"""SQLAlchemy async engine + session。"""
from __future__ import annotations

from collections.abc import AsyncIterator

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

from src.core.config import settings


class Base(DeclarativeBase):
    pass


engine = create_async_engine(
    settings.DATABASE_URL,
    echo=False,
    pool_pre_ping=True,
    pool_size=settings.DB_POOL_SIZE,
    max_overflow=settings.DB_MAX_OVERFLOW,
    pool_timeout=settings.DB_POOL_TIMEOUT,
    pool_recycle=settings.DB_POOL_RECYCLE,
)

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


async def get_db() -> AsyncIterator[AsyncSession]:
    """写路由用: 退出时自动 commit。"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()


async def get_db_read() -> AsyncIterator[AsyncSession]:
    """读路由用: 不 commit(只读)。"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
        finally:
            await session.close()


async def init_db() -> None:
    """验证数据库连接(不建表)。

    生产环境 schema 由 Alembic 管理。
    本地开发/测试需要建表时调用 `create_all()`。
    """
    async with engine.begin() as conn:
        # 只验证连接,不自动建表
        await conn.run_sync(lambda conn: None)


async def create_all() -> None:
    """创建所有表(仅用于本地开发/测试)。"""
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)