from sqlalchemy import nullslast, asc, desc

from utils.exceptions import ValidationError


def sorting_expression(sort_keys: dict, sorting_option: str):
    sort = sorting_option
    sort_dir = asc
    if sort.startswith("-"):
        sort = sort[1:]
        sort_dir = desc

    valid_options = ", ".join([k for k in sort_keys.keys()])
    if not sort or sort not in valid_options:
        raise ValidationError(f"Invalid sort criterion. Valid options are: {valid_options}.")

    return map(lambda x: nullslast(sort_dir(x)), sort_keys[sort])