"""多渠道网关 Bot 循环防护。"""

from __future__ import annotations

from collections import OrderedDict, deque
from typing import TYPE_CHECKING

from yuxi.channel.constants import InboundRejectionReason

from .policy import SecurityCheckResult

if TYPE_CHECKING:
    from .registry import SecurityContext


class BotLoopDetector:
    """按 sender_id 维护近期 bot 消息比例，避免全局误杀。

    使用 OrderedDict 实现 LRU 淘汰，当跟踪的 sender 数量超过
    ``max_senders`` 时自动移除最久未活跃的条目，防止内存无限增长。
    """

    name = "bot_loop"
    default_priority = 300

    def __init__(self, window_size: int = 10, max_bot_replies: int = 3, max_senders: int = 10000):
        self.window_size = window_size
        self.max_bot_replies = max_bot_replies
        self.max_senders = max_senders
        self._history: OrderedDict[str, deque[bool]] = OrderedDict()

    async def check(self, ctx: SecurityContext) -> SecurityCheckResult | None:
        """SecurityChecker 协议入口。"""
        actor_id = ctx.resolved_sender_id or ctx.inbound.sender_id or ctx.inbound.peer_id or ""
        is_bot = False
        if isinstance(ctx.inbound.raw_event, dict):
            is_bot = bool(ctx.inbound.raw_event.get("is_bot", False))

        if self.is_allowed(actor_id, is_bot):
            return None
        return SecurityCheckResult(
            allowed=False,
            reason=InboundRejectionReason.BOT_LOOP_DETECTED,
        )

    def is_allowed(self, sender_id: str, is_bot: bool) -> bool:
        """原有 check(sender_id, is_bot) 逻辑，改名以避免覆盖协议方法。"""
        if sender_id in self._history:
            self._history.move_to_end(sender_id)
        history = self._history.setdefault(sender_id, deque(maxlen=self.window_size))
        history.append(is_bot)

        # LRU 淘汰：超出上限时移除最久未活跃的条目
        while len(self._history) > self.max_senders:
            self._history.popitem(last=False)

        recent_bot_count = sum(history)
        return recent_bot_count <= self.max_bot_replies