package util

import (
	"crypto/md5"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"math/rand"
	"time"
)

type Entity struct {
	Username string `json:"username"`
	// Token    string `json:"token"`
}

type AuthEntity struct {
	Entity
	Time      int64  `json:"time"`
	Authtoken string `json:"authtoken"`
}

func VerifyAuth(a *AuthEntity, salt string) bool {
	current := time.Now()
	if current.Sub(time.Unix(a.Time, 0)).Minutes() > 5 {
		return false
	}

	return a.Authtoken == GenAuthToken(a, salt)
}

func GenAuthToken(a *AuthEntity, salt string) string {
	str := fmt.Sprintf("%s:%d:%s", a.Username, a.Time, salt)
	h := md5.New()
	h.Write([]byte(str))
	return hex.EncodeToString(h.Sum(nil))
}

func ParseAuthEntity(str string) (a *AuthEntity, err error) {
	dbytes, err := base64.StdEncoding.DecodeString(str)
	if err != nil {
		return nil, err
	}
	a = new(AuthEntity)
	err = json.Unmarshal(dbytes, a)
	return a, err
}

func GenRandomstring(n int) string {
	// 生成长度为n的随机字符串
	// rand.Seed(time.Now().UnixNano())
	const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	b := make([]byte, n)
	for i := range b {
		b[i] = letterBytes[rand.Intn(len(letterBytes))]
	}
	return string(b)
}