"""Time helpers for API serialization."""

from __future__ import annotations

from datetime import UTC, datetime


def ensure_utc(value: datetime | None) -> datetime | None:
    if value is None:
        return None
    if value.tzinfo is None:
        return value.replace(tzinfo=UTC)
    return value.astimezone(UTC)


def to_iso8601_utc(value: datetime | None) -> str | None:
    normalized = ensure_utc(value)
    if normalized is None:
        return None
    return normalized.isoformat().replace("+00:00", "Z")