from contextlib import asynccontextmanager
from typing import AsyncGenerator
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
from sqlalchemy.pool import NullPool

from Backend.core.config import settings

database_url = settings.database_url.replace("postgresql://", "postgresql+asyncpg://")

engine = create_async_engine(
    database_url,
    poolclass=NullPool,
    echo=False,
    connect_args={
        "statement_cache_size": 0,
        "prepared_statement_cache_size": 0,
    },
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise


@asynccontextmanager
async def get_db_context() -> AsyncGenerator[AsyncSession, None]:
    async with async_session_factory() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise


async def init_db() -> None:
    from Backend.database.models import Base
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)


async def close_db() -> None:
    await engine.dispose()