"""Redis 会话：内置连接池的 asyncio 客户端单例。"""
import redis.asyncio as aioredis
from redis.backoff import FullJitterBackoff
from redis.retry import Retry

from config.settings import settings

_client: aioredis.Redis | None = None


def client() -> aioredis.Redis:
    global _client
    if _client is None:
        _client = aioredis.Redis(
            host=settings.redis.host,
            port=settings.redis.port,
            db=settings.redis.db,
            password=settings.redis.password,
            socket_connect_timeout=settings.redis.socket_connect_timeout,
            socket_timeout=settings.redis.socket_timeout,
            socket_keepalive=True,          # 长连接保活，防代理/防火墙断连
            retry_on_timeout=True,          # 读超时自动重试，吸收瞬时抖动
            health_check_interval=settings.redis.health_check_interval,
            retry=Retry(FullJitterBackoff(base=1, cap=10), retries=3),
            max_connections=settings.redis.max_connections,
            decode_responses=True,
            protocol=2,                     # redis-py 8 默认 RESP3（HELLO 3），Redis < 6.0 不支持
        )
    return _client


async def init_db() -> None:
    await client()  # 构造是同步懒加载，启动时只需确保单例被建出


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


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