"""数据库：SQLite（aiosqlite）+ SQLAlchemy async。"""
from __future__ import annotations

from collections.abc import AsyncGenerator

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

from config import get_settings


class Base(DeclarativeBase):
    pass


_engine = None
_session_factory: async_sessionmaker[AsyncSession] | None = None


def get_engine():
    global _engine, _session_factory
    if _engine is None:
        settings = get_settings()
        db_path = f"{settings.data_dir}/app.db"
        _engine = create_async_engine(f"sqlite+aiosqlite:///{db_path}", echo=False)
        _session_factory = async_sessionmaker(_engine, expire_on_commit=False)
    return _engine


def get_session_factory() -> async_sessionmaker[AsyncSession]:
    get_engine()
    assert _session_factory is not None
    return _session_factory


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


async def init_db() -> None:
    """启动时建表（MVP 不引 Alembic，模型变更删库重建即可）。"""
    import models  # noqa: F401  确保模型注册

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