package middleware

import (
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
	"golang.org/x/time/rate"

	"filestoragesystem/internal/repository"
	"filestoragesystem/internal/utils"
)

// RateLimit 令牌桶限流中间件
// 限额从系统设置api_rate_limit读取(次/分钟)，按用户ID(已认证)或IP进行限制
func RateLimit(settingRepo *repository.SettingRepo) gin.HandlerFunc {
	var mu sync.Mutex
	buckets := make(map[string]*rate.Limiter)
	lastClean := time.Now()

	getLimit := func() int {
		if v, err := settingRepo.GetValue("api_rate_limit"); err == nil {
			var n int
			if _, e := fmt.Sscanf(v, "%d", &n); e == nil && n > 0 {
				return n
			}
		}
		return 100
	}

	return func(c *gin.Context) {
		// 管理员后台不限流
		if IsAdmin(c) {
			c.Next()
			return
		}

		key := utils.ClientIP(c)
		if uid := CurrentUserID(c); uid > 0 {
			key = fmt.Sprintf("user:%d", uid)
		}

		limit := getLimit()
		mu.Lock()
		// 定期清理空闲桶
		if time.Since(lastClean) > 10*time.Minute {
			buckets = make(map[string]*rate.Limiter)
			lastClean = time.Now()
		}
		limiter, ok := buckets[key]
		if !ok {
			// 每分钟limit次：速率=limit/60每秒，突发=limit
			limiter = rate.NewLimiter(rate.Limit(float64(limit)/60.0), limit)
			buckets[key] = limiter
		}
		mu.Unlock()

		if !limiter.Allow() {
			c.Header("Retry-After", "60")
			c.AbortWithStatusJSON(http.StatusTooManyRequests, utils.Response{
				Code: 429, Message: "请求过于频繁，请稍后再试",
			})
			return
		}
		c.Next()
	}
}