package wx

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

var Wxapp = &wxapp{}

type wxapp struct {
	appid  string
	secret string
}

// InitWxapp @Title 初始化wxapp
func InitWxapp(appid, secret string) {
	Wxapp.appid = appid
	Wxapp.secret = secret
}

type resLogin struct {
	LoginInfo
	Errcode int    `json:"errcode"`
	Errmsg  string `json:"errmsg"`
}
type LoginInfo struct {
	SessionKey string `json:"session_key"`
	Openid     string `json:"openid"`
	Unionid    string `json:"unionid"`
}

// GetLoginInfo @Title 获取登录信息
func (w *wxapp) GetLoginInfo(code string) (info LoginInfo, err error) {
	bytes, err := request("get", fmt.Sprintf("https://api.weixin.qq.com/sns/jscode2session?appid=%s&secret=%s&js_code=%s&grant_type=authorization_code",
		w.appid, w.secret, code), "")
	if err != nil {
		return
	}
	log.Println(string(bytes))
	res := resLogin{}
	if err = json.Unmarshal(bytes, &res); err != nil {
		return
	}
	if res.Errcode > 0 {
		return info, errors.New(res.Errmsg)
	}
	return res.LoginInfo, nil
}

type UserInfo struct {
	OpenID    string `json:"openId"`
	UnionID   string `json:"unionId"`
	NickName  string `json:"nickName"`
	Gender    int    `json:"gender"`
	City      string `json:"city"`
	Province  string `json:"province"`
	Country   string `json:"country"`
	AvatarURL string `json:"avatarUrl"`
	Language  string `json:"language"`
	Watermark struct {
		Timestamp int64  `json:"timestamp"`
		AppID     string `json:"appid"`
	} `json:"watermark"`
}

// GetUserInfo @Title 获取用户信息
func (w *wxapp) GetUserInfo(sessionKey, encryptedData, iv string) (userInfo UserInfo, err error) {
	decrypt, err := w.Decrypt(sessionKey, encryptedData, iv)
	if err != nil {
		return
	}
	err = json.Unmarshal(decrypt, &userInfo)
	if err != nil {
		return
	}
	if userInfo.Watermark.AppID != w.appid {
		return userInfo, errors.New("app id not match")
	}
	return
}

type UserPhone struct {
	PhoneNumber     string `json:"phoneNumber"`
	PurePhoneNumber string `json:"purePhoneNumber"`
	CountryCode     string `json:"countryCode"`
	Watermark       struct {
		Timestamp int    `json:"timestamp"`
		Appid     string `json:"appid"`
	} `json:"watermark"`
}

// GetPhone @Title 获取用户手机号
func (w *wxapp) GetPhone(sessionKey, encryptedData, iv string) (userPhone UserPhone, err error) {
	decrypt, err := w.Decrypt(sessionKey, encryptedData, iv)
	if err != nil {
		return
	}
	if err = json.Unmarshal(decrypt, &userPhone); err != nil {
		return
	}
	return
}

// Decrypt @Title 解密数据
func (w *wxapp) Decrypt(sessionKey, encryptedData, iv string) (decrypt []byte, err error) {
	aesKey, err := base64.StdEncoding.DecodeString(sessionKey)
	if err != nil {
		return
	}
	cipherText, err := base64.StdEncoding.DecodeString(encryptedData)
	if err != nil {
		return
	}
	ivBytes, err := base64.StdEncoding.DecodeString(iv)
	if err != nil {
		return
	}
	block, err := aes.NewCipher(aesKey)
	if err != nil {
		return
	}
	mode := cipher.NewCBCDecrypter(block, ivBytes)
	mode.CryptBlocks(cipherText, cipherText)
	decrypt, err = w.pkcs7Unpad(cipherText, block.BlockSize())
	if err != nil {
		return
	}
	return
}

func (w *wxapp) pkcs7Unpad(data []byte, blockSize int) ([]byte, error) {
	if blockSize <= 0 {
		return nil, errors.New("invalid block size")
	}
	if len(data)%blockSize != 0 || len(data) == 0 {
		return nil, errors.New("invalid PKCS7 data")
	}
	c := data[len(data)-1]
	n := int(c)
	if n == 0 || n > len(data) {
		return nil, errors.New("invalid padding on input")
	}
	for i := 0; i < n; i++ {
		if data[len(data)-n+i] != c {
			return nil, errors.New("invalid padding on input")
		}
	}
	return data[:len(data)-n], nil
}