package response

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"encoding/base64"
	"math/rand"
	"strings"
	"time"
)

var (
	isDebug    bool
	encryptKey string
)

// Init 初始化响应加密相关配置（对应旧项目 base.is_debug / encrypt.encrypt_key）
func Init(debug bool, key string) {
	isDebug = debug
	encryptKey = key
}

func GetConfigBool(key string) bool {
	if key == "base.is_debug" {
		return isDebug
	}
	return false
}

func GetConfigString(key string) string {
	if key == "encrypt.encrypt_key" {
		return encryptKey
	}
	return ""
}

func GetEncrypt(key string, nums ...int8) string {
	original := GetConfigString(key)
	str := original
	//TODO 后台切换到新版时开启
	//for _, num := range nums {
	//	str = str[num:] + str[:num]
	//}
	return str
}

// GetRandString 取得随机字符串:使用字符串拼接
func GetRandString(length int) string {
	if length < 1 {
		return ""
	}
	char := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	charArr := strings.Split(char, "")
	charlen := len(charArr)
	ran := rand.New(rand.NewSource(time.Now().Unix()))

	var rchar string = ""
	for i := 1; i <= length; i++ {
		rchar = rchar + charArr[ran.Intn(charlen)]
	}
	return rchar
}

type Crypto struct{}

// EncryptKey 加密
func (c Crypto) EncryptKey(data []byte, key string) (map[string]string, Error) {
	info, err := c.aesCBCEncryptKey(data, key)
	if err != nil {
		return nil, err
	}

	return info, nil
}

func (c Crypto) aesCBCEncryptKey(data []byte, key string) (map[string]string, Error) {
	k := []byte(key)
	iv := GetRandString(NumberSixteen)

	// 分组密钥
	block, err := aes.NewCipher(k)
	if err != nil {
		return nil, ErrorEncryptAesKeyError
	}
	// 获取密钥块的长度
	blockSize := block.BlockSize()
	// 补充码
	data = c.pKCS7Padding(data, blockSize)
	// 加密模式
	blockMode := cipher.NewCBCEncrypter(block, []byte(iv))
	// 创建数组
	crypted := make([]byte, len(data))

	// 加密
	blockMode.CryptBlocks(crypted, data)
	return map[string]string{
		"data": base64.StdEncoding.EncodeToString(crypted),
		"iv":   iv,
	}, nil
}

func (c Crypto) pKCS7Padding(ciphertext []byte, blockSize int) []byte {
	// 判断缺少几位长度，最少为 1，最多为 blockSize
	padding := blockSize - len(ciphertext)%blockSize
	// 补足位数，把切片 []byte{byte(padding)} 复制 padding 个
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}