package libPassword

import "golang.org/x/crypto/pbkdf2"
import "hash"
import "strconv"
import "encoding/base64"
import "crypto/sha1"
import "crypto/sha256"
import "crypto/sha512"
import "crypto/rand"
import "fmt"
import "strings"

const (
	salt_length = 8
	hesh_length = 20
	interations = 10000
	hashfunc string = "sha256"
)
var hashlib = map[string] func()hash.Hash{
		"sha1":sha1.New,
		"sha256":sha256.New,
		"sha512":sha512.New,
	}

func Validate(hash,password string)(output,replace bool){
	parts := strings.Split(hash,"$")
	if len(parts) == 3 {
		return false,false
	}
	cur_iter,err := strconv.Atoi(parts[1])
	if err != nil {
		return false,false
	}
	hashfunc_c := strings.Split(parts[0],"_")[1]
	replace = (hashfunc_c!=hashfunc)

	dk := pbkdf2.Key([]byte(password), []byte(parts[2]), cur_iter, len(parts[3])-8, hashlib[hashfunc_c])
	x := fmt.Sprintf("pbkdf2_%s$%s$%s$%s",hashfunc_c,parts[1],parts[2],base64.StdEncoding.EncodeToString(dk))
	output = (x==hash)
	return
}
func GenerateRandomString(n int) (string, error) {
	b := make([]byte, n)
	_, err := rand.Read(b)
	if err != nil {
		return "", err
	}
	return base64.URLEncoding.EncodeToString(b), nil
}
func NewHesh(password string)string{
	salt,_ := GenerateRandomString(salt_length)
	dk := pbkdf2.Key([]byte(password), []byte(salt), interations, hesh_length, hashlib[hashfunc])
	return fmt.Sprintf("pbkdf2_%s$%d$%s$%s",hashfunc,interations,salt,base64.StdEncoding.EncodeToString(dk))
}