package middleware

import (
	"fmt"
	"net/http"

	"github.com/gin-gonic/gin"

	"laic-backend/common"
	"laic-backend/logger"
)

// rateLimitLua 固定窗口计数：首次计数设置过期时间，返回当前窗口计数
const rateLimitLua = `
local key = KEYS[1]
local ttl = tonumber(ARGV[1])
local n = redis.call('INCR', key)
if n == 1 then
  redis.call('EXPIRE', key, ttl)
end
return n
`

// RateLimitMiddleware 基于 Redis 固定窗口的按 IP 限流（默认 300 次/分钟）
func RateLimitMiddleware(limit int64, windowSeconds int64) gin.HandlerFunc {
	if limit <= 0 {
		limit = 300
	}
	if windowSeconds <= 0 {
		windowSeconds = 60
	}
	return func(c *gin.Context) {
		key := fmt.Sprintf("laic:ratelimit:%s", c.ClientIP())
		n, err := common.GetLuaInt64(rateLimitLua, []string{key}, windowSeconds)
		if err != nil {
			// 限流依赖 Redis，异常时放行（避免 Redis 故障拖垮全站）
			logger.ERROR("限流计数失败", err)
			c.Next()
			return
		}
		if n > limit {
			common.FailWithBusiErrorWithHttpStatus(c, http.StatusTooManyRequests, common.NewBusiError(http.StatusTooManyRequests, "请求过于频繁，请稍后再试"))
			return
		}
		c.Next()
	}
}