# -*- coding: utf-8 -*-
"""看板聚合结果的内存 TTL 缓存。

缓存键包含数据库路径和数据版本；版本存放在 ``kv``（``cache:v:<group>``），
因此同一个进程内的调度任务和 Web 线程都会看到一致的失效，跨进程的 CLI
导入也可以通过提升版本让旧缓存失效。
"""

from __future__ import annotations

import threading
import time
from typing import Any, Callable, Hashable

TTL_VIDEOS = 3600
TTL_FANS = 86400


class TTLCache:
    def __init__(self, *, clock: Callable[[], float] = time.time, max_items: int = 256) -> None:
        self._clock = clock
        self._max_items = max(16, int(max_items))
        self._lock = threading.RLock()
        self._items: dict[Hashable, tuple[float, Any]] = {}

    def get(self, key: Hashable) -> Any | None:
        with self._lock:
            entry = self._items.get(key)
            if entry is None:
                return None
            expires_at, value = entry
            if expires_at <= self._clock():
                self._items.pop(key, None)
                return None
            return value

    def set(self, key: Hashable, ttl: float, value: Any) -> None:
        with self._lock:
            now = self._clock()
            self._items[key] = (now + float(ttl), value)
            if len(self._items) > self._max_items:
                expired = [k for k, (exp, _) in self._items.items() if exp <= now]
                for item in expired:
                    self._items.pop(item, None)
                if len(self._items) > self._max_items:
                    oldest = sorted(self._items.items(), key=lambda kv: kv[1][0])
                    for item, _ in oldest[: len(self._items) - self._max_items]:
                        self._items.pop(item, None)

    def clear(self) -> None:
        with self._lock:
            self._items.clear()

    def __len__(self) -> int:
        with self._lock:
            return len(self._items)


DASHBOARD_CACHE = TTLCache()


def build_cache_key(
    scope: str,
    group: str,
    version: int,
    params: dict[str, Any] | None = None,
) -> tuple[Any, ...]:
    frozen = tuple(sorted((str(key), str(value)) for key, value in (params or {}).items()))
    return (scope, group, int(version), frozen)