"""数据库会话与引擎管理。"""

from __future__ import annotations

from collections.abc import AsyncGenerator

from sqlalchemy.ext.asyncio import (
    AsyncEngine,
    AsyncSession,
    async_sessionmaker,
    create_async_engine,
)

from .core.config import settings

DATABASE_URL = settings.database_url


def _is_sqlite() -> bool:
    return DATABASE_URL.lower().startswith("sqlite")


engine: AsyncEngine = create_async_engine(
    DATABASE_URL,
    echo=settings.debug,
    future=True,
    pool_pre_ping=not _is_sqlite(),
)

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


async def get_db() -> AsyncGenerator[AsyncSession, None]:
    """FastAPI 依赖：提供数据库会话。"""
    async with AsyncSessionLocal() as session:
        yield session