"""Declarative base and shared column mixins."""
from datetime import datetime

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

# Explicit naming convention so Alembic autogenerate produces stable, nameable
# constraints (required for reliable downgrades / ALTERs).
NAMING_CONVENTION = {
    "ix": "ix_%(table_name)s_%(column_0_N_name)s",
    "uq": "uq_%(table_name)s_%(column_0_N_name)s",
    "ck": "ck_%(table_name)s_%(constraint_name)s",
    "fk": "fk_%(table_name)s_%(column_0_N_name)s_%(referred_table_name)s",
    "pk": "pk_%(table_name)s",
}


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


class TimestampMixin:
    """created_at / updated_at on every table, in UTC."""

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


class SoftDeleteMixin:
    """Soft delete for business entities (append-only ledgers omit this)."""

    is_deleted: Mapped[bool] = mapped_column(
        Boolean, default=False, server_default="false", nullable=False, index=True
    )
    deleted_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)