# app/utils/throttler.py
from redis.asyncio import Redis
from datetime import datetime, timedelta
from typing import Optional, Any, Tuple

class RedisThrottler:
    """基于 Redis 的变化感知限流器"""
    @staticmethod
    async def should_throttle(
        redis: Redis, 
        key: str, 
        current_signature: str, 
        expire_seconds: int = 1800
    ) -> bool:
        """
        如果 signature 没变且未过期，则建议限流 (Return True)
        如果 signature 变了，则更新 Redis 并允许通过 (Return False)
        """
        try:
            last_val = await redis.get(key)
            if last_val and last_val == current_signature:
                return True
            
            # 记录新状态并设置过期时间
            await redis.set(key, current_signature, ex=expire_seconds)
            return False
        except Exception:
            # Redis 异常时，默认不限流（保证业务可用性）
            return False

class BusinessRateLimiter:
    """基于业务元数据的复杂限流器（冷却时间、每日上限、状态变更检查）"""
    
    @staticmethod
    def check_notification_limit(
        meta: dict,
        current_id: str, # 例如 earliest_date 或 status
        cooldown_hours: int = 8,
        daily_max: int = 3
    ) -> Tuple[bool, dict]:
        """
        返回: (是否允许发送, 更新后的 meta)
        """
        now = datetime.utcnow()
        today = now.date().isoformat()
        
        last_notify_at = meta.get("last_notify_at")
        last_id = meta.get("last_id")
        daily_count_date = meta.get("daily_count_date")
        daily_count = int(meta.get("daily_count") or 0)

        # 1. 内容变化检查: 如果 ID 没变，直接拦截
        if last_id == current_id:
            return False, meta

        # 2. 冷却时间检查
        if last_notify_at:
            last_dt = datetime.fromisoformat(last_notify_at)
            if (now - last_dt) < timedelta(hours=cooldown_hours):
                return False, meta

        # 3. 每日上限检查
        if daily_count_date == today and daily_count >= daily_max:
            return False, meta

        # 更新元数据
        new_meta = meta.copy()
        new_meta["last_notify_at"] = now.isoformat()
        new_meta["last_id"] = current_id
        new_meta["daily_count_date"] = today
        new_meta["daily_count"] = daily_count + 1 if daily_count_date == today else 1
        new_meta["notify_count"] = int(new_meta.get("notify_count") or 0) + 1
        
        return True, new_meta