package spark

import (
	"crypto/hmac"
	"crypto/md5"
	"crypto/sha1"
	"encoding/base64"
	"strconv"
)

// spark 接口签名计算
// MD5_TABLE 定义 MD5 转换表
var MD5_TABLE = []rune{
	'0', '1', '2', '3', '4', '5', '6', '7',
	'8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
}

// ApiAuthAlgorithm 定义 API 认证算法结构体
type ApiAuthAlgorithm struct{}

// GetSignature 获取签名
func (a *ApiAuthAlgorithm) GetSignature(appId, secret string, ts int64) string {
	auth := a.md5(appId + strconv.FormatInt(ts, 10))
	if auth == "" {
		return ""
	}
	return a.hmacSHA1Encrypt(auth, secret)
}

// hmacSHA1Encrypt sha1 加密
func (a *ApiAuthAlgorithm) hmacSHA1Encrypt(encryptText, encryptKey string) string {
	h := hmac.New(sha1.New, []byte(encryptKey))
	h.Write([]byte(encryptText))
	return base64.StdEncoding.EncodeToString(h.Sum(nil))
}

// md5 MD5 加密
func (a *ApiAuthAlgorithm) md5(cipherText string) string {
	hash := md5.Sum([]byte(cipherText))
	result := make([]rune, 32)
	for i, v := range hash {
		result[i*2] = MD5_TABLE[v>>4&0xf]
		result[i*2+1] = MD5_TABLE[v&0xf]
	}
	return string(result)
}