package utils

import (
	"crypto/rand"
	"fmt"
	"math/big"
	"strings"
)

// randomCharset 去掉了易混淆字符（0/O、1/l/I）。
const randomCharset = "abcdefghijkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789"

// RandomString 生成指定长度的随机字符串。
func RandomString(length int) (string, error) {
	limit := big.NewInt(int64(len(randomCharset)))
	var builder strings.Builder
	builder.Grow(length)
	for i := 0; i < length; i++ {
		n, err := rand.Int(rand.Reader, limit)
		if err != nil {
			return "", fmt.Errorf("生成随机字符串失败: %w", err)
		}
		builder.WriteByte(randomCharset[n.Int64()])
	}
	return builder.String(), nil
}