"""
Database connection and session management using SQLAlchemy with async support.
"""

from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
from sqlalchemy.orm import declarative_base
from app.config import settings

# Create async engine
engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    pool_pre_ping=True,
    pool_size=10,
    max_overflow=20,
)

# Create async session factory
AsyncSessionLocal = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)

# Base class for declarative models
Base = declarative_base()


async def get_db() -> AsyncSession:
    """
    Dependency for FastAPI endpoints to get database session.

    Usage:
        @app.get("/users")
        async def get_users(db: AsyncSession = Depends(get_db)):
            ...
    """
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def init_db():
    """
    Initialize database - create all tables.
    Should be called on application startup.
    """
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


async def close_db():
    """
    Close database connections.
    Should be called on application shutdown.
    """
    await engine.dispose()