"""客服对话中的重复兴趣主题计数。"""

from __future__ import annotations

import hashlib
from datetime import datetime


class InterestTopicTracker:
    """使用 Redis 统计客户当天对同一主题的重复关注次数。"""

    KEY_PREFIX = "customer:memory:interest"
    WINDOW_SECONDS = 24 * 60 * 60
    DEFAULT_THRESHOLD = 3

    def __init__(self, redis, *, threshold: int = DEFAULT_THRESHOLD):
        self.redis = redis
        self.threshold = threshold

    @classmethod
    def key(cls, customer_id: int, tag: str, now: datetime | None = None) -> str:
        """生成按客户、自然日和主题隔离的 Redis 计数 Key。"""
        day = (now or datetime.now()).strftime("%Y%m%d")
        digest = hashlib.sha256(tag.strip().lower().encode("utf-8")).hexdigest()[:16]
        return f"{cls.KEY_PREFIX}:{customer_id}:{day}:{digest}"

    async def record(self, customer_id: int, tag: str) -> tuple[int, bool]:
        """记录一次主题关注，返回累计次数和是否达到长期记忆阈值。"""
        if not tag or not tag.strip():
            raise ValueError("兴趣主题不能为空")
        key = self.key(customer_id, tag)
        count = await self.redis.incr(key)
        if count == 1:
            await self.redis.expire(key, self.WINDOW_SECONDS)
        return int(count), int(count) >= self.threshold


__all__ = ["InterestTopicTracker"]