"""
Database engine and session management.
"""
from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.orm import DeclarativeBase

from app.core.config import settings

engine = create_async_engine(
    settings.database_url_async,
    echo=settings.DEBUG,
    pool_pre_ping=True,
    pool_size=20,
    max_overflow=10,
)

async_session_factory = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
)


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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """
    Dependency that provides a database session.
    Commits on success, rolls back on exception.
    """
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()