package utils

import (
	"crypto/hmac"
	"crypto/sha512"
	"encoding/base64"
	"math/rand"
)

var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

func RandomString(n int) string {
	s := make([]rune, n)
	for i := range s {
		s[i] = letters[rand.Intn(len(letters))]
	}

	return string(s)
}

func SignString(s string, key []byte) string {
	mac := hmac.New(sha512.New, key)
	mac.Write([]byte(s))

	return base64.StdEncoding.EncodeToString(mac.Sum(nil))
}

func SignAndCompare(s string, exp string, key []byte) bool {
	mac := hmac.New(sha512.New, key)
	mac.Write([]byte(s))

	decoded, err := base64.StdEncoding.DecodeString(exp)
	if err != nil {
		return false
	}

	return hmac.Equal(mac.Sum(nil), decoded)
}