package Middlewares
import (
	"github.com/gin-gonic/gin"
	"strconv"
	"time"
	"voteapi/pkg/app/response"
	"voteapi/pkg/gredis"
	"voteapi/pkg/util"
)
const IP_LIMIT_NUM_KEY = "ipLimit:ipLimitNum"
const IP_BLACK_LIST_KEY = "ipLimit:ipBlackList"
var prefix = "{gateway}"
var delaySeconds int64 = 60  // 觀察時間跨度，秒
var maxAttempts int64 = 10000 // 限制請求數
var blackSeconds int64 = 0  // 封禁時長，秒，0-不封禁
func GateWayPlus() gin.HandlerFunc {
	return func(c *gin.Context) {
		path := c.FullPath()
		clientIp := c.ClientIP()
		// redis配置集群時必須
		param := make(map[string]string)
		param["path"] = path
		param["clientIp"] = clientIp
		if !main(param) {
			c.Abort()
			response.JsonResponseError(c, "當前IP請求過于頻繁，暫時被封禁~")
		}
	}
}
func main(param map[string]string) bool {
	// 預知的IP黑名單
	var blackList []string
	if util.InStringArray(param["clientIp"], blackList) {
		return false
	}
	// 預知的IP白名單
	var whiteList []string
	if util.InStringArray(param["clientIp"], whiteList) {
		return false
	}
	blackKey := prefix + ":" + IP_BLACK_LIST_KEY
	limitKey := prefix + ":" + IP_LIMIT_NUM_KEY
	curr := time.Now().Unix()
	item := util.Md5(param["path"] + "|" + param["clientIp"])
	return normal(blackKey, limitKey, item, curr)
}
// 普通模式
func normal(blackKey string, limitKey string, item string, time int64) (res bool) {
	if blackSeconds > 0 {
		timeout, _ := gredis.RawCommand("HGET", blackKey, item)
		if timeout != nil {
			to, _ := strconv.Atoi(string(timeout.([]uint8)))
			if int64(to) > time {
				// 未解封
				return false
			}
			// 已解封，移除黑名單
			gredis.RawCommand("HDEL", blackKey, item)
		}
	}
	l, _ := gredis.RawCommand("HGET", limitKey, item)
	if l != nil {
		last, _ := strconv.Atoi(string(l.([]uint8)))
		if int64(last) >= maxAttempts {
			return false
		}
	}
	num, _ := gredis.RawCommand("HINCRBY", limitKey, item, 1)
	if ttl, _ := gredis.TTLKey(limitKey); ttl == int64(-1) {
		gredis.Expire(limitKey, int64(delaySeconds))
	}
	if num.(int64) >= maxAttempts  blackSeconds > 0 {
		// 加入黑名單
		gredis.RawCommand("HSET", blackKey, item, time+blackSeconds)
		// 刪除記錄
		gredis.RawCommand("HDEL", limitKey, item)
	}
	return true
}
// LUA腳本模式
// 支持redis集群部署
func luaScript(blackKey string, limitKey string, item string, time int64) (res bool) {
	script := `
local blackSeconds = tonumber(ARGV[5])
if(blackSeconds > 0)
then
  local timeout = redis.call('hget', KEYS[1], ARGV[1])
  if(timeout ~= false)
  then
    if(tonumber(timeout) > tonumber(ARGV[2]))
    then
      return false
    end
    redis.call('hdel', KEYS[1], ARGV[1])
  end
end
local last = redis.call('hget', KEYS[2], ARGV[1])
if(last ~= false and tonumber(last) >= tonumber(ARGV[3]))
then
  return false
end
local num = redis.call('hincrby', KEYS[2], ARGV[1], 1)
local ttl = redis.call('ttl', KEYS[2])
if(ttl == -1)
then
  redis.call('expire', KEYS[2], ARGV[4])
end
if(tonumber(num) >= tonumber(ARGV[3]) and blackSeconds > 0)
then 
  redis.call('hset', KEYS[1], ARGV[1], ARGV[2] + ARGV[5])
  redis.call('hdel', KEYS[2], ARGV[1])
end
return true
`
	result, err := gredis.RawCommand("EVAL", script, 2, blackKey, limitKey, item, time, maxAttempts, delaySeconds, blackSeconds)
	if err != nil {
		return false
	}
	if result == int64(1) {
		return true
	} else {
		return false
	}
}

// 加鎖限頻，輸出次數大概率小于最大值
func ExecLimit(lastExecTime *time.Time, l *sync.RWMutex ,maxTimes int, perDuration time.Duration, f func()) {
  l.Lock()
  defer l.Unlock()
 // per times cost time(s)
 SecondsPerTimes := float64(perDuration) / float64(time.Second) / float64(maxTimes)
 now := time.Now()
 interval := now.Sub(*lastExecTime).Seconds()
 if interval  SecondsPerTimes {
 time.Sleep(time.Duration(int64((SecondsPerTimes-interval)*1000000000)) * time.Nanosecond)
 }
 f()
 *lastExecTime = time.Now()
}
// 官方的，需要引用 "golang.org/x/time/rate"
// 基本上可以達到滿值，比自己寫的更優
func ExecLimit2(l *rate.Limiter, f func()) {
 go func() {
 l.Wait(context.Background())
 f()
 }()
}

func TestExecLimit(t *testing.T) {
 runtime.GOMAXPROCS(runtime.NumCPU())
 go func() {
 var lastExecTime time.Time
 var l sync.RWMutex
 for {
  ExecLimit(lastExecTime, l, 10, time.Second, func() {
  fmt.Println("do")
  })
 }
 }()
 select {
 case -time.After(1 * time.Second):
 fmt.Println("1秒到時")
 }
}
func TestExecLimit2(t *testing.T) {
 runtime.GOMAXPROCS(runtime.NumCPU())
 l := rate.NewLimiter(1, 30)
 go func() {
 for {
      ExecLimit2(l, func() {
  fmt.Println("do")
  })
 }
 }()
 select {
 case -time.After(1 * time.Second):
 fmt.Println("1秒到時")
 }
}