package main

import(
   "fmt"
   "crypto/aes"
   "crypto/cipher"
   "encoding/base64"
   "errors"
   "log"
   "encoding/json"
)



type  WXBizDataCrypt struct {
   appId string
   sessionKey string
}


 type WaterMark struct {
   TimeStamp string `json:"timestamp"`
   AppID string `json:"appid"`
 }


type EncryptedDataUserInfo struct {
   OpenID    string `json:"openId"`
   NickName  string `json:"nickName"`
   Gender    int `json:"gender"`
   Language  string `json:"language"`
   City      string `json:"city"`
   Province  string `json:"province"`
   Country   string `json:"country"`
   AvatarURL string `json:"avatarUrl"`
   UnionID   string `json:"unionId"`
   Watermark struct {
      Timestamp int `json:"timestamp"`
      Appid     string `json:"appid"`
   } `json:"watermark"`
}

func checkError(err  error, id string) {
   if err!= nil {
      log.Fatal("Wrong position is " + id, err)
   }
}


func (wx *WXBizDataCrypt) decrypt(encryptedData string, iv string)  string {

   // The sessionkey & encryptedData & iv are base64 encode
   // So we need to use base64 to decode it first
   sessionKey,err := base64.StdEncoding.DecodeString(wx.sessionKey)
   checkError(err, "1")
   encryptedDataByte,err := base64.StdEncoding.DecodeString(encryptedData)
   checkError(err, "2")
   ivByte,err := base64.StdEncoding.DecodeString(iv)
   checkError(err, "3")

   block,err := aes.NewCipher(sessionKey)
   checkError(err, "4")

   if len(encryptedDataByte) < aes.BlockSize {
      err = errors.New("Ciphertext block size is too short!")
      checkError(err, "5")
   }

   //The wechat biz data use mode CBC, which use block
   mode := cipher.NewCBCDecrypter(block, ivByte)
   mode.CryptBlocks(encryptedDataByte, encryptedDataByte)

    var dat EncryptedDataUserInfo
   fmt.Println(string(encryptedDataByte))
    json.Unmarshal(encryptedDataByte, &dat)
   //fmt.Println(dat.UnionID)
    return dat.UnionID
   /*openId,err := jsonparser.GetString(encryptedDataByte,"openId")
   checkError(err, "6")
   return openId*/
}


 func main(){
   ha := WXBizDataCrypt{
      appId: "wx4f4bc4dec97d474b",
      sessionKey : "tiihtNczf5v6AKRyjwEUhQ=="}
   encryptedData := "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"
   iv := "r7BXXKkLb8qrSNn05n0qiA=="

/*  ha := WXBizDataCrypt{
       appId: "wxb8776b4df5c6ef6a",
       sessionKey : "ezcAawD6urUDuNetdZulOg=="}
    encryptedData := "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"
    iv := "FYmK+E8nT6SLJUP9ytvSvQ=="*/


   res := ha.decrypt(encryptedData, iv)


   fmt.Println(res)
 }