"""Declarative base and shared column mixins."""

from __future__ import annotations

import datetime as dt

from sqlalchemy import DateTime, MetaData, func
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

# Deterministic constraint names. This has to be in place *before* the first
# migration: MySQL will otherwise invent its own names, and Alembic autogenerate
# then produces diffs referencing constraints it cannot reliably drop.
NAMING_CONVENTION = {
    "ix": "ix_%(column_0_label)s",
    "uq": "uq_%(table_name)s_%(column_0_name)s",
    "ck": "ck_%(table_name)s_%(constraint_name)s",
    "fk": "fk_%(table_name)s_%(column_0_name)s_%(referred_table_name)s",
    "pk": "pk_%(table_name)s",
}


class Base(DeclarativeBase):
    metadata = MetaData(naming_convention=NAMING_CONVENTION)


class TimestampMixin:
    """Server-side created/updated timestamps.

    Defaults are rendered by MySQL rather than Python so rows written outside
    the application (migrations, manual SQL) are stamped consistently.
    """

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