"""
Database engine, session factory, and declarative base.
"""

from typing import AsyncGenerator

from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import sessionmaker, declarative_base

from ..config import shared_settings

_engine_kwargs: dict = {"echo": False}
if "sqlite" not in shared_settings.DATABASE_URL:
    _engine_kwargs.update(pool_size=20, max_overflow=30, pool_pre_ping=True)

engine = create_async_engine(shared_settings.DATABASE_URL, **_engine_kwargs)

AsyncSessionLocal = sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
)

Base = declarative_base()


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """Dependency that yields an async database session."""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()