from datetime import datetime, timezone
from typing import Annotated

from pydantic import BaseModel, ConfigDict, PlainSerializer


def _serialize_utc(dt: datetime) -> str:
    """All DB datetimes are naive UTC; emit RFC3339 with Z so browsers parse
    them into the user's local timezone."""
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt.isoformat().replace("+00:00", "Z")


UTCDateTime = Annotated[datetime, PlainSerializer(_serialize_utc, return_type=str)]


class AppModel(BaseModel):
    model_config = ConfigDict(from_attributes=True)