package util

import (
	"math/rand"
	"regexp"
	"time"
)

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

func RandString(n int) string {
	result := make([]byte, n)
	// A rand.Int63() generates 63 random bits, enough for letterIdxMax characters!
	rand.Seed(time.Now().UnixNano())
	for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = rand.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			result[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}
	return string(result)
}

// MsgFormat 格式化消息字符串 字符串里面有多个冒号，仅删除冒号前后的空格（如果存在）
func MsgFormat(input string) string {
	// 定义正则表达式，用于匹配冒号两边的空格
	re := regexp.MustCompile(`\s*:\s*`)

	// 使用正则表达式替换所有匹配的部分
	return re.ReplaceAllString(input, ":")
}