from collections.abc import AsyncGenerator

from sqlalchemy import text
from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine

from app.config import settings
from app.db.base import Base

engine = create_async_engine(
    settings.sqlalchemy_database_url,
    pool_pre_ping=True,
)

AsyncSessionLocal = async_sessionmaker(
    engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autoflush=False,
    autobegin=False,
)


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    async with AsyncSessionLocal() as session:
        yield session


async def check_database() -> None:
    async with engine.connect() as conn:
        await conn.execute(text("SELECT 1"))


async def init_db_schema() -> None:
    """创建缺失的表（开发/首次部署；生产可改为 Alembic 迁移）。"""
    import app.db.models  # noqa: F401 - register ORM tables on Base.metadata

    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)