"""SQLAlchemy-Basis, Engine und Sitzungen."""

from collections.abc import Iterator
from contextlib import contextmanager
from datetime import UTC, datetime

from sqlalchemy import DateTime, MetaData, create_engine
from sqlalchemy.engine import Engine
from sqlalchemy.orm import DeclarativeBase, Session, sessionmaker

# Einheitliche Namen für Constraints, damit Alembic-Migrationen stabil bleiben
NAMING = {
    "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)
    type_annotation_map = {datetime: DateTime(timezone=True)}


def now() -> datetime:
    return datetime.now(UTC)


class Database:
    def __init__(self, url: str):
        self.engine: Engine = create_engine(url, pool_pre_ping=True)
        self.sessions = sessionmaker(self.engine, expire_on_commit=False)

    @contextmanager
    def session(self) -> Iterator[Session]:
        """Eine Transaktion: commit am Ende, rollback bei Fehler."""
        with self.sessions() as session, session.begin():
            yield session

    def dispose(self) -> None:
        self.engine.dispose()