"""Async SQLAlchemy database engine, session factory, and base model."""

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

from app.config import settings


class Base(DeclarativeBase):
    """Declarative base for all SQLAlchemy models."""

    pass


engine = create_async_engine(
    settings.DATABASE_URL,
    echo=(settings.APP_ENV == "development"),
    pool_pre_ping=True,
    pool_size=10,
    max_overflow=20,
)

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


async def get_db() -> AsyncSession:
    """FastAPI dependency that yields an async DB session."""
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db():
    """Create all tables. Used for testing and first-run setup."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


async def drop_db():
    """Drop all tables. Used in test teardown."""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.drop_all)