// Copyright 2021 Tencent Inc. All rights reserved.

package utils

import (
	"crypto/rand"
)

const (
	// NonceSymbols 随机字符串可用字符集
	NonceSymbols = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
	// NonceLength 随机字符串的长度
	NonceLength = 32
)

// GenerateNonce 生成一个长度为 NonceLength 的随机字符串（只包含大小写字母与数字）
func GenerateNonce() (string, error) {
	bytes := make([]byte, NonceLength)
	_, err := rand.Read(bytes)
	if err != nil {
		return "", err
	}
	symbolsByteLength := byte(len(NonceSymbols))
	for i, b := range bytes {
		bytes[i] = NonceSymbols[b%symbolsByteLength]
	}
	return string(bytes), nil
}