import yaml
from pathlib import Path


class BadConfig(Exception):
    """Raised when the configuration is incorrect"""


class Configuration:
    """Parses the configuration file, and caches it.

    The configuration is a YAML file.
    """

    BASE_CONFIG_PATH = Path.home() / "config.yml"

    def __init__(self):
        try:
            with self.BASE_CONFIG_PATH.open("r") as handle:
                self.raw = yaml.safe_load(handle)
        except yaml.YAMLError as exn:
            raise BadConfig("Cannot parse yaml") from exn
        except FileNotFoundError as exn:
            raise BadConfig("Configuration file not found") from exn
        except PermissionError as exn:
            raise BadConfig("Configuration file not readable") from exn
        self._healthcheck()

    def _healthcheck(self):
        """Checks that the configuration is ok"""
        if "fifo_hooks" not in self.raw:
            raise BadConfig("No `fifo_hooks`")
        for hook, data in self.raw["fifo_hooks"].items():
            for mandatory in ("secret", "fifo_path"):
                if mandatory not in data:
                    raise BadConfig("Fifo hook {}: no `{}`".format(hook, mandatory))