package utils

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

const (
	letterBytes = "0123456789"
)

var mu sync.Mutex
var generatedCodes = make(map[string]struct{})

func init() {
	rand.Seed(time.Now().UnixNano())
}

func randomString(lens int) string {
	b := make([]byte, lens)
	for i := range b {
		b[i] = letterBytes[rand.Intn(len(letterBytes))]
	}
	return string(b)
}
func GenerateUniqueInvitationCode(lens int) string {
	var code string
	for {
		code = randomString(lens)
		mu.Lock()
		if _, ok := generatedCodes[code]; !ok {
			generatedCodes[code] = struct{}{}
			mu.Unlock()
			return code
		}
		mu.Unlock()
	}
}