/*
 * Copyright 2022 Oleg Borodin  <borodin@unix7.org>
 */

package dsrpc

import (
	"bytes"
	"crypto/sha256"
	"encoding/json"
	"math/rand"
	"time"
)

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

type Auth struct {
	Ident []byte `msgpack:"ident"    json:"ident"`
	Salt  []byte `msgpack:"salt"     json:"salt"`
	Hash  []byte `msgpack:"hash"     json:"hash"`
}

func NewAuth() *Auth {
	return &Auth{}
}

func (this *Auth) Json() []byte {
	jBytes, _ := json.Marshal(this)
	return jBytes
}

func CreateAuth(ident, pass []byte) *Auth {
	salt := CreateSalt()
	hash := CreateHash(ident, pass, salt)
	auth := &Auth{}
	auth.Ident = ident
	auth.Salt = salt
	auth.Hash = hash
	return auth
}

func CreateSalt() []byte {
	const saltSize = 16
	randBytes := make([]byte, saltSize)
	rand.Read(randBytes)
	return randBytes
}

func CreateHash(ident, pass, salt []byte) []byte {
	vec := make([]byte, 0, len(ident)+len(salt)+len(pass))
	vec = append(vec, ident...)
	vec = append(vec, salt...)
	vec = append(vec, pass...)
	hasher := sha256.New()
	hash := hasher.Sum(vec)
	return hash
}

func CheckHash(ident, pass, reqSalt, reqHash []byte) bool {
	localHash := CreateHash(ident, pass, reqSalt)
	return bytes.Equal(reqHash, localHash)
}