"""Neo4j 会话：全局单例 AsyncDriver（内部自带连接池与事务重试）。"""
from neo4j import AsyncGraphDatabase
from config.settings import settings

_driver = None


def client():
    global _driver
    if _driver is None:
        _driver = AsyncGraphDatabase.driver(
            settings.neo4j.uri,
            auth=(settings.neo4j.user, settings.neo4j.password),
            max_connection_pool_size=settings.neo4j.max_connection_pool_size,
            connection_acquisition_timeout=settings.neo4j.connection_acquisition_timeout,
            connection_timeout=settings.neo4j.connection_timeout,
            max_transaction_retry_time=settings.neo4j.max_transaction_retry_time,
        )
    return _driver


async def init_db() -> None:
    client()  # 构造为懒连接，仅建出 driver 单例


async def get_session():
    """每次操作取一个轻量 pool 内 session；execute_read/write 自带事务重试。"""
    async with client().session() as s:
        yield s


async def dispose() -> None:
    global _driver
    if _driver is not None:
        await _driver.close()
        _driver = None


async def check_health() -> None:
    await client().verify_connectivity()