from datetime import datetime
from typing import Annotated
from pydantic import PlainSerializer

# SQLite strips tzinfo on read-back, so naive datetimes from DB are actually UTC.
# This serializer appends "Z" so browsers parse them correctly as UTC.
UTCDatetime = Annotated[
    datetime,
    PlainSerializer(
        lambda dt: (dt.isoformat() + "Z") if dt.tzinfo is None else dt.isoformat(),
        return_type=str,
        when_used="json",
    ),
]