"""SQLAlchemy 2.0 async base and session factory."""
from datetime import datetime, timezone
from uuid import uuid4

from sqlalchemy import DateTime, func
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column


class Base(DeclarativeBase):
    """Base class for all models."""

    pass


class TimestampMixin:
    """Adds created_at and updated_at columns."""

    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        server_default=func.now(),
        nullable=False,
    )
    updated_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True),
        server_default=func.now(),
        onupdate=func.now(),
        nullable=False,
    )


class UUIDMixin:
    """Adds UUID primary key."""

    id: Mapped[str] = mapped_column(
        UUID(as_uuid=True),
        primary_key=True,
        default=uuid4,
        index=True,
    )


def utc_now() -> datetime:
    """Return timezone-aware UTC now."""
    return datetime.now(timezone.utc)