package utils

import (
	"bytes"
	"crypto/aes"
	"crypto/cipher"
	"crypto/md5"
	"encoding/base64"
	"fmt"
	"math/rand"
	"strconv"
	"strings"
	"time"

	"github.com/astaxie/beego"
)

// 将字符串加密成 md5
func String2md5(str string) string {
	data := []byte(str)
	has := md5.Sum(data)
	return fmt.Sprintf("%x", has) //将[]byte转成16进制
}

// RandomString 在数字、大写字母、小写字母范围内生成num位的随机字符串
func RandomString(length int) string {
	// 48 ~ 57 数字
	// 65 ~ 90 A ~ Z
	// 97 ~ 122 a ~ z
	// 一共62个字符，在0~61进行随机，小于10时，在数字范围随机，
	// 小于36在大写范围内随机，其他在小写范围随机
	rand.Seed(time.Now().UnixNano())
	result := make([]string, 0, length)
	for i := 0; i < length; i++ {
		t := rand.Intn(62)
		if t < 10 {
			result = append(result, strconv.Itoa(rand.Intn(10)))
		} else if t < 36 {
			result = append(result, string(rand.Intn(26)+65))
		} else {
			result = append(result, string(rand.Intn(26)+97))
		}
	}
	return strings.Join(result, "")
}

// AES加密
func AESEncrypt(origin string) string {
	aes_key := beego.AppConfig.String("aes_key")
	xpass, _ := _aesEncrypt([]byte(origin), []byte(aes_key))
	pass64 := base64.StdEncoding.EncodeToString(xpass)
	return pass64
}

func AESDecrypt(crypted []byte) string {
	aes_key := beego.AppConfig.String("aes_key")
	origData, err := _aesDecrypt(crypted, []byte(aes_key))
	if err != nil {
		return ""
	}
	return string(origData)
}

func _PKCS5Padding(ciphertext []byte, blockSize int) []byte {
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(ciphertext, padtext...)
}

func _PKCS5UnPadding(origData []byte) []byte {
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}

func _aesEncrypt(origData, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	blockSize := block.BlockSize()
	origData = _PKCS5Padding(origData, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, key[:blockSize])
	crypted := make([]byte, len(origData))
	blockMode.CryptBlocks(crypted, origData)
	return crypted, nil
}

func _aesDecrypt(crypted, key []byte) ([]byte, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}

	blockSize := block.BlockSize()
	blockMode := cipher.NewCBCDecrypter(block, key[:blockSize])
	origData := make([]byte, len(crypted))
	blockMode.CryptBlocks(origData, crypted)
	origData = _PKCS5UnPadding(origData)
	return origData, nil
}