"""Redis 读缓存（可选基础设施）。

- REDIS_URL 留空、连接失败或超时：所有操作静默退化为「无缓存」，接口照常直查数据库，
  且本进程内禁用重试（避免每个请求都陪跑一次连接超时）。
- 失效策略：TTL 自然过期 + 版本号（INCR）作废。自选股增删等写操作只 INCR 版本 key，
  旧缓存 key 里带着旧版本号，无需 SCAN 批量删除。
- 只缓存「读多写少、可容忍短暂陈旧」的聚合数据（股票列表、筛选项等）；
  K线/回测等口径敏感数据不走这里。
"""
from __future__ import annotations

import hashlib
import json
from typing import Any

import redis.asyncio as aioredis

from .config import settings

_pool: aioredis.ConnectionPool | None = None
_disabled = False  # 一次失败后本进程禁用（Redis 属加速件，坏了不能拖慢接口）


def _client() -> aioredis.Redis | None:
    global _pool, _disabled
    if not settings.redis_url or _disabled:
        return None
    if _pool is None:
        _pool = aioredis.ConnectionPool.from_url(
            settings.redis_url,
            decode_responses=True,
            socket_connect_timeout=1.0,
            socket_timeout=1.0,
            health_check_interval=60,
            max_connections=32,
        )
    return aioredis.Redis(connection_pool=_pool)


def _bail() -> None:
    global _disabled
    _disabled = True


def digest(*parts: Any) -> str:
    """参数指纹（拼接后 md5，仅用于拼缓存 key，非安全用途）"""
    raw = "\x1f".join(repr(p) for p in parts)
    return hashlib.md5(raw.encode()).hexdigest()  # noqa: S324


async def cache_get(key: str) -> Any | None:
    c = _client()
    if c is None:
        return None
    try:
        raw = await c.get(key)
        return json.loads(raw) if raw is not None else None
    except Exception:  # noqa: BLE001 —— 缓存层任何故障都不影响主流程
        _bail()
        return None


async def cache_set(key: str, value: Any, ttl: int) -> None:
    c = _client()
    if c is None:
        return
    try:
        await c.set(key, json.dumps(value, ensure_ascii=False), ex=max(1, ttl))
    except Exception:  # noqa: BLE001
        _bail()


async def get_version(name: str) -> int:
    """读版本号（缺省 0）。版本号参与缓存 key：INCR 后旧 key 全部失效。"""
    c = _client()
    if c is None:
        return 0
    try:
        v = await c.get(f"ver:{name}")
        return int(v) if v is not None else 0
    except Exception:  # noqa: BLE001
        _bail()
        return 0


async def bump_version(name: str) -> None:
    c = _client()
    if c is None:
        return
    try:
        await c.incr(f"ver:{name}")
    except Exception:  # noqa: BLE001
        _bail()


async def aclose() -> None:
    """进程退出时释放连接池（由 main.lifespan 调用）。"""
    global _pool
    if _pool is not None:
        try:
            await _pool.disconnect()
        except Exception:  # noqa: BLE001
            pass
        _pool = None