class AppServiceError(Exception):
    """Base class for service-layer errors."""

    status_code: int = 500
    error_code: str = "APP_SERVICE_ERROR"

    def __init__(self, message: str) -> None:
        super().__init__(message)
        self.message = message


class NotFoundError(AppServiceError):
    status_code = 404
    error_code = "NOT_FOUND"


class BadRequestError(AppServiceError):
    status_code = 400
    error_code = "BAD_REQUEST"


class UnauthorizedError(AppServiceError):
    status_code = 401
    error_code = "UNAUTHORIZED"


class ServiceUnavailableError(AppServiceError):
    status_code = 503
    error_code = "SERVICE_UNAVAILABLE"