"""Authorisation utilities."""
from functools import wraps

from flask import flash, redirect

from uploader import session

def require_login(function):
    """Check that the user is logged in before executing `func`."""
    @wraps(function)
    def __is_session_valid__(*args, **kwargs):
        """Check that the user is logged in and their token is valid."""
        def __clear_session__(_no_token):
            session.clear_session_info()
            flash("You need to be logged in.", "alert-danger")
            return redirect("/")

        return session.user_token().either(
            __clear_session__,
            lambda token: function(*args, **kwargs))
    return __is_session_valid__