package helper

import (
	"crypto/rand"
	"encoding/base64"

	"golang.org/x/crypto/scrypt"
)

// Recommended https://pkg.go.dev/golang.org/x/crypto/scrypt
const SCRYPT_N = 32768
const SCRYPT_R = 8
const SCRYPT_P = 1
const SCRYPT_L = 64

const SALT_LENGTH = SCRYPT_L

func getEncoding() *base64.Encoding {
	return base64.StdEncoding.WithPadding(base64.NoPadding)
}

// Generates truly random bytes.
func generateRandomBytes(len int) ([]byte, error) {
	salt := make([]byte, len)
	_, err := rand.Read(salt)
	if err != nil {
		return nil, err
	}
	return salt, nil
}

func GenerateSalt() (string, error) {
	salt, err := generateRandomBytes(SALT_LENGTH)
	if err != nil {
		return "", err
	}
	return getEncoding().EncodeToString(salt), nil
}

func GenerateHash(password string, salt string) (string, error) {
	hash, err := scrypt.Key([]byte(password), []byte(salt), SCRYPT_N, SCRYPT_R, SCRYPT_P, SCRYPT_L)
	if err != nil {
		return "", err
	}
	return getEncoding().EncodeToString(hash), nil
}