self.required_vars:
            if var not in self.config:
                return False, None, f'Required variable "{var}" is missing from the config file'

        return True, self.config, None