from datetime import date


DEFAULT_WORKING_DAYS = (0, 1, 2, 3, 4)


def normalize_working_days(days: list[int] | set[int] | tuple[int, ...]) -> list[int]:
    normalized = sorted({int(day) for day in days if 0 <= int(day) <= 6})
    if not normalized:
        return list(DEFAULT_WORKING_DAYS)
    return normalized


def serialize_working_days(days: list[int] | set[int] | tuple[int, ...]) -> str:
    return ",".join(str(day) for day in normalize_working_days(days))


def parse_working_days_csv(value: str | None) -> set[int]:
    if not value:
        return set(DEFAULT_WORKING_DAYS)

    parsed: list[int] = []
    for part in value.split(","):
        item = part.strip()
        if not item:
            continue
        try:
            parsed.append(int(item))
        except ValueError:
            continue

    normalized = normalize_working_days(parsed)
    return set(normalized)


def is_workday(day: date, relevant_weekdays: set[int]) -> bool:
    return day.weekday() in relevant_weekdays