from __future__ import annotations

import time
from collections import OrderedDict
from typing import Any

SENT_CACHE_MAX = 500
SENT_CACHE_TTL_S = 600
BOT_CACHE_TTL_S = 600
REACTION_BOT_CACHE_TTL_S = 600
USER_CACHE_TTL_S = 300
CHANNEL_CACHE_TTL_S = 300
DM_CHANNEL_CACHE_TTL_S = 300
DM_CHANNEL_CACHE_MAX = 200


class TTLCache:
    """通用 TTL 缓存基类。"""

    def __init__(self, ttl_s: int = 300, max_size: int = 1000):
        self._cache: dict[str, tuple[float, object]] = {}
        self._ttl_s = ttl_s
        self._max_size = max_size

    def get(self, key: str) -> object | None:
        entry = self._cache.get(key)
        if entry is None:
            return None
        ts, value = entry
        if time.monotonic() - ts > self._ttl_s:
            del self._cache[key]
            return None
        return value

    def set(self, key: str, value: object) -> None:
        now = time.monotonic()
        self._cache[key] = (now, value)
        self._evict(now)

    def delete(self, key: str) -> bool:
        return self._cache.pop(key, None) is not None

    def _evict(self, now: float) -> None:
        cutoff = now - self._ttl_s
        expired = [k for k, (ts, _) in self._cache.items() if ts < cutoff]
        for k in expired:
            del self._cache[k]
        if len(self._cache) > self._max_size:
            sorted_keys = sorted(self._cache, key=lambda k: self._cache[k][0])
            for k in sorted_keys[: len(self._cache) - self._max_size]:
                del self._cache[k]

    def clear(self) -> None:
        self._cache.clear()


class LRUCache:
    """LRU 缓存，适合 DM channel ID 缓存。"""

    def __init__(self, max_size: int = DM_CHANNEL_CACHE_MAX, ttl_s: int = DM_CHANNEL_CACHE_TTL_S):
        self._cache: OrderedDict[str, tuple[float, Any]] = OrderedDict()
        self._max_size = max_size
        self._ttl_s = ttl_s

    def get(self, key: str) -> Any | None:
        entry = self._cache.get(key)
        if entry is None:
            return None
        ts, value = entry
        if time.monotonic() - ts > self._ttl_s:
            del self._cache[key]
            return None
        self._cache.move_to_end(key)
        return value

    def set(self, key: str, value: Any) -> None:
        now = time.monotonic()
        if key in self._cache:
            self._cache.move_to_end(key)
        self._cache[key] = (now, value)
        self._evict_expired(now)
        while len(self._cache) > self._max_size:
            self._cache.popitem(last=False)

    def _evict_expired(self, now: float) -> None:
        cutoff = now - self._ttl_s
        expired = [k for k, (ts, _) in self._cache.items() if ts < cutoff]
        for k in expired:
            del self._cache[k]

    def clear(self) -> None:
        self._cache.clear()

    def size(self) -> int:
        return len(self._cache)


class MattermostChannelCache:
    """Mattermost 渠道缓存集合。

    - botUserCache: bot 用户信息缓存 (TTL 10min)
    - userByNameCache: 用户名 → 用户ID 缓存
    - channelByNameCache: 频道名 → 频道ID 缓存
    - dmChannelCache: DM 频道 ID 缓存 (LRU)
    """

    def __init__(self):
        self.bot_user: TTLCache = TTLCache(ttl_s=BOT_CACHE_TTL_S, max_size=1)
        self.user_by_name: TTLCache = TTLCache(ttl_s=USER_CACHE_TTL_S, max_size=500)
        self.channel_by_name: TTLCache = TTLCache(ttl_s=CHANNEL_CACHE_TTL_S, max_size=500)
        self.dm_channel: LRUCache = LRUCache(max_size=DM_CHANNEL_CACHE_MAX, ttl_s=DM_CHANNEL_CACHE_TTL_S)

    def clear(self) -> None:
        self.bot_user.clear()
        self.user_by_name.clear()
        self.channel_by_name.clear()
        self.dm_channel.clear()

    def stats(self) -> dict[str, int]:
        return {
            "bot_user": 1 if self.bot_user.get("_cached") else 0,
            "user_by_name": len(self.user_by_name._cache),
            "channel_by_name": len(self.channel_by_name._cache),
            "dm_channel": self.dm_channel.size(),
        }


class SentMessageCache:
    """已发送消息缓存 — 支持自动追加 thread_ts。"""

    def __init__(self, max_size: int = SENT_CACHE_MAX, ttl_s: int = SENT_CACHE_TTL_S):
        self._cache: dict[str, dict] = {}
        self._max_size = max_size
        self._ttl_s = ttl_s

    def record(
        self,
        msg_id: str,
        chat_id: str,
        channel_id: str = "",
        thread_id: str = "",
        user_id: str = "",
    ) -> None:
        now = time.monotonic()
        self._cache[msg_id] = {
            "msg_id": msg_id,
            "chat_id": chat_id,
            "channel_id": channel_id,
            "thread_id": thread_id,
            "user_id": user_id,
            "recorded_at": now,
        }
        self._evict_if_needed(now)

    def get(self, msg_id: str) -> dict | None:
        entry = self._cache.get(msg_id)
        if entry is None:
            return None
        if time.monotonic() - entry["recorded_at"] > self._ttl_s:
            del self._cache[msg_id]
            return None
        return entry

    def get_thread_id(self, msg_id: str) -> str | None:
        entry = self.get(msg_id)
        if entry:
            return entry.get("thread_id") or None
        return None

    def clear(self) -> None:
        self._cache.clear()

    def size(self) -> int:
        return len(self._cache)

    def _evict_if_needed(self, now: float) -> None:
        cutoff = now - self._ttl_s
        expired = [k for k, v in self._cache.items() if v["recorded_at"] < cutoff]
        for k in expired:
            del self._cache[k]

        if len(self._cache) > self._max_size:
            sorted_entries = sorted(
                self._cache.items(),
                key=lambda item: item[1]["recorded_at"],
            )
            excess = len(self._cache) - self._max_size
            for k, _ in sorted_entries[:excess]:
                del self._cache[k]